Chubb Limited (CB) 10-K 25 Feb 21 2020 FY Annual report Financial data

Document and Entity Information

Document and Entity Information $ in Billions	12 Months Ended
	Dec. 31, 2020SFr / shares	Feb. 11, 2021shares	Jun. 30, 2020USD ($)	Dec. 31, 2019SFr / shares
Document Annual Report	true
Document Transition Report	false
Entity Address, Address Line One	Baerengasse 32
Entity Address, City or Town	Zurich
ICFR Auditor Attestation Flag	true
Common Shares, par value | SFr / shares	SFr 24.15			SFr 24.15
Entity Common Stock, Shares Outstanding | shares		450,224,906
Document Type	10-K
Document Period End Date	Dec. 31, 2020
Entity File Number	1-11778
Entity Registrant Name	Chubb Ltd
Entity Incorporation, State or Country Code	V8
Entity Tax Identification Number	98-0091805
Entity Address, Country	CH
Entity Address, Postal Zip Code	8001
Country Region	41
City Area Code	(0)43
Local Phone Number	456 76 00
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Entity Central Index Key	0000896159
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float | $			$ 57
Common Class A [Member]
Title of 12(b) Security	Common Shares, par value CHF 24.15 per share
Trading Symbol	CB
Security Exchange Name	NYSE
INA Senior Notes Due December 2024 [Member]
Title of 12(b) Security	Guarantee of Chubb INA Holdings Inc. 0.30% Senior Notes due 2024
Trading Symbol	CB/24A
Security Exchange Name	NYSE
INA Senior Notes Due June 2027 [Member]
Title of 12(b) Security	Guarantee of Chubb INA Holdings Inc. 0.875% Senior Notes due 2027
Trading Symbol	CB/27
Security Exchange Name	NYSE
INA Senior Notes Due March 2028 [Member]
Title of 12(b) Security	Guarantee of Chubb INA Holdings Inc. 1.55% Senior Notes due 2028
Trading Symbol	CB/28
Security Exchange Name	NYSE
INA Senior Notes Due December 2029 [Member]
Title of 12(b) Security	Guarantee of Chubb INA Holdings Inc. 0.875% Senior Notes due 2029
Trading Symbol	CB/29A
Security Exchange Name	NYSE
INA Senior Notes Due June 2031 [Member]
Title of 12(b) Security	Guarantee of Chubb INA Holdings Inc. 1.40% Senior Notes due 2031
Trading Symbol	CB/31
Security Exchange Name	NYSE
INA Senior Notes Due March 2038 [Member]
Title of 12(b) Security	Guarantee of Chubb INA Holdings Inc. 2.50% Senior Notes due 2038
Trading Symbol	CB/38A
Security Exchange Name	NYSE

Consolidated Balance Sheets

Consolidated Balance Sheets $ in Millions		Dec. 31, 2020USD ($)shares		Dec. 31, 2019USD ($)shares
Assets
Fixed maturities available for sale, at fair value, net of valuatuon allowance - $20 at December 31, 2010 (amortized cost – $85,188 and $82,580)		$ 90,699		$ 85,488
Debt securities, held to maturity, net carrying value		11,653
Debt Securities, Held-to-maturity		11,697		12,581
Equity Securities, at fair value		4,027		812
short-term investments amortized cost		4,349		4,291
Short-term investments, at fair value (amortized cost - $4,349 and $4,291)		4,345		4,291
Other investments, at fair value		7,945		6,062
Total investments		118,669		109,234
Cash		1,747	[1]	1,537	[2]
Restricted Cash		89		109
Securities lending collateral		1,844		994
Accrued investment income		867		867
Premium Receivable, Allowance for Credit Loss		44		44
Insurance and reinsurance balances receivable, net of valuation allowance - $44 and $44		10,480		10,357
Reinsurance Recoverable, Allowance for Credit Loss		314		316
Reinsurance recoverable on losses and loss expenses, net of valuation allowance - $314 and $316	[3]	15,592		15,181
Reinsurance recoverable on policy benefits		206		197
Deferred policy acquisition costs		5,402		5,242
Value of business acquired		263		306
Goodwill		15,400		15,296
Other intangible assets		5,811		6,063
Prepaid reinsurance premiums		2,769		2,647
Investments in partially-owned insurance companies		2,813		1,332
Other assets		8,822		7,581
Total assets		190,774		176,943
Liabilities
Unpaid losses and loss expenses		67,811		62,690
Unearned premiums		17,652		16,771
Future policy benefits		5,713		5,373
Insurance and reinsurance balances payable		6,708		6,184
Securities lending payable		1,844		994
Accounts payable, accrued expenses, and other liabilities		14,052		12,214
Deferred Income Tax Liabilities		892		804
Repurchase agreements		1,405		1,416
Short-term debt		0		1,299
Long-term debt		14,948		13,559
Trust preferred securities		308		308
Total liabilities		131,333		121,612
Commitments and contingencies (refer to Note 10)
Shareholders' equity
Common Shares (CHF 24.15 par value; 477,605,264 and 479,783,864 shares issued; 450,732,625 and 451,971,567 shares outstanding)		11,064		11,121
Common Shares in treasury (26,872,639 and 27,812,297 shares)		(3,644)		(3,754)
Additional Paid in Capital		9,815		11,203
Retained earnings		39,337		36,142
Accumulated other comprehensive income (AOCI)		2,869		619
Total shareholders' equity		59,441		55,331
Total liabilities and shareholders’ equity		190,774		176,943
Debt Securities, Available-for-sale, Allowance for Credit Loss		20		0
Fixed maturities available for sale, at amortized cost		85,188		82,580
Debt Securities, Held-to-maturity, Allowance for Credit Loss		44		0
Debt Securities, Held-to-maturity, Fair Value		$ 12,510		$ 13,005
Common Shares, shares issued | shares		477,605,264		479,783,864
Common Shares, shares outstanding | shares		450,732,625		451,971,567
Treasury Stock, Shares | shares		26,872,639		27,812,297
[1]	Chubb maintains two notional multicurrency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information. At December 31, 2020, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.
[2]	Chubb maintains two notional multicurrency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information.
[3]	Net of valuation allowance for uncollectible reinsurance.

Consolidated Statements Of Oper

Consolidated Statements Of Operations and Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenues
Net premiums written	$ 33,820	$ 32,275	$ 30,579
Increase in unearned premiums	(703)	(985)	(515)
Net premiums earned	33,117	31,290	30,064
Net investment income	3,375	3,426	3,305
Realized Investment Gains (Losses)	(498)	(530)	(652)
Net realized gains (losses):
Other-than-temporary impairment (OTTI) losses gross		(90)	(52)
Portion of OTTI losses recognized in other comprehensive income (OCI)	0	32	3
Net OTTI losses recognized in income		(58)	(49)
Net realized, Gain (Loss), Excluding Other-than-temporary Impairment Loss	(498)	(472)	(603)
Total revenues	35,994	34,186	32,717
Expenses
Losses and loss expenses	21,710	18,730	18,067
Policy benefits	784	740	590
Policy Acquisition Costs	6,547	6,153	5,912
Administrative expenses	2,979	3,030	2,886
Interest expense	516	552	641
Other (income) expense	(994)	(596)	(434)
Amortization of Purchased Intangibles	290	305	339
Chubb integration expenses	0	23	59
Total expenses	31,832	28,937	28,060
Income before income tax	4,162	5,249	4,657
Income tax expense (includes benefit of $(36), nil, and $(41) on unrealized gains and losses reclassified from AOCI)	629	795	695
Net income	3,533	4,454	3,962
Other comprehensive income (loss)
Unrealized appreciation (depreciation)	2,311	3,704	(2,298)
Reclassification adjustment for net realized (gains) losses included in net income	281	31	302
Other comprehensive income (loss) after reclassification for net realized gains included in net income	2,592	3,735	(1,996)
Change in:
Cumulative foreign currency translation adjustment	306	13	(802)
Postretirement benefit liability adjustment	(232)	(76)	(321)
Other comprehensive income (loss), before income tax	2,666	3,672	(3,119)
Income tax (expense) benefit related to OCI items	(416)	(605)	399
Other comprehensive income (loss)	2,250	3,067	(2,720)
Comprehensive income	$ 5,783	$ 7,521	$ 1,242
Earnings per share
Basic earnings per share	$ 7.82	$ 9.77	$ 8.55
Diluted earnings per share	$ 7.79	$ 9.71	$ 8.49

Consolidated Statements of Op_2

Consolidated Statements of Operations and Comprehensive Income (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income tax expense (benefit)	$ 36	$ 0	$ 41
Reclassification out of Accumulated Other Comprehensive Income [Member] | AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-sale, Parent [Member]
Net realized gains (losses)	(281)	(31)	(302)
Income tax expense (benefit)	$ (36)	$ 0	$ (41)

Consolidated Statements Of Shar

Consolidated Statements Of Shareholders' Equity - USD ($) $ in Millions	Total	Common Shares	Common Shares in Treasury	Additional Paid-in Capital	Retained Earnings	Retained EarningsCumulative Effect, Period of Adoption, Adjustment [Member]	Retained EarningsCumulative Effect, Period of Adoption, Adjusted Balance [Member]	AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-sale, Parent [Member]	AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-sale, Parent [Member]Cumulative Effect, Period of Adoption, Adjustment [Member]	AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-sale, Parent [Member]Cumulative Effect, Period of Adoption, Adjusted Balance [Member]	Cumulative Translation Adjustment	Cumulative Translation AdjustmentCumulative Effect, Period of Adoption, Adjustment [Member]	Cumulative Translation AdjustmentCumulative Effect, Period of Adoption, Adjusted Balance [Member]	Accumulated Defined Benefit Plans Adjustment [Member]	Accumulated Defined Benefit Plans Adjustment [Member]Cumulative Effect, Period of Adoption, Adjustment [Member]	Accumulated Defined Benefit Plans Adjustment [Member]Cumulative Effect, Period of Adoption, Adjusted Balance [Member]	Accumulated Other Comprehensive Income
Balance – beginning of year at Dec. 31, 2017		$ 11,121	$ (1,944)	$ 13,978	$ 27,474	$ 264	$ 27,738	$ 1,450	$ (296)	$ 1,154	$ (1,187)	$ (22)	$ (1,209)	$ 280	$ 47	$ 327
Treasury Stock, Retired, Cost Method, Amount		0	0		0
Common Shares repurchased	$ (1,021)		(1,021)
Net shares redeemed under employee share-based compensation plans			347	(313)
Stock Issued During Period, Value, Stock Options Exercised				(49)
Share-based compensation expense				285
FundingDividendsDeclaredToRetainedEarnings				(1,344)
Net income	3,962				3,962
Funding Dividends Declared From Additional Paid In Capital					1,344
Dividends declared on Common Shares					(1,344)
Change in year, before reclassification from AOCI, net of income tax (expense) benefit of $(426), $(647), and $338								(1,960)
Amounts reclassified from AOCI, net of income tax (expense) of $(36), nil, and $(41)								261
Change in year, net of income tax (expense) benefit of $(462), $(647), and $297								(1,699)
Change in year, net of income tax (expense) benefit of $(4), $24, and $35											(767)
Change in year, net of income tax benefit of $50, $18, and $67														(254)
Balance – Ending of year at Dec. 31, 2018	50,312	11,121	(2,618)	12,557	31,700	(12)	31,688	(545)	0	(545)	(1,976)		(1,976)	73	0	73	$ (2,448)
Treasury Stock, Retired, Cost Method, Amount		0	0		0
Common Shares repurchased	(1,531)		(1,531)
Net shares redeemed under employee share-based compensation plans			395	(178)
Stock Issued During Period, Value, Stock Options Exercised				(82)
Share-based compensation expense				266
FundingDividendsDeclaredToRetainedEarnings				(1,360)
Net income	4,454				4,454
Funding Dividends Declared From Additional Paid In Capital					1,360
Dividends declared on Common Shares					(1,360)
Change in year, before reclassification from AOCI, net of income tax (expense) benefit of $(426), $(647), and $338								3,057
Amounts reclassified from AOCI, net of income tax (expense) of $(36), nil, and $(41)								31
Change in year, net of income tax (expense) benefit of $(462), $(647), and $297								3,088
Change in year, net of income tax (expense) benefit of $(4), $24, and $35											37
Change in year, net of income tax benefit of $50, $18, and $67														(58)
Balance – Ending of year at Dec. 31, 2019	55,331	11,121	(3,754)	11,203	36,142	$ (72)	$ 36,070	2,543	$ 0	$ 2,543	(1,939)		$ (1,939)	15	$ 0	$ 15	619
Treasury Stock, Retired, Cost Method, Amount		(57)	323		(266)
Common Shares repurchased	(516)		(516)
Net shares redeemed under employee share-based compensation plans			303	(195)
Stock Issued During Period, Value, Stock Options Exercised				(50)
Share-based compensation expense				255
FundingDividendsDeclaredToRetainedEarnings				(1,398)
Net income	3,533				3,533
Funding Dividends Declared From Additional Paid In Capital					1,398
Dividends declared on Common Shares					(1,398)
Change in year, before reclassification from AOCI, net of income tax (expense) benefit of $(426), $(647), and $338								1,885
Amounts reclassified from AOCI, net of income tax (expense) of $(36), nil, and $(41)								245
Change in year, net of income tax (expense) benefit of $(462), $(647), and $297								2,130
Change in year, net of income tax (expense) benefit of $(4), $24, and $35											302
Change in year, net of income tax benefit of $50, $18, and $67														(182)
Balance – Ending of year at Dec. 31, 2020	$ 59,441	$ 11,064	$ (3,644)	$ 9,815	$ 39,337			$ 4,673			$ (1,637)			$ (167)			$ 2,869

Statement of Shareholders' Equi

Statement of Shareholders' Equity (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement of Stockholders' Equity [Abstract]
Other Comprehensive Income (Loss), Available-for-sale Securities, before Reclassification Adjustments, Tax	$ (426)	$ (647)	$ 338
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Tax	(36)	0	(41)
Net unrealized appreciation on investments, Change in year, income tax (expense) benefit	(462)	(647)	297
Cumulative translation adjustment, Change in year, income tax(expense) benefit	(4)	24	35
Pension liability adjustment, Change in year, income tax (expense) benefit	$ 50	$ 18	$ 67

Consolidated Statements Of Cash

Consolidated Statements Of Cash Flows - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020		Dec. 31, 2019		Dec. 31, 2018
Cash flows from operating activities
Net income		$ 3,533		$ 4,454		$ 3,962
Adjustments to reconcile net income to net cash flows from operating activities
Net Realized Gains Losses		498		530		652
Amortization of premiums/discounts on fixed maturities		367		395		592
Amortization of purchased intangibles		290		305		339
Deferred income taxes		(333)		(97)		16
Unpaid losses and loss expenses		4,664		(257)		570
Unearned premiums		846		1,051		654
Future policy benefits		236		215		235
Insurance and reinsurance balances payable		535		(302)		722
Accounts payable, accrued expenses, and other liabilities		(98)		(207)		375
Income taxes payable		46		(7)		161
Insurance and reinsurance balances receivable		(114)		(270)		(981)
Reinsurance recoverable		(336)		838		(1,165)
Deferred policy acquisition costs		(89)		(344)		(301)
Other		(260)		38		(351)
Net cash flows from operating activities		9,785		6,342		5,480
Cash flows from investing activities
Purchases of fixed maturities available for sale		(26,298)		(25,846)		(24,700)
Purchases of to be announced mortgage-backed securities		0		0		(35)
Purchases of fixed maturities held to maturity		(202)		(229)		(456)
Purchases of equity securities		(6,419)		(531)		(207)
Sales of fixed maturities available for sale		11,377		13,110		14,001
Sales of to be announced mortgage-backed securities		0		6		29
Sales of equity securities		3,880		611		315
Maturities and redemptions of fixed maturities available for sale		12,450		9,039		7,352
Maturities and redemptions of fixed maturities held to maturity		995		946		1,124
Net change in short-term investments		(81)		(1,117)		516
Net derivative instruments settlements		(113)		(703)		16
Private equity contributions		(1,924)		(1,315)		(1,337)
Private equity distributions		907		1,390		980
Acquisition of subsidiaries (net of cash acquired of nil, $45, and nil)		0		(29)		0
Payment, including deposit, for Huatai Group Interest		(1,623)		(580)
Other		(470)		(657)		(533)
Net Cash Provided by (Used in) Investing Activities		(7,521)		(5,905)		(2,935)
Cash flows from financing activities
Dividends paid on Common Shares		(1,388)		(1,354)		(1,337)
Common Shares repurchased		(523)		(1,530)		(1,044)
Proceeds from issuance of long-term debt		988		2,828		2,171
Proceeds from issuance of repurchase agreements		2,354		2,817		2,029
Repayments of Long-term Debt		(1,301)		(510)		(2,001)
Repayment of repurchase agreements		(2,354)		(2,817)		(2,019)
Proceeds from share-based compensation plans		145		204		115
Policyholder contract deposits		470		514		453
Policyholder contract withdrawals		(386)		(303)		(358)
Other		(87)		0		0
Net cash flows (used for) from financing activities		(2,082)		(151)		(1,991)
Effect of foreign currency rate changes on cash and restricted cash		8		20		(65)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect		190		306		489
Cash and restricted cash - beginning of year		1,646	[1],[2]	1,340	[2],[3]	851	[3]
Cash and restricted cash - end of year	[2]	1,836		1,646	[1]	1,340	[3]
Supplemental cash flow information
Taxes paid		902		912		503
Interest paid		524		512		621
Cash Acquired from Acquisition		0		45		0
CHINA | Huatai Group [Member]
Cash flows from investing activities
Payment, including deposit, for Huatai Group Interest		$ (1,623)		$ (580)		$ 0
[1]	Chubb maintains two notional multi-currency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information. At December 31, 2018, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.
[2]	Chubb maintains two notional multi-currency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information. At December 31, 2020, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.
[3]	Chubb maintains two notional multi-currency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information. At December 31, 2018 and 2017, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.

Summary of significant accounti

Summary of significant accounting policies	12 Months Ended
	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Summary of significant accounting policies	Summary of significant accounting policies a) Basis of presentation Chubb Limited is a holding company incorporated in Zurich, Switzerland. Chubb Limited, through its subsidiaries, provides a broad range of insurance and reinsurance products to insureds worldwide. Our results are reported through the following business segments: North America Commercial P&C Insurance, North America Personal P&C Insurance, North America Agricultural Insurance, Overseas General Insurance, Global Reinsurance, and Life Insurance. Refer to Note 15 for additional information. The accompanying Consolidated Financial Statements, which include the accounts of Chubb Limited and its subsidiaries (collectively, Chubb, we, us, or our), have been prepared in accordance with accounting principles generally accepted in the United States of America (GAAP) and, in the opinion of management, reflect all adjustments necessary for a fair statement of the results and financial position for such periods. All significant intercompany accounts and transactions, including internal reinsurance transactions, have been eliminated. The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. Amounts included in the Consolidated Financial Statements reflect our best estimates and assumptions; actual amounts could differ materially from these estimates. Chubb's principal estimates include: • unpaid loss and loss expense reserves, including long-tail asbestos and environmental (A&E) reserves and non-A&E casualty exposures; • future policy benefits reserves; • amortization of deferred policy acquisition costs and value of business acquired (VOBA); • reinsurance recoverable, including a valuation allowance for uncollectible reinsurance; • the assessment of risk transfer for certain structured insurance and reinsurance contracts; • the valuation of the investment portfolio and assessment of valuation allowance for expected credit losses; • the valuation of deferred income taxes; • the valuation of derivative instruments related to guaranteed living benefits (GLB); • the valuation and amortization of purchased intangibles; and • the assessment of goodwill for impairment. b) Premiums Premiums are generally recorded as written upon inception of the policy. For multi-year policies for which premiums written are payable in annual installments, only the current annual premium is included as written at policy inception due to the ability of the insured/reinsured to commute or cancel coverage within the policy term. The remaining annual premiums are recorded as written at each successive anniversary date within the multi-year term. For property and casualty (P&C) insurance and reinsurance products, premiums written are primarily earned on a pro-rata basis over the policy terms to which they relate. Unearned premiums represent the portion of premiums written applicable to the unexpired portion of the policies in force. For retrospectively-rated policies, written premiums are adjusted to reflect expected ultimate premiums consistent with changes to incurred losses, or other measures of exposure as stated in the policy, and earned over the policy coverage period. Mandatory reinstatement premiums assessed on reinsurance policies are earned in the period of the loss event that gave rise to the reinstatement premiums. All remaining unearned premiums are recognized over the remaining coverage period. Premiums from long-duration contracts such as certain traditional term life, whole life, endowment, and long-duration personal accident and health (A&H) policies are generally recognized as revenue when due from policyholders. Traditional life policies include those contracts with fixed and guaranteed premiums and benefits. Benefits and expenses are matched with income to result in the recognition of profit over the life of the contracts. Retroactive loss portfolio transfer (LPT) contracts in which the insured loss events occurred prior to contract inception are evaluated to determine whether they meet criteria for reinsurance accounting. If reinsurance accounting is appropriate, written premiums are fully earned and corresponding losses and loss expenses recognized at contract inception. These contracts can cause significant variances in gross premiums written, net premiums written, net premiums earned, and net incurred losses in the years in which they are written. Reinsurance contracts sold not meeting the criteria for reinsurance accounting are recorded using the deposit method as described below in Note 1 k). Reinsurance premiums assumed are based on information provided by ceding companies supplemented by our own estimates of premium when we have not received ceding company reports. Estimates are reviewed and adjustments are recorded in the period in which they are determined. Premiums are earned over the coverage terms of the related reinsurance contracts and range from one c) Deferred policy acquisition costs and value of business acquired Policy acquisition costs consist of commissions (direct and ceded), premium taxes, and certain underwriting costs related directly to the successful acquisition of new or renewal insurance contracts. A VOBA intangible asset is established upon the acquisition of blocks of long-duration contracts in a business combination and represents the present value of estimated net cash flows for the contracts in force at the acquisition date. Acquisition costs and VOBA, collectively policy acquisition costs, are deferred and amortized. Amortization is recorded in Policy acquisition costs in the Consolidated statements of operations. Policy acquisition costs on P&C contracts are generally amortized ratably over the period in which premiums are earned. Policy acquisition costs on traditional long-duration contracts are amortized over the estimated life of the contracts, generally in proportion to premium revenue recognized based upon the same assumptions used in estimating the liability for future policy benefits. For non-traditional long-duration contracts, we amortize policy acquisition costs over the expected life of the contracts in proportion to expected gross profits. The effect of changes in estimates of expected gross profits is reflected in the period the estimates are revised. Policy acquisition costs are reviewed to determine if they are recoverable from future income, including investment income. Unrecoverable policy acquisition costs are expensed in the period identified. Advertising costs are expensed as incurred except for direct-response campaigns that qualify for cost deferral, principally related to long-duration A&H business produced by the Overseas General Insurance segment, which are deferred and recognized as a component of Policy acquisition costs . For individual direct-response marketing campaigns that we can demonstrate have specifically resulted in incremental sales to customers and such sales have probable future economic benefits, incremental costs directly related to the marketing campaigns are capitalized as Deferred policy acquisition costs. Deferred policy acquisition costs, including deferred marketing costs, are reviewed regularly for recoverability from future income, including investment income, and amortized in proportion to premium revenue recognized, primarily over a ten d) Reinsurance Chubb assumes and cedes reinsurance with other insurance companies to provide greater diversification of business and minimize the net loss potential arising from large risks. Ceded reinsurance contracts do not relieve Chubb of its primary obligation to policyholders. For both ceded and assumed reinsurance, risk transfer requirements must be met in order to account for a contract as reinsurance, principally resulting in the recognition of cash flows under the contract as premiums and losses. To meet risk transfer requirements, a reinsurance contract must include insurance risk, consisting of both underwriting and timing risk, and a reasonable possibility of a significant loss for the assuming entity. To assess risk transfer for certain contracts, Chubb generally develops expected discounted cash flow analyses at contract inception. Deposit accounting is used for contracts that do not meet risk transfer requirements. Deposit accounting requires that consideration received or paid be recorded in the balance sheet as opposed to recording premiums written or losses incurred in the statement of operations. Non-refundable fees on deposit contracts are earned based on the terms of the contract described below in Note 1 k). Reinsurance recoverable includes balances due from reinsurance companies for paid and unpaid losses and loss expenses and future policy benefits that will be recovered from reinsurers, based on contracts in force. The method for determining the reinsurance recoverable on unpaid losses and loss expenses incurred but not reported (IBNR) involves actuarial estimates consistent with those used to establish the associated liability for unpaid losses and loss expenses as well as a determination of Chubb's ability to cede unpaid losses and loss expenses under the terms of the reinsurance agreement. Reinsurance recoverable is presented net of a valuation allowance for uncollectible reinsurance determined based upon a review of the financial condition of reinsurers and other factors. The valuation allowance for uncollectible reinsurance is based on an estimate of the reinsurance recoverable balance that will ultimately be unrecoverable due to reinsurer insolvency, a contractual dispute, or any other reason. The valuation of this allowance includes several judgments including certain aspects of the allocation of reinsurance recoverable on IBNR claims by reinsurer and a default analysis to estimate uncollectible reinsurance. The primary components of the default analysis are reinsurance recoverable balances by reinsurer, net of collateral, and default factors used to determine the portion of a reinsurer's balance deemed uncollectible. The definition of collateral for this purpose requires some judgment and is generally limited to assets held in a Chubb-only beneficiary trust, letters of credit, and liabilities held with the same legal entity for which Chubb believes there is a contractual right of offset. The determination of the default factor is principally based on the financial strength rating of the reinsurer. Default factors require considerable judgment and are determined using the current financial strength rating, or rating equivalent, of each reinsurer as well as other key considerations and assumptions. Changes in the valuation allowance for uncollectible reinsurance recoverables are recorded in Losses and loss expenses in the Consolidated statements of operations. Our methodology to calculate the valuation allowance was consistent with the new expected credit loss guidance adopted on January 1, 2020. Therefore, there was no change to the valuation allowance upon adoption . The more significant considerations include, but are not necessarily limited to, the following: • For reinsurers that maintain a financial strength rating from a major rating agency, and for which recoverable balances are considered representative of the larger population (i.e., default probabilities are consistent with similarly rated reinsurers and payment durations conform to averages), the financial rating is based on a published source and the default factor is based on published default statistics of a major rating agency applicable to the reinsurer's particular rating class. When a recoverable is expected to be paid in a brief period of time by a highly rated reinsurer, such as certain property catastrophe claims, a default factor may not be applied; • For balances recoverable from reinsurers that are both unrated by a major rating agency and for which management is unable to determine a credible rating equivalent based on a parent, affiliate, or peer company, we determine a rating equivalent based on an analysis of the reinsurer that considers an assessment of the creditworthiness of the particular entity, industry benchmarks, or other factors as considered appropriate. We then apply the applicable default factor for that rating class. For balances recoverable from unrated reinsurers for which the ceded reserve is below a certain threshold, we generally apply a default factor of 34 percent, consistent with published statistics of a major rating agency; • For balances recoverable from reinsurers that are either insolvent or under regulatory supervision, we establish a default factor and resulting valuation allowance for uncollectible reinsurance based on reinsurer-specific facts and circumstances. Upon initial notification of an insolvency, we generally recognize an expense for a substantial portion of all balances outstanding, net of collateral, through a combination of write-offs of recoverable balances and increases to the valuation allowance for uncollectible reinsurance. When regulatory action is taken on a reinsurer, we generally recognize a default factor by estimating an expected recovery on all balances outstanding, net of collateral. When sufficient credible information becomes available, we adjust the valuation allowance for uncollectible reinsurance by establishing a default factor pursuant to information received; and • For other recoverables, management determines the valuation allowance for uncollectible reinsurance based on the specific facts and circumstances. The methods used to determine the reinsurance recoverable balance and related valuation allowance for uncollectible reinsurance are regularly reviewed and updated, and any resulting adjustments are reflected in earnings in the period identified. The methods used to determine the valuation allowance for uncollectible high deductible recoverable amounts and valuation allowance for insurance and reinsurance balances receivable are similar to the processes used to determine the valuation allowance for uncollectible reinsurance recoverable. For information on high deductible policies, refer to section h) Unpaid losses and loss expenses, below. Prepaid reinsurance premiums represent the portion of premiums ceded to reinsurers applicable to the unexpired coverage terms of the reinsurance contracts in-force. The value of reinsurance business assumed is the deferred gain or loss related to loss portfolio transfers assumed and is calculated as the difference between the estimated ultimate value of the liabilities assumed under retroactive reinsurance contracts over consideration received. The gain or loss is amortized and recorded to Losses and loss expenses based on the payment pattern of the losses assumed. The unamortized value is reviewed regularly to determine if it is recoverable based upon the terms of the contract, estimated losses and loss expenses, and anticipated investment income. Unrecoverable amounts are expensed in the period identified. The value of reinsurance business assumed at December 31, 2020 and 2019 were immaterial. e) Investments Fixed maturities, equity securities, and short-term investments Fixed maturities are classified as either available for sale or held to maturity. • Available for sale (AFS) portfolio is reported at fair value, net of a valuation allowance for credit losses, with changes in fair value recorded as a separate component of AOCI in Shareholders' equity. • Held to maturity (HTM) portfolio includes securities for which we have the ability and intent to hold to maturity or redemption and is reported at amortized cost, net of a valuation allowance for credit losses. Equity securities are reported at fair value with changes in fair value recorded in net realized gains (losses) on the Consolidated statement of operations. Short-term investments comprise securities due to mature within one year of the date of purchase and are recorded at fair value which typically approximates cost. Interest, dividend income, and amortization of fixed maturity market premiums and discounts, related to these securities are recorded in Net investment income, net of investment management and custody fees, in the Consolidated statement of operations. In addition, net investment income includes the amortization of the fair value adjustment related to the acquired invested assets of The Chubb Corporation (Chubb Corp). An adjustment of $1,652 million related to the fair value of Chubb Corp’s fixed maturities securities was recorded (fair value adjustment) at the date of acquisition. At December 31, 2020, the remaining balance of this fair value adjustment was $213 million which is expected to amortize over the next two years; however, the estimate could vary materially based on current market conditions, bond calls, and the duration of the acquired investment portfolio. In addition, sales of these acquired fixed maturities would also reduce the fair value adjustment balance. For mortgage-backed securities and any other holdings for which there is a prepayment risk, prepayment assumptions are evaluated and revised as necessary. Any adjustments required due to the resultant change in effective yields and maturities are recognized prospectively. Prepayment fees or call premiums that are only payable when a security is called prior to its maturity are earned when received and reflected in Net investment income. Valuation allowance for fixed income securities Management evaluates current expected credit losses (CECL) for all HTM securities each quarter. U.S. treasury and agency securities and U.S. government agency mortgage-backed securities are assumed to have no risk of non-payment and therefore are excluded from the CECL evaluation. The remaining HTM securities are evaluated for potential credit loss on a collective pool basis. We elected to pool HTM securities by 1) external credit rating and 2) time to maturity (duration). These characteristics are the most representative of similar risk characteristics within our portfolio. Chubb pools HTM securities and calculates an expected credit loss for each pool using Moody’s corporate bond default average, corporate bond recovery rate, and an economic cycle multiplier. The multiplier is based on the leading economic index and will adjust the average default frequency for a forward-looking economic outlook. Management monitors the credit quality of HTM securities through the review of external credit ratings on a quarterly basis. Management evaluates expected credit losses (ECL) for AFS securities when fair value is below amortized cost. AFS securities are evaluated for potential credit loss on an individual security level but the evaluation may use assumptions consistent with expectations of credit losses for a group of similar securities. If management has the intent to sell or will be required to sell the security before recovery, the entire impairment loss will be recorded through income to net realized gains and losses. If management does not have the intent to sell or will not be required to sell the security before recovery, an allowance for credit losses is established and is recorded through income to net realized gains and losses, and the non-credit loss portion is recorded through other comprehensive income. Examples of criteria that are collectively evaluated to determine if a credit loss has occurred include the following: • The extent to which the fair value is less than amortized cost; • Adverse conditions related to the security, industry, or geographic area; • Downgrades in the security's credit rating by a rating agency; and • Failure of the issuer to make scheduled principal or interest payments AFS securities that meet any one of the criteria included above will be subject to a discounted cash flow analysis by comparing the present value of expected future cash flows with the amortized cost basis. Projected cash flows are driven primarily by assumptions regarding probability of default and the timing and amount of recoveries associated with defaults. Chubb developed the projected cash flows using market data, issuer-specific information, and credit ratings. In combination with contractual cash flows and the use of historical default and recovery data by Moody's Investors Service (Moody's) rating category we generate expected cash flows using the average cumulative issuer-weighted global default rates by letter rating. If the present value of expected future cash flows is less than the amortized cost, a credit loss exists and an allowance for credit losses will be recognized. If the present value of expected future cash flows is equal to or greater than the amortized cost basis, management will conclude an expected credit loss does not exist. Management reviews credit losses and the valuation allowance for expected credit losses each quarter. When all or a portion of a fixed maturity security is identified to be uncollectible and written off, the valuation allowance for expected credit losses is reduced by the same amount. In general, a security is considered uncollectible no later than when all efforts to collect contractual cash flows have been exhausted. Below are considerations for when a security may be deemed uncollectible: • We have sufficient information to determine that the issuer of the security is insolvent; • We receive notice that the issuer of the security has filed for bankruptcy, and the collectability is expected to be adversely impacted by the bankruptcy; • The issuer of a security has violated multiple debt covenants; • Amounts have been past due for a specified period of time with no response from the issuer; • A significant deterioration in the value of the collateral has occurred; • We have received correspondence from the issuer of the security indicating that it doesn’t intend to pay the contractual principal and interest. We elected to not measure an allowance for accrued investment income as uncollectible balances are written off in a timely manner, typically 30 to 45 days after uncollected balances are due. Prior to January 1, 2020, fixed income securities were evaluated individually for other-than-temporary impairment (OTTI) and a realized loss was recognized once certain criteria were met. Other investments Other investments principally comprise investment funds, limited partnerships, partially-owned investment companies, life insurance policies, policy loans, and non-qualified separate account assets. Investment funds and limited partnerships Investment funds, limited partnerships, and all other investments over which Chubb cannot exercise significant influence are accounted for as follows. Generally, we own less than three percent of the investee’s shares. • Income and expenses from these funds are reported within Net investment income. • These funds are carried at net asset value, which approximates fair value with changes in fair value recorded in net realized gains (losses) on the Consolidated statement of operations. Refer to Note 4 for a further discussion on net asset value. • As a result of the timing of the receipt of valuation data from the investment managers, these investments are generally reported on a three-month lag. • Sales of these investments are reported within Net realized gains (losses). Partially-owned investment companies Partially-owned investment companies where our ownership interest is in excess of three percent are accounted for under the equity method because Chubb exerts significant influence. These investments apply investment company accounting to determine operating results, and Chubb retains the investment company accounting in applying the equity method. • This means that investment income, realized gains or losses, and unrealized gains or losses are included in the portion of equity earnings reflected in Other (income) expense. • As a result of the timing of the receipt of valuation data from the investment managers, these investments are generally reported on a three-month lag. Other • Policy loans are carried at outstanding balance and interest income is reflected in Net investment income. • Life insurance policies are carried at policy cash surrender value and income is reflected in Other (income) expense. • Non-qualified separate account assets are supported by assets that do not qualify for separate accounting reporting under GAAP. The underlying securities are recorded on a trade date basis and carried at fair value. Unrealized gains and losses on non-qualified separate account assets are reflected in Other (income) expense. Investments in partially-owned insurance companies Investments in partially-owned insurance companies primarily represent direct investments in which Chubb has significant influence and as such, meet the requirements for equity accounting. Generally, we own twenty percent or more of the investee’s shares. We report our share of the net income or loss of the partially-owned insurance companies in Other (income) expense. Derivative instruments Chubb recognizes all derivatives at fair value in the Consolidated balance sheets in either Accounts payable, accrued expenses, and other liabilities or Other assets. Changes in fair value are included in Net realized gains (losses) in the Consolidated statements of operations. We did not designate any derivatives as accounting hedges. We participate in derivative instruments in two principal ways: (i) To sell protection to customers as an insurance or reinsurance contract that meets the definition of a derivative for accounting purposes . This category principally comprised our GLB contracts; and (ii) To mitigate financial risks and manage certain investment portfolio risks and exposures, including assets and liabilities held in foreign currencies. We use derivative instruments including futures, options, swaps, and foreign currency forward contracts. Refer to Note 10 for additional information. Securities lending program Chubb participates in a securities lending program operated by a third-party banking institution whereby certain assets are loaned to qualified borrowers and from which we earn an incremental return which is recorded within Net investment income in the Consolidated statement of operations. Borrowers provide collateral, in the form of either cash or approved securities, at a minimum of 102 percent of the fair value of the loaned securities. Each security loan is deemed to be an overnight transaction. Cash collateral is invested in a collateral pool which is managed by the banking institution. The collateral pool is subject to written investment guidelines with key objectives which include the safeguard of principal and adequate liquidity to meet anticipated redemptions. The fair value of the loaned securities is monitored on a daily basis, with additional collateral obtained or refunded as the fair value of the loaned securities changes. The collateral is held by the third-party banking institution, and the collateral can only be accessed in the event that the institution borrowing the securities is in default under the lending agreement. As a result of these restrictions, we consider our securities lending activities to be non-cash investing and financing activities. An indemnification agreement with the lending agent protects us in the event a borrower becomes insolvent or fails to return any of the securities on loan. The fair value of the securities on loan is included in fixed maturities and equity securities in the Consolidated balance sheets. The securities lending collateral is reported as a separate line in the Consolidated balance sheets with a related liability reflecting our obligation to return the collateral plus interest. Repurchase agreements Similar to securities lending arrangements, securities sold under repurchase agreements, whereby Chubb sells securities and repurchases them at a future date for a predetermined price, are accounted for as collateralized investments and borrowings and are recorded at the contractual repurchase amounts plus accrued interest. Assets to be repurchased are the same or substantially the same as the assets transferred, and the transferor, through right of substitution, maintains the right and ability to redeem the collateral on short notice. The fair value of the underlying securities is included in fixed maturities and equity securities. In contrast to securities lending programs, the use of cash received is not restricted. We report the obligation to return the cash as Repurchase agreements in the Consolidated balance sheets and record the fees under these repurchase agreements within Interest expense on the Consolidated statement of operations. Refer to Note 4 for a discussion on the determination of fair value for Chubb's various investment securities. f) Cash We have agreements with a third-party bank provider which implemented two international multi-currency notional cash pooling programs. In each program, participating Chubb entities establish deposit accounts in different currencies with the bank provider and each day the credit or debit balances in every account are notionally translated into a single currency (U.S. dollars) and then notionally pooled. The bank extends overdraft credit to any participating Chubb entity as needed, provided that the overall notionally-pooled balance of all accounts in each pool at the end of each day is at least zero. Actual cash balances are not physically converted and are not commingled between legal entities. Any overdraft balances incurred under this program by a Chubb entity would be guaranteed by Chubb Limited (up to $300 million in the aggregate). Our syndicated letter of credit facility allows for same day drawings to fund a net pool overdraft should participating Chubb entities overdraw contributed funds from the pool. Restricted cash Restricted cash in the Consolidated balance sheets represents amounts held for the benefit of third parties and is legally or contractually restricted as to withdrawal or usage. Amounts include deposits with U.S. and non-U.S. regulatory authorities, trust funds set up for the benefit of ceding companies, and amounts pledged as collateral to meet financing arrangements. The following table provides a reconciliation of cash and restricted cash reported within the Consolidated balance sheets that total to the amounts shown in the Consolidated statements of cash flows: December 31 (in millions of U.S. dollars) 2020 2019 2018 Cash $ 1,747 $ 1,537 $ 1,247 Restricted cash 89 109 93 Total cash and restricted cash shown in the Consolidated statements of cash flows $ 1,836 $ 1,646 $ 1,340 g) Goodwill and Other intangible assets Goodwill represents the excess of the cost of acquisitions over the fair value of net assets acquired and is not amortized. Goodwill is assigned at acquisition to the applicable reporting unit of the acquired entities giving rise to the goodwill. Goodwill impairment tests are performed annually or more frequently if circumstances indicate a possible impairment. For goodwill impairment testing, we use a qualitative assessment to determine whether it is more likely than not (i.e., more than a 50 percent probability) that the fair value of a reporting unit is greater than its carrying amount. If our assessment indicates less than a 50 percent probability that fair value exceeds carrying value, we quantitatively estimate a reporting unit's fair value. Goodwill recorded in connection with investments in partially-owned insurance companies is recorded in Investments in partially-owned insurance companies and is also measured for impairment annually. Indefinite lived intangible assets are not subject to amortization. Finite lived intangible assets are amortized over their useful lives, generally with an average original useful life of 25 years. Intangible assets are regularly reviewed for indicators of impairment. Impairment is recognized if the carrying amount is not recoverable from its undiscounted cash flows and is measured as the difference between the carrying amount and fair value. h) Unpaid losses and loss expenses A liability is established for the estimated unpaid losses and loss expenses under the terms of, and with respect to, Chubb's policies and agreements. Similar to premiums that are recognized as revenues over the coverage period of the policy, a liability for unpaid losses and loss expenses is recognized as expense when insured events occur o

Acquisitions (Notes)

Acquisitions (Notes)	12 Months Ended
	Dec. 31, 2020
Acquisitions [Abstract]
Mergers, Acquisitions and Dispositions Disclosures [Text Block]	Acquisitions Huatai Group Chubb maintains a direct investment in Huatai Insurance Group Co., Ltd. (Huatai Group). Huatai Group is the parent company of, and owns 100 percent of, Huatai Property & Casualty Insurance Co., Ltd. (Huatai P&C), approximately 80 percent of Huatai Life Insurance Co., Ltd. (Huatai Life), and approximately 82 percent of Huatai Asset Management Co., Ltd. (collectively, Huatai). Huatai Group's insurance operations have more than 600 branches and 11 million customers in China. In 2019, Chubb entered into agreements to acquire an additional 22.4 percent ownership in Huatai Group through two separate purchases, a 15.3 percent ownership interest for approximately $1.1 billion and a 7.1 percent ownership interest for approximately $493 million. On July 13, 2020, we completed the 15.3 percent purchase. The purchase of the additional 7.1 percent ownership interest is contingent upon important conditions. In connection with these purchase agreements, we paid $1.6 billion, including a collateralized deposit for the 7.1 percent tranche, in 2020. These transactions are recorded within investing activities on the Consolidated statement of cash flows. Separately, in November 2020, we completed the purchase of an incremental 0.9 percent ownership interest in Huatai Group for approximately $65 million. As of December 31, 2020, Chubb's aggregate ownership interest in Huatai Group was approximately 47.1 percent. Chubb applies the equity method of accounting to its investment in Huatai Group by recording its share of net income or loss in Other (income) expense in the Consolidated statements of operations. Refer to Note 14 for additional information. The Consolidated statements of operations include the equity income from the additional ownership interests as of each respective closing date. Upon completion of the 7.1 percent purchase, which will result in majority ownership of Huatai Group, Chubb is expected to obtain control of Huatai. At that time, Chubb is expected to apply consolidation accounting and discontinue the application of the equity method of accounting. Prior year acquisition Banchile Seguros de Vida On December 30, 2019, we acquired Banchile Seguros de Vida, an insurance company providing both life and property and casualty coverages in Chile, for $74 million in cash. The results of this acquisition are included in the Overseas General Insurance and Life Insurance segments as appropriate, determined by the type of policy written.

Investments

Investments	12 Months Ended
	Dec. 31, 2020
Investments, Debt and Equity Securities [Abstract]
Investments	Investments a) Fixed maturities Effective January 1, 2020, we adopted new accounting guidance that requires a valuation allowance for credit losses to be established for fixed maturity securities classified as held to maturity (HTM) or available for sale (AFS). December 31, 2020 Amortized Cost Valuation Allowance Gross Unrealized Appreciation Gross Unrealized Depreciation Fair Value (in millions of U.S. dollars) Available for sale U.S. Treasury / Agency $ 2,471 $ — $ 199 $ — $ 2,670 Non-U.S. 24,594 (6) 1,808 (42) 26,354 Corporate and asset-backed securities 34,095 (14) 2,322 (72) 36,331 Mortgage-backed securities 17,456 — 1,022 (8) 18,470 Municipal 6,572 — 304 (2) 6,874 $ 85,188 $ (20) $ 5,655 $ (124) $ 90,699 Amortized Cost Valuation Allowance Net Carrying Value Gross Unrealized Appreciation Gross Unrealized Depreciation Fair Held to maturity U.S. Treasury / Agency $ 1,392 $ — $ 1,392 $ 60 $ — $ 1,452 Non-U.S. 1,295 (7) 1,288 118 (1) 1,405 Corporate and asset-backed securities 2,185 (35) 2,150 288 — 2,438 Mortgage-backed securities 2,000 (1) 1,999 148 (1) 2,146 Municipal 4,825 (1) 4,824 245 — 5,069 $ 11,697 $ (44) $ 11,653 $ 859 $ (2) $ 12,510 December 31, 2019 Amortized Gross Gross Fair OTTI Recognized (in millions of U.S. dollars) Available for sale U.S. Treasury / Agency $ 3,188 $ 96 $ (1) $ 3,283 $ — Non-U.S. 22,670 1,099 (62) 23,707 (25) Corporate and asset-backed securities 30,689 1,180 (78) 31,791 (5) Mortgage-backed securities 18,712 494 (14) 19,192 — Municipal 7,321 205 (11) 7,515 — $ 82,580 $ 3,074 $ (166) $ 85,488 $ (30) Held to maturity U.S. Treasury / Agency $ 1,318 $ 29 $ — $ 1,347 $ — Non-U.S. 1,423 62 — 1,485 — Corporate and asset-backed securities 2,349 121 (2) 2,468 — Mortgage-backed securities 2,331 65 — 2,396 — Municipal 5,160 150 (1) 5,309 — $ 12,581 $ 427 $ (3) $ 13,005 $ — The following table presents the amortized cost of our HTM securities according to S&P rating: December 31, 2020 (in millions of U.S. dollars) Amortized cost % of Total AAA $ 2,511 22 % AA 6,193 53 % A 2,138 18 % BBB 826 7 % BB 28 — % Other 1 — % Total $ 11,697 100 % The following table presents fixed maturities by contractual maturity: December 31 December 31 2020 2019 (in millions of U.S. dollars) Net Carrying Value Fair Value Amortized Cost Fair Value Available for sale Due in 1 year or less $ 4,760 $ 4,760 $ 3,951 $ 3,973 Due after 1 year through 5 years 26,227 26,227 27,142 27,720 Due after 5 years through 10 years 27,232 27,232 23,901 24,874 Due after 10 years 14,010 14,010 8,874 9,729 72,229 72,229 63,868 66,296 Mortgage-backed securities 18,470 18,470 18,712 19,192 $ 90,699 $ 90,699 $ 82,580 $ 85,488 Held to maturity Due in 1 year or less $ 1,231 $ 1,240 $ 478 $ 479 Due after 1 year through 5 years 3,592 3,760 3,869 3,940 Due after 5 years through 10 years 3,029 3,228 3,756 3,883 Due after 10 years 1,802 2,136 2,147 2,307 9,654 10,364 10,250 10,609 Mortgage-backed securities 1,999 2,146 2,331 2,396 $ 11,653 $ 12,510 $ 12,581 $ 13,005 Expected maturities could differ from contractual maturities because borrowers may have the right to call or prepay obligations, with or without call or prepayment penalties. b) Gross unrealized loss Fixed maturities in an unrealized loss position at December 31, 2020, comprised both investment grade and below investment grade securities for which fair value declined primarily due to widening credit spreads since the date of purchase. The following table presents, for AFS fixed maturities in an unrealized loss position (including securities on loan) that are not deemed to have credit losses, the aggregate fair value and gross unrealized loss by length of time the security has continuously been in an unrealized loss position: 0 – 12 Months Over 12 Months Total December 31, 2020 Fair Value Gross Fair Value Gross Fair Value Gross (in millions of U.S. dollars) Non-U.S. $ 1,628 $ (35) $ 114 $ (5) $ 1,742 $ (40) Corporate and asset-backed securities 2,212 (33) 593 (14) 2,805 (47) Mortgage-backed securities 875 (6) 35 (2) 910 (8) Municipal 40 (1) 16 (1) 56 (2) Total AFS fixed maturities $ 4,755 $ (75) $ 758 $ (22) $ 5,513 $ (97) The following table presents, for all securities in an unrealized loss position (including securities on loan), the aggregate fair value and gross unrealized loss by length of time the security has continuously been in an unrealized loss position: 0 – 12 Months Over 12 Months Total December 31, 2019 Fair Value Gross Fair Value Gross Fair Value Gross (in millions of U.S. dollars) U.S. Treasury / Agency $ 234 $ (1) $ 339 $ — $ 573 $ (1) Non-U.S. 1,846 (34) 802 (28) 2,648 (62) Corporate and asset-backed securities 2,121 (40) 988 (40) 3,109 (80) Mortgage-backed securities 1,174 (6) 932 (8) 2,106 (14) Municipal 188 — 276 (12) 464 (12) Total fixed maturities $ 5,563 $ (81) $ 3,337 $ (88) $ 8,900 $ (169) c) Net realized gains (losses) The following table presents a roll-forward of pre-tax credit losses related to fixed maturities for which a portion of OTTI was recognized in OCI: Year Ended December 31 (in millions of U.S. dollars) 2019 2018 Balance of credit losses related to securities still held – beginning of year $ 34 $ 22 Additions where no OTTI was previously recorded 33 20 Additions where an OTTI was previously recorded 4 5 Reductions for securities sold during the period (41) (13) Balance of credit losses related to securities still held – end of year $ 30 $ 34 The following table presents the components of Net realized gains (losses) and the change in net unrealized appreciation (depreciation) of investments: Year Ended December 31 (in millions of U.S. dollars) 2020 2019 2018 Fixed maturities: OTTI on fixed maturities, gross $ — $ (90) $ (52) OTTI on fixed maturities recognized in OCI (pre-tax) — 32 3 OTTI on fixed maturities, net — (58) (49) Gross realized gains excluding OTTI 244 203 334 Gross realized losses excluding OTTI (366) (176) (587) Recovery of expected credit losses 11 — — Impairment (1) (170) — — Total fixed maturities (281) (31) (302) Equity securities 586 104 (59) Other investments (32) (20) (5) Foreign exchange gains (losses) (483) 7 131 Investment and embedded derivative instruments 81 (435) (75) Fair value adjustments on insurance derivative (202) (4) (248) S&P futures (108) (138) (4) Other derivative instruments 1 (8) (3) Other (60) (5) (87) Net realized gains (losses) (pre-tax) $ (498) $ (530) $ (652) Change in net unrealized appreciation (depreciation) on investments (pre-tax): Fixed maturities available for sale $ 2,628 $ 3,769 $ (1,958) Fixed maturities held to maturity (24) (31) (38) Other (12) (3) — Income tax (expense) benefit (462) (647) 297 Change in net unrealized appreciation (depreciation) on investments (after-tax) $ 2,130 $ 3,088 $ (1,699) (1) Relates to certain securities we intended to sell and securities written to market entering default. Realized gains and losses from Equity securities and Other investments from the table above include sales of securities and unrealized gains and losses from fair value changes as follows: Year Ended December 31, 2020 Year Ended December 31, 2019 Year Ended December 31, 2018 (in millions of U.S. dollars) Equity Securities Other Investments Total Equity Securities Other Investments Total Equity Securities Other Investments Total Net gains (losses) recognized during the period $ 586 $ (32) $ 554 $ 104 $ (20) $ 84 $ (59) $ (5) $ (64) Less: Net gains (losses) recognized from sales of securities 455 — 455 58 (5) 53 70 121 191 Unrealized gains (losses) recognized for securities still held at reporting date $ 131 $ (32) $ 99 $ 46 $ (15) $ 31 $ (129) $ (126) $ (255) The following table presents a roll-forward of valuation allowance for expected credit losses on fixed maturities: Year Ended December 31 (in millions of U.S. dollars) 2020 Available for sale Valuation allowance for expected credit losses - beginning of period $ — Impact of adoption of new accounting guidance 25 Provision for expected credit loss 188 Initial allowance for purchased securities with credit deterioration 5 Write-offs charged against the expected credit loss (5) Recovery of expected credit loss (193) Valuation allowance for expected credit losses - end of period $ 20 Held to maturity Valuation allowance for expected credit losses - beginning of period $ — Impact of adoption of new accounting guidance 44 Provision for expected credit loss 9 Recovery of expected credit loss (9) Valuation allowance for expected credit losses - end of period $ 44 Purchased Credit Deterioration (PCD) Securities During the year ended December 31, 2020, we purchased $108 million of securities with credit deterioration, categorized as available for sale, and assessed an allowance for expected credit losses of $5 million at acquisition. These PCD securities had a par value at acquisition of $144 million. d) Other investments December 31 (in millions of U.S. dollars) 2020 2019 Alternative investments: Partially-owned investment companies $ 5,969 $ 4,142 Limited partnerships 547 508 Investment funds 254 271 Alternative investments 6,770 4,921 Life insurance policies 438 377 Policy loans 233 247 Non-qualified separate account assets (1) 316 283 Other 188 234 Total $ 7,945 $ 6,062 (1) Non-qualified separate account assets are comprised of mutual funds, supported by assets that do not qualify for separate account reporting under GAAP. Alternative investments Alternative investments include partially-owned investment companies, investment funds, and limited partnerships measured at fair value using net asset value (NAV) as a practical expedient. The following table presents, by investment category, the expected liquidation period, fair value, and maximum future funding commitments of alternative investments: December 31 December 31 2020 2019 (in millions of U.S. dollars) Expected Liquidation Fair Value Maximum Fair Value Maximum Financial 2 to 10 Years $ 673 $ 237 $ 611 $ 329 Real Assets 2 to 11 Years 805 598 712 422 Distressed 2 to 8 Years 358 970 263 80 Private Credit 3 to 8 Years 88 270 104 272 Traditional 2 to 14 Years 4,519 1,125 2,844 2,160 Vintage 1 to 2 Years 73 — 116 — Investment funds Not Applicable 254 — 271 — $ 6,770 $ 3,200 $ 4,921 $ 3,263 Included in all categories in the above table, except for Investment funds, are investments for which Chubb will never have the contractual option to redeem but receives distributions based on the liquidation of the underlying assets. Further, for all categories except for Investment funds, Chubb does not have the ability to sell or transfer the investments without the consent from the general partner of individual funds. Investment Category Consists of investments in private equity funds: Financial targeting financial services companies, such as financial institutions and insurance services worldwide Real Assets targeting investments related to hard physical assets, such as real estate, infrastructure and natural resources Distressed targeting distressed corporate debt/credit and equity opportunities in the U.S. Private Credit targeting privately originated corporate debt investments, including senior secured loans and subordinated bonds Traditional employing traditional private equity investment strategies such as buyout and growth equity globally Vintage funds where the initial fund term has expired Included in partially-owned investment companies and limited partnerships are 130 individual limited partnerships covering a broad range of investment strategies including large cap buyouts, specialist buyouts, growth capital, distressed, mezzanine, real estate, and co-investments. The underlying portfolio consists of various public and private debt and equity securities of publicly traded and privately held companies and real estate assets. The underlying investments across various partnerships, geographies, industries, asset types, and investment strategies provide risk diversification within the limited partnership portfolio and the overall investment portfolio. Investment funds employ various investment strategies such as long/short equity and arbitrage/distressed. Included in this category are investments for which Chubb has the option to redeem at agreed upon value as described in each investment fund’s subscription agreement. Depending on the terms of the various subscription agreements, investment fund investments may be redeemed monthly, quarterly, semi-annually, or annually. If Chubb wishes to redeem an investment fund investment, it must first determine if the investment fund is still in a lock-up period (a time when Chubb cannot redeem its investment so that the investment fund manager has time to build the portfolio). If the investment fund is no longer in its lock-up period, Chubb must then notify the investment fund manager of its intention to redeem by the notification date prescribed by the subscription agreement. Subsequent to notification, the investment fund can redeem Chubb’s investment within several months of the notification. Notice periods for redemption of the investment funds are up to 270 days. Chubb can redeem its investment funds without consent from the investment fund managers. e) Investments in partially-owned insurance companies The following table presents Investments in partially-owned insurance companies: December 31, 2020 December 31, 2019 (in millions of U.S. dollars, except for percentages) Carrying Value Goodwill Direct Ownership Percentage Carrying Value Goodwill Direct Ownership Percentage Domicile Huatai Group $ 2,461 $ 1,313 47 % $ 1,053 $ 460 31 % China Huatai Life Insurance Company 201 69 20 % 147 64 20 % China Freisenbruch-Meyer 10 3 40 % 10 3 40 % Bermuda Chubb Arabia Cooperative Insurance Company 23 — 30 % 20 — 30 % Saudi Arabia Russian Reinsurance Company 4 — 23 % 2 — 23 % Russia ABR Reinsurance Ltd. 114 — 16 % 100 — 12 % Bermuda Total $ 2,813 $ 1,385 $ 1,332 $ 527 Chubb’s aggregate direct and indirect ownership in Huatai Life is approximately 57.5 percent, comprising 20 percent direct and 37.5 percent indirect ownership interest. The table above excludes the 7.1 percent of additional ownership commitment in Huatai Group that is contingent upon important conditions. Refer to Note 2 for additional information. f) Net investment income Year Ended December 31 (in millions of U.S. dollars) 2020 2019 2018 Fixed maturities (1) $ 3,321 $ 3,385 $ 3,128 Short-term investments 48 84 90 Other interest income 19 25 118 Equity securities 81 26 33 Other investments 82 78 104 Gross investment income (1) 3,551 3,598 3,473 Investment expenses (176) (172) (168) Net investment income (1) $ 3,375 $ 3,426 $ 3,305 (1) Includes amortization expense related to fair value adjustment of acquired invested assets related to the Chubb Corp acquisition $ (116) $ (161) $ (248) g) Restricted assets Chubb is required to maintain assets on deposit with various regulatory authorities to support its insurance and reinsurance operations. These requirements are generally promulgated in the statutory regulations of the individual jurisdictions. The assets on deposit are available to settle insurance and reinsurance liabilities. Chubb is also required to restrict assets pledged under repurchase agreements, which represent Chubb's agreement to sell securities and repurchase them at a future date for a predetermined price. We use trust funds in certain large reinsurance transactions where the trust funds are set up for the benefit of the ceding companies and generally take the place of letter of credit (LOC) requirements. We have investments in segregated portfolios primarily to provide collateral or guarantees for LOC and derivative transactions. Included in restricted assets are investments, primarily fixed maturities, totaling $19.6 billion and $21.0 billion, and cash of $89 million and $109 million, at December 31, 2020 and 2019, respectively. The following table presents the components of restricted assets: December 31 December 31 (in millions of U.S. dollars) 2020 2019 Trust funds $ 12,305 $ 14,004 Deposits with U.S. regulatory authorities 2,438 2,466 Deposits with non-U.S. regulatory authorities 2,905 2,709 Assets pledged under repurchase agreements 1,462 1,464 Other pledged assets 584 490 Total $ 19,694 $ 21,133

Fair value measurements

Fair value measurements	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Fair value measurements	Fair value measurements a) Fair value hierarchy Fair value of financial assets and financial liabilities is estimated based on the framework established in the fair value accounting guidance. The guidance defines fair value as the price to sell an asset or transfer a liability (an exit price) in an orderly transaction between market participants and establishes a three-level valuation hierarchy based on the reliability of the inputs. The fair value hierarchy gives the highest priority to quoted prices in active markets and the lowest priority to unobservable data. The three levels of the hierarchy are as follows: • Level 1 – Unadjusted quoted prices for identical assets or liabilities in active markets; • Level 2 – Includes, among other items, inputs other than quoted prices that are observable for the asset or liability such as interest rates and yield curves, quoted prices for similar assets and liabilities in active markets, and quoted prices for identical or similar assets and liabilities in markets that are not active; and • Level 3 – Inputs that are unobservable and reflect management’s judgments about assumptions that market participants would use in pricing an asset or liability. We categorize financial instruments within the valuation hierarchy at the balance sheet date based upon the lowest level of inputs that are significant to the fair value measurement. We use pricing services to obtain fair value measurements for the majority of our investment securities. Based on management’s understanding of the methodologies used, these pricing services only produce an estimate of fair value if there is observable market information that would allow them to make a fair value estimate. Based on our understanding of the market inputs used by the pricing services, all applicable investments have been valued in accordance with GAAP. We do not adjust prices obtained from pricing services. The following is a description of the valuation techniques and inputs used to determine fair values for financial instruments carried at fair value, as well as the general classification of such financial instruments pursuant to the valuation hierarchy. Fixed maturities We use pricing services to estimate fair value measurements for the majority of our fixed maturities. The pricing services use market quotations for fixed maturities that have quoted prices in active markets; such securities are classified within Level 1. For fixed maturities other than U.S. Treasury securities that generally do not trade on a daily basis, the pricing services prepare estimates of fair value measurements using their pricing applications or pricing models, which include available relevant market information, benchmark curves, benchmarking of like securities, sector groupings, and matrix pricing. Additional valuation factors that can be taken into account are nominal spreads, dollar basis, and liquidity adjustments. The pricing services evaluate each asset class based on relevant market and credit information, perceived market movements, and sector news. The market inputs used in the pricing evaluation, listed in the approximate order of priority include: benchmark yields, reported trades, broker/dealer quotes, issuer spreads, two-sided markets, benchmark securities, bids, offers, reference data, and industry and economic events. The extent of the use of each input is dependent on the asset class and the market conditions. Given the asset class, the priority of the use of inputs may change, or some market inputs may not be relevant. Additionally, fixed maturities valuation is more subjective when markets are less liquid due to the lack of market based inputs (i.e., stale pricing) and may require the use of models to be priced. The lack of market based inputs may increase the potential that an investment's estimated fair value is not reflective of the price at which an actual transaction would occur. The overwhelming majority of fixed maturities are classified within Level 2 because the most significant inputs used in the pricing techniques are observable. For a small number of fixed maturities, we obtain a single broker quote (typically from a market maker). Due to the disclaimers on the quotes that indicate that the price is indicative only, we include these fair value estimates in Level 3. Equity securities Equity securities with active markets are classified within Level 1 as fair values are based on quoted market prices. For equity securities in markets which are less active, fair values are based on market valuations and are classified within Level 2. Equity securities for which pricing is unobservable are classified within Level 3. Short-term investments Short-term investments, which comprise securities due to mature within one year of the date of purchase that are traded in active markets, are classified within Level 1 as fair values are based on quoted market prices. Securities such as commercial paper and discount notes are classified within Level 2 because these securities are typically not actively traded due to their approaching maturity, and as such, their cost approximates fair value. Short-term investments for which pricing is unobservable are classified within Level 3. Other investments Fair values for the majority of Other investments including investments in partially-owned investment companies, investment funds, and limited partnerships are based on their respective net asset values or equivalent (NAV) and are excluded from the fair value hierarchy table below. Certain of our long-duration contracts are supported by assets that do not qualify for separate account reporting under GAAP. These assets comprise mutual funds, classified within Level 1 in the valuation hierarchy on the same basis as other equity securities traded in active markets. Other investments also include equity securities, classified within Level 1 and fixed maturities, classified within Level 2, held in rabbi trusts maintained by Chubb for deferred compensation plans and supplemental retirement plans and are classified within the valuation hierarchy on the same basis as other equity securities and fixed maturities. Other investments for which pricing is unobservable are classified within Level 3. Securities lending collateral The underlying assets included in Securities lending collateral in the Consolidated balance sheets are fixed maturities which are classified in the valuation hierarchy on the same basis as other fixed maturities. Excluded from the valuation hierarchy is the corresponding liability related to Chubb’s obligation to return the collateral plus interest as it is reported at contract value and not fair value in the Consolidated balance sheets. Investment derivative instruments Actively traded investment derivative instruments, including futures, options, and forward contracts are classified within Level 1 as fair values are based on quoted market prices. The fair value of cross-currency swaps and interest rate swaps is based on market valuations and is classified within Level 2. Investment derivative instruments are recorded in either Other assets or Accounts payable, accrued expenses, and other liabilities in the Consolidated balance sheets. Other derivative instruments We maintain positions in exchange-traded equity futures contracts designed to limit exposure to a severe equity market decline, which would cause an increase in expected claims and, therefore, an increase in future policy benefit reserves for our guaranteed minimum death benefits (GMDB) and an increase in the fair value liability for our guaranteed living benefits (GLB) reinsurance business. Our positions in exchange-traded equity futures contracts are classified within Level 1. The fair value of the majority of the remaining positions in other derivative instruments is based on significant observable inputs including equity security and interest rate indices. Accordingly, these are classified within Level 2. Other derivative instruments based on unobservable inputs are classified within Level 3. Other derivative instruments are recorded in either Other assets or Accounts payable, accrued expenses, and other liabilities in the Consolidated balance sheets. Separate account assets Separate account assets represent segregated funds where investment risks are borne by the customers, except to the extent of certain guarantees made by Chubb. Separate account assets comprise mutual funds classified within Level 1 in the valuation hierarchy on the same basis as other equity securities traded in active markets. Separate account assets also include fixed maturities classified within Level 2 because the most significant inputs used in the pricing techniques are observable. Excluded from the valuation hierarchy are the corresponding liabilities as they are reported at contract value and not fair value in the Consolidated balance sheets. Separate account assets are recorded in Other assets in the Consolidated balance sheets. Guaranteed living benefits The GLB arises from life reinsurance programs covering living benefit guarantees whereby we assume the risk of guaranteed minimum income benefits (GMIB) associated with variable annuity contracts. GLB’s are recorded in Accounts payable, accrued expenses, and other liabilities in the Consolidated balance sheets. Prior to 2020, a portion of the GLB liability that represented expected losses allocated to premiums received was recorded as incurred losses within Future policy benefits, with changes in these estimates recorded in Future policy benefits. We reclassified $441 million, $409 million, and $346 million of GLB liability as of December 31, 2019, 2018, and 2017, respectively, to Accounts payable, accrued expenses, and other liabilities in the Consolidated balance sheets to conform with the new presentation. For GLB reinsurance, Chubb estimates fair value using an internal valuation model which includes current market information and estimates of policyholder behavior. All of the treaties contain claim limits, which are factored into the valuation model. The fair value depends on a number of factors, including interest rates, equity markets, credit risk, current account value, market volatility, expected annuitization rates and other policyholder behavior, and changes in policyholder mortality. Because of the significant use of unobservable inputs including policyholder behavior, GLB reinsurance is classified within Level 3. Financial instruments measured at fair value on a recurring basis, by valuation hierarchy December 31, 2020 Level 1 Level 2 Level 3 Total (in millions of U.S. dollars) Assets: Fixed maturities available for sale U.S. Treasury / Agency $ 2,148 $ 522 $ — $ 2,670 Non-U.S. — 25,808 546 26,354 Corporate and asset-backed securities — 34,758 1,573 36,331 Mortgage-backed securities — 18,410 60 18,470 Municipal — 6,874 — 6,874 2,148 86,372 2,179 90,699 Equity securities 3,954 — 73 4,027 Short-term investments 2,866 1,474 5 4,345 Other investments (1) 434 438 10 882 Securities lending collateral — 1,844 — 1,844 Investment derivative instruments 35 — — 35 Separate account assets 4,264 124 — 4,388 Total assets measured at fair value (1) $ 13,701 $ 90,252 $ 2,267 $ 106,220 Liabilities: Investment derivative instruments $ 52 $ — $ — $ 52 Other derivative instruments 17 — — 17 GLB (2) — — 1,089 1,089 Total liabilities measured at fair value $ 69 $ — $ 1,089 $ 1,158 (1) Excluded from the table above are partially-owned investments, investment funds, and limited partnerships of $6,770 million, policy loans of $233 million and other investments of $60 million at December 31, 2020 measured using NAV as a practical expedient. (2) Our GLB reinsurance product meets the definition of a derivative instrument for accounting purposes and is accordingly carried at fair value. December 31, 2019 Level 1 Level 2 Level 3 Total (in millions of U.S. dollars) Assets: Fixed maturities available for sale U.S. Treasury / Agency $ 2,664 $ 619 $ — $ 3,283 Non-U.S. — 23,258 449 23,707 Corporate and asset-backed securities — 30,340 1,451 31,791 Mortgage-backed securities — 19,132 60 19,192 Municipal — 7,515 — 7,515 2,664 80,864 1,960 85,488 Equity securities 728 15 69 812 Short-term investments 2,803 1,482 6 4,291 Other investments (1) 412 377 10 799 Securities lending collateral — 994 — 994 Investment derivative instruments 24 — — 24 Other derivative instruments 2 — — 2 Separate account assets 3,437 136 — 3,573 Total assets measured at fair value (1) $ 10,070 $ 83,868 $ 2,045 $ 95,983 Liabilities: Investment derivative instruments $ 93 $ — $ — $ 93 Other derivative instruments 13 — — 13 GLB (2) — — 897 897 Total liabilities measured at fair value $ 106 $ — $ 897 $ 1,003 (1) Excluded from the table above are partially-owned investments, investment funds, and limited partnerships of $4,921 million and other investments of $95 million at December 31, 2019 measured using NAV as a practical expedient. (2) Our GLB reinsurance product meets the definition of a derivative instrument for accounting purposes and is accordingly carried at fair value. Level 3 financial instruments The following table presents the significant unobservable inputs used in the Level 3 liability valuations. Excluded from the table below are inputs used to determine the fair value of Level 3 assets which are based on single broker quotes and contain no quantitative unobservable inputs developed by management. The majority of our fixed maturities classified as Level 3 used external pricing when markets are less liquid due to the lack of market inputs (i.e., stale pricing, broker quotes). (in millions of U.S. dollars, except for percentages) Fair Value at December 31 2020 Valuation Significant Ranges Weighted Average (1) GLB (1) $ 1,089 Actuarial model Lapse rate 3% - 34% 4.7 % Annuitization rate 0% - 100% 3.6 % (1) The weighted average lapse and annuitization rates are determined by weighting each treaty's rates by the GLB contracts fair value. The most significant policyholder behavior assumptions include lapse rates and the GMIB annuitization rates. Assumptions regarding lapse rates and GMIB annuitization rates differ by treaty, but the underlying methodologies to determine rates applied to each treaty are comparable. A lapse rate is the percentage of in-force policies surrendered in a given calendar year. All else equal, as lapse rates increase, ultimate claim payments will decrease. In general, the base lapse function assumes low lapse rates during the surrender charge period of the GMIB contract, followed by a “spike” lapse rate in the year immediately following the surrender charge period, and then reverting to an ultimate lapse rate, typically over a 2-year period. This base rate is adjusted downward for policies with more valuable guarantees (policies with guaranteed values far in excess of their account values). Partial withdrawals and the impact of older policyholders with tax-qualified contracts (due to required minimum distributions) are also reflected in our modeling. The GMIB annuitization rate is the percentage of policies for which the policyholder will elect to annuitize using the guaranteed benefit provided under the GMIB. All else equal, as GMIB annuitization rates increase, ultimate claim payments will increase, subject to treaty claim limits. All GMIB reinsurance treaties include claim limits to protect Chubb in the event that actual annuitization behavior is significantly higher than expected. In general, Chubb assumes that GMIB annuitization rates will be higher for policies with more valuable guarantees (policies with guaranteed values far in excess of their account values). Chubb also assumes that GMIB annuitization rates increase as policyholders get older. In addition, we also assume that GMIB annuitization rates are higher in the first year immediately following the waiting period (the first year the policies are eligible to annuitize using the GMIB) in comparison to all subsequent years. We do not yet have fully credible annuitization experience for all clients. The effect of changes in key market factors on assumed lapse and annuitization rates reflect emerging trends using data available from cedants. For treaties with limited experience, rates are established in line with data received from other ceding companies adjusted, as appropriate, with industry estimates. The model and related assumptions are regularly re-evaluated by management and enhanced, as appropriate, based upon additional experience obtained related to policyholder behavior and availability of updated information such as market conditions, market participant assumptions, and demographics of in-force annuities. In the fourth quarter of 2020, we completed a review of policyholder behavior related to annuitizations, partial withdrawals, lapses, and mortality for our variable annuity reinsurance business. As a result, we refined our policyholder behavior assumptions (mainly those relating to annuitizations and partial withdrawals), which had an insignificant impact on net income. During the year ended December 31, 2020, we also made routine model refinements to the internal valuation model which had an insignificant impact on net income. The following tables present a reconciliation of the beginning and ending balances of financial instruments measured at fair value using significant unobservable inputs (Level 3): Assets Liabilities Available-for-Sale Debt Securities Equity Short-term investments Other GLB (1) Year Ended December 31, 2020 Non-U.S. Corporate and asset-backed securities MBS (in millions of U.S. dollars) Balance, beginning of year $ 449 $ 1,451 $ 60 $ 69 $ 6 $ 10 $ 897 Transfers into Level 3 — 134 — — — — — Transfers out of Level 3 (16) (73) (1) (3) — — — Change in Net Unrealized Gains/Losses in OCI 19 (8) — — — — — Net Realized Gains/Losses (1) (30) — 1 (1) — 202 Purchases 274 708 2 23 14 — — Sales (122) (186) — (17) (2) — — Settlements (57) (423) (1) — (12) — — Other — — — — — — (10) Balance, end of year $ 546 $ 1,573 $ 60 $ 73 $ 5 $ 10 $ 1,089 Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date $ — $ (5) $ — $ 4 $ — $ — $ 202 Change in Net Unrealized Gains/Losses included in OCI at the Balance Sheet Date $ 16 $ (6) $ — $ — $ — $ — $ — (1) Our GLB reinsurance product meets the definition of a derivative instrument for accounting purposes and is accordingly carried at fair value. Assets Liabilities Available-for-Sale Debt Securities Equity Short-term investments Other GLB (1) Year Ended December 31, 2019 Non-U.S. Corporate and asset-backed securities MBS (in millions of U.S. dollars) Balance, beginning of year $ 345 $ 1,299 $ 61 $ 57 $ 1 $ 11 $ 861 Transfers into Level 3 11 23 — — — — — Transfers out of Level 3 (24) (38) (16) — — — — Change in Net Unrealized Gains/Losses in OCI 13 (2) — 1 — — — Net Realized Gains/Losses (1) (4) — (2) — — 4 Purchases 228 577 19 34 6 — — Sales (70) (125) (1) (21) — — — Settlements (53) (279) (3) — (1) (1) — Other — — — — — — 32 Balance, end of year $ 449 $ 1,451 $ 60 $ 69 $ 6 $ 10 $ 897 Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date $ — $ (2) $ — $ (3) $ — $ — $ 4 Change in Net Unrealized Gains/Losses included in OCI at the Balance Sheet Date $ 7 $ (8) $ — $ — $ — $ — $ — (1) Our GLB reinsurance product meets the definition of a derivative instrument for accounting purposes and is accordingly carried at fair value. Assets Liabilities Available-for-Sale Debt Securities Short-term investments Other GLB (1) Year Ended December 31, 2018 Non-U.S. Corporate and asset-backed securities MBS Equity Other (in millions of U.S. dollars) Balance, beginning of year $ 93 $ 1,037 $ 78 $ 44 $ — $ 263 $ 2 $ 550 Transfers into Level 3 13 24 1 — 5 — — — Transfers out of Level 3 (2) (31) (3) — — (252) — — Change in Net Unrealized Gains/Losses in OCI (12) (4) — (2) — (2) — — Net Realized Gains/Losses (3) (5) — 6 — 1 (2) 248 Purchases 334 672 5 37 9 50 — — Sales (69) (164) — (28) — — — — Settlements (9) (230) (20) — (13) (49) — — Other — — — — — — — 63 Balance, end of year $ 345 $ 1,299 $ 61 $ 57 $ 1 $ 11 $ — $ 861 Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date $ (1) $ (7) $ — $ (1) $ — $ 1 $ — $ 248 (1) Our GLB reinsurance product meets the definition of a derivative instrument for accounting purposes and is accordingly carried at fair value. b) Financial instruments disclosed, but not measured, at fair value Chubb uses various financial instruments in the normal course of its business. Our insurance contracts are excluded from fair value of financial instruments accounting guidance, and therefore, are not included in the amounts discussed below. The carrying values of cash, other assets, other liabilities, and other financial instruments not included below approximated their fair values. Investments in partially-owned insurance companies Fair values for investments in partially-owned insurance companies are based on Chubb’s share of the net assets based on the financial statements provided by those companies and are excluded from the valuation hierarchy tables below. Short- and long-term debt, repurchase agreements, and trust preferred securities Where practical, fair values for short-term debt, long-term debt, repurchase agreements, and trust preferred securities are estimated using discounted cash flow calculations based principally on observable inputs including incremental borrowing rates, which reflect Chubb’s credit rating, for similar types of borrowings with maturities consistent with those remaining for the debt being valued. The following tables present fair value, by valuation hierarchy, and carrying value of the financial instruments not measured at fair value: December 31, 2020 Fair Value Net Carrying Value (in millions of U.S. dollars) Level 1 Level 2 Level 3 Total Assets: Fixed maturities held to maturity U.S. Treasury / Agency $ 1,395 $ 57 $ — $ 1,452 $ 1,392 Non-U.S. — 1,405 — 1,405 1,288 Corporate and asset-backed securities — 2,438 — 2,438 2,150 Mortgage-backed securities — 2,146 — 2,146 1,999 Municipal — 5,069 — 5,069 4,824 Total assets $ 1,395 $ 11,115 $ — $ 12,510 $ 11,653 Liabilities: Repurchase agreements $ — $ 1,405 $ — $ 1,405 $ 1,405 Short-term debt — — — — — Long-term debt — 17,487 — 17,487 14,948 Trust preferred securities — 473 — 473 308 Total liabilities $ — $ 19,365 $ — $ 19,365 $ 16,661 December 31, 2019 Fair Value Carrying Value (in millions of U.S. dollars) Level 1 Level 2 Level 3 Total Assets: Fixed maturities held to maturity U.S. Treasury / Agency $ 1,292 $ 55 $ — $ 1,347 $ 1,318 Non-U.S. — 1,485 — 1,485 1,423 Corporate and asset-backed securities — 2,436 32 2,468 2,349 Mortgage-backed securities — 2,396 — 2,396 2,331 Municipal — 5,309 — 5,309 5,160 Total assets $ 1,292 $ 11,681 $ 32 $ 13,005 $ 12,581 Liabilities: Repurchase agreements $ — $ 1,416 $ — $ 1,416 $ 1,416 Short-term debt — 1,307 — 1,307 1,299 Long-term debt — 15,048 — 15,048 13,559 Trust preferred securities — 467 — 467 308 Total liabilities $ — $ 18,238 $ — $ 18,238 $ 16,582

Reinsurance

Reinsurance	12 Months Ended
	Dec. 31, 2020
Reinsurance Disclosures [Abstract]
Reinsurance	Reinsurance a) Consolidated reinsurance Chubb purchases reinsurance to manage various exposures including catastrophe risks. Although reinsurance agreements contractually obligate Chubb's reinsurers to reimburse it for the agreed-upon portion of its gross paid losses, they do not discharge Chubb's primary liability. The amounts for net premiums written and net premiums earned in the Consolidated statements of operations are net of reinsurance. The following table presents direct, assumed, and ceded premiums: Year Ended December 31 (in millions of U.S. dollars) 2020 2019 2018 Premiums written Direct $ 37,749 $ 36,848 $ 34,782 Assumed 3,512 3,276 3,186 Ceded (7,441) (7,849) (7,389) Net $ 33,820 $ 32,275 $ 30,579 Premiums earned Direct $ 37,037 $ 35,876 $ 34,108 Assumed 3,323 3,107 3,175 Ceded (7,243) (7,693) (7,219) Net $ 33,117 $ 31,290 $ 30,064 Ceded losses and loss expenses incurred were $5.0 billion, $4.9 billion, and $5.6 billion for the years ended December 31, 2020, 2019, and 2018, respectively. b) Reinsurance recoverable on ceded reinsurance December 31, 2020 December 31, 2019 (in millions of U.S. dollars) Net Reinsurance Recoverable (1) Valuation allowance Net Reinsurance Recoverable (1) Valuation allowance Reinsurance recoverable on unpaid losses and loss expenses $ 14,647 $ 257 $ 14,181 $ 240 Reinsurance recoverable on paid losses and loss expenses 945 57 1,000 76 Reinsurance recoverable on losses and loss expenses $ 15,592 $ 314 $ 15,181 $ 316 Reinsurance recoverable on policy benefits $ 206 $ 5 $ 197 $ 4 (1) Net of valuation allowance for uncollectible reinsurance. The increase in reinsurance recoverable on losses and loss expenses in 2020 was primarily due to catastrophe losses, partially offset by crop activity and prior period development. We evaluate the financial condition of our reinsurers and potential reinsurers on a regular basis and also monitor concentrations of credit risk with reinsurers. The valuation allowance for uncollectible reinsurance is required principally due to the potential failure of reinsurers to indemnify Chubb, primarily because of disputes under reinsurance contracts and insolvencies. We have established a valuation allowance for amounts estimated to be uncollectible on both unpaid and paid losses as well as future policy benefits. Refer to Note 1 d) for a discussion of the valuation allowance methodology. The following table presents a roll-forward of valuation allowance for uncollectible reinsurance related to Reinsurance recoverable on loss and loss expenses: (in millions of U.S. dollars) Year Ended December 31, 2020 Valuation allowance for uncollectible reinsurance - beginning of period $ 316 Provision for uncollectible reinsurance 21 Write-offs charged against the valuation allowance (25) Foreign exchange revaluation 2 Valuation allowance for uncollectible reinsurance - end of period $ 314 The following tables present a listing, at December 31, 2020, of the categories of Chubb's reinsurers: December 31, 2020 Gross Reinsurance Recoverable on Loss and Loss Expenses Valuation allowance for Uncollectible Reinsurance % of Gross Reinsurance Recoverable (in millions of U.S. dollars, except for percentages) Categories Largest reinsurers $ 7,267 $ 88 1.2 % Other reinsurers rated A- or better 4,901 58 1.2 % Other reinsurers rated lower than A- or not rated 466 64 13.7 % Pools 366 14 3.8 % Structured settlements 521 11 2.1 % Captives 2,107 11 0.5 % Other 278 68 24.5 % Total $ 15,906 $ 314 2.0 % Largest Reinsurers ABR Reinsurance Capital Holdings HDI Group (Hannover Re) Munich Re Group Swiss Re Group Berkshire Hathaway Insurance Group Lloyd's of London Partner Re Group Categories of Chubb's reinsurers Comprises: Largest reinsurers • All groups of reinsurers or captives where the gross recoverable exceeds one percent of Chubb's total shareholders' equity. Other reinsurers rated A- or better • All reinsurers rated A- or better that were not included in the largest reinsurer category. Other reinsurers rated lower than A- or not rated • All reinsurers rated lower than A- or not rated that were not included in the largest reinsurer category. Pools • Related to Chubb's voluntary pool participation and Chubb's mandatory pool participation required by law in certain states. Structured settlements • Annuities purchased from life insurance companies to settle claims. Since we retain ultimate liability in the event that the life company fails to pay, we reflect the amounts as both a liability and a recoverable/receivable for GAAP purposes. Captives • Companies established and owned by our insurance clients to assume a significant portion of their direct insurance risk from Chubb; structured to allow clients to self-insure a portion of their reinsurance risk. It generally is our policy to obtain collateral equal to expected losses. Where appropriate, exceptions are granted but only with review and approval at a senior officer level. Excludes captives included in the largest reinsurer category. Other • Amounts recoverable that are in dispute or are from companies that are in supervision, rehabilitation, or liquidation.

Intangible Assets

Intangible Assets	12 Months Ended
	Dec. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible Assets Disclosure [Text Block]	Goodwill and Other intangible assets Goodwill The following table presents a roll-forward of Goodwill by segment: (in millions of U.S. dollars) North America Commercial P&C Insurance North America Personal P&C Insurance North America Agricultural Insurance Overseas General Insurance Global Reinsurance Life Insurance Chubb Consolidated Balance at December 31, 2018 $ 6,946 $ 2,230 $ 134 $ 4,770 $ 371 $ 820 $ 15,271 Foreign exchange revaluation and other 9 4 — 15 — (3) 25 Balance at December 31, 2019 $ 6,955 $ 2,234 $ 134 $ 4,785 $ 371 $ 817 $ 15,296 Acquisition of Banchile Seguros de Vida — — — 16 — 28 44 Foreign exchange revaluation and other 17 6 — 35 — 2 60 Balance at December 31, 2020 $ 6,972 $ 2,240 $ 134 $ 4,836 $ 371 $ 847 $ 15,400 Other intangible assets Other intangible assets at December 31, 2020 and 2019 were $5,811 million and $6,063 million, respectively, principally acquired from the Chubb Corp acquisition. Other intangible assets in 2020 and 2019 comprised $2,846 million and $3,114 million, respectively, that are subject to amortization, principally agency distribution relationships and renewal rights, and $2,965 million and $2,949 million, respectively, that are not subject to amortization, principally trademarks. Amortization expense related to purchased intangibles was $290 million, $305 million, and $339 million for the years ended December 31, 2020, 2019, and 2018, principally related to agency distribution relationships and renewal rights. The following table presents, as of December 31, 2020, the expected estimated pre-tax amortization expense (benefit) of purchased intangibles, at current foreign currency exchange rates, for the next five years: Associated with the Chubb Corp Acquisition For the Years Ending December 31 (in millions of U.S. dollars) Agency Fair value adjustment on Unpaid losses and loss expense (1) Total Other intangible assets Total Amortization of purchased intangibles 2021 $ 217 $ (20) $ 197 $ 89 $ 286 2022 197 (14) 183 101 284 2023 178 (7) 171 96 267 2024 160 (6) 154 90 244 2025 145 (6) 139 89 228 Total $ 897 $ (53) $ 844 $ 465 $ 1,309 (1) In connection with the Chubb Corp acquisition, we recorded an increase to Unpaid losses and loss expenses acquired to adjust the carrying value of Chubb Corp's historical Unpaid losses and loss expenses to fair value as of the acquisition date. This fair value adjustment amortizes through Amortization of purchased intangibles on the Consolidated statements of operations through the year 2032. The balance of the fair value adjustment on Unpaid losses and loss expense was $110 million and $145 million at December 31, 2020 and 2019, respectively. Refer to Note 1(h) for additional information. VOBA The following table presents a roll-forward of VOBA: (in millions of U.S. dollars) 2020 2019 2018 Balance, beginning of year $ 306 $ 295 $ 326 Amortization of VOBA (1) (27) (24) (25) Foreign exchange revaluation and other (16) 35 (6) Balance, end of year $ 263 $ 306 $ 295 (1) Recognized in Policy acquisition costs in the Consolidated statements of operations. The following table presents, as of December 31, 2020, the expected estimated pre-tax amortization expense related to VOBA for the next five years at current foreign exchange rates: For the Years Ending December 31 VOBA (in millions of U.S. dollars) 2021 $ 22 2022 21 2023 19 2024 17 2025 16 Total $ 95

Unpaid losses and loss expenses

Unpaid losses and loss expenses	12 Months Ended
	Dec. 31, 2020
Liability for Claims and Claims Adjustment Expense [Abstract]
Unpaid Losses and Loss Expenses	Unpaid losses and loss expenses Chubb establishes reserves for the estimated unpaid ultimate liability for losses and loss expenses under the terms of its policies and agreements. Reserves include estimates for both claims that have been reported and for IBNR claims, and include estimates of expenses associated with processing and settling these claims. Reserves are recorded in Unpaid losses and loss expenses in the consolidated balance sheets. While we believe that our reserves for unpaid losses and loss expenses at December 31, 2020 are adequate, new information or trends may lead to future developments in incurred loss and loss expenses significantly greater or less than the reserves provided. Any such revisions could result in future changes in estimates of losses or reinsurance recoverable and would be reflected in our results of operations in the period in which the estimates are changed. The following table presents a reconciliation of beginning and ending Unpaid losses and loss expenses: Year Ended December 31 (in millions of U.S. dollars) 2020 2019 2018 Gross unpaid losses and loss expenses, beginning of year $ 62,690 $ 62,960 $ 63,179 Reinsurance recoverable on unpaid losses (1) (14,181) (14,689) (14,014) Net unpaid losses and loss expenses, beginning of year 48,509 48,271 49,165 Net losses and loss expenses incurred in respect of losses occurring in: Current year 22,124 19,575 19,048 Prior years (2) (414) (845) (981) Total 21,710 18,730 18,067 Net losses and loss expenses paid in respect of losses occurring in: Current year 7,782 7,894 7,544 Prior years 9,652 10,579 10,796 Total 17,434 18,473 18,340 Foreign currency revaluation and other 379 (19) (621) Net unpaid losses and loss expenses, end of year 53,164 48,509 48,271 Reinsurance recoverable on unpaid losses (1) 14,647 14,181 14,689 Gross unpaid losses and loss expenses, end of year $ 67,811 $ 62,690 $ 62,960 (1) Net of valuation allowance for uncollectible reinsurance. (2) Relates to prior period loss reserve development only and excludes prior period development related to reinstatement premiums, expense adjustments and earned premiums totaling $19 million, $53 million, and $85 million for 2020, 2019, and 2018, respectively. The increase in gross and net unpaid losses and loss expense in 2020 was driven by catastrophe losses incurred, principally from the COVID-19 pandemic. The increase in net unpaid losses and loss expense in 2019 reflected an increase in underlying reserves, offset by favorable prior period development and payments related to catastrophic events. The loss development tables under section c) below, present Chubb’s historical incurred and paid claims development by broad product line through December 31, 2020, net of reinsurance, as well as the cumulative number of reported claims, IBNR balances, and other supplementary information. The following table presents a reconciliation of the loss development tables to the liability for unpaid losses and loss expenses in the consolidated balance sheet: Reconciliation of Reserve Balances to Liability for Unpaid Loss and Loss Expenses (in millions of U.S. dollars) December 31, 2020 Presented in the loss development tables: North America Commercial P&C Insurance — Workers' Compensation $ 9,600 North America Commercial P&C Insurance — Liability 17,441 North America Commercial P&C Insurance — Other Casualty 2,124 North America Commercial P&C Insurance — Non-Casualty 2,491 North America Personal P&C Insurance 3,025 Overseas General Insurance — Casualty 6,832 Overseas General Insurance — Non-Casualty 2,725 Global Reinsurance — Casualty 1,200 Global Reinsurance — Non-Casualty 312 Excluded from the loss development tables: Other 4,742 Net unpaid loss and allocated loss adjustment expense 50,492 Ceded unpaid loss and allocated loss adjustment expense: North America Commercial P&C Insurance — Workers' Compensation $ 1,461 North America Commercial P&C Insurance — Liability 5,743 North America Commercial P&C Insurance — Other Casualty 564 North America Commercial P&C Insurance — Non-Casualty 1,380 North America Personal P&C Insurance 141 Overseas General Insurance — Casualty 2,426 Overseas General Insurance — Non-Casualty 1,686 Global Reinsurance — Casualty 29 Global Reinsurance — Non-Casualty 104 Other 1,153 Ceded unpaid loss and allocated loss adjustment expense 14,687 Unpaid loss and loss expense on other than short-duration contracts (1) 1,109 Unpaid unallocated loss adjustment expenses 1,523 Unpaid losses and loss expenses $ 67,811 (1) Primarily includes the claims reserve of our International A&H business and Life Insurance segment reserves. Business excluded from the loss development tables “Other” shown in the reconciliation table comprises businesses excluded from the loss development tables: • North America Agricultural Insurance segment business, which is short-tailed with the majority of the liabilities expected to be resolved in the ensuing twelve months; • Corporate, which includes run-off liabilities such as asbestos and environmental and other mass tort exposures and which impact accident years older than those shown in the loss development tables below; • Life Insurance segment business, which is generally written using long-duration contracts; and • Certain subsets of our business due to data limitations or unsuitability to the loss development table presentation, including: ◦ We underwrite loss portfolio transfers at various times; by convention, all premium and losses associated with these transactions are recorded to the policy period of the transaction, even though the accident dates of the claims covered may be a decade or more in the past. We also underwrite certain high attachment, high limit, multiple-line and excess of aggregate coverages for large commercial clients. Changes in incurred loss and cash flow patterns are volatile and sufficiently different from those of typical insureds. This category includes the loss portfolio transfer of Fireman’s Fund personal lines run-off liabilities and Alternative Risk Solutions business within the North America Commercial P&C Insurance segment; ◦ 2015 and prior paid history on a subset of previously acquired international businesses, within the Overseas General Insurance segment, due to limitations on the data prior to the acquisition; ◦ Reinsurance recoverable bad debt; and ◦ Purchase accounting adjustments related to unpaid losses and loss expenses for Chubb Corp. a) Description of Reserving Methodologies Our recorded reserves represent management's best estimate of the provision for unpaid claims as of the balance sheet date. The process of establishing loss and loss expense reserves can be complex and is subject to considerable uncertainty as it requires the use of estimates and judgments based on circumstances underlying the insured loss at the date of accrual. The reserves for our various product lines each require different qualitative and quantitative assumptions and judgments to be made. Management's best estimate is developed after collaboration with actuarial, underwriting, claims, legal, and finance departments and culminates with the input of reserve committees. Each business unit reserve committee includes the participation of the relevant parties from actuarial, finance, claims, and unit senior management and has the responsibility for finalizing, recommending and approving the estimate to be used as management's best estimate. Reserves are further reviewed by Chubb's Chief Actuary and senior management. The objective of such a process is to determine a single estimate that we believe represents a better estimate than any other and which is viewed by management to be the best estimate of ultimate loss settlements. This estimate is based on a combination of exposure and experience-based actuarial methods (described below) and other considerations such as claims reviews, reinsurance recovery assumptions and/or input from other knowledgeable parties such as underwriting. Exposure-based methods are most commonly used on relatively immature origin years (i.e., the year in which the losses were incurred — “accident year” or “report year”), while experience-based methods provide a view based on the projection of loss experience that has emerged as of the valuation date. Greater reliance is placed upon experience-based methods as the pool of emerging loss experience grows and where it is deemed sufficiently credible and reliable as the basis for the estimate. In comparing the held reserve for any given origin year to the actuarial projections, judgment is required as to the credibility, uncertainty and inherent limitations of applying actuarial techniques to historical data to project future loss experience. Examples of factors that impact such judgments include, but are not limited to, the following: • nature and complexity of underlying coverage provided and net limits of exposure provided; • segmentation of data to provide sufficient homogeneity and credibility for loss projection methods; • extent of credible internal historical loss data and reliance upon industry information as required; • historical variability of actual loss emergence compared with expected loss emergence; • reported and projected loss trends; • extent of emerged loss experience relative to the remaining expected period of loss emergence; • rate monitor information for new and renewal business; • changes in claims handling practice; • inflation; • the legal environment; • facts and circumstances of large claims; • terms and conditions of the contracts sold to our insured parties; • impact of applicable reinsurance recoveries; and • nature and extent of underlying assumptions. We have actuarial staff within each of our business units who analyze loss reserves (including loss expenses) and regularly project estimates of ultimate losses and the corresponding indications of the required IBNR reserve. Our reserving approach is a comprehensive ground-up process using data at a detailed level that reflects the specific types and coverages of the diverse products written by our various operations. The data presented in this disclosure was prepared on a more aggregated basis and with a focus on changes in incurred loss estimates over time as well as associated cash flows. We note that data prepared on this basis may not demonstrate the full spectrum of characteristics that are evident in the more detailed level studied internally. We perform an actuarial reserve review for each product line at least once a year. For most product lines, one or more standard actuarial reserving methods may be used to determine estimates of ultimate losses and loss expenses, and from these estimates, a single actuarial central estimate is selected. The actuarial central estimate is an input to the reserve committee process described above. For the few product lines that do not lend themselves to standard actuarial reserving methods, appropriate techniques are applied to produce the actuarial central estimates. For example, run-off asbestos and environmental liability estimates are better suited to the application of account-specific exposure-based analyses to best evaluate their associated aggregate reserve levels. b) Standard actuarial reserving methods The judgments involved in projecting the ultimate losses include the use and interpretation of various standard actuarial reserving methods that place reliance on the extrapolation of actual historical data, loss development patterns, industry data, and other benchmarks as appropriate. Standard actuarial reserving methods include, but are not limited to, expected loss ratio, paid and reported loss development, and Bornhuetter-Ferguson methods. A general description of these methods is provided below. In addition to these standard methods, depending upon the product line characteristics and available data, we may use other recognized actuarial methods and approaches. Implicit in the standard actuarial methods that we generally utilize is the need for two fundamental assumptions: first, the pattern by which losses are expected to emerge over time for each origin year, and second the expected loss ratio for each origin year. The expected loss ratio for any particular origin year is selected after consideration of a number of factors, including historical loss ratios adjusted for rate changes, premium and loss trends, industry benchmarks, the results of policy level loss modeling at the time of underwriting, and/or other more subjective considerations for the product line (e.g., terms and conditions) and external environment as noted above. The expected loss ratio for a given origin year is initially established at the start of the origin year as part of the planning process. This analysis is performed in conjunction with underwriters and management. The expected loss ratio method arrives at an ultimate loss estimate by multiplying the expected ultimate loss ratio by the corresponding premium base. This method is most commonly used as the basis for the actuarial central estimate for immature origin periods on product lines where the actual paid or reported loss experience is not yet deemed sufficiently credible to serve as the principal basis for the selection of ultimate losses. The expected loss ratio for a given origin year may be modified over time if the underlying assumptions differ from the original assumptions (e.g., the assessment of prior year loss ratios, loss trend, rate changes, actual claims, or other information). Our selected paid and reported development patterns provide a benchmark against which the actual emerging loss experience can be monitored. Where possible, development patterns are selected based on historical loss emergence by origin year. For product lines where the historical data is viewed to have low statistical credibility, the selected development patterns also reflect relevant industry benchmarks and/or experience from similar product lines written elsewhere within Chubb. This most commonly occurs for relatively new product lines that have limited historical data or for high severity/low frequency portfolios where our historical experience exhibits considerable volatility and/or lacks credibility. The paid and reported loss development methods convert the selected loss emergence pattern to a set of multiplicative factors which are then applied to actual paid or reported losses to arrive at an estimate of ultimate losses for each period. Due to their multiplicative nature, the paid and reported loss development methods will leverage differences between actual and expected loss emergence. These methods tend to be utilized for more mature origin periods and for those portfolios where the loss emergence has been relatively consistent over time. The Bornhuetter-Ferguson method is a combination of the expected loss ratio method and the loss development method, where the loss development method is given more weight as the origin year matures. This approach allows a logical transition between the expected loss ratio method which is generally utilized at earlier maturities and the loss development methods which are typically utilized at later maturities. We usually apply this method using reported loss data although paid data may also be used. Short-tail business Short-tail business generally describes product lines for which losses are typically known and paid shortly after the loss occurs. This would include, for example, most property, personal accident, and automobile physical damage policies that we write. Due to the short reporting and development pattern for these product lines, the uncertainty associated with our estimate of ultimate losses for any particular accident period diminishes relatively quickly as actual loss experience emerges. We typically assign credibility to methods that incorporate actual loss emergence, such as the paid and reported loss development and Bornhuetter-Ferguson methods, sooner than would be the case for long-tail lines at a similar stage of development for a given origin year. The reserving process for short-tail losses arising from catastrophic events typically involves an assessment by the claims department, in conjunction with underwriters and actuaries, of our exposure and estimated losses immediately following an event and then subsequent revisions of the estimated losses as our insureds provide updated actual loss information. Long-tail business Long-tail business describes lines of business for which specific losses may not be known/reported for some period and for which claims can take significant time to settle/close. This includes most casualty lines such as general liability, D&O, and workers' compensation. There are various factors contributing to the uncertainty and volatility of long-tail business. Among these are: • The nature and complexity of underlying coverage provided and net limits of exposure provided; • Our historical loss data and experience is sometimes too immature and lacking in credibility to rely upon for reserving purposes. Where this is the case, in our reserve analysis we may utilize industry loss ratios or industry benchmark development patterns that we believe reflect the nature and coverage of the underwritten business and its future development, where available. For such product lines, actual loss experience may differ from industry loss statistics as well as loss experience for previous underwriting years; • The difficulty in estimating loss trends, claims inflation (e.g., medical and judicial) and underlying economic conditions; • The need for professional judgment to estimate loss development patterns beyond that represented by historical data using supplemental internal or industry data, extrapolation, or a blend of both; • The need to address shifts in business mix or volume over time when applying historical paid and reported loss development patterns from older origin years to more recent origin years. For example, changes over time in the processes and procedures for establishing case reserves can distort reported loss development patterns or changes in ceded reinsurance structures by origin year can alter the development of paid and reported losses; • Loss reserve analyses typically require loss or other data be grouped by common characteristics in some manner. If data from two combined lines of business exhibit different characteristics, such as loss payment patterns, the credibility of the reserve estimate could be affected. Additionally, since casualty lines of business can have significant intricacies in the terms and conditions afforded to the insured, there is an inherent risk as to the homogeneity of the underlying data used in performing reserve analyses; and • The applicability of the price change data used to estimate ultimate loss ratios for most recent origin years. As described above, various factors are considered when determining appropriate data, assumptions, and methods used to establish the loss reserve estimates for long-tail product lines. These factors may also vary by origin year for given product lines. The derivation of loss development patterns from data and the selection of a tail factor to project ultimate losses from actual loss emergence require considerable judgment, particularly with respect to the extent to which historical loss experience is relied upon to support changes in key reserving assumptions. c) Loss Development Tables The tables were designed to present business with similar risk characteristics which exhibit like development patterns and generally similar trends, in order to provide insight into the nature, amount, timing and uncertainty of cash flows related to our claims liabilities. Each table follows a similar format and reflects the following: • The incurred loss triangle includes both reported case reserves and IBNR liabilities. • Both the incurred and paid loss triangles include allocated loss adjustment expense (i.e., defense and investigative costs particular to individual claims) but exclude unallocated loss adjustment expense (i.e., the costs associated with internal claims staff and third-party administrators). • The amounts in both triangles for the years ended December 31, 2011 to December 31, 2019 and average historical claim duration as of December 31, 2020, are presented as supplementary information. • All data presented in the triangles is net of reinsurance recoverables. • The IBNR reserves shown to the right of each incurred loss development exhibit reflect the net IBNR recorded as of December 31, 2020. • The tables are presented retrospectively with respect to acquisitions where these are material and doing so is practicable. Most notably, the Chubb Corp acquisition is presented retrospectively. The unaudited consolidated data is presented solely for informational purposes and is not necessarily indicative of the consolidated data that might have been observed had the transactions been completed prior to the date indicated. Historical dollar amounts are presented in this footnote on a constant-dollar basis, which is achieved by assuming constant foreign exchange rates for all periods in the loss triangles, translating prior period amounts using the same local currency exchange rates as the current year end. The impact of this conversion is to show the change between periods exclusive of the effect of fluctuations in exchange rates, which would otherwise distort the change in incurred loss and cash flow patterns shown. The change in incurred loss shown will differ from other GAAP disclosures of incurred prior period reserve development amounts, which include the effect of fluctuations in exchanges rates. We provided guidance above on key assumptions that should be considered when reviewing this disclosure and information relating to how loss reserve estimates are developed. We believe the information provided in the “Loss Development Tables” section of the disclosure is of limited use for independent analysis or application of standard actuarial estimations. Cumulative Number of Reported Claims Reported claim counts, on a cumulative basis, are provided to the far right of each incurred loss development table. In our North America segments, we generally consider a reported claim to be one claim per coverage per claimant. For our North America segments, we refined our claim count methodology in 2020 for our U.S. operations. For workers' compensation, we moved from including losses below the deductible in our reported claims to excluding them. This reduction in reported claims aligns claim counts to the portion of the claims to which Chubb has incurred losses, which we view as a more meaningful presentation. For non-casualty, personal and liability, we aligned our claim count methodology to reflect a reported claim per claimant, per coverage basis, and including all reported claims with either an indemnity or expense transaction. These changes resulted in fewer reported claims in non-casualty and additional reported claims in personal and liability. In our Overseas General Insurance segment, we generally consider a reported claim to be on a per occurrence basis. Global Reinsurance segment’s portfolio comprises a mix of proportional and non-proportional treaties. The proportional treaties are reported on a bulk basis and do not lend themselves to meaningful claim count data. As such, we do not provide claim count information for our Global Reinsurance segment. We exclude claims closed without payment. Claims are counted on a direct basis without consideration of ceded reinsurance. Use of the presented claim counts in analysis of company experience has significant limitations, including: • Claims for certain events and/or product lines, such as portions of our A&H business, are not reported on an individual basis, but rather in bulk and thus not available for inclusion in this disclosure. • Each segment typically has a mixture of primary and excess experience which has shifted over time. • Captive business, especially in Workers' Compensation and Liability, largely represents fronted business where our net exposure to loss is minimal; however, since the claim count is based on direct claims, there is a mismatch between direct claims and net loss dollars, the extent of which varies by accident year . Reported claim counts include open claims which have case reserves but exclude claims that have been incurred but not reported. As such the reported claims are not consistent with the incurred losses in the triangle, which include incurred but not reported losses. One can calculate reported losses by subtracting incurred but not reported losses from incurred losses in the triangle. Reported claim counts are also inconsistent with losses in the paid loss triangle, since reported counts would include claims with case reserves but no payments to date. North America Commercial P&C Insurance — Workers' Compensation — Long-tail This product line has a substantial geographic spread and a broad mix across industries. Types of coverage include risk management business predominantly with high deductible policies, loss sensitive business (i.e., retrospectively-rated policies), business fronted for captives, as well as excess and primary guaranteed cost coverages. The triangle below shows all loss and allocated expense development for the workers' compensation product line. In our prior period development disclosure, we exclude any loss development where there is a directly related premium adjustment. For workers' compensation, changes in the exposure base due to payroll audits will drive changes in ultimate losses. In addition, we record involuntary pool assumptions (premiums and losses) on a lagged basis. Both of these items will influence the development in the triangle, particularly the first prior accident year, and are included in the reconciliation table presented on page F-58. North America Commercial P&C Insurance — Workers' Compensation — Long-tail (continued) Net Incurred Loss and Allocated Loss Adjustment Expenses Years Ended December 31 As of December 31 2020 (in millions of U.S. dollars) Unaudited Net IBNR Reserves Reported Claims (in thousands) Accident Year 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2011 $ 1,037 $ 1,030 $ 1,046 $ 1,049 $ 1,053 $ 1,022 $ 1,012 $ 1,009 $ 988 $ 973 $ 208 45 2012 1,050 1,011 1,030 1,040 1,011 989 986 977 953 234 44 2013 1,109 1,108 1,122 1,127 1,086 1,073 1,037 1,014 280 43 2014 1,207 1,201 1,217 1,215 1,163 1,100 1,073 347 45 2015 1,282 1,259 1,276 1,279 1,217 1,154 419 50 2016 1,367 1,361 1,383 1,378 1,269 530 51 2017 1,413 1,380 1,399 1,393 723 50 2018 1,359 1,361 1,379 709 51 2019 1,391 1,384 767 47 2020 1,367 1,086 24 Total $ 11,959 Net Cumulative Paid Loss and Allocated Loss Adjustment Expenses Years Ended December 31 (in millions of U.S. dollars) Unaudited Accident Year 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2011 $ 119 $ 294 $ 411 $ 484 $ 533 $ 567 $ 595 $ 616 $ 640 $ 654 2012 111 271 365 436 486 532 574 592 612 2013 107 286 422 506 553 587 616 633 2014 113 295 410 484 532 566 599 2015 116 301 418 501 564 606 2016 122 326 452 529 584 2017 120 313 437 516 2018 130 329 451 2019 143 341 2020 111 Total $ 5,107 Net Liabilities for Loss and Allocated Loss Adjustment Expenses (in millions of U.S. dollars) December 31, 2020 Accident years prior to 2011 $ 2,748 Accident years 2011 - 2020 from tables above 6,852 All Accident years $ 9,600 Supplementary Information: (Favorable)/ Adverse Prior Period Development (in millions of U.S. dollars) December 31, 2020 Accident years prior to 2011 $ (94) Accident years 2011 - 2020 from tables above (256) All Accident years $ (350) Supplementary Information: Average Annual Percentage Payout of Net Incurred Claims by Age, as of December 31, 2020 (Unaudited) Age in Years 1 2 3 4 5 6 7 8 9 10 Percentage 10 % 16 % 10 % 7 % 5 % 4 % 3 % 2 % 2 % 1 % North America Commercial P&C Insurance — Liability — Long-tail This line consists of primary and excess liability exposures, including medical liability and professional lines, including directors and officers (D&O) liability, errors and omissions (E&O) liability, employment practices liability (EPL), fidelity bonds, and fiduciary liability. The primary and excess liability business represents the largest part of these exposures. The former includes both monoline and commercial package liability. The latter includes a substantial proportion of commercial umbrella, excess and high excess business, where loss activity can produce significant volatility in the loss triangles at later ages within an accident year (and sometimes across years) due to the size of the limits afforded and the complex nature of the underlying losses. This line includes management and professional liability products provided to a wide variety of clients, from national accounts to small firms along with private and not-for-profit organizations, distributed through brokers, agents, wholesalers and MGAs. Many of these coverages, particularly D&O and E&O, are typically written on a claims-made form. While most of the coverages are underwritten on a primary basis, there are significant amounts of excess exposure with large policy limits. Net Incurred Loss and Allocated Loss Adjustment Expenses Years Ended December 31 As of December 31 2020 (in millions of U.S. dollars) Unaudited Net IBNR Reserves Reported Claims (in thousands) Accident Year 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2011 $ 3,500 $ 3,586 $ 3,630 $ 3,665 $ 3,593 $ 3,498 $ 3,384 $ 3,316 $ 3,193 $ 3,143 $ 226 25 2012 3,552 3,628 3,613 3,565 3,524 3,426 3,331 3,235 3,235 353 25 2013 3,547 3,542 3,543 3,533 3,430 3,216 3,122 2,964 317 25 2014 3,535 3,586 3,674 3,717 3,656 3,470 3,346 572 25 2015 3,560 3,709 3,819 3,976 3,943 3,736 855 27 2016 3,534 3,595 3,692 3,805 3,799 962 27 2017 3,322 3,499 3,581 3,631 1,475 27 2018 3,375 3,494 3,696 1,737 28 2019 3,452 3,628 2,381 28 2020 4,098 3,695 24 Total $ 35,276 Net Cumulative Paid Loss and Allocated Loss Adjustment Expenses Years Ended December 31 (in millions of U.S. dollars) Unaudited Accident Year 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2011 $ 160 $ 652 $ 1,209 $ 1,805 $ 2,214 $ 2,477 $ 2,659 $ 2,741 $ 2,827 $ 2,863 2012 166 656 1,172 1,680 2,092 2,326 2,502 2,619 2,688 2013 130 548 1,192 1,597 2,007 2,232 2,374 2,465 2014 164 679 1,250 1,804 2,202 2,442 2,584 2015 138 605 1,206 1,856 2,291 2,533 2016 171 663 1,336 1,975 2,334 2017 161 617 1,162 1,701 2018 190 754 1,303 2019 176 671 2020 152 Total $ 19,294 North America Commercial P&C Insurance — Liability — Long-tail (continued) Net Liabilities for Loss and Allocated Loss Adjustment Expenses (in millions of U.S. dollars) December 31, 2020 Accident years prior to 2011 $ 1,459 Accident years 2011 - 2020 from tables above 15,982 All Accident years $ 17,441 Supplementary Information: (Favorable)/ Adverse Prior Period Development (in millions of U.S. dollars) December 31, 2020 Accident years prior to 2011 $ (176) Accident years 2011 - 2020 from tables above (117) All Accident years $ (293) Supplementary Information: Average Annual Percentage Payout of Net Incurred Claims by Age, as of December 31, 2020 (Unaudited) Age in Years 1 2 3 4 5 6 7 8 9 10 Percentage 5 % 14 % 17 % 16 % 12 % 7 % 5 % 3 % 2 % 1 % North America Commercial P&C Insurance — Other Casualty — Long-tail This product line consists of the remaining commercial casualty coverages such as automobile liability and aviation. There is also a small portion of commercial multi-peril (CMP) business in accident years 2014 and prior. The paid and reported data are impacted by some catastrophe loss activity primarily on the CMP exposures just noted. Net Incurred Loss and Allocated Loss Adjustment Expenses Years Ended December 31 As of December 31 2020 (in millions of U.S. dollars) Unaudited Net IBNR Reserves Reported Claims (in thousands) Accident Year 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2011 $ 581 $ 590 $ 581 $ 549 $ 533 $ 525 $ 517 $ 511 $ 513 $ 503 $ 13 16 2012 634 606 577 561 520 519 509 507 505 2 16 2013 527 531 523 516 469 462 462 458 21 18 2014 595 583 581 597 555 539 539 25 17 2015 487 470 502 515 458 455 35 15 2016 504 502 527 524 481 61 16 2017 532 566 577 616 118 17 2018 536 564 575 198 17 2019 606 637 284 16 2020 646 517 9 Total $ 5,415 North America Commercial P&C Insurance — Other-Casualty — Long-tail (continued) Net Cumulative Paid Loss and Allocated Loss Adjustment Expenses Years Ended December 31 (in millions of U.S. dollars) Unaudited Accident Year 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2011 $ 86 $ 235 $ 341 $ 400 $ 437 $ 461 $ 466 $ 480

Taxation

Taxation	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Taxation	Taxation Under Swiss law through December 31, 2020, a resident company is subject to income tax at the federal, cantonal, and communal levels that is levied on net worldwide income. Income attributable to permanent establishments or real estate located abroad is excluded from the Swiss tax base. Furthermore, participation relief (i.e., tax relief) is granted to Chubb Limited at the federal, cantonal, and communal level for qualifying dividend income and capital gains related to the sale of qualifying participations (i.e., subsidiaries). Chubb Limited is subject to an annual cantonal and communal capital tax on the taxable equity of Chubb Limited in Switzerland. Chubb has two Swiss operating subsidiaries, an insurance company, Chubb Insurance (Switzerland) Limited and a reinsurance company, Chubb Reinsurance (Switzerland) Limited. Both are subject to federal, cantonal, and communal income tax and to annual cantonal and communal capital tax. Under current Bermuda law, Chubb Limited and its Bermuda subsidiaries are not required to pay any taxes on income or capital gains. If a Bermuda law were enacted that would impose taxes on income or capital gains, Chubb Limited and the Bermuda subsidiaries have received an undertaking from the Minister of Finance in Bermuda that would exempt such companies from Bermudian taxation until March 2035. Income from Chubb's operations at Lloyd's is subject to United Kingdom (U.K.) corporation income taxes. Lloyd's is required to pay U.S. income tax on U.S. connected income written by Lloyd's syndicates. Lloyd's has a closing agreement with the Internal Revenue Service (IRS) whereby the amount of tax due on this business is calculated by Lloyd's and remitted directly to the IRS. These amounts are then charged to the accounts of Chubb's Corporate Members in proportion to their participation in the relevant syndicates. Chubb's Corporate Members are subject to this arrangement but, as U.K. domiciled companies, will receive U.K. corporation tax credits for any U.S. income tax incurred up to the value of the equivalent U.K. corporation income tax charge on this income. Chubb Group Holdings and its respective subsidiaries are subject to income taxes imposed by U.S. authorities and file a consolidated U.S. Federal income tax return. Should Chubb Group Holdings pay a dividend to Chubb Limited, withholding taxes would apply. Currently, however, no withholding taxes are accrued with respect to such un-remitted earnings as management has no intention of remitting these earnings. Similarly, no taxes have been provided on the un-remitted earnings of certain foreign subsidiaries (Hong Kong and Korea life insurance companies) as management has no intention of remitting these earnings. The cumulative amount that would be subject to withholding tax, if distributed, as well as the determination of the associated tax liability are not practicable to compute; however, such amount would be material. Certain international operations of Chubb are also subject to income taxes imposed by the jurisdictions in which they operate. Chubb's domestic operations are in Switzerland, the jurisdiction where we are legally organized, incorporated, and registered. As a result of Swiss tax reform legislation effective in 2020, the Swiss tax rate increased from 7.83 percent in years 2018 and 2019 to 21.2 percent in 2020. The following table presents pre-tax income and the related provision for income taxes: Year Ended December 31 (in millions of U.S. dollars) 2020 2019 2018 Pre-tax income: Switzerland $ 350 $ 440 $ 950 Outside Switzerland 3,812 4,809 3,707 Total pre-tax income $ 4,162 $ 5,249 $ 4,657 Provision for income taxes Current tax expense: Switzerland $ 52 $ 29 $ 89 Outside Switzerland 876 879 563 Total current tax expense 928 908 652 Deferred tax expense (benefit): Switzerland 2 11 3 Outside Switzerland (301) (124) 40 Total deferred tax expense (benefit) (299) (113) 43 Provision for income taxes $ 629 $ 795 $ 695 The most significant jurisdictions contributing to the overall taxation of Chubb are calculated using the following rates in 2020: Switzerland 21.2 percent, U.S. 21.0 percent, U.K. 19.0 percent, and Bermuda 0.0 percent. The following table presents a reconciliation of the difference between the provision for income taxes and the expected tax provision at the Swiss statutory income tax rate: Year Ended December 31 (in millions of U.S. dollars) 2020 2019 2018 Expected tax provision at Swiss statutory tax rate $ 880 $ 411 $ 365 Permanent differences: Taxes on earnings subject to rate other than Swiss statutory rate (337) 376 372 Tax-exempt interest and dividends received deduction, net of proration (41) (49) (75) Net withholding taxes 67 40 33 Share-based compensation (10) (12) (19) Impact of 2017 Tax Act — — (25) Other 70 29 44 Provision for income taxes $ 629 $ 795 $ 695 The following table presents the components of net deferred tax assets and liabilities: December 31 December 31 (in millions of U.S. dollars) 2020 2019 Deferred tax assets: Loss reserve discount $ 884 $ 826 Unearned premiums reserve 496 519 Foreign tax credits 222 247 Provision for uncollectible balances 46 37 Loss carry-forwards 123 143 Debt related amounts 69 74 Compensation related amounts 281 261 Cumulative translation adjustments 120 33 Investments 75 — Lease liability 121 140 Total deferred tax assets 2,437 2,280 Deferred tax liabilities: Deferred policy acquisition costs 522 588 Other intangible assets, including VOBA 1,425 1,468 Un-remitted foreign earnings 77 73 Investments — 40 Unrealized appreciation on investments 957 470 Depreciation 123 157 Lease right-of-use asset 111 129 Other, net 31 45 Total deferred tax liabilities 3,246 2,970 Valuation allowance 83 114 Net deferred tax liabilities $ (892) $ (804) The valuation allowance of $83 million and $114 million at December 31, 2020 and 2019, respectively, reflects management's assessment, based on available information, that it is more likely than not that a portion of the deferred tax assets will not be realized due to the inability of certain non-U.S. subsidiaries to generate sufficient taxable income. Adjustments to the valuation allowance are made when there is a change in management's assessment of the amount of deferred tax assets that are realizable. At December 31, 2020, Chubb has net operating loss carry-forwards of $407 million which, if unused, will expire starting in 2021, and a foreign tax credit carry-forward in the amount of $222 million which, if unused, will expire starting in 2026. The following table presents a reconciliation of the beginning and ending amount of gross unrecognized tax benefits: December 31 December 31 (in millions of U.S. dollars) 2020 2019 Balance, beginning of year $ 47 $ 14 Additions based on tax positions related to the current year 5 12 Additions based on tax positions related to prior years 24 23 Reductions for the lapse of the applicable statutes of limitations — (2) Balance, end of year $ 76 $ 47 At December 31, 2020 and 2019, the gross unrecognized tax benefits of $76 million and $47 million, respectively, can be reduced by $31 million and $19 million, respectively, associated with foreign tax credits. The net amounts of $45 million and $28 million at December 31, 2020 and 2019, respectively, if recognized, would favorably affect the effective tax rate. We made a settlement of a liability in January 2021 for $23 million, including interest. It is reasonably possible that over the next twelve months, that the amount of unrecognized tax benefits may change further resulting from the re-evaluation of unrecognized tax benefits arising from examinations by taxing authorities and the lapses of statutes of limitations. Chubb recognizes accruals for interest and penalties, if any, related to unrecognized tax benefits in income tax expense in the Consolidated statements of operations. Tax-related interest expense and penalties reported in the Consolidated statements of operations were $8 million at December 31, 2020, $5 million at December 31, 2019, and were immaterial for 2018. Liabilities for tax-related interest and penalties in our Consolidated balance sheets were $16 million and $8 million at December 31, 2020 and 2019, respectively. In March 2017, the IRS commenced its field examination of Chubb Group Holdings’ U.S. Federal income tax returns for 2014 and 2015. The Chubb Group Holdings examination for 2014 and 2015 tax years is still ongoing with no material adjustments proposed to date. In July 2020, the IRS commenced its field examination of Chubb Group Holdings' U.S. Federal income tax returns for 2016, 2017 and 2018. As a multinational company, we also have examinations under way in several foreign jurisdictions. With few exceptions, Chubb is no longer subject to income tax examinations for years prior to 2010. The following table summarizes tax years open for examination by major income tax jurisdiction: At December 31, 2020 Australia 2014 - 2020 Canada 2012 - 2020 France 2018 - 2020 Germany 2015 - 2020 Italy 2010 - 2020 Mexico 2014 - 2020 Spain 2012 - 2020 Switzerland 2016 - 2020 United Kingdom 2015 - 2020 United States 2014 - 2020

Debt

Debt	12 Months Ended
	Dec. 31, 2020
Debt Disclosure [Abstract]
Debt	Debt December 31 December 31 (in millions of U.S. dollars) 2020 2019 Early Redemption Option Repurchase agreements (weighted average interest rate of 0.3% in 2020 and 2.2% in 2019) $ 1,405 $ 1,416 None Short-term debt Chubb INA: $1,300 million 2.3% due November 2020 $ — $ 1,298 Make-whole premium plus 15 bps Other short-term debt 2.75% due September 2020 — 1 None Total short-term debt $ — $ 1,299 Long-term debt Chubb INA: $1,000 million 2.875% senior notes due November 2022 $ 998 $ 997 Make-whole premium plus 20 bps $475 million 2.7% senior notes due March 2023 474 473 Make-whole premium plus 10 bps $700 million 3.35% senior notes due May 2024 698 697 Make-whole premium plus 15 bps €700 million 0.3% senior notes due December 2024 841 776 Make-whole premium plus 15 bps $800 million 3.15% senior notes due March 2025 797 796 Make-whole premium plus 15 bps $1,500 million 3.35% senior notes due May 2026 1,493 1,492 Make-whole premium plus 20 bps €575 million 0.875% senior notes due June 2027 691 635 Make-whole premium plus 20 bps €900 million 1.55% senior notes due March 2028 1,079 993 Make-whole premium plus 15 bps $100 million 8.875% debentures due August 2029 100 100 None €700 million 0.875% senior notes due December 2029 840 775 Make-whole premium plus 20 bps $1,000 million 1.375% senior notes due September 2030 991 — Make-whole premium plus 15 bps €575 million 1.4% senior notes due June 2031 687 633 Make-whole premium plus 25 bps $200 million 6.8% debentures due November 2031 242 246 Make-whole premium plus 25 bps $300 million 6.7% senior notes due May 2036 298 297 Make-whole premium plus 20 bps $800 million 6.0% senior notes due May 2037 945 953 Make-whole premium plus 20 bps €900 million 2.5% senior notes due March 2038 1,077 992 Make-whole premium plus 25 bps $600 million 6.5% senior notes due May 2038 743 751 Make-whole premium plus 30 bps $475 million 4.15% senior notes due March 2043 470 470 Make-whole premium plus 15 bps $1,500 million 4.35% senior notes due November 2045 1,484 1,483 Make-whole premium plus 25 bps Total long-term debt $ 14,948 $ 13,559 Trust preferred securities Chubb INA capital securities due April 2030 $ 308 $ 308 Redemption prices (1) (1) Redemption prices are equal to accrued and unpaid interest to the redemption date plus the greater of (i) 100 percent of the principal amount thereof, or (ii) sum of present value of scheduled payments of principal and interest on the capital securities from the redemption date to April 1, 2030. a) Repurchase agreements Chubb has executed repurchase agreements with certain counterparties under which Chubb agreed to sell securities and repurchase them at a future date for a predetermined price. b) Short-term debt Short-term debt comprises the current maturities of our long-term debt instruments described below. These short-term debt instruments were reclassified from long-term debt and are reflected in the table above. Chubb INA Holdings Inc.'s (Chubb INA) $1,300 million of 2.3 percent senior notes due November 2020 was paid upon maturity. c) Long-term debt The $100 million of 8.875 percent debentures due August 2029 do not have an early redemption option. The remaining Chubb INA senior notes and debentures, including the $1,000 million of 1.375 percent senior notes issued September 2020, and capital securities are redeemable at any time at Chubb INA's option subject to the provisions described in the table above. A "make-whole" premium is the present value of the remaining principal and interest discounted at the applicable U.S. Treasury rate. These debt securities are also redeemable at par plus accrued and unpaid interest in the event of certain changes in tax law. The senior notes and debentures do not have the benefit of any sinking fund and are guaranteed on a senior basis by Chubb Limited and they rank equally with all of Chubb's other senior obligations. They also contain customary limitations on lien provisions as well as customary events of default provisions which, if breached, could result in the accelerated maturity of such senior debt. d) Trust preferred securities In March 2000, ACE Capital Trust II, a Delaware statutory business trust, publicly issued $300 million of 9.7 percent Capital Securities (the Capital Securities) due to mature in April 2030. At the same time, Chubb INA purchased $9.2 million of common securities of ACE Capital Trust II. The sole assets of ACE Capital Trust II consist of $309 million principal amount of 9.7 percent Junior Subordinated Deferrable Interest Debentures (the Subordinated Debentures) issued by Chubb INA due to mature in April 2030. Distributions on the Capital Securities are payable semi-annually and may be deferred for up to ten consecutive semi-annual periods (but no later than April 1, 2030). Any deferred payments would accrue interest compounded semi-annually if Chubb INA defers interest on the Subordinated Debentures. Interest on the Subordinated Debentures is payable semi-annually. Chubb INA may defer such interest payments (but no later than April 1, 2030), with such deferred payments accruing interest compounded semi-annually. The Capital Securities and the ACE Capital Trust II Common Securities will be redeemed upon repayment of the Subordinated Debentures. Chubb Limited has guaranteed, on a subordinated basis, Chubb INA's obligations under the Subordinated Debentures, and distributions and other payments due on the Capital Securities. These guarantees, when taken together with Chubb's obligations under expense agreements entered into with ACE Capital Trust II, provide a full and unconditional guarantee of amounts due on the Capital Securities.

Commitments, contingencies, and

Commitments, contingencies, and guarantees	12 Months Ended
	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Commitments, contingencies, and guarantees	Commitments, contingencies, and guarantees a) Derivative instruments Foreign currency management As a global company, Chubb entities transact business in multiple currencies. Our policy is to generally match assets, liabilities, and required capital for each individual jurisdiction in local currency, which would include the use of derivatives discussed below. We do not hedge our net asset non-U.S. dollar capital positions; however, we do consider economic hedging for planned cross border transactions. Derivative instruments employed Chubb maintains positions in derivative instruments such as futures, options, swaps, and foreign currency forward contracts for which the primary purposes are to manage duration and foreign currency exposure, yield enhancement, or to obtain an exposure to a particular financial market. Chubb also maintains positions in convertible securities that contain embedded derivatives. Investment derivative instruments are recorded in either Other assets (OA) or Accounts payable, accrued expenses, and other liabilities (AP), convertible bonds are recorded in Fixed maturities available for sale (FM AFS), and convertible equity securities are recorded in Equity securities (ES) in the Consolidated balance sheets. These are the most numerous and frequent derivative transactions. In addition, Chubb purchases to be announced mortgage-backed securities (TBAs) as part of its investing activities. Under reinsurance programs covering GLBs, Chubb assumes the risk of GLBs, principally GMIB, associated with variable annuity contracts. The GMIB risk is triggered if, at the time the contract holder elects to convert the accumulated account value to a periodic payment stream (annuitize), the accumulated account value is not sufficient to provide a guaranteed minimum level of monthly income. The GLB reinsurance product meets the definition of a derivative instrument and is classified within AP. Chubb also generally maintains positions in exchange-traded equity futures contracts on equity market indices to limit equity exposure in the GMDB and GLB book of business. All derivative instruments are carried at fair value with changes in fair value recorded in Net realized gains (losses) in the Consolidated statements of operations. None of the derivative instruments are designated as hedges for accounting purposes. The following table presents the balance sheet locations, fair values of derivative instruments in an asset or (liability) position, and notional values/payment provisions of our derivative instruments: December 31, 2020 December 31, 2019 Consolidated Fair Value Notional Fair Value Notional Derivative Asset Derivative (Liability) Derivative Asset Derivative (Liability) (in millions of U.S. dollars) Investment and embedded derivative instruments: Foreign currency forward contracts OA / (AP) $ 22 $ (49) $ 2,807 $ 11 $ (78) $ 2,579 Options/Futures contracts on notes, bonds, and equities OA / (AP) 13 (3) 1,749 13 (15) 1,615 Convertible securities (1) FM AFS / ES 9 — 11 4 — 5 $ 44 $ (52) $ 4,567 $ 28 $ (93) $ 4,199 Other derivative instruments: Futures contracts on equities (2) OA / (AP) $ — $ (17) $ 709 $ — $ (13) $ 613 Other OA / (AP) — — 16 2 — 63 $ — $ (17) $ 725 $ 2 $ (13) $ 676 GLB (3) (AP) $ — $ (1,089) $ 1,658 $ — $ (897) $ 1,510 (1) Includes fair value of embedded derivatives. (2) Related to GMDB and GLB book of business. (3) Note that the payment provision related to GLB is the net amount at risk. The concept of a notional value does not apply to the GLB reinsurance contracts. At December 31, 2020 and 2019, net derivative liabilities of $30 million and $75 million, respectively, included in the table above were subject to a master netting agreement. The remaining derivatives included in the table above were not subject to a master netting agreement. b) Derivative instrument objectives (i) Foreign currency exposure management A foreign currency forward contract (forward) is an agreement between participants to exchange specific currencies at a future date. Chubb uses forwards to minimize the effect of fluctuating foreign currencies as discussed above. (ii) Duration management and market exposure Futures Futures contracts give the holder the right and obligation to participate in market movements, determined by the index or underlying security on which the futures contract is based. Settlement is made daily in cash by an amount equal to the change in value of the futures contract times a multiplier that scales the size of the contract. Exchange-traded futures contracts on money market instruments, notes and bonds are used in fixed maturity portfolios to more efficiently manage duration, as substitutes for ownership of the money market instruments, bonds and notes without significantly increasing the risk in the portfolio. Investments in futures contracts may be made only to the extent that there are assets under management not otherwise committed. Exchange-traded equity futures contracts are used to limit exposure to a severe equity market decline, which would cause an increase in expected claims and therefore, an increase in future policy benefit reserves for GMDB and an increase in the fair value liability for GLB reinsurance business. Options An option contract conveys to the holder the right, but not the obligation, to purchase or sell a specified amount or value of an underlying security at a fixed price. Option contracts are used in our investment portfolio as protection against unexpected shifts in interest rates, which would affect the duration of the fixed maturity portfolio. By using options in the portfolio, the overall interest rate sensitivity of the portfolio can be reduced. Option contracts may also be used as an alternative to futures contracts in the synthetic strategy as described above. The price of an option is influenced by the underlying security, expected volatility, time to expiration, and supply and demand. The credit risk associated with the above derivative financial instruments relates to the potential for non-performance by counterparties. Although non-performance is not anticipated, in order to minimize the risk of loss, management monitors the creditworthiness of its counterparties and obtains collateral. The performance of exchange-traded instruments is guaranteed by the exchange on which they trade. For non-exchange-traded instruments, the counterparties are principally banks which must meet certain criteria according to our investment guidelines. Interest rate swaps An interest rate swap is a contract between two counterparties in which interest payments are made based on a notional principal amount, which itself is never paid or received. Under the terms of an interest rate swap, one counterparty makes interest payments based on a fixed interest rate and the other counterparty’s payments are based on a floating rate. Interest rate swap contracts are used occasionally in our investment portfolio as protection against unexpected shifts in interest rates, which would affect the fair value of the fixed maturity portfolio. By using interest rate swaps in the portfolio, the overall duration or interest rate sensitivity of the portfolio can be impacted. Cross-currency swaps Cross-currency swaps are agreements under which two counterparties exchange interest payments and principal denominated in different currencies at a future date. We use cross-currency swaps to reduce the foreign currency and interest rate risk by converting cash flows back into local currency. We invest in foreign currency denominated investments to improve credit diversification and also to obtain better duration matching to our liabilities that is limited in the local currency market. Other Included within Other are derivatives intended to reduce potential losses which may arise from certain exposures in our insurance business. The economic benefit provided by these derivatives is similar to purchased reinsurance. For example, Chubb may enter into crop derivative contracts to protect underwriting results in the event of a significant decline in commodity prices. (iii) Convertible security investments A convertible security is a debt instrument or preferred stock that can be converted into a predetermined amount of the issuer’s equity. The convertible option is an embedded derivative within the host instruments which are classified in the investment portfolio as either available for sale or as an equity security. Chubb purchases convertible securities for their total return and not specifically for the conversion feature. (iv) TBA By acquiring TBAs, we make a commitment to purchase a future issuance of mortgage-backed securities. For the period between purchase of the TBAs and issuance of the underlying security, we account for our position as a derivative in the Consolidated Financial Statements. Chubb purchases TBAs both for their total return and for the flexibility they provide related to our mortgage-backed security strategy. (v) GLB Under the GLB program, as the assuming entity, Chubb is obligated to provide coverage until the expiration or maturity of the underlying deferred annuity contracts or the expiry of the reinsurance treaty. The GLB is accounted for as a derivative and is recorded at fair value. Fair value represents management’s estimate of an exit price and thus, includes a risk margin. We may recognize a realized loss for other changes in fair value due to adverse changes in the capital markets (e.g., declining interest rates and/or declining U.S. and/or international equity markets) and changes in actual or estimated future policyholder behavior (e.g., increased annuitization or decreased lapse rates) although we expect the business to be profitable. To mitigate adverse changes in the capital markets, we maintain positions in exchange-traded equity futures contracts, as noted under section "(ii) Futures" above. These futures increase in fair value when the S&P 500 index decreases (and decrease in fair value when the S&P 500 index increases). The net impact of gains or losses related to changes in fair value of the GLB liability and the exchange-traded equity futures are included in Net realized gains (losses). c) Securities lending and secured borrowings Chubb participates in a securities lending program operated by a third-party banking institution whereby certain assets are loaned to qualified borrowers and from which we earn an incremental return. The securities lending collateral can only be drawn down by Chubb in the event that the institution borrowing the securities is in default under the lending agreement. An indemnification agreement with the lending agent protects us in the event a borrower becomes insolvent or fails to return any of the securities on loan. The collateral is recorded in Securities lending collateral and the liability is recorded in Securities lending payable in the Consolidated balance sheets. The following table presents the carrying value of collateral held under securities lending agreements by investment category and remaining contractual maturity of the underlying agreements: Remaining contractual maturity December 31, 2020 December 31, 2019 (in millions of U.S. dollars) Overnight and Continuous Collateral held under securities lending agreements: Cash $ 551 $ 346 U.S. Treasury / Agency 148 6 Non-U.S. 1,032 595 Corporate and asset-backed securities 30 5 Mortgage-backed securities 4 18 Equity securities 79 24 $ 1,844 $ 994 Gross amount of recognized liability for securities lending payable $ 1,844 $ 994 At December 31, 2020 and 2019, our repurchase agreement obligations of $1,405 million and $1,416 million, respectively, were fully collateralized. In contrast to securities lending programs, the use of cash received is not restricted for the repurchase obligations. The fair value of the underlying securities sold remains in Fixed maturities available for sale, and the repurchase agreement obligation is recorded in Repurchase agreements in the Consolidated balance sheets. The following table presents the carrying value of collateral pledged under repurchase agreements by investment category and remaining contractual maturity of the underlying agreements: Remaining contractual maturity December 31, 2020 December 31, 2019 30-90 Days Greater than 90 Days Up to 30 Days 30-90 Days Greater than 90 Days Total (in millions of U.S. dollars) Total Collateral pledged under repurchase agreements: Cash $ — $ 4 $ 4 $ 2 $ — $ — $ 2 U.S. Treasury / Agency — 106 106 107 — — 107 Mortgage-backed securities 481 871 1,352 399 476 480 1,355 $ 481 $ 981 $ 1,462 $ 508 $ 476 $ 480 $ 1,464 Gross amount of recognized liabilities for repurchase agreements $ 1,405 $ 1,416 Difference (1) $ 57 $ 48 (1) Per the repurchase agreements, the amount of collateral posted is required to exceed the amount of gross liability. Potential risks exist in our secured borrowing transactions due to market conditions and counterparty exposure. With collateral that we pledge, there is a risk that the collateral may not be returned at the expiration of the agreement. If the counterparty fails to return the collateral, Chubb will have free use of the borrowed funds until our collateral is returned. In addition, we may encounter the risk that Chubb may not be able to renew outstanding borrowings with a new term or with an existing counterparty due to market conditions including a decrease in demand as well as more restrictive terms from banks due to increased regulatory and capital constraints. Should this condition occur, Chubb may seek alternative borrowing sources or reduce borrowings. Additionally, increased margins and collateral requirements due to market conditions would increase our restricted assets as we are required to provide additional collateral to support the transaction. The following table presents net realized gains (losses) related to derivative instrument activity in the Consolidated statements of operations: Year Ended December 31 (in millions of U.S. dollars) 2020 2019 2018 Investment and embedded derivative instruments: Foreign currency forward contracts $ 65 $ (79) $ 3 Interest rate swaps — (270) (115) All other futures contracts, options, and equities 16 (88) 39 Convertible securities (1) — 2 (2) Total investment and embedded derivative instruments $ 81 $ (435) $ (75) GLB and other derivative instruments: GLB $ (202) $ (4) $ (248) Futures contracts on equities (2) (108) (138) (4) Other 1 (8) (3) Total GLB and other derivative instruments $ (309) $ (150) $ (255) $ (228) $ (585) $ (330) (1) Includes embedded derivatives. (2) Related to GMDB and GLB book of business. d) Concentrations of credit risk Our investment portfolio is managed following prudent standards of diversification. Specific provisions limit the allowable holdings of a single issue and issuer. We believe that there are no significant concentrations of credit risk associated with our investments. Our three largest corporate exposures by issuer at December 31, 2020, were Wells Fargo & Co., Bank of America Corp, and JP Morgan Chase & Co. Our largest exposure by industry at December 31, 2020 was financial services. We market our insurance and reinsurance worldwide primarily through insurance and reinsurance brokers. We assume a degree of credit risk associated with brokers with whom we transact business. For the years ended December 31, 2020, 2019 and 2018, approximately 12 percent, 12 percent, and 10 percent, respectively, of our gross premiums written was generated from or placed by Marsh & McLennan Companies, Inc. This entity is a large, well-established company, and there are no indications that it is financially troubled at December 31, 2020. No other broker or one insured accounted for more than 10 percent of our gross premiums written for these years. e) Fixed maturities At December 31, 2020, we have commitments to purchase fixed income securities of $605 million over the next several years. f) Other investments At December 31, 2020, included in Other investments in the Consolidated balance sheet are investments in limited partnerships and partially-owned investment companies with a carrying value of $6.5 billion. In connection with these investments, we have commitments that may require funding of up to $3.2 billion over the next several years. At December 31, 2019, these investments had a carrying value of $4.7 billion with a commitment that may require funding of up to $3.3 billion. g) Letters of credit We have access to capital markets and to credit facilities with letter of credit capacity of $4.0 billion with a sub-limit of $1.9 billion for revolving credit. Our existing credit facilities have remaining terms expiring through October 2022. At December 31, 2020, our LOC usage was $1.7 billion. h) Legal proceedings Our insurance subsidiaries are subject to claims litigation involving disputed interpretations of policy coverages and, in some jurisdictions, direct actions by allegedly-injured persons seeking damages from policyholders. These lawsuits, involving claims on policies issued by our subsidiaries which are typical to the insurance industry in general and in the normal course of business, are considered in our loss and loss expense reserves. In addition to claims litigation, we are subject to lawsuits and regulatory actions in the normal course of business that do not arise from or directly relate to claims on insurance policies. This category of business litigation typically involves, among other things, allegations of underwriting errors or misconduct, employment claims, regulatory activity, or disputes arising from our business ventures. In the opinion of management, our ultimate liability for these matters could be, but we believe is not likely to be, material to our consolidated financial condition and results of operations. i) Lease commitments At December 31, 2020 and 2019, the right-of-use asset was $473 million and $551 million, respectively, recorded within Other assets on the Consolidated balance sheets, and the lease liability was $517 million and $603 million, respectively, which was recorded within Accounts payable, accrued expenses, and other liabilities Future minimum lease payments under the operating leases are expected to be as follows: For the years ending December 31 (in millions of U.S. dollars) Undiscounted cash flows: 2021 $ 150 2022 123 2023 96 2024 68 2025 38 Thereafter 75 Total undiscounted lease payments $ 550 Less: Present value adjustment 33 Net lease liabilities reported as of December 31, 2020 $ 517

Shareholders' equity note

Shareholders' equity note	12 Months Ended
	Dec. 31, 2020
Stockholders' Equity Note [Abstract]
Shareholders' equity	Shareholders’ equity a) Common Shares All of Chubb’s Common Shares are authorized under Swiss corporate law. Though the par value of Common Shares is stated in Swiss francs, Chubb continues to use U.S. dollars as its reporting currency for preparing the Consolidated Financial Statements. Under Swiss corporate law, we are generally prohibited from issuing Common Shares below their par value. If there were a need to raise common equity at a time when the trading price of Chubb's Common Shares is below par value, we would need in advance to obtain shareholder approval to decrease the par value of the Common Shares. Dividend approval At our May 2019 and 2018 annual general meetings, our shareholders approved annual dividends for the following year of up to $3.00 per share and $2.92 per share, respectively, which were paid in four quarterly installments of $0.75 per share and $0.73 per share, respectively, at dates determined by the Board of Directors (Board) after the annual general meeting by way of a distribution from capital contribution reserves, transferred to free reserves for payment. At our May 2020 annual general meeting, our shareholders approved an annual dividend for the following year of up to $3.12 per share, expected to be paid in four quarterly installments of $0.78 per share after the annual general meeting by way of distribution from capital contribution reserves, transferred to free reserves for payment. The Board will determine the record and payment dates at which the annual dividend may be paid until the date of the 2021 annual general meeting, and is authorized to abstain from distributing a dividend at its discretion. The first three quarterly installments each of $0.78 per share, have been distributed by the Board as expected. Dividend distributions Under Swiss corporate law, dividends must be stated in Swiss francs though dividend payments are made by Chubb in U.S. dollars. We issue dividends without subjecting them to withholding tax by way of distributions from capital contribution reserves and payment out of free reserves. The following table presents dividend distributions per Common Share in Swiss francs (CHF) and U.S. dollars (USD): Year Ended December 31 2020 2019 2018 CHF USD CHF USD CHF USD Total dividend distributions per common share 2.89 $ 3.09 2.94 $ 2.98 2.84 $ 2.90 b) Shares issued, outstanding, authorized, and conditional Year Ended December 31 2020 2019 2018 Common Shares authorized and issued, beginning of year 479,783,864 479,783,864 479,783,864 Cancellation of treasury shares (2,178,600) — — Common Shares authorized and issued, end of year 477,605,264 479,783,864 479,783,864 Common Shares in treasury, beginning of year (at cost) (27,812,297) (20,580,486) (15,950,685) Net shares issued under employee share-based compensation plans 2,345,208 3,210,427 3,089,234 Shares repurchased (3,584,150) (10,442,238) (7,719,035) Cancellation of treasury shares 2,178,600 — — Common Shares in treasury, end of year (at cost) (26,872,639) (27,812,297) (20,580,486) Common Shares outstanding, end of year 450,732,625 451,971,567 459,203,378 Increases in Common Shares in treasury are due to open market repurchases of Common Shares and the surrender of Common Shares to satisfy tax withholding obligations in connection with the vesting of restricted stock and the forfeiture of unvested restricted stock. Decreases in Common Shares in treasury are principally due to grants of restricted stock, exercises of stock options, purchases under the Employee Stock Purchase Plan (ESPP), and share cancellations. At our May 2020 annual general meeting, our shareholders approved the cancellation of 2,178,600 shares purchased under our share repurchase program during the period beginning September 23, 2019 and ending December 31, 2019. The capital reduction by cancellation of shares was subject to publication requirements and a two-month waiting period in accordance with Swiss law and became effective August 3, 2020. Authorized share capital for general purposes under Swiss law In accordance with Swiss law, the Board has shareholder-approved authority as set forth in the Articles of Association to increase Chubb's share capital from time to time until May 20, 2022, by the issuance for general purposes of up to 200,000,000 fully paid up Common Shares, with a par value equal to the par value of Chubb's Common Shares as set forth in the Articles of Association at the time of any such issuance. Any such increases would be subject to Swiss rules and procedure. Conditional share capital for bonds and similar debt instruments Chubb's share capital may be increased through the issuance of a maximum of 33,000,000 fully paid up Common Shares (with a par value of CHF 24.15 as of December 31, 2020) through the exercise of conversion and/or option or warrant rights granted in connection with bonds, notes, or similar instruments, issued or to be issued by Chubb, including convertible debt instruments. Conditional share capital for employee benefit plans Chubb's share capital may be increased through the issuance of a maximum of 25,410,929 fully paid up Common Shares (with a par value of CHF 24.15 as of December 31, 2020) in connection with the exercise of option rights granted to any employee of Chubb, director or other person providing services to Chubb. c) Chubb Limited securities repurchases From time to time, we repurchase shares as part of our capital management program and to partially offset potential dilution from the exercise of stock options and the granting of restricted stock under share-based compensation plans. The Board has authorized share repurchase programs as follows: • $1.0 billion of Chubb Common Shares from January 1, 2018 through December 31, 2018 • $1.5 billion of Chubb Common Shares from December 1, 2018 through December 31, 2019 • $1.5 billion of Chubb Common Shares from November 21, 2019 through December 31, 2020 • $1.5 billion of Chubb Common Shares from November 19, 2020 through December 31, 2021 Subsequently, in February 2021, the Board approved an increase to the November 2020 share repurchase program of $1.0 billion to a total of $2.5 billion, effective through December 31, 2021. Share repurchases may be in the open market, in privately negotiated transactions, block trades, accelerated repurchases and through option or other forward transactions. The following table presents repurchases of Chubb's Common Shares conducted in a series of open market transactions under the Board authorizations: Year Ended December 31 January 1, 2021 through (in millions of U.S. dollars, except share data) 2020 2019 2018 February 24, 2021 Number of shares repurchased 3,584,150 10,442,238 7,719,035 1,971,000 Cost of shares repurchased (1) $ 516 $ 1,531 $ 1,021 $ 327 (1) On April 22, 2020, we suspended share repurchases, given the economic environment and to preserve capital for both risk and opportunity. Subsequently, we announced and then resumed share repurchases on October 29, 2020. d) General restrictions The holders of the Common Shares are entitled to receive dividends as approved by the shareholders. Holders of Common Shares are allowed one vote per share provided that, if the controlled shares of any shareholder constitute ten percent or more of the outstanding Common Shares of Chubb, only a fraction of the vote will be allowed so as not to exceed ten percent in aggregate. Entry of acquirers of Common Shares as shareholders with voting rights in the share register may be refused if it would confer voting rights with respect to ten percent or more of the registered share capital recorded in the commercial register.

Share-based compensation

Share-based compensation	12 Months Ended
	Dec. 31, 2020
Share-based Payment Arrangement [Abstract]
Share-based compensation	Share-based compensation Chubb has share-based compensation plans which currently provide the Board the ability to grant awards of stock options, restricted stock, and restricted stock units to its employees and members of the Board. In May 2016, our shareholders approved the Chubb Limited 2016 Long-Term Incentive Plan (the 2016 LTIP), which replaced both the ACE Limited 2004 LTIP (the 2004 LTIP) and The Chubb Corporation Long-Term Incentive Plan (2014). The 2016 LTIP is substantially similar to the 2004 LTIP in its operation and the types of awards that may be granted. Under the 2016 LTIP, Common Shares of Chubb were authorized to be issued pursuant to awards made as stock options, stock appreciation rights, performance shares, performance units, restricted stock, and restricted stock units. Chubb principally issues restricted stock grants and stock options on a graded vesting schedule, with equal percentages of the award subject to vesting over a number of years (typically three or four). Chubb recognizes compensation cost for vesting of restricted stock and stock option grants with only service conditions on a straight-line basis over the requisite service period for each separately vesting portion of the award as if the award were, in-substance, multiple awards. We incorporate an estimate of future forfeitures in determining compensation cost for both grants of restricted stock and stock options. In addition, Chubb grants performance-based restricted stock to certain executives that vest based on certain performance criteria as compared to a defined group of peer companies. Performance-based stock awards comprise target awards and premium awards that cliff vest at the end of a 3-year performance period based on both our tangible book value (shareholders' equity less goodwill and intangible assets, net of tax) per share growth and P&C combined ratio compared to our peer group. Premium awards are subject to an additional vesting provision based on total shareholder return (TSR) compared to our peer group. Shares representing target awards and premium awards are issued when the awards are approved and are subject to forfeiture if applicable performance criteria are not met at the end of the 3-year performance period. Prior to January 2017, performance-based restricted stock awards had a 4-year vesting period with the potential to vest as to a portion each year, and excluded the P&C combined ratio and TSR additional vesting criteria. Under the 2016 LTIP, 19,500,000 Common Shares are authorized to be issued. This is in addition to any shares that have not been delivered pursuant to the 2004 LTIP and remain available for grant pursuant to the 2004 LTIP and includes any shares covered by awards granted under the 2004 LTIP that have forfeited, expired or canceled after the effective date of the 2016 LTIP. At December 31, 2020, a total of 7,576,239 shares remain available for future issuance under the 2016 LTIP, which includes shares canceled or forfeited from the 2004 LTIP, in addition to common shares that were previously registered and authorized to be issued. Under the Employee Stock Purchase Plan (ESPP), 6,500,000 shares are authorized to be issued. At December 31, 2020, a total of 1,402,017 shares remain available for issuance under the ESPP. Chubb generally issues Common Shares for the exercise of stock options, restricted stock, and purchases under the ESPP from Common Shares in treasury. The following table presents pre-tax and after-tax share-based compensation expense: Year Ended December 31 (in millions of U.S. dollars) 2020 2019 2018 Stock options and shares issued under ESPP: Pre-tax $ 45 $ 42 $ 50 After-tax (1) $ 38 $ 39 $ 40 Restricted stock: Pre-tax $ 210 $ 224 $ 235 After-tax (1) $ 164 $ 180 $ 178 (1) The windfall tax benefit recorded to Income tax expense in the Consolidated statement of operations was $10 million, $12 million, and $19 million for the years ended December 31, 2020, 2019, and 2018, respectively. Unrecognized compensation expense related to the unvested portion of Chubb's employee share-based awards of restricted stock, restricted stock units, and stock options was $199 million at December 31, 2020 and is expected to be recognized over a weighted-average period of approximately 1 year. Stock options Both incentive and non-qualified stock options are principally granted at an option price per share equal to the grant date fair value of Chubb's Common Shares. Stock options are generally granted with a 3-year vesting period and a 10-year term. Stock options vest in equal annual installments over the respective vesting period, which is also the requisite service period. Chubb's 2020 share-based compensation expense includes a portion of the cost related to the 2017 through 2020 stock option grants. Stock option fair value was estimated on the grant date using the Black-Scholes option-pricing model that uses the weighted-average assumptions noted below: Year Ended December 31 2020 2019 2018 Dividend yield 2.1 % 2.2 % 2.0 % Expected volatility 18.0 % 16.0 % 23.2 % Risk-free interest rate 1.2 % 2.6 % 2.7 % Expected life 5.7 years 5.7 years 5.7 years The risk-free interest rate is based on the U.S. Treasury yield curve in effect at the time of grant. The expected life (estimated period of time from grant to exercise date) is estimated using the historical exercise behavior of employees. For years 2020 and 2019, expected volatility is calculated as a blend of (a) historical volatility based on daily closing prices over a period equal to the expected life assumption and (b) implied volatility derived from Chubb's publicly traded options. For year 2018, expected volatility was calculated as a blend of (a) historical volatility based on daily closing prices over a period equal to the expected life assumption, (b) long-term historical volatility based on daily closing prices over the period from Chubb's initial public trading date through the most recent quarter, and (c) implied volatility derived from Chubb's publicly traded options. The following table presents a roll-forward of Chubb's stock options: (Intrinsic Value in millions of U.S. dollars) Number of Options Weighted-Average Exercise Price Weighted-Average Fair Value Total Intrinsic Value Options outstanding, December 31, 2017 10,433,316 $ 99.20 Granted 1,842,690 $ 143.07 $ 29.71 Exercised (1,065,384) $ 73.57 $ 71 Forfeited and expired (202,900) $ 133.92 Options outstanding, December 31, 2018 11,007,722 $ 108.25 Granted 2,073,940 $ 133.90 $ 18.76 Exercised (1,944,604) $ 84.13 $ 122 Forfeited and expired (251,801) $ 136.87 Options outstanding, December 31, 2019 10,885,257 $ 116.79 Granted 1,958,279 $ 150.10 $ 19.89 Exercised (1,158,633) $ 86.90 $ 76 Forfeited and expired (206,720) $ 138.77 Options outstanding, December 31, 2020 11,478,183 $ 125.09 $ 331 Options exercisable, December 31, 2020 7,792,343 $ 116.35 $ 293 The weighted-average remaining contractual term was 6.0 years for stock options outstanding and 4.8 years for stock options exercisable at December 31, 2020. Cash received from the exercise of stock options for the year ended December 31, 2020 was $100 million. Restricted stock and restricted stock units Grants of restricted stock and restricted stock units awarded under both the 2004 LTIP and 2016 LTIP typically have a 4-year vesting period, subject to vesting as to one-quarter of the award each anniversary of grant. Restricted stock and restricted stock units are granted at market close price on the day of grant. Each restricted stock unit represents our obligation to deliver to the holder one Common Share upon vesting. Chubb also grants restricted stock awards to non-management directors which vest at the following year's annual general meeting. Chubb's 2020 share-based compensation expense includes a portion of the cost related to the restricted stock granted in the years 2016 through 2020. The following table presents a roll-forward of our restricted stock awards. Included in the roll-forward below are 27,679 restricted stock awards, 19,019 restricted stock awards, and 20,784 restricted stock awards that were granted to non-management directors during the years ended December 31, 2020, 2019, and 2018, respectively: Service-based Performance-based Number of Shares Weighted-Average Number of Shares Weighted-Average Unvested restricted stock, December 31, 2017 4,709,442 $ 121.16 975,497 $ 118.28 Granted 1,326,979 $ 142.76 180,065 $ 143.07 Vested (2,545,090) $ 114.83 (244,332) $ 103.03 Forfeited (196,482) $ 131.06 — $ — Unvested restricted stock, December 31, 2018 3,294,849 $ 134.17 911,230 $ 127.27 Granted 1,492,900 $ 134.38 212,059 $ 133.90 Vested (1,292,864) $ 129.18 (196,640) $ 115.62 Forfeited (200,875) $ 135.98 (50,437) $ 132.36 Unvested restricted stock, December 31, 2019 3,294,010 $ 136.20 876,212 $ 131.16 Granted 1,425,667 $ 148.56 186,291 $ 151.14 Vested (1,304,308) $ 134.02 (490,185) $ 125.66 Forfeited (152,074) $ 140.72 — $ — Unvested restricted stock, December 31, 2020 3,263,295 $ 142.32 572,318 $ 142.38 Prior to 2009, legacy ACE granted restricted stock units with a 1-year vesting period to non-management directors. Delivery of Common Shares on account of these restricted stock units to non-management directors is deferred until after the date of the non-management directors' termination from the Board. Legacy Chubb Corp historically allowed directors and certain key employees of Chubb Corp and its subsidiaries to defer a portion of their compensation earned with respect to services performed in the form of deferred stock units. In addition, legacy Chubb Corp provided supplemental retirement benefits for certain employees through its Defined Contribution Excess Benefit Plan in the form of deferred shares of stock. The minimum vesting period under these legacy Chubb Corp deferred plans was 1-year and the maximum was 3-years. Employees and directors had the option to elect to receive their awards at a future specified date or upon their termination of service with Chubb. At December 31, 2020, there were 166,624 deferred restricted stock units. ESPP The ESPP gives participating employees the right to purchase Common Shares through payroll deductions during consecutive subscription periods at a purchase price of 85 percent of the fair value of a Common Share on the exercise date (Purchase Price). Annual purchases by participants are limited to the number of whole shares that can be purchased by an amount equal to ten percent of the participant's compensation or $25,000, whichever is less. The ESPP has two six-month subscription periods each year, the first of which runs between January 1 and June 30 and the second of which runs between July 1 and December 31. The amounts collected from participants during a subscription period are used on the exercise date to purchase full shares of Common Shares. An exercise date is generally the last trading day of a subscription period. The number of shares purchased is equal to the total amount, at the exercise date, collected from the participants through payroll deductions for that subscription period, divided by the Purchase Price, rounded down to the next full share. Participants may withdraw from an offering before the exercise date and obtain a refund of amounts withheld through payroll deductions. Pursuant to the provisions of the ESPP, during the years ended December 31, 2020, 2019, and 2018, employees paid $45 million, $41 million, and $37 million to purchase 383,751 shares, 321,800 shares, and 347,116 shares, respectively.

Postretirement benefits

Postretirement benefits	12 Months Ended
	Dec. 31, 2020
Retirement Benefits [Abstract]
Postretirement benefits	Postretirement benefits Chubb provides postretirement benefits to eligible employees and their dependents through various defined contribution plans sponsored by Chubb. In addition, for certain employees, Chubb sponsors other postretirement benefit plans, and prior to 2020, Chubb sponsored defined benefit pension plans. Defined contribution plans (including 401(k)) Under these plans, employees' contributions may be supplemented by Chubb matching contributions based on the level of employee contribution. These contributions are invested at the election of each employee in one or more of several investment portfolios offered by a third-party investment advisor. Expenses for these plans totaled $211 million, $171 million, and $171 million for the years ended December 31, 2020, 2019, and 2018, respectively. Defined benefit pension plans We maintain non-contributory defined benefit pension plans that cover certain employees located in the U.S., U.K., Canada, and various other statutorily required countries. We account for pension benefits using the accrual method. Benefits under these plans are based on employees' years of service and compensation during final years of service. All underlying plans are subject to periodic actuarial valuations by qualified actuarial firms using actuarial models to calculate the expense and liability for each plan. We use December 31 as the measurement date for our defined benefit pension plans. Under the Chubb Corp plans, prior to 2001, benefits were generally based on an employee’s years of service and average compensation during the last five years of employment. Effective January 1, 2001, the formula for providing pension benefits was changed from the final average pay formula to a cash balance formula. Under the cash balance formula, a notional account is established for each employee, which is credited semi-annually with an amount equal to a percentage of eligible compensation based on age and years of service plus interest based on the account balance. Chubb Corp employees hired prior to 2001 will generally be eligible to receive vested benefits based on the higher of the final average pay or cash balance formulas. Other postretirement benefit plans Our assumption of Chubb Corp's other postretirement benefit plans, principally healthcare and life insurance, covers retired employees, their beneficiaries, and covered dependents. Healthcare coverage is contributory. Retiree contributions vary based upon the retiree’s age, type of coverage, and years of service requirements. Life insurance coverage is non-contributory. Chubb funds a portion of the healthcare benefits obligation where such funding can be accomplished on a tax-effective basis. Benefits are paid as covered expenses are incurred. Amendments to U.S. qualified and excess pension plans and U.S. retiree healthcare plan On October 31, 2016, we harmonized and amended several of our U.S. retirement programs to create a unified retirement savings program. In 2020, we transitioned from a traditional defined benefit pension program that had been in effect for certain employees to a defined contribution program. Additionally, after 2025, we plan to eliminate a subsidized U.S. retiree healthcare and life insurance plan that had been in place for certain employees. Both amendments required a remeasurement of the plan assets and benefit obligations with updated assumptions, including discount rates and the expected return on assets. The amendment of the retiree healthcare plan resulted in a reduction in the obligation of $383 million, of which $410 million will be amortized as a reduction to expense through 2021 as it relates to benefits already accrued. For the years ended December 31, 2020, 2019, and 2018, $79 million, $79 million, and $80 million, respectively, were amortized as a reduction to expense. At December 31, 2020, the remaining curtailment benefit balance was $26 million which will be amortized as a reduction to expense through June 2021. Obligations and funded status The funded status of the pension and other postretirement benefit plans as well as the amounts recognized in Accumulated other comprehensive income at December 31, 2020 and 2019 was as follows: Pension Benefit Plans Other Postretirement 2020 2019 2020 2019 U.S. Plans Non-U.S. Plans U.S. Plans Non-U.S. Plans (in millions of U.S. dollars) Benefit obligation, beginning of year $ 3,569 $ 1,042 $ 3,092 $ 942 $ 103 $ 113 Service cost — 4 49 11 1 — Interest cost 99 22 118 27 2 4 Actuarial loss (gain) 441 135 443 124 1 3 Benefits paid (127) (31) (121) (39) (20) (17) Curtailments — (2) — (4) — — Settlements (15) — (12) (61) — — Foreign currency revaluation and other — 29 — 42 (1) — Benefit obligation, end of year $ 3,967 $ 1,199 $ 3,569 $ 1,042 $ 86 $ 103 Plan assets at fair value, beginning of year $ 3,301 $ 1,141 $ 2,784 $ 1,008 $ 152 $ 143 Actual return on plan assets 563 126 636 169 6 9 Employer contributions 17 19 14 16 1 — Benefits paid (127) (31) (121) (39) (39) — Settlements (15) — (12) (61) — — Foreign currency revaluation and other — 29 — 48 — — Plan assets at fair value, end of year $ 3,739 $ 1,284 $ 3,301 $ 1,141 $ 120 $ 152 Funded status at end of year $ (228) $ 85 $ (268) $ 99 $ 34 $ 49 Amounts recognized in Accumulated other comprehensive Net actuarial loss (gain) $ 78 $ 163 $ (21) $ 110 $ (5) $ (3) Prior service cost (benefit) — 9 — 10 (31) (114) Total $ 78 $ 172 $ (21) $ 120 $ (36) $ (117) For the U.S. pension plans, the $441 million and $443 million actuarial loss experienced in 2020 and 2019, respectively, was principally driven by the decrease in the discount rate from the respective prior year. The accumulated benefit obligation for the pension benefit plans was $5.1 billion and $4.6 billion at December 31, 2020 and 2019, respectively. The accumulated benefit obligation is the present value of pension benefits earned as of the measurement date based on employee service and compensation prior to that date. It differs from the pension (projected) benefit obligation in the table above in that the accumulated benefit obligation includes no assumptions regarding future compensation levels. The net components of the funded status of the pension and other postretirement benefit plans are included in Accounts payable, accrued expenses, and other liabilities in the Consolidated balance sheets. Chubb’s funding policy is to contribute amounts that meet regulatory requirements plus additional amounts determined based on actuarial valuations, market conditions and other factors. All benefit plans satisfy minimum funding requirements of the Employee Retirement Income Security Act of 1974 (ERISA). The following table provides information on pension plans where the benefit obligation is in excess of plan assets at December 31, 2020 and 2019: 2020 2019 U.S. Plans Non-U.S. Plans U.S. Plans Non-U.S. Plans (in millions of U.S. dollars) Plans with projected benefit obligation in excess of plan assets: Projected benefit obligation $ 3,967 $ 629 $ 3,569 $ 236 Fair value of plan assets 3,739 568 3,301 175 Net funded status $ (228) $ (61) $ (268) $ (61) Plans with accumulated benefit obligation in excess of plan assets: Accumulated benefit obligation $ 3,967 $ 593 $ 3,569 $ 173 Fair value of plan assets $ 3,739 $ 565 $ 3,301 $ 140 For other postretirement benefit plans with an accumulated benefit obligation in excess of plan assets, the accumulated benefit obligation was $23 million and $25 million at December 31, 2020 and 2019, respectively. These plans have no plan assets. At December 31, 2020, we estimate that we will contribute $20 million to the pension plans and $1 million to the other postretirement benefits plan in 2021. The estimate is subject to change due to contribution decisions that are affected by various factors including our liquidity, market performance and management discretion. At December 31, 2020, our estimated expected future benefit payments are as follows: Pension Benefit Plans Other Postretirement Benefit Plans For the years ending December 31 U.S. Non-U.S. Plans (in millions of U.S. dollars) 2021 $ 159 $ 30 $ 19 2022 166 28 20 2023 171 30 16 2024 175 32 12 2025 180 32 7 2026-2030 947 185 5 The weighted-average assumptions used to determine the projected benefit obligation were as follows: Pension Benefit Plans U.S. Non-U.S. Other Postretirement Benefit Plans December 31, 2020 Discount rate 2.32 % 1.80 % 1.36 % Rate of compensation increase (1) N/A 3.24 % N/A Interest crediting rate 4.10 % December 31, 2019 Discount rate 3.20 % 2.39 % 2.70 % Rate of compensation increase (1) N/A 3.26 % N/A Interest crediting rate 4.10 % (1) For the U.S. Pension Plans, benefit accruals were frozen as of December 31, 2019. The projected benefit cash flows were discounted using the corresponding spot rates derived from a yield curve, which resulted in a single discount rate that would produce the same liability at the respective measurement dates. The same process was applied to service cost cash flows to determine the discount rate associated with the service cost. In general, the discount rates for the non-U.S. plans were developed using a similar methodology by using country-specific yield curves. The components of net pension and other postretirement benefit costs reflected in Net income and other changes in plan assets and benefit obligations recognized in other comprehensive income were as follows: Pension Benefit Plans Other Postretirement U.S. Plans Non-U.S. Plans Year Ended December 31 2020 2019 2018 2020 2019 2018 2020 2019 2018 (in millions of U.S. dollars) Costs reflected in Net income: Service cost $ — $ 49 $ 57 $ 4 $ 11 $ 12 $ 1 $ — $ 1 Non-service cost: Interest cost 99 118 105 22 27 27 2 4 3 Expected return on plan assets (224) (189) (212) (41) (45) (50) (5) (4) (5) Amortization of net actuarial loss — — — 2 3 1 — — — Amortization of prior service cost — — — — — — (83) (84) (85) Curtailments — — — (1) (1) — — — (2) Settlements 3 2 2 — 1 3 — — — Total non-service benefit (122) (69) (105) (18) (15) (19) (86) (84) (89) Net periodic benefit $ (122) $ (20) $ (48) $ (14) $ (4) $ (7) $ (85) $ (84) $ (88) Changes in plan assets and benefit obligations recognized in other comprehensive income Net actuarial loss (gain) $ 102 $ (4) $ 214 $ 56 $ 6 $ 34 $ (2) $ (2) $ (11) Prior service cost (benefit) — — — — 1 3 — — — Amortization of net actuarial loss — — — (2) (3) (1) — — (1) Amortization of prior service cost — — — (1) — — 83 84 85 Curtailments — — — (1) (3) — — — 3 Settlements (3) (2) (2) — (1) (3) — — — Total decrease (increase) in other comprehensive income $ 99 $ (6) $ 212 $ 52 $ — $ 33 $ 81 $ 82 $ 76 The line items in which the service and non-service cost components of net periodic (benefit) cost are included in the Consolidated statements of operations were as follows: Pension Benefit Plans Other Postretirement Benefit Plans Year Ended December 31 2020 2019 2018 2020 2019 2018 (in millions of U.S. dollars) Service cost: Losses and loss expenses $ — $ 6 $ 7 $ — $ — $ — Administrative expenses 4 54 62 1 — 1 Total service cost 4 60 69 1 — 1 Non-service cost: Losses and loss expenses (12) (7) (10) (9) (8) (9) Administrative expenses (128) (77) (114) (77) (76) (80) Total non-service benefit (140) (84) (124) (86) (84) (89) Net periodic benefit $ (136) $ (24) $ (55) $ (85) $ (84) $ (88) The weighted-average assumptions used to determine the net periodic pension and other postretirement benefit costs were as follows: Pension Benefit Plans U.S. Plans Non-U.S. Plans Other Postretirement Benefit Plans Year Ended December 31 2020 Discount rate in effect for determining service cost N/A 6.04 % 3.00 % Discount rate in effect for determining interest cost 2.85 % 2.24 % 2.64 % Rate of compensation increase N/A 3.26 % N/A Expected long-term rate of return on plan assets 7.00 % 3.83 % 3.00 % Interest crediting rate 4.10 % N/A N/A 2019 Discount rate in effect for determining service cost 4.23 % 4.48 % 4.04 % Discount rate in effect for determining interest cost 3.94 % 2.88 % 3.69 % Rate of compensation increase 4.00 % 3.37 % N/A Expected long-term rate of return on plan assets 7.00 % 4.40 % 3.00 % Interest crediting rate 4.10 % N/A N/A 2018 Discount rate in effect for determining service cost 3.62 % 3.97 % 2.84 % Discount rate in effect for determining interest cost 3.27 % 2.55 % 2.62 % Rate of compensation increase 4.00 % 3.46 % N/A Expected long-term rate of return on plan assets 7.00 % 4.32 % 2.59 % Interest crediting rate 4.10 % N/A N/A The weighted-average healthcare cost trend rate assumptions used to measure the expected cost of healthcare benefits were as follows: U.S. Plans Non-U.S. Plans 2020 2019 2018 2020 2019 2018 Healthcare cost trend rate 5.96 % 6.32 % 6.68 % 5.04 % 5.24 % 6.29 % Rate to which the cost trend rate is assumed to decline (the ultimate trend rate) 4.50 % 4.50 % 4.50 % 4.00 % 4.00 % 4.50 % Year that the rate reaches the ultimate trend rate 2038 2038 2038 2040 2040 2029 Plan Assets The long term objective of the pension plan is to provide sufficient funding to cover expected benefit obligations, while assuming a prudent level of portfolio risk. The assets of the pension plan are invested, either directly or through pooled funds, in a diversified portfolio of predominately equity securities and fixed maturities. We seek to obtain a rate of return that over time equals or exceeds the returns of the broad markets in which the plan assets are invested. The target allocation of U.S. plan assets is 55 percent to 65 percent invested in equity securities (including certain other investments measured using NAV), with the remainder primarily invested in fixed maturities. The target allocation of non-U.S. plans varies by country, but the plan assets are principally invested in fixed maturities. We rebalance our pension assets to the target allocation as market conditions permit. We determined the expected long term rate of return assumption for each asset class based on an analysis of the historical returns and the expectations for future returns. The expected long term rate of return for the portfolio is a weighted aggregation of the expected returns for each asset class. In order to minimize risk, the Plan maintains a listing of permissible and prohibited investments. In addition, the Plan has certain concentration limits and investment quality requirements imposed on permissible investments options. Investment risk is measured and monitored on an ongoing basis. The following tables present the fair values of the pension plan assets, by valuation hierarchy. For additional information on how we classify these assets within the valuation hierarchy, refer to Note 4 to the Consolidated Financial Statements. December 31, 2020 Pension Benefit Plans (in millions of U.S. dollars) Level 1 Level 2 Level 3 Total U.S. Plans: Short-term investments $ 59 $ — $ — $ 59 U.S. Treasury / Agency 250 186 — 436 Non-U.S. and corporate bonds — 793 — 793 Municipal — 2 — 2 Equity securities 1,818 — — 1,818 Total U.S. Plan assets (1) $ 2,127 $ 981 $ — $ 3,108 Non-U.S. Plans: Short-term investments $ 5 $ — $ — $ 5 Non-U.S. and corporate bonds — 609 — 609 Equity securities 127 388 — 515 Total Non-U.S. Plan assets (1) $ 132 $ 997 $ — $ 1,129 (1) Excluded from the table above are $543 million and $147 million of other investments related to the U.S. Plans and Non-U.S. Plans, respectively, limited partnerships of $74 million and $8 million in U.S. Plans and Non-U.S. Plans, respectively, measured using NAV as a practical expedient, and $14 million in cash related to the U.S. Plans. December 31, 2019 Pension Benefit Plans (in millions of U.S. dollars) Level 1 Level 2 Level 3 Total U.S. Plans: Short-term investments $ 18 $ 37 $ — $ 55 U.S. Treasury / Agency 466 134 — 600 Non-U.S. and corporate bonds — 749 — 749 Municipal — 2 — 2 Equity securities 1,467 — — 1,467 Total U.S. Plan assets (1) $ 1,951 $ 922 $ — $ 2,873 Non-U.S. Plans: Short-term investments $ 2 $ — $ — $ 2 Non-U.S. and corporate bonds — 598 — 598 Equity securities 112 318 — 430 Total Non-U.S. Plan assets (1) $ 114 $ 916 $ — $ 1,030 (1) Excluded from the table above are $428 million and $107 million of other investments related to the U.S. Plans and Non-U.S. Plans, respectively, and limited partnerships of $4 million in Non-U.S. Plans, measured using NAV as a practical expedient.

Other (income) expense

Other (income) expense	12 Months Ended
	Dec. 31, 2020
Other Income and Expenses [Abstract]
Other (income) expense	Other income and expense Year Ended December 31 (in millions of U.S. dollars) 2020 2019 2018 Equity in net income of partially-owned entities (1) $ 1,019 $ 617 $ 514 Gains (losses) from fair value changes in separate account assets (2) 58 44 (38) Federal excise and capital taxes (22) (23) (12) Other (61) (42) (30) Total $ 994 $ 596 $ 434 (1) Equity in net income of partially-owned entities includes $167 million, $74 million, and $43 million attributable to our investments in Huatai (Huatai Group, Huatai P&C, and Huatai Life) for the years ended December 31, 2020, 2019, and 2018, respectively. (2) Related to gains (losses) from fair value changes in separate account assets that do not qualify for separate account reporting under GAAP.

Segment information

Segment information	12 Months Ended
	Dec. 31, 2020
Segment Reporting [Abstract]
Segment information	Segment information Chubb operates through six business segments: North America Commercial P&C Insurance, North America Personal P&C Insurance, North America Agricultural Insurance, Overseas General Insurance, Global Reinsurance, and Life Insurance. These segments distribute their products through various forms of brokers, agencies, and direct marketing programs. All business segments have established relationships with reinsurance intermediaries. • The North America Commercial P&C Insurance segment provides both commercial and consumer P&C products and services. This segment includes the business written by Chubb divisions that provide property and casualty (P&C) insurance and services to large, middle market and small commercial businesses in the U.S., Canada, and Bermuda. This segment includes our retail divisions: Major Accounts, Commercial Insurance, including Small Commercial Insurance; and our wholesale and specialty divisions: Westchester and Chubb Bermuda. These divisions write a variety of coverages, including property, casualty, workers’ compensation, package policies, risk management, financial lines, marine, construction, environmental, medical risk, cyber risk, surety, and excess casualty; as well as group accident and health (A&H) insurance. • The North America Personal P&C Insurance segment includes the business written by Chubb Personal Risk Services division, which includes high net worth personal lines business, with operations in the U.S. and Canada. This segment provides affluent and high net worth individuals and families with homeowners, automobile and collector cars, valuable articles (including fine arts), personal and excess liability, travel insurance, and recreational marine insurance and services. • The North America Agricultural Insurance segment includes the business written by Rain and Hail Insurance Service, Inc. in the U.S. and Canada, which provides comprehensive multiple peril crop insurance (MPCI) and crop-hail insurance, and Chubb Agribusiness, which offers farm and ranch property as well as specialty P&C coverages, including commercial agriculture products. • The Overseas General Insurance segment includes the business written by two Chubb divisions that provides both commercial and consumer P&C insurance and services in the 51 countries and territories outside of North America where the company operates. Chubb International provides commercial P&C, A&H and traditional and specialty personal lines for large corporations, middle markets and small customers through retail brokers, agents and other channels locally around the world. Chubb Global Markets (CGM) provides commercial P&C excess and surplus lines and A&H through wholesale brokers in the London market and through Lloyd’s. These divisions write a variety of coverages, including traditional commercial P&C, specialty categories such as financial lines, marine, energy, aviation, political risk and construction, as well as group A&H and traditional and specialty personal lines. • The Global Reinsurance segment includes the reinsurance business written by Chubb Tempest Re, comprising Chubb Tempest Re Bermuda, Chubb Tempest Re USA, Chubb Tempest Re International, and Chubb Tempest Re Canada. Chubb Tempest Re provides a broad range of traditional and specialty reinsurance coverages to a diverse array of primary P&C companies, including small, mid-sized, and multinational ceding companies. • The Life Insurance segment includes international life operations written by Chubb Life and Chubb Tempest Life Re, and the North American supplemental A&H and life business of Combined Insurance. Corporate primarily includes the results of all run-off asbestos and environmental (A&E) exposures, run-off Brandywine business, Westchester specialty operations for 1996 and prior years, and certain other non-A&E run-off exposures. In addition, Corporate includes the results of our non-insurance companies including Chubb Limited, Chubb Group Management and Holdings Ltd., and Chubb INA Holdings Inc. Our exposure to A&E claims principally arises out of liabilities acquired when we purchased Westchester Specialty in 1998, CIGNA’s P&C business in 1999, and The Chubb Corporation (Chubb Corp) in 2016. In addition, revenue and expenses managed at the corporate level, including realized gains and losses, interest expense, the non-operating income of our partially-owned entities, Chubb integration expenses and income taxes are reported within Corporate. In addition, the amortization expense of purchased intangibles, amortization of the fair value adjustment on acquired invested assets and assumed long-term debt as part of the Chubb Corp acquisition are considered Corporate costs as these are incurred by the overall company. The Chief Executive Officer does not manage segment results or allocate resources to segments when considering these costs and they are therefore excluded from our definition of segment income (loss). Management uses underwriting income (loss) as the basis for segment performance. Chubb calculates underwriting income (loss) by subtracting Losses and loss expenses, Policy benefits, Policy acquisition costs, and Administrative expenses from Net premiums earned. Segment income (loss) includes underwriting income (loss), net investment income (loss), and other operating income and expense items such as each segment's share of the operating income (loss) related to partially-owned insurance companies and miscellaneous income and expense items for which the segments are held accountable. Our main measure of segment performance is Segment income (loss), which also includes amortization of purchased intangibles acquired by the segment. We determined that this definition of segment income (loss) is appropriate and aligns with how the business is managed. We continue to evaluate our segments as our business continues to evolve and may further refine our segments and segment income (loss) measures. To calculate Segment income (loss), include Net investment income (loss), Other (income) expense, and Amortization expense of purchased intangibles. Certain items are presented in a different manner for segment reporting purposes than in the Consolidated Financial Statements. These items are reconciled to the consolidated presentation in the Segment measure reclass column below and include: • Losses and loss expenses include realized gains and losses on crop derivatives. These derivatives were purchased to provide economic benefit, in a manner similar to reinsurance protection, in the event that a significant decline in commodity pricing impacts underwriting results. We view gains and losses on these derivatives as part of the results of our underwriting operations, and therefore, realized gains (losses) from these derivatives are reclassified to losses and loss expenses. • Policy benefits include gains and losses from fair value changes in separate account assets, as well as the offsetting movement in separate account liabilities. The gains and losses from fair value changes in separate account assets that do not qualify for separate account reporting under GAAP have been reclassified from Other (income) expense. We view gains and losses from fair value changes in both separate account assets and liabilities as part of the results of our underwriting operations, and therefore these gains and losses are reclassified to policy benefits. • Net investment income includes investment income reclassified from Other (income) expense related to partially-owned investment companies (private equity partnerships) where our ownership interest is in excess of three percent. We view investment income from these equity-method private equity partnerships as net investment income. The following tables present the Statement of Operations by segment: For the Year Ended December 31, 2020 (in millions of U.S. dollars) North America Commercial P&C Insurance North America Personal P&C Insurance North America Agricultural Insurance Overseas General Insurance Global Life Insurance Corporate Segment Measure Reclass Chubb Net premiums written $ 14,474 $ 4,920 $ 1,846 $ 9,335 $ 731 $ 2,514 $ — $ — $ 33,820 Net premiums earned 13,964 4,866 1,822 9,285 698 2,482 — — 33,117 Losses and loss expenses 10,129 3,187 1,544 5,255 435 724 435 1 21,710 Policy benefits — — — — — 726 — 58 784 Policy acquisition costs 1,942 974 123 2,568 174 766 — — 6,547 Administrative expenses 1,006 270 9 1,034 37 320 303 — 2,979 Underwriting income (loss) 887 435 146 428 52 (54) (738) (59) 1,097 Net investment income (loss) 2,061 260 30 534 307 385 (87) (115) 3,375 Other (income) expense 23 5 1 13 2 (74) (791) (173) (994) Amortization expense of purchased intangibles — 11 27 45 — 4 203 — 290 Segment income (loss) $ 2,925 $ 679 $ 148 $ 904 $ 357 $ 401 $ (237) $ (1) $ 5,176 Net realized gains (losses) (499) 1 (498) Interest expense 516 — 516 Income tax expense 629 — 629 Net income (loss) $ (1,881) $ — $ 3,533 For the Year Ended December 31, 2019 (in millions of U.S. dollars) North America Commercial P&C Insurance North America Personal P&C Insurance North America Agricultural Insurance Overseas General Insurance Global Life Insurance Corporate Segment Measure Reclass Chubb Net premiums written $ 13,375 $ 4,787 $ 1,810 $ 9,262 $ 649 $ 2,392 $ — $ — $ 32,275 Net premiums earned 12,922 4,694 1,795 8,882 654 2,343 — — 31,290 Losses and loss expenses 8,206 3,043 1,616 4,606 352 757 158 (8) 18,730 Policy benefits — — — — — 696 — 44 740 Policy acquisition costs 1,831 948 84 2,501 169 620 — — 6,153 Administrative expenses 1,028 286 6 1,033 35 323 319 — 3,030 Underwriting income (loss) 1,857 417 89 742 98 (53) (477) (36) 2,637 Net investment income (loss) 2,109 258 30 588 279 373 (125) (86) 3,426 Other (income) expense 24 3 1 12 1 (48) (459) (130) (596) Amortization expense of purchased intangibles — 12 28 45 — 2 218 — 305 Segment income (loss) $ 3,942 $ 660 $ 90 $ 1,273 $ 376 $ 366 $ (361) $ 8 $ 6,354 Net realized gains (losses) including OTTI (522) (8) (530) Interest expense 552 — 552 Chubb integration expenses 23 — 23 Income tax expense 795 — 795 Net income (loss) $ (2,253) $ — $ 4,454 For the Year Ended December 31, 2018 (in millions of U.S. dollars) North America Commercial P&C Insurance North America Personal P&C Insurance North America Agricultural Insurance Overseas General Insurance Global Life Insurance Corporate Segment Measure Reclass Chubb Net premiums written $ 12,485 $ 4,674 $ 1,577 $ 8,902 $ 671 $ 2,270 $ — $ — $ 30,579 Net premiums earned 12,402 4,593 1,569 8,612 670 2,218 — — 30,064 Losses and loss expenses 8,000 3,229 1,114 4,429 479 766 53 (3) 18,067 Policy benefits — — — — — 628 — (38) 590 Policy acquisition costs 1,829 939 79 2,346 162 557 — — 5,912 Administrative expenses 966 269 (9) 1,014 41 310 295 — 2,886 Underwriting income (loss) 1,607 156 385 823 (12) (43) (348) 41 2,609 Net investment income (loss) 2,061 236 28 622 289 341 (209) (63) 3,305 Other (income) expense 3 1 2 3 — (12) (406) (25) (434) Amortization expense of purchased intangibles — 13 28 41 — 2 255 — 339 Segment income (loss) $ 3,665 $ 378 $ 383 $ 1,401 $ 277 $ 308 $ (406) $ 3 $ 6,009 Net realized gains (losses) including OTTI (649) (3) (652) Interest expense 641 — 641 Chubb integration expenses 59 — 59 Income tax expense 695 — 695 Net income (loss) $ (2,450) $ — $ 3,962 Underwriting assets are reviewed in total by management for purposes of decision-making. Other than Unpaid losses and loss expenses, Future policy benefits, Reinsurance recoverables, Goodwill and Other intangible assets, Chubb does not allocate assets to its segments. The following table presents net premiums earned for each segment by line of business: For the Year Ended December 31 (in millions of U.S. dollars) 2020 2019 2018 North America Commercial P&C Insurance Property & other short-tail lines $ 2,423 $ 1,987 $ 1,861 Casualty & all other 10,812 10,136 9,773 A&H 729 799 768 Total North America Commercial P&C Insurance 13,964 12,922 12,402 North America Personal P&C Insurance Personal automobile 822 829 803 Personal homeowners 3,327 3,183 3,127 Personal other 717 682 663 Total North America Personal P&C Insurance 4,866 4,694 4,593 North America Agricultural Insurance 1,822 1,795 1,569 Overseas General Insurance Property & other short-tail lines 2,468 2,244 2,134 Casualty & all other 2,738 2,494 2,429 Personal lines 1,981 1,896 1,784 A&H 2,098 2,248 2,265 Total Overseas General Insurance 9,285 8,882 8,612 Global Reinsurance Property 104 131 123 Property catastrophe 173 142 170 Casualty & all other 421 381 377 Total Global Reinsurance 698 654 670 Life Insurance Life 1,317 1,101 1,022 A&H 1,165 1,242 1,196 Total Life Insurance 2,482 2,343 2,218 Total net premiums earned $ 33,117 $ 31,290 $ 30,064 The following table presents net premiums earned by geographic region. Allocations have been made on the basis of location of risk: North America Europe (1) Asia Pacific / Far East Latin America 2020 70 % 11 % 12 % 7 % 2019 70 % 11 % 12 % 7 % 2018 70 % 11 % 12 % 7 % (1) Europe includes Eurasia and Africa regions.

Earnings per share

Earnings per share	12 Months Ended
	Dec. 31, 2020
Earnings Per Share [Abstract]
Earnings per share	Earnings per share Year Ended December 31 (in millions of U.S. dollars, except share and per share data) 2020 2019 2018 Numerator: Net income $ 3,533 $ 4,454 $ 3,962 Denominator: Denominator for basic earnings per share: Weighted-average shares outstanding 451,602,820 455,910,463 463,629,203 Denominator for diluted earnings per share: Share-based compensation plans 1,838,692 3,004,200 3,173,145 Weighted-average shares outstanding and assumed conversions 453,441,512 458,914,663 466,802,348 Basic earnings per share $ 7.82 $ 9.77 $ 8.55 Diluted earnings per share $ 7.79 $ 9.71 $ 8.49 Potential anti-dilutive share conversions 6,811,966 2,410,337 3,543,188

Related party transaction

Related party transaction	12 Months Ended
	Dec. 31, 2020
Related Party Transactions [Abstract]
Related party transactions	Related party transactions Starr Indemnity & Liability Company and its affiliates (collectively, Starr) We have a number of agency and reinsurance agreements with Starr, the Chairman of which is related to a member of our senior management team. The Board has reviewed and approved our arrangements with Starr. We have agency, claims services and underwriting services agreements with various Starr subsidiaries. Under the agency agreement, we secure the ability to sell our insurance policies through Starr as one of our non-exclusive agents for writing policies, contracts, binders, or agreements of insurance or reinsurance. Under the claims services agreements, Starr adjusts the claims under policies and arranges for third party treaty and facultative agreements covering such policies. Under the underwriting services agreements, Starr underwrites insurance policies on our behalf and we agree to reinsure such policies to Starr under quota share reinsurance agreements. The agency agreement also contains a profit-sharing arrangement based on loss ratios, triggered if Starr underwrites a minimum of $20 million of annual program business net premiums written on our behalf. No profit share commission has been payable yet under this arrangement. Transactions generated under Starr agreements were as follows: Year Ended December 31 (in millions of U.S. dollars) 2020 2019 2018 Consolidated statement of operations Gross premiums written $ 507 $ 394 $ 411 Ceded premiums written $ 253 $ 207 $ 188 Commissions paid $ 97 $ 77 $ 84 Commissions received $ 59 $ 46 $ 42 Losses and loss expenses $ 170 $ 185 $ 188 Consolidated balance sheets Reinsurance recoverable on losses and loss expenses $ 432 $ 440 Ceded reinsurance premium payable $ 80 $ 56 ABR Re We own 15.6 percent of the common equity of ABR Reinsurance Capital Holdings Ltd. and warrants to acquire 0.5 percent of additional equity. ABR Reinsurance Capital Holdings Ltd., is the parent company of ABR Reinsurance Ltd. (ABR Re), an independent reinsurance company. Through long-term arrangements, Chubb will be the sole source of reinsurance risks ceded to ABR Re, and BlackRock, Inc. will be ABR Re’s exclusive investment management service provider. As an investor, Chubb is expected to benefit from underwriting profit generated by ABR Re’s reinsuring a wide range of Chubb’s primary insurance business and the income and capital appreciation BlackRock, Inc. seeks to deliver through its investment management services. In addition, Chubb has entered into an arrangement with BlackRock, Inc. under which both Chubb and BlackRock, Inc. will be entitled to an equal share of the aggregate amount of certain fees, including underwriting and investment management performance related fees, in connection with their respective reinsurance and investment management arrangements with ABR Re. ABR Re is a variable interest entity; however, Chubb is not the primary beneficiary and does not consolidate ABR Re because Chubb does not have the power to control and direct ABR Re’s most significant activities, including investing and underwriting. Our minority ownership interest is accounted for under the equity method of accounting. Chubb cedes premiums to ABR Re and recognizes the associated commissio ns. Transactions generated under ABR Re agreements were as follows: Year Ended December 31 (in millions of U.S. dollars) 2020 2019 2018 Consolidated statement of operations Ceded premiums written $ 350 $ 321 $ 329 Commissions received $ 100 $ 92 $ 96 Consolidated balance sheets Reinsurance recoverable on losses and loss expenses $ 806 $ 674 Ceded reinsurance premium payable $ 67 $ 62

Statutory Financial Information

Statutory Financial Information	12 Months Ended
	Dec. 31, 2020
Statutory Financial Information [Abstract]
Statutory financial information	Statutory financial information Our subsidiaries file financial statements prepared in accordance with statutory accounting practices prescribed or permitted by insurance regulators. Statutory accounting differs from GAAP in the reporting of certain reinsurance contracts, investments, subsidiaries, acquisition expenses, fixed assets, deferred income taxes, and certain other items. Some jurisdictions impose complex regulatory requirements on insurance companies while other jurisdictions impose fewer requirements. In some jurisdictions, we must obtain licenses issued by governmental authorities to conduct local insurance business. These licenses may be subject to reserves and minimum capital and solvency tests. Jurisdictions may impose fines, censure, and/or criminal sanctions for violation of regulatory requirements. The 2020 amounts below are based on estimates. Chubb's insurance and reinsurance subsidiaries are subject to insurance laws and regulations in the jurisdictions in which they operate. These regulations include restrictions that limit the amount of dividends or other distributions, such as loans or cash advances, available to shareholders without prior approval of the local insurance regulatory authorities. The amount of dividends available to be paid in 2021 without prior approval totals $6.4 billion. The statutory capital and surplus of our insurance subsidiaries met regulatory requirements for 2020, 2019, and 2018. The minimum amounts of statutory capital and surplus necessary to satisfy regulatory requirements was $29.4 billion and $26.7 billion for December 31, 2020 and 2019, respectively. These minimum regulatory capital requirements were significantly lower than the corresponding amounts required by the rating agencies which review Chubb’s insurance and reinsurance subsidiaries. The following tables present the combined statutory capital and surplus and statutory net income (loss) of our Property and casualty and Life subsidiaries: December 31 (in millions of U.S. dollars) 2020 2019 Statutory capital and surplus Property and casualty $ 45,964 $ 43,077 Life $ 1,641 $ 1,573 Year Ended December 31 (in millions of U.S. dollars) 2020 2019 2018 Statutory net income (loss) Property and casualty $ 4,294 $ 6,046 $ 7,521 Life $ (247) $ (210) $ (102) Several insurance subsidiaries follow accounting practices prescribed or permitted by the jurisdiction of domicile that differ from the applicable local statutory practice. The application of prescribed or permitted accounting practices does not have a material impact on Chubb's statutory surplus and income. As prescribed by the Restructuring discussed previously in Note 7, certain of our U.S. subsidiaries discount certain A&E liabilities, which increased statutory capital and surplus by approximately $140 million and $147 million at December 31, 2020 and 2019, respectively. Federal Insurance Company (Federal), a direct subsidiary of Chubb INA Holdings Inc., has a permitted practice granted by the Indiana Department of Insurance that relates to its investments in foreign subsidiaries and affiliates. Under Statement of Statutory Accounting Principles No. 97, Investments in Subsidiary, Controlled and Affiliated Entities, in order for a reporting entity to admit its investments in foreign subsidiaries and affiliates, audited financial statements of the subsidiary or affiliate must be obtained to support the carrying value. Such financial statements must be prepared in accordance with U.S. GAAP, or alternatively, in accordance with the local statutory requirements in the subsidiary’s or affiliate’s country of domicile, with an audited footnote reconciliation of net income and shareholder’s equity as reported to a U.S. GAAP basis. With the explicit permission of the Indiana Department of Insurance, Federal obtains audited financial statements for its admitted foreign subsidiaries and affiliates, which had an aggregate carrying value of approximately $55 million and $54 million at December 31, 2020 and 2019, respectively, prepared in accordance with their respective local statutory requirements and supplemented with a separate unaudited reconciliation of shareholder’s equity as reported to a U.S. GAAP basis.

Information provided in connect

Information provided in connection with outstanding debt of subsidiaries	12 Months Ended
	Dec. 31, 2020
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Abstract]
Information provided in connection with outstanding debt of subsidiaries	Information provided in connection with outstanding debt of subsidiaries The following tables present condensed consolidating financial information at December 31, 2020 and 2019, and for the years ended December 31, 2020, 2019, and 2018 for Chubb Limited (Parent Guarantor) and Chubb INA Holdings Inc. (Subsidiary Issuer). The Subsidiary Issuer is an indirect 100 percent-owned subsidiary of the Parent Guarantor. The Parent Guarantor fully and unconditionally guarantees certain of the debt of the Subsidiary Issuer. Condensed consolidating financial information of the Parent Guarantor and Subsidiary Issuer are presented on the equity method of accounting. The revenues and expenses and cash flows of the subsidiaries of the Subsidiary Issuer are presented in the Other Chubb Limited Subsidiaries column on a combined basis. Condensed Consolidating Balance Sheet at December 31, 2020 (in millions of U.S. dollars) Chubb Limited Chubb INA Other Chubb Consolidating Chubb Limited Assets Investments $ — $ 197 $ 118,472 $ — $ 118,669 Cash (1) 84 1 1,934 (272) 1,747 Restricted Cash — — 89 — 89 Insurance and reinsurance balances receivable — — 13,926 (3,446) 10,480 Reinsurance recoverable on losses and loss expenses — — 25,217 (9,625) 15,592 Reinsurance recoverable on policy benefits — — 299 (93) 206 Value of business acquired — — 263 — 263 Goodwill and other intangible assets — — 21,211 — 21,211 Investments in subsidiaries 56,148 55,231 — (111,379) — Due from subsidiaries and affiliates, net 3,522 — 171 (3,693) — Other assets 10 463 23,921 (1,877) 22,517 Total assets $ 59,764 $ 55,892 $ 205,503 $ (130,385) $ 190,774 Liabilities Unpaid losses and loss expenses $ — $ — $ 77,180 $ (9,369) $ 67,811 Unearned premiums — — 18,853 (1,201) 17,652 Future policy benefits — — 5,806 (93) 5,713 Due to subsidiaries and affiliates, net — 3,008 685 (3,693) — Affiliated notional cash pooling programs (1) — 272 — (272) — Repurchase agreements — — 1,405 — 1,405 Long-term debt — 14,948 — — 14,948 Trust preferred securities — 308 — — 308 Other liabilities 323 1,418 26,133 (4,378) 23,496 Total liabilities 323 19,954 130,062 (19,006) 131,333 Total shareholders’ equity 59,441 35,938 75,441 (111,379) 59,441 Total liabilities and shareholders’ equity $ 59,764 $ 55,892 $ 205,503 $ (130,385) $ 190,774 (1) Chubb maintains two notional multicurrency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information. At December 31, 2020, the cash balance of one or more entities was negative; however, the overall Pool balances were positive. Condensed Consolidating Balance Sheet at December 31, 2019 (in millions of U.S. dollars) Chubb Limited Chubb INA Other Chubb Consolidating Chubb Limited Assets Investments $ — $ 1,013 $ 108,221 $ — $ 109,234 Cash (1) 2 442 1,093 — 1,537 Restricted Cash — — 109 — 109 Insurance and reinsurance balances receivable — — 12,920 (2,563) 10,357 Reinsurance recoverable on losses and loss expenses — — 24,780 (9,599) 15,181 Reinsurance recoverable on policy benefits — — 292 (95) 197 Value of business acquired — — 306 — 306 Goodwill and other intangible assets — — 21,359 — 21,359 Investments in subsidiaries 50,853 52,076 — (102,929) — Due from subsidiaries and affiliates, net 4,776 — — (4,776) — Other assets 12 408 20,072 (1,829) 18,663 Total assets $ 55,643 $ 53,939 $ 189,152 $ (121,791) $ 176,943 Liabilities Unpaid losses and loss expenses $ — $ — $ 71,916 $ (9,226) $ 62,690 Unearned premiums — — 17,978 (1,207) 16,771 Future policy benefits — — 5,468 (95) 5,373 Due to subsidiaries and affiliates, net — 4,446 330 (4,776) — Repurchase agreements — — 1,416 — 1,416 Short-term debt — 1,298 1 — 1,299 Long-term debt — 13,559 — — 13,559 Trust preferred securities — 308 — — 308 Other liabilities 312 1,649 21,793 (3,558) 20,196 Total liabilities 312 21,260 118,902 (18,862) 121,612 Total shareholders’ equity 55,331 32,679 70,250 (102,929) 55,331 Total liabilities and shareholders’ equity $ 55,643 $ 53,939 $ 189,152 $ (121,791) $ 176,943 (1) Chubb maintains two notional multicurrency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information. Condensed Consolidating Statements of Operations and Comprehensive Income For the Year Ended December 31, 2020 Chubb Limited Chubb INA Other Chubb Consolidating Chubb Limited (in millions of U.S. dollars) Net premiums written $ — $ — $ 33,820 $ — $ 33,820 Net premiums earned — — 33,117 — 33,117 Net investment income (1) 6 3,370 — 3,375 Equity in earnings of subsidiaries 3,457 2,052 — (5,509) — Net realized gains (losses) 20 (397) (121) — (498) Losses and loss expenses — — 21,710 — 21,710 Policy benefits — — 784 — 784 Policy acquisition costs and administrative 94 (130) 9,562 — 9,526 Interest (income) expense (136) 596 56 — 516 Other (income) expense (39) (24) (931) — (994) Amortization of purchased intangibles — — 290 — 290 Income tax expense (benefit) 24 (181) 786 — 629 Net income $ 3,533 $ 1,400 $ 4,109 $ (5,509) $ 3,533 Comprehensive income $ 5,783 $ 3,236 $ 6,512 $ (9,748) $ 5,783 Condensed Consolidating Statements of Operations and Comprehensive Income For the Year Ended December 31, 2019 Chubb Limited Chubb INA Other Chubb Consolidating Chubb Limited (in millions of U.S. dollars) Net premiums written $ — $ — $ 32,275 $ — $ 32,275 Net premiums earned — — 31,290 — 31,290 Net investment income 1 (15) 3,440 — 3,426 Equity in earnings of subsidiaries 4,307 3,022 — (7,329) — Net realized gains (losses) including OTTI (17) (31) (482) — (530) Losses and loss expenses — — 18,730 — 18,730 Policy benefits — — 740 — 740 Policy acquisition costs and administrative expenses 92 (26) 9,117 — 9,183 Interest (income) expense (243) 705 90 — 552 Other (income) expense (27) 6 (575) — (596) Amortization of purchased intangibles — — 305 — 305 Chubb integration expenses 1 2 20 — 23 Income tax expense (benefit) 14 (175) 956 — 795 Net income $ 4,454 $ 2,464 $ 4,865 $ (7,329) $ 4,454 Comprehensive income $ 7,521 $ 4,988 $ 7,922 $ (12,910) $ 7,521 Condensed Consolidating Statements of Operations and Comprehensive Income (Loss) For the Year Ended December 31, 2018 Chubb Limited Chubb INA Other Chubb Consolidating Chubb Limited (in millions of U.S. dollars) Net premiums written $ — $ — $ 30,579 $ — $ 30,579 Net premiums earned — — 30,064 — 30,064 Net investment income 6 13 3,286 — 3,305 Equity in earnings of subsidiaries 3,753 2,578 — (6,331) — Net realized gains (losses) including OTTI — 117 (769) — (652) Losses and loss expenses — — 18,067 — 18,067 Policy benefits — — 590 — 590 Policy acquisition costs and administrative expenses 87 (58) 8,769 — 8,798 Interest (income) expense (299) 806 134 — 641 Other (income) expense (24) 26 (436) — (434) Amortization of purchased intangibles — — 339 — 339 Chubb integration expenses 14 1 44 — 59 Income tax expense (benefit) 19 (148) 824 — 695 Net income $ 3,962 $ 2,081 $ 4,250 $ (6,331) $ 3,962 Comprehensive income (loss) $ 1,242 $ (27) $ 1,808 $ (1,781) $ 1,242 Condensed Consolidating Statement of Cash Flows For the Year Ended December 31, 2020 Chubb Limited Chubb INA Other Chubb Consolidating Chubb Limited (in millions of U.S. dollars) Net cash flows from operating activities $ 1,933 $ 274 $ 10,788 $ (3,210) $ 9,785 Cash flows from investing activities Purchases of fixed maturities available for sale — (49) (26,249) — (26,298) Purchases of fixed maturities held to maturity — — (202) — (202) Purchases of equity securities — — (6,419) — (6,419) Sales of fixed maturities available for sale — 9 11,368 — 11,377 Sales of equity securities — — 3,880 — 3,880 Maturities and redemptions of fixed maturities available for sale — 50 12,400 — 12,450 Maturities and redemptions of fixed maturities held to maturity — — 995 — 995 Net change in short-term investments — 772 (853) — (81) Net derivative instruments settlements — 55 (168) — (113) Private equity contributions — — (1,924) — (1,924) Private equity distributions — — 907 — 907 Payment, including deposit, for Huatai Group interest — — (1,623) — (1,623) Capital contribution (1,200) (72) — 1,272 — Other (2) 4 (472) — (470) Net cash flows from (used for) investing activities (1,202) 769 (8,360) 1,272 (7,521) Cash flows from financing activities Dividends paid on Common Shares (1,388) — — — (1,388) Common Shares repurchased (523) — — — (523) Proceeds from issuance of long-term debt — 988 — — 988 Proceeds from issuance of repurchase agreements — — 2,354 — 2,354 Repayment of long-term debt — (1,301) — — (1,301) Repayment of repurchase agreements — — (2,354) — (2,354) Proceeds from share-based compensation plans — — 145 — 145 Advances (to) from affiliates 1,265 (1,438) 173 — — Dividends to parent company — — (3,210) 3,210 — Capital contribution — — 1,272 (1,272) — Net proceeds from affiliated notional cash pooling programs (1) — 272 — (272) — Policyholder contract deposits and other — — 470 — 470 Policyholder contract withdrawals and other — — (386) — (386) Other — — (87) — (87) Net cash flows used for financing activities (646) (1,479) (1,623) 1,666 (2,082) Effect of foreign currency rate changes on cash and (3) (5) 16 — 8 Net increase (decrease) in cash and restricted cash 82 (441) 821 (272) 190 Cash and restricted cash – beginning of year (1) 2 442 1,202 — 1,646 Cash and restricted cash – end of year (1) $ 84 $ 1 $ 2,023 $ (272) $ 1,836 (1) Chubb maintains two notional multi-currency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information. At December 31, 2020, the cash balance of one or more entities was negative; however, the overall Pool balances were positive. Condensed Consolidating Statement of Cash Flows For the Year Ended December 31, 2019 Chubb Limited Chubb INA Other Chubb Consolidating Chubb Limited (in millions of U.S. dollars) Net cash flows from operating activities $ 412 $ 2,926 $ 6,878 $ (3,874) $ 6,342 Cash flows from investing activities Purchases of fixed maturities available for sale — (21) (25,825) — (25,846) Purchases of fixed maturities held to maturity — — (229) — (229) Purchases of equity securities — — (531) — (531) Sales of fixed maturities available for sale — 1 13,115 — 13,116 Sales of equity securities — — 611 — 611 Maturities and redemptions of fixed maturities available for sale — 41 8,998 — 9,039 Maturities and redemptions of fixed maturities held to maturity — — 946 — 946 Net change in short-term investments — (808) (309) — (1,117) Net derivative instruments settlements — (74) (629) — (703) Private equity contributions — — (1,315) — (1,315) Private equity distributions — — 1,390 — 1,390 Capital contribution (1,000) (110) — 1,110 — Acquisition of subsidiaries (net of cash acquired of $45) — — (29) — (29) Payment, including deposit, for Huatai Group interest — — (580) — (580) Other — (4) (653) — (657) Net cash flows used for investing activities (1,000) (975) (5,040) 1,110 (5,905) Cash flows from financing activities Dividends paid on Common Shares (1,354) — — — (1,354) Common Shares repurchased (327) — (1,203) — (1,530) Proceeds from issuance of long-term debt — 2,828 — — 2,828 Proceeds from issuance of repurchase agreements — — 2,817 — 2,817 Repayment of long-term debt — (500) (10) — (510) Repayment of repurchase agreements — — (2,817) — (2,817) Proceeds from share-based compensation plans — — 204 — 204 Advances (to) from affiliates 2,301 (3,223) 922 — — Dividends to parent company — — (3,874) 3,874 — Capital contribution — — 1,110 (1,110) — Net proceeds payments to affiliated notional cash pooling programs (1) (35) (617) — 652 — Policyholder contract deposits — — 514 — 514 Policyholder contract withdrawals — — (303) — (303) Net cash flows from (used for) financing activities 585 (1,512) (2,640) 3,416 (151) Effect of foreign currency rate changes on cash and restricted cash 4 1 15 — 20 Net increase (decrease) in cash and restricted cash 1 440 (787) 652 306 Cash and restricted cash – beginning of year (1) 1 2 1,989 (652) 1,340 Cash and restricted cash – end of year (1) $ 2 $ 442 $ 1,202 $ — $ 1,646 (1) Chubb maintains two notional multi-currency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information. At December 31, 2018, the cash balance of one or more entities was negative; however, the overall Pool balances were positive. Condensed Consolidating Statement of Cash Flows For the Year Ended December 31, 2018 Chubb Limited Chubb INA Other Chubb Consolidating Chubb Limited (in millions of U.S. dollars) Net cash flows from operating activities $ 256 $ 4,654 $ 5,878 $ (5,308) $ 5,480 Cash flows from investing activities Purchases of fixed maturities available for sale — (38) (24,697) — (24,735) Purchases of fixed maturities held to maturity — — (456) — (456) Purchases of equity securities — — (207) — (207) Sales of fixed maturities available for sale — 11 14,019 — 14,030 Sales of equity securities — — 315 — 315 Maturities and redemptions of fixed maturities available for sale — 17 7,335 — 7,352 Maturities and redemptions of fixed maturities held to maturity — — 1,124 — 1,124 Net change in short-term investments — 3 513 — 516 Net derivative instruments settlements — (7) 23 — 16 Private equity contributions — — (1,337) — (1,337) Private equity distributions — — 980 — 980 Capital contribution (1,475) (3,550) — 5,025 — Other — (18) (515) — (533) Net cash flows used for investing activities (1,475) (3,582) (2,903) 5,025 (2,935) Cash flows from financing activities Dividends paid on Common Shares (1,337) — — — (1,337) Common Shares repurchased — — (1,044) — (1,044) Proceeds from issuance of long-term debt — 2,171 — — 2,171 Proceeds from issuance of repurchase agreements — — 2,029 — 2,029 Repayment of long-term debt — (2,000) (1) — (2,001) Repayment of repurchase agreements — — (2,019) — (2,019) Proceeds from share-based compensation plans — — 115 — 115 Advances (to) from affiliates 2,519 (1,744) (775) — — Dividends to parent company — — (5,308) 5,308 — Capital contribution — — 5,025 (5,025) — Net payments to affiliated notional cash pooling programs (1) 35 502 — (537) — Policyholder contract deposits — — 453 — 453 Policyholder contract withdrawals — — (358) — (358) Net cash flows from (used for) financing activities 1,217 (1,071) (1,883) (254) (1,991) Effect of foreign currency rate changes on cash and restricted cash — — (65) — (65) Net increase (decrease) in cash and restricted cash (2) 1 1,027 (537) 489 Cash and restricted cash – beginning of year (1) 3 1 962 (115) 851 Cash and restricted cash – end of year (1) $ 1 $ 2 $ 1,989 $ (652) $ 1,340 (1) Chubb maintains two notional multi-currency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information. At December 31, 2018 and 2017, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.

Schedule I

Schedule I	12 Months Ended
	Dec. 31, 2020
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Abstract]
Schedule I: SUMMARY OF INVESTEMENTS - OTHER THAN INVESTMENTS IN RELATED PARTIES	SUMMARY OF INVESTMENTS – OTHER THAN INVESTMENTS IN RELATED PARTIES December 31, 2020 (in millions of U.S. dollars) Cost or Amortized Cost, Net (1) Fair Value Amount at Which Shown in the Balance Sheet Fixed maturities available for sale U.S. Treasury / Agency $ 2,471 $ 2,670 $ 2,670 Non-U.S. 24,588 26,354 26,354 Corporate and asset-backed securities 34,081 36,331 36,331 Mortgage-backed securities 17,456 18,470 18,470 Municipal 6,572 6,874 6,874 Total fixed maturities available for sale 85,168 90,699 90,699 Fixed maturities held to maturity U.S. Treasury / Agency 1,392 1,452 1,392 Non-U.S. 1,288 1,405 1,288 Corporate and asset-backed securities 2,150 2,438 2,150 Mortgage-backed securities 1,999 2,146 1,999 Municipal 4,824 5,069 4,824 Total fixed maturities held to maturity 11,653 12,510 11,653 Equity securities Industrial, miscellaneous, and all other 4,027 4,027 4,027 Short-term investments 4,349 4,345 4,345 Other investments (2) 7,826 7,826 7,826 Total investments - other than investments in related parties $ 113,023 $ 119,407 $ 118,550 (1) Net of valuation allowance for expected credit losses. (2) Excludes $119 million of related party investments.

Schedule II

Schedule II	12 Months Ended
	Dec. 31, 2020
Condensed Financial Information Disclosure [Abstract]
Schedule II - CONDENSED FINANCIAL INFORMATION OF REGISTRANT	CONDENSED FINANCIAL INFORMATION OF REGISTRANT BALANCE SHEETS (Parent Company Only) December 31 December 31 (in millions of U.S. dollars) 2020 2019 Assets Investments in subsidiaries and affiliates on equity basis $ 56,148 $ 50,853 Total investments 56,148 50,853 Cash 84 2 Due from subsidiaries and affiliates, net 3,522 4,776 Other assets 10 12 Total assets $ 59,764 $ 55,643 Liabilities Accounts payable, accrued expenses, and other liabilities $ 323 $ 312 Total liabilities 323 312 Shareholders' equity Common Shares 11,064 11,121 Common Shares in treasury (3,644) (3,754) Additional paid-in capital 9,815 11,203 Retained earnings 39,337 36,142 Accumulated other comprehensive income 2,869 619 Total shareholders' equity 59,441 55,331 Total liabilities and shareholders' equity $ 59,764 $ 55,643 The condensed financial information should be read in conjunction with the Consolidated Financial Statements and notes thereto. CONDENSED FINANCIAL INFORMATION OF REGISTRANT STATEMENTS OF OPERATIONS (Parent Company Only) Year Ended December 31 (in millions of U.S. dollars) 2020 2019 2018 Revenues Investment income (1) $ 155 $ 227 $ 305 Equity in net income of subsidiaries and affiliates 3,457 4,307 3,753 3,612 4,534 4,058 Expenses Administrative and other (income) expense 55 65 63 Chubb integration expenses — 1 14 Income tax expense 24 14 19 79 80 96 Net income $ 3,533 $ 4,454 $ 3,962 Comprehensive income $ 5,783 $ 7,521 $ 1,242 (1) Includes net investment income, interest income, and net realized gains (losses). The condensed financial information should be read in conjunction with the Consolidated Financial Statements and notes thereto . STATEMENTS OF CASH FLOWS (Parent Company Only) Year Ended December 31 (in millions of U.S. dollars) 2020 2019 2018 Net cash flows from operating activities (1) $ 1,933 $ 412 $ 256 Cash flows from investing activities Capital contribution (1,200) (1,000) (1,475) Other (2) — — Net cash flows used for investing activities (1,202) (1,000) (1,475) Cash flows from financing activities Dividends paid on Common Shares (1,388) (1,354) (1,337) Common Shares repurchased (523) (327) — Advances from affiliates 1,265 2,301 2,519 Net proceeds from (payments to) affiliated notional cash pooling programs (2) — (35) 35 Net cash flows from (used for) financing activities (646) 585 1,217 Effect of foreign currency rate changes on cash and restricted cash (3) 4 — Net increase (decrease) in cash and restricted cash 82 1 (2) Cash and restricted cash – beginning of year 2 1 3 Cash and restricted cash – end of year $ 84 $ 2 $ 1 (1) Includes cash dividends received from subsidiaries of $2.0 billion, $200 million, and $75 million in 2020, 2019, and 2018, respectively. (2) Chubb maintains two notional multicurrency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information. The condensed financial information should be read in conjunction with the Consolidated Financial Statements and notes thereto.

Schedule IV

Schedule IV	12 Months Ended
	Dec. 31, 2020
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Abstract]
SUPPLEMENTAL INFORMATION CONCERNING REINSURANCE	SUPPLEMENTAL INFORMATION CONCERNING REINSURANCE Premiums Earned For the years ended December 31, 2020, 2019, and 2018 (in millions of U.S. dollars, except for percentages) Direct Amount Ceded To Other Companies Assumed From Other Companies Net Amount Percentage of Amount Assumed to Net 2020 Property and Casualty $ 31,546 $ 6,782 $ 3,044 $ 27,808 11 % Accident and Health 4,249 368 111 3,992 3 % Life 1,242 93 168 1,317 13 % Total $ 37,037 $ 7,243 $ 3,323 $ 33,117 10 % 2019 Property and Casualty $ 30,339 $ 7,236 $ 2,797 $ 25,900 11 % Accident and Health 4,546 376 119 4,289 3 % Life 991 81 191 1,101 17 % Total $ 35,876 $ 7,693 $ 3,107 $ 31,290 10 % 2018 Property and Casualty $ 28,793 $ 6,792 $ 2,812 $ 24,813 11 % Accident and Health 4,409 342 162 4,229 4 % Life 906 85 201 1,022 20 % Total $ 34,108 $ 7,219 $ 3,175 $ 30,064 11 %

Schedule VI

Schedule VI	12 Months Ended
	Dec. 31, 2020
SEC Schedule, 12-18, Supplemental Information, Property-Casualty Insurance Underwriters [Abstract]
SUPPLEMENTARY INFORMATION CONCERNING PROPERTY AND CASUALTY OPERATIONS	SUPPLEMENTARY INFORMATION CONCERNING PROPERTY AND CASUALTY OPERATIONS As of and for the years ended December 31, 2020, 2019, and 2018 (in millions of U.S. dollars) Deferred Policy Acquisition Costs Net Reserves for Unpaid Losses and Loss Expenses Unearned Premiums Net Premiums Earned Net Investment Income Net Losses and Loss Expenses Incurred Related to Amortization of Deferred Policy Acquisition Costs Net Paid Losses and Loss Expenses Net Premiums Written Current Year Prior Year 2020 $ 4,244 $ 53,164 $ 17,652 $ 31,800 $ 3,074 $ 22,124 $ (414) $ 6,076 $ 17,434 $ 32,471 2019 $ 4,161 $ 48,509 $ 16,771 $ 30,189 $ 3,141 $ 19,575 $ (845) $ 5,831 $ 18,473 $ 31,126 2018 $ 3,926 $ 48,271 $ 15,532 $ 29,042 $ 3,047 $ 19,048 $ (981) $ 5,630 $ 18,340 $ 29,505

Summary of significant accoun_2

Summary of significant accounting policies (Policies)	12 Months Ended
	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of presentation	Basis of presentation Chubb Limited is a holding company incorporated in Zurich, Switzerland. Chubb Limited, through its subsidiaries, provides a broad range of insurance and reinsurance products to insureds worldwide. Our results are reported through the following business segments: North America Commercial P&C Insurance, North America Personal P&C Insurance, North America Agricultural Insurance, Overseas General Insurance, Global Reinsurance, and Life Insurance. Refer to Note 15 for additional information. The accompanying Consolidated Financial Statements, which include the accounts of Chubb Limited and its subsidiaries (collectively, Chubb, we, us, or our), have been prepared in accordance with accounting principles generally accepted in the United States of America (GAAP) and, in the opinion of management, reflect all adjustments necessary for a fair statement of the results and financial position for such periods. All significant intercompany accounts and transactions, including internal reinsurance transactions, have been eliminated. The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. Amounts included in the Consolidated Financial Statements reflect our best estimates and assumptions; actual amounts could differ materially from these estimates. Chubb's principal estimates include: • unpaid loss and loss expense reserves, including long-tail asbestos and environmental (A&E) reserves and non-A&E casualty exposures; • future policy benefits reserves; • amortization of deferred policy acquisition costs and value of business acquired (VOBA); • reinsurance recoverable, including a valuation allowance for uncollectible reinsurance; • the assessment of risk transfer for certain structured insurance and reinsurance contracts; • the valuation of the investment portfolio and assessment of valuation allowance for expected credit losses; • the valuation of deferred income taxes; • the valuation of derivative instruments related to guaranteed living benefits (GLB); • the valuation and amortization of purchased intangibles; and • the assessment of goodwill for impairment.
Premiums	Premiums Premiums are generally recorded as written upon inception of the policy. For multi-year policies for which premiums written are payable in annual installments, only the current annual premium is included as written at policy inception due to the ability of the insured/reinsured to commute or cancel coverage within the policy term. The remaining annual premiums are recorded as written at each successive anniversary date within the multi-year term. For property and casualty (P&C) insurance and reinsurance products, premiums written are primarily earned on a pro-rata basis over the policy terms to which they relate. Unearned premiums represent the portion of premiums written applicable to the unexpired portion of the policies in force. For retrospectively-rated policies, written premiums are adjusted to reflect expected ultimate premiums consistent with changes to incurred losses, or other measures of exposure as stated in the policy, and earned over the policy coverage period. Mandatory reinstatement premiums assessed on reinsurance policies are earned in the period of the loss event that gave rise to the reinstatement premiums. All remaining unearned premiums are recognized over the remaining coverage period. Premiums from long-duration contracts such as certain traditional term life, whole life, endowment, and long-duration personal accident and health (A&H) policies are generally recognized as revenue when due from policyholders. Traditional life policies include those contracts with fixed and guaranteed premiums and benefits. Benefits and expenses are matched with income to result in the recognition of profit over the life of the contracts. Retroactive loss portfolio transfer (LPT) contracts in which the insured loss events occurred prior to contract inception are evaluated to determine whether they meet criteria for reinsurance accounting. If reinsurance accounting is appropriate, written premiums are fully earned and corresponding losses and loss expenses recognized at contract inception. These contracts can cause significant variances in gross premiums written, net premiums written, net premiums earned, and net incurred losses in the years in which they are written. Reinsurance contracts sold not meeting the criteria for reinsurance accounting are recorded using the deposit method as described below in Note 1 k). Reinsurance premiums assumed are based on information provided by ceding companies supplemented by our own estimates of premium when we have not received ceding company reports. Estimates are reviewed and adjustments are recorded in the period in which they are determined. Premiums are earned over the coverage terms of the related reinsurance contracts and range from one
Deferred policy acquisition costs and value of business acquired	Deferred policy acquisition costs and value of business acquired Policy acquisition costs consist of commissions (direct and ceded), premium taxes, and certain underwriting costs related directly to the successful acquisition of new or renewal insurance contracts. A VOBA intangible asset is established upon the acquisition of blocks of long-duration contracts in a business combination and represents the present value of estimated net cash flows for the contracts in force at the acquisition date. Acquisition costs and VOBA, collectively policy acquisition costs, are deferred and amortized. Amortization is recorded in Policy acquisition costs in the Consolidated statements of operations. Policy acquisition costs on P&C contracts are generally amortized ratably over the period in which premiums are earned. Policy acquisition costs on traditional long-duration contracts are amortized over the estimated life of the contracts, generally in proportion to premium revenue recognized based upon the same assumptions used in estimating the liability for future policy benefits. For non-traditional long-duration contracts, we amortize policy acquisition costs over the expected life of the contracts in proportion to expected gross profits. The effect of changes in estimates of expected gross profits is reflected in the period the estimates are revised. Policy acquisition costs are reviewed to determine if they are recoverable from future income, including investment income. Unrecoverable policy acquisition costs are expensed in the period identified. Advertising costs are expensed as incurred except for direct-response campaigns that qualify for cost deferral, principally related to long-duration A&H business produced by the Overseas General Insurance segment, which are deferred and recognized as a component of Policy acquisition costs . ten
Reinsurance	Reinsurance Chubb assumes and cedes reinsurance with other insurance companies to provide greater diversification of business and minimize the net loss potential arising from large risks. Ceded reinsurance contracts do not relieve Chubb of its primary obligation to policyholders. For both ceded and assumed reinsurance, risk transfer requirements must be met in order to account for a contract as reinsurance, principally resulting in the recognition of cash flows under the contract as premiums and losses. To meet risk transfer requirements, a reinsurance contract must include insurance risk, consisting of both underwriting and timing risk, and a reasonable possibility of a significant loss for the assuming entity. To assess risk transfer for certain contracts, Chubb generally develops expected discounted cash flow analyses at contract inception. Deposit accounting is used for contracts that do not meet risk transfer requirements. Deposit accounting requires that consideration received or paid be recorded in the balance sheet as opposed to recording premiums written or losses incurred in the statement of operations. Non-refundable fees on deposit contracts are earned based on the terms of the contract described below in Note 1 k). Reinsurance recoverable includes balances due from reinsurance companies for paid and unpaid losses and loss expenses and future policy benefits that will be recovered from reinsurers, based on contracts in force. The method for determining the reinsurance recoverable on unpaid losses and loss expenses incurred but not reported (IBNR) involves actuarial estimates consistent with those used to establish the associated liability for unpaid losses and loss expenses as well as a determination of Chubb's ability to cede unpaid losses and loss expenses under the terms of the reinsurance agreement. Reinsurance recoverable is presented net of a valuation allowance for uncollectible reinsurance determined based upon a review of the financial condition of reinsurers and other factors. The valuation allowance for uncollectible reinsurance is based on an estimate of the reinsurance recoverable balance that will ultimately be unrecoverable due to reinsurer insolvency, a contractual dispute, or any other reason. The valuation of this allowance includes several judgments including certain aspects of the allocation of reinsurance recoverable on IBNR claims by reinsurer and a default analysis to estimate uncollectible reinsurance. The primary components of the default analysis are reinsurance recoverable balances by reinsurer, net of collateral, and default factors used to determine the portion of a reinsurer's balance deemed uncollectible. The definition of collateral for this purpose requires some judgment and is generally limited to assets held in a Chubb-only beneficiary trust, letters of credit, and liabilities held with the same legal entity for which Chubb believes there is a contractual right of offset. The determination of the default factor is principally based on the financial strength rating of the reinsurer. Default factors require considerable judgment and are determined using the current financial strength rating, or rating equivalent, of each reinsurer as well as other key considerations and assumptions. Changes in the valuation allowance for uncollectible reinsurance recoverables are recorded in Losses and loss expenses in the Consolidated statements of operations. Our methodology to calculate the valuation allowance was consistent with the new expected credit loss guidance adopted on January 1, 2020. Therefore, there was no change to the valuation allowance upon adoption . The more significant considerations include, but are not necessarily limited to, the following: • For reinsurers that maintain a financial strength rating from a major rating agency, and for which recoverable balances are considered representative of the larger population (i.e., default probabilities are consistent with similarly rated reinsurers and payment durations conform to averages), the financial rating is based on a published source and the default factor is based on published default statistics of a major rating agency applicable to the reinsurer's particular rating class. When a recoverable is expected to be paid in a brief period of time by a highly rated reinsurer, such as certain property catastrophe claims, a default factor may not be applied; • For balances recoverable from reinsurers that are both unrated by a major rating agency and for which management is unable to determine a credible rating equivalent based on a parent, affiliate, or peer company, we determine a rating equivalent based on an analysis of the reinsurer that considers an assessment of the creditworthiness of the particular entity, industry benchmarks, or other factors as considered appropriate. We then apply the applicable default factor for that rating class. For balances recoverable from unrated reinsurers for which the ceded reserve is below a certain threshold, we generally apply a default factor of 34 percent, consistent with published statistics of a major rating agency; • For balances recoverable from reinsurers that are either insolvent or under regulatory supervision, we establish a default factor and resulting valuation allowance for uncollectible reinsurance based on reinsurer-specific facts and circumstances. Upon initial notification of an insolvency, we generally recognize an expense for a substantial portion of all balances outstanding, net of collateral, through a combination of write-offs of recoverable balances and increases to the valuation allowance for uncollectible reinsurance. When regulatory action is taken on a reinsurer, we generally recognize a default factor by estimating an expected recovery on all balances outstanding, net of collateral. When sufficient credible information becomes available, we adjust the valuation allowance for uncollectible reinsurance by establishing a default factor pursuant to information received; and • For other recoverables, management determines the valuation allowance for uncollectible reinsurance based on the specific facts and circumstances. The methods used to determine the reinsurance recoverable balance and related valuation allowance for uncollectible reinsurance are regularly reviewed and updated, and any resulting adjustments are reflected in earnings in the period identified. The methods used to determine the valuation allowance for uncollectible high deductible recoverable amounts and valuation allowance for insurance and reinsurance balances receivable are similar to the processes used to determine the valuation allowance for uncollectible reinsurance recoverable. For information on high deductible policies, refer to section h) Unpaid losses and loss expenses, below. Prepaid reinsurance premiums represent the portion of premiums ceded to reinsurers applicable to the unexpired coverage terms of the reinsurance contracts in-force.
Investments	Investments Fixed maturities, equity securities, and short-term investments Fixed maturities are classified as either available for sale or held to maturity. • Available for sale (AFS) portfolio is reported at fair value, net of a valuation allowance for credit losses, with changes in fair value recorded as a separate component of AOCI in Shareholders' equity. • Held to maturity (HTM) portfolio includes securities for which we have the ability and intent to hold to maturity or redemption and is reported at amortized cost, net of a valuation allowance for credit losses. Equity securities are reported at fair value with changes in fair value recorded in net realized gains (losses) on the Consolidated statement of operations. Short-term investments comprise securities due to mature within one year of the date of purchase and are recorded at fair value which typically approximates cost. Interest, dividend income, and amortization of fixed maturity market premiums and discounts, related to these securities are recorded in Net investment income, net of investment management and custody fees, in the Consolidated statement of operations. In addition, net investment income includes the amortization of the fair value adjustment related to the acquired invested assets of The Chubb Corporation (Chubb Corp). An adjustment of $1,652 million related to the fair value of Chubb Corp’s fixed maturities securities was recorded (fair value adjustment) at the date of acquisition. At December 31, 2020, the remaining balance of this fair value adjustment was $213 million which is expected to amortize over the next two years; however, the estimate could vary materially based on current market conditions, bond calls, and the duration of the acquired investment portfolio. In addition, sales of these acquired fixed maturities would also reduce the fair value adjustment balance. For mortgage-backed securities and any other holdings for which there is a prepayment risk, prepayment assumptions are evaluated and revised as necessary. Any adjustments required due to the resultant change in effective yields and maturities are recognized prospectively. Prepayment fees or call premiums that are only payable when a security is called prior to its maturity are earned when received and reflected in Net investment income. Valuation allowance for fixed income securities Management evaluates current expected credit losses (CECL) for all HTM securities each quarter. U.S. treasury and agency securities and U.S. government agency mortgage-backed securities are assumed to have no risk of non-payment and therefore are excluded from the CECL evaluation. The remaining HTM securities are evaluated for potential credit loss on a collective pool basis. We elected to pool HTM securities by 1) external credit rating and 2) time to maturity (duration). These characteristics are the most representative of similar risk characteristics within our portfolio. Chubb pools HTM securities and calculates an expected credit loss for each pool using Moody’s corporate bond default average, corporate bond recovery rate, and an economic cycle multiplier. The multiplier is based on the leading economic index and will adjust the average default frequency for a forward-looking economic outlook. Management monitors the credit quality of HTM securities through the review of external credit ratings on a quarterly basis. Management evaluates expected credit losses (ECL) for AFS securities when fair value is below amortized cost. AFS securities are evaluated for potential credit loss on an individual security level but the evaluation may use assumptions consistent with expectations of credit losses for a group of similar securities. If management has the intent to sell or will be required to sell the security before recovery, the entire impairment loss will be recorded through income to net realized gains and losses. If management does not have the intent to sell or will not be required to sell the security before recovery, an allowance for credit losses is established and is recorded through income to net realized gains and losses, and the non-credit loss portion is recorded through other comprehensive income. Examples of criteria that are collectively evaluated to determine if a credit loss has occurred include the following: • The extent to which the fair value is less than amortized cost; • Adverse conditions related to the security, industry, or geographic area; • Downgrades in the security's credit rating by a rating agency; and • Failure of the issuer to make scheduled principal or interest payments AFS securities that meet any one of the criteria included above will be subject to a discounted cash flow analysis by comparing the present value of expected future cash flows with the amortized cost basis. Projected cash flows are driven primarily by assumptions regarding probability of default and the timing and amount of recoveries associated with defaults. Chubb developed the projected cash flows using market data, issuer-specific information, and credit ratings. In combination with contractual cash flows and the use of historical default and recovery data by Moody's Investors Service (Moody's) rating category we generate expected cash flows using the average cumulative issuer-weighted global default rates by letter rating. If the present value of expected future cash flows is less than the amortized cost, a credit loss exists and an allowance for credit losses will be recognized. If the present value of expected future cash flows is equal to or greater than the amortized cost basis, management will conclude an expected credit loss does not exist. Management reviews credit losses and the valuation allowance for expected credit losses each quarter. When all or a portion of a fixed maturity security is identified to be uncollectible and written off, the valuation allowance for expected credit losses is reduced by the same amount. In general, a security is considered uncollectible no later than when all efforts to collect contractual cash flows have been exhausted. Below are considerations for when a security may be deemed uncollectible: • We have sufficient information to determine that the issuer of the security is insolvent; • We receive notice that the issuer of the security has filed for bankruptcy, and the collectability is expected to be adversely impacted by the bankruptcy; • The issuer of a security has violated multiple debt covenants; • Amounts have been past due for a specified period of time with no response from the issuer; • A significant deterioration in the value of the collateral has occurred; • We have received correspondence from the issuer of the security indicating that it doesn’t intend to pay the contractual principal and interest. We elected to not measure an allowance for accrued investment income as uncollectible balances are written off in a timely manner, typically 30 to 45 days after uncollected balances are due. Prior to January 1, 2020, fixed income securities were evaluated individually for other-than-temporary impairment (OTTI) and a realized loss was recognized once certain criteria were met. Other investments Other investments principally comprise investment funds, limited partnerships, partially-owned investment companies, life insurance policies, policy loans, and non-qualified separate account assets. Investment funds and limited partnerships Investment funds, limited partnerships, and all other investments over which Chubb cannot exercise significant influence are accounted for as follows. Generally, we own less than three percent of the investee’s shares. • Income and expenses from these funds are reported within Net investment income. • These funds are carried at net asset value, which approximates fair value with changes in fair value recorded in net realized gains (losses) on the Consolidated statement of operations. Refer to Note 4 for a further discussion on net asset value. • As a result of the timing of the receipt of valuation data from the investment managers, these investments are generally reported on a three-month lag. • Sales of these investments are reported within Net realized gains (losses). Partially-owned investment companies Partially-owned investment companies where our ownership interest is in excess of three percent are accounted for under the equity method because Chubb exerts significant influence. These investments apply investment company accounting to determine operating results, and Chubb retains the investment company accounting in applying the equity method. • This means that investment income, realized gains or losses, and unrealized gains or losses are included in the portion of equity earnings reflected in Other (income) expense. • As a result of the timing of the receipt of valuation data from the investment managers, these investments are generally reported on a three-month lag. Other • Policy loans are carried at outstanding balance and interest income is reflected in Net investment income. • Life insurance policies are carried at policy cash surrender value and income is reflected in Other (income) expense. • Non-qualified separate account assets are supported by assets that do not qualify for separate accounting reporting under GAAP. The underlying securities are recorded on a trade date basis and carried at fair value. Unrealized gains and losses on non-qualified separate account assets are reflected in Other (income) expense. Investments in partially-owned insurance companies Investments in partially-owned insurance companies primarily represent direct investments in which Chubb has significant influence and as such, meet the requirements for equity accounting. Generally, we own twenty percent or more of the investee’s shares. We report our share of the net income or loss of the partially-owned insurance companies in Other (income) expense. Derivative instruments Chubb recognizes all derivatives at fair value in the Consolidated balance sheets in either Accounts payable, accrued expenses, and other liabilities or Other assets. Changes in fair value are included in Net realized gains (losses) in the Consolidated statements of operations. We did not designate any derivatives as accounting hedges. We participate in derivative instruments in two principal ways: (i) To sell protection to customers as an insurance or reinsurance contract that meets the definition of a derivative for accounting purposes . This category principally comprised our GLB contracts; and (ii) To mitigate financial risks and manage certain investment portfolio risks and exposures, including assets and liabilities held in foreign currencies. We use derivative instruments including futures, options, swaps, and foreign currency forward contracts. Refer to Note 10 for additional information. Securities lending program Chubb participates in a securities lending program operated by a third-party banking institution whereby certain assets are loaned to qualified borrowers and from which we earn an incremental return which is recorded within Net investment income in the Consolidated statement of operations. Borrowers provide collateral, in the form of either cash or approved securities, at a minimum of 102 percent of the fair value of the loaned securities. Each security loan is deemed to be an overnight transaction. Cash collateral is invested in a collateral pool which is managed by the banking institution. The collateral pool is subject to written investment guidelines with key objectives which include the safeguard of principal and adequate liquidity to meet anticipated redemptions. The fair value of the loaned securities is monitored on a daily basis, with additional collateral obtained or refunded as the fair value of the loaned securities changes. The collateral is held by the third-party banking institution, and the collateral can only be accessed in the event that the institution borrowing the securities is in default under the lending agreement. As a result of these restrictions, we consider our securities lending activities to be non-cash investing and financing activities. An indemnification agreement with the lending agent protects us in the event a borrower becomes insolvent or fails to return any of the securities on loan. The fair value of the securities on loan is included in fixed maturities and equity securities in the Consolidated balance sheets. The securities lending collateral is reported as a separate line in the Consolidated balance sheets with a related liability reflecting our obligation to return the collateral plus interest. Repurchase agreements Similar to securities lending arrangements, securities sold under repurchase agreements, whereby Chubb sells securities and repurchases them at a future date for a predetermined price, are accounted for as collateralized investments and borrowings and are recorded at the contractual repurchase amounts plus accrued interest. Assets to be repurchased are the same or substantially the same as the assets transferred, and the transferor, through right of substitution, maintains the right and ability to redeem the collateral on short notice. The fair value of the underlying securities is included in fixed maturities and equity securities. In contrast to securities lending programs, the use of cash received is not restricted. We report the obligation to return the cash as Repurchase agreements in the Consolidated balance sheets and record the fees under these repurchase agreements within Interest expense on the Consolidated statement of operations. Refer to Note 4 for a discussion on the determination of fair value for Chubb's various investment securities.
Cash	Cash We have agreements with a third-party bank provider which implemented two international multi-currency notional cash pooling programs. In each program, participating Chubb entities establish deposit accounts in different currencies with the bank provider and each day the credit or debit balances in every account are notionally translated into a single currency (U.S. dollars) and then notionally pooled. The bank extends overdraft credit to any participating Chubb entity as needed, provided that the overall notionally-pooled balance of all accounts in each pool at the end of each day is at least zero. Actual cash balances are not physically converted and are not commingled between legal entities. Any overdraft balances incurred under this program by a Chubb entity would be guaranteed by Chubb Limited (up to $300 million in the aggregate). Our syndicated letter of credit facility allows for same day drawings to fund a net pool overdraft should participating Chubb entities overdraw contributed funds from the pool. Restricted cash Restricted cash in the Consolidated balance sheets represents amounts held for the benefit of third parties and is legally or contractually restricted as to withdrawal or usage. Amounts include deposits with U.S. and non-U.S. regulatory authorities, trust funds set up for the benefit of ceding companies, and amounts pledged as collateral to meet financing arrangements.
Goodwill and other intangible assets	Goodwill and Other intangible assets Goodwill represents the excess of the cost of acquisitions over the fair value of net assets acquired and is not amortized. Goodwill is assigned at acquisition to the applicable reporting unit of the acquired entities giving rise to the goodwill. Goodwill impairment tests are performed annually or more frequently if circumstances indicate a possible impairment. For goodwill impairment testing, we use a qualitative assessment to determine whether it is more likely than not (i.e., more than a 50 percent probability) that the fair value of a reporting unit is greater than its carrying amount. If our assessment indicates less than a 50 percent probability that fair value exceeds carrying value, we quantitatively estimate a reporting unit's fair value. Goodwill recorded in connection with investments in partially-owned insurance companies is recorded in Investments in partially-owned insurance companies and is also measured for impairment annually. Indefinite lived intangible assets are not subject to amortization. Finite lived intangible assets are amortized over their useful lives, generally with an average original useful life of 25 years. Intangible assets are regularly reviewed for indicators of impairment. Impairment is recognized if the carrying amount is not recoverable from its undiscounted cash flows and is measured as the difference between the carrying amount and fair value.
Unpaid losses and loss expenses	Unpaid losses and loss expensesA liability is established for the estimated unpaid losses and loss expenses under the terms of, and with respect to, Chubb's policies and agreements. Similar to premiums that are recognized as revenues over the coverage period of the policy, a liability for unpaid losses and loss expenses is recognized as expense when insured events occur over the coverage period of the policy. This liability includes a provision for both reported claims (case reserves) and incurred but not reported claims (IBNR reserves). IBNR reserve estimates are generally calculated by first projecting the ultimate cost of all losses that have occurred (expected losses), and then subtracting paid losses, case reserves, and loss expenses. The methods of determining such estimates and establishing the resulting liability are reviewed regularly and any adjustments are reflected in income in the period in which they become known. Future developments may result in losses and loss expenses materially greater or less than recorded amounts. Except for net unpaid loss and loss expense reserves of $26 million, net of discount, held at December 31, 2020, representing certain structured settlements for which the timing and amount of future claim payments are reliably determinable and $42 million, net of discount, of certain reserves for unsettled claims, Chubb does not discount its P&C loss reserves. This compares with reserves of $31 million for certain structured settlements and $43 million of certain reserves for unsettled claims at December 31, 2019. Structured settlements represent contracts purchased from life insurance companies primarily to settle workers' compensation claims, where payments to the claimant by the life insurance company are expected to be made in the form of an annuity. Chubb retains the liability to the claimant in the event that the life insurance company fails to pay. At December 31, 2020, the liability due to claimants was $548 million, net of discount, and reinsurance recoverables due from the life insurance companies was $522 million, net of discount. For structured settlement contracts where payments are guaranteed regardless of claimant life expectancy, the amounts recoverable from the life insurance companies at December 31, 2020 are included in Other assets in the Consolidated balance sheets, as they do not meet the requirements for reinsurance accounting. Included in Unpaid losses and loss expenses are liabilities for asbestos and environmental (A&E) claims and expenses. These unpaid losses and loss expenses are principally related to claims arising from remediation costs associated with hazardous waste sites and bodily-injury claims related to asbestos products and environmental hazards. The estimation of these liabilities is particularly sensitive to changes in the legal environment including specific settlements that may be used as precedents to settle future claims. However, Chubb does not anticipate future changes in laws and regulations in setting its A&E reserve levels. Also included in Unpaid losses and loss expenses is the fair value adjustment of $110 million and $145 million at December 31, 2020 and 2019, respectively, related to Chubb Corp’s historical unpaid losses and loss expenses. The estimated fair value consists of the present value of the expected net unpaid loss and loss adjustment expense payments adjusted for an estimated risk margin. The estimated cash flows are discounted at a risk free rate. The estimated risk margin varies based on the inherent risks associated with each type of reserve. The fair value is amortized through Amortization of purchased intangibles on the consolidated statements of operations through the year 2032, based on the estimated payout patterns of unpaid loss and loss expenses at the acquisition date. Our loss reserves are presented net of contractual deductible recoverable amounts due from policyholders. Under the terms of certain high deductible policies which we offer, such as workers’ compensation and general liability, our customers are responsible to reimburse us for an agreed-upon dollar amount per claim. In nearly all cases we are required under such policies to pay covered claims first, and then seek reimbursement for amounts within the applicable deductible from our customers. We generally seek to mitigate this risk through collateral agreements. Prior period development arises from changes to loss estimates recognized in the current year that relate to loss reserves first reported in previous calendar years and excludes the effect of losses from the development of earned premiums from previous accident years. For purposes of analysis and disclosure, management views prior period development to be changes in the nominal value of loss estimates from period to period, net of premium and profit commission adjustments on loss sensitive contracts. Prior period development generally excludes changes in loss estimates that do not arise from the emergence of claims, such as those related to uncollectible reinsurance, interest, unallocated loss adjustment expenses, or foreign currency. Accordingly, specific items excluded from prior period development include the following: gains/losses related to foreign currency remeasurement; losses recognized from the early termination or commutation of reinsurance agreements that principally relate to the time value of money; changes in the value of reinsurance business assumed reflected in losses incurred but principally related to the time value of money; and losses that arise from changes in estimates of earned premiums from prior accident years. Except for foreign currency remeasurement, which is included in Net realized gains (losses), these items are included in current year losses.
Future policy benefits	Future policy benefits The valuation of long-duration contract reserves requires management to make estimates and assumptions regarding expenses, mortality, persistency, and investment yields. Estimates are primarily based on historical experience and include a margin for adverse deviation. Interest rates used in calculating reserves range from less than 1.0 percent to 9.0 percent at December 31, 2020 compared to less than 1.0 percent to 11.0 percent at December 31, 2019. Actual results could differ materially from these estimates. Management monitors actual experience and where circumstances warrant, will revise assumptions and the related reserve estimates. Revisions are recorded in the period they are determined. Certain of our long-duration contracts are supported by assets that do not qualify for separate account reporting under GAAP. These assets are classified as non-qualified separate account assets and reported in Other investments and the offsetting liabilities are reported in Future policy benefits in the Consolidated balance sheets. Changes in the fair value of separate account assets that do not qualify for separate account reporting under GAAP are reported in Other income (expense) and the offsetting movements in the liabilities are included in Policy benefits in the Consolidated statements of operations.
Assumed reinsurance programs involving minimum benefit guarantees under annuity contracts	Assumed reinsurance programs involving minimum benefit guarantees under variable annuity contracts Chubb reinsures various death and living benefit guarantees associated with variable annuities issued primarily in the United States. We generally receive a monthly premium during the accumulation phase of the covered annuities (in-force) based on a percentage of either the underlying accumulated account values or the underlying accumulated guaranteed values. Depending on an annuitant's age, the accumulation phase can last many years. To limit our exposure under these programs, all reinsurance treaties include annual or aggregate claim limits and many include an aggregate deductible. The guarantees which are payable on death, referred to as guaranteed minimum death benefits (GMDB), principally cover shortfalls between accumulated account value at the time of an annuitant's death and either i) an annuitant's total deposits; ii) an annuitant's total deposits plus a minimum annual return; or iii) the highest accumulated account value attained at any policy anniversary date. In addition, a death benefit may be based on a formula specified in the variable annuity contract that uses a percentage of the growth of the underlying contract value. Liabilities for GMDBs are based on cumulative assessments or premiums to date multiplied by a benefit ratio that is determined by estimating the present value of benefit payments and related adjustment expenses divided by the present value of cumulative assessment or expected premiums during the contract period. Under reinsurance programs covering GLBs, we assume the risk of guaranteed minimum income benefits (GMIB) associated with variable annuity contracts. The GMIB risk is triggered if, at the time the contract holder elects to convert the accumulated account value to a periodic payment stream (annuitize), the accumulated account value is not sufficient to provide a guaranteed minimum level of monthly income. Our GLB reinsurance products meet the definition of a derivative for accounting purposes and are carried at fair value with changes in fair value recognized in Realized gains (losses) in the Consolidated statement of operations. Refer to Note 10 a) for additional information.
Deposit assets and liabilities	Deposit assets and liabilities Deposit assets arise from ceded reinsurance contracts purchased that do not transfer significant underwriting or timing risk. Deposit liabilities include reinsurance deposit liabilities and contract holder deposit funds. The reinsurance deposit liabilities arise from contracts sold for which there is not a significant transfer of risk. Contract holder deposit funds represent a liability for investment contracts sold that do not meet the definition of an insurance contract, and certain of these contracts are sold with a guaranteed rate of return. Under deposit accounting, consideration received or paid is recorded as a deposit asset or liability in the balance sheet as opposed to recording premiums and losses in the statement of operations. Interest income on deposit assets, representing the consideration received or to be received in excess of cash payments related to the deposit contract, is earned based on an effective yield calculation. The calculation of the effective yield is based on the amount and timing of actual cash flows at the balance sheet date and the estimated amount and timing of future cash flows. The effective yield is recalculated periodically to reflect revised estimates of cash flows. When a change in the actual or estimated cash flows occurs, the resulting change to the carrying amount of the deposit asset is reported as income or expense. Deposit assets of $107 million and $93 million at December 31, 2020 and 2019, respectively, are reflected in Other assets in the Consolidated balance sheets and the accretion of deposit assets related to interest pursuant to the effective yield calculation is reflected in Net investment income in the Consolidated statements of operations. Deposit liabilities include reinsurance deposit liabilities of $86 million and $88 million and contract holder deposit funds of $2.2 billion and $2.0 billion at December 31, 2020 and 2019, respectively. Deposit liabilities are reflected in Accounts payable, accrued expenses, and other liabilities in the Consolidated balance sheets. At contract inception, the deposit liability equals net cash received. An accretion rate is established based on actuarial estimates whereby the deposit liability is increased to the estimated amount payable over the contract term. The deposit accretion rate is the rate of return required to fund expected future payment obligations. We periodically reassess the estimated ultimate liability and related expected rate of return. Changes to the deposit liability are generally reflected through Interest expense to reflect the cumulative effect of the period the contract has been in force, and by an adjustment to the future accretion rate of the liability over the remaining estimated contract term. The liability for contract holder deposit funds equals accumulated policy account values, which consist of the deposit payments plus credited interest less withdrawals and amounts assessed through the end of the period.
Property, Plant and Equipment, Policy [Policy Text Block]	Property and EquipmentProperty and equipment used in operations are capitalized and carried at cost less accumulated depreciation and are reported within Other assets in the Consolidated balance sheets. At December 31, 2020, property and equipment totaled $2.0 billion, consisting principally of capitalized software costs of $1.3 billion incurred to develop or obtain computer software for internal use and company-owned facilities of $260 million. Depreciation is calculated using the straight-line method over the estimated useful lives of the assets. For capitalized software, the estimated useful life is generally three
Foreign currency remeasurement and translation	Foreign currency remeasurement and translationThe functional currency for each of our foreign operations is generally the currency of the local operating environment. Transactions in currencies other than a foreign operation's functional currency are remeasured into the functional currency, and the resulting foreign exchange gains and losses are reflected in Net realized gains (losses) in the Consolidated statements of operations. Functional currency assets and liabilities are translated into the reporting currency, U.S. dollars, using period end exchange rates and the related translation adjustments are recorded as a separate component of AOCI in Shareholders' equity. Functional statement of operations amounts expressed in functional currencies are translated using average exchange rates.
Administrative expenses	Administrative expensesAdministrative expenses generally include all operating costs other than policy acquisition costs. The North America Commercial P&C Insurance segment manages and uses an in-house third-party claims administrator, ESIS Inc. (ESIS). ESIS performs claims management and risk control services for domestic and international organizations that self-insure P&C exposures as well as internal P&C exposures. The net operating income of ESIS is included within Administrative expenses in the Consolidated statements of operations and were $18 million, $47 million, and $49 million for the years ended December 31, 2020, 2019, and 2018, respectively.
Income taxes	Income taxesIncome taxes have been recorded related to those operations subject to income tax. Deferred tax assets and liabilities result from temporary differences between the amounts recorded in the Consolidated Financial Statements and the tax basis of our assets and liabilities. The effect on deferred tax assets and liabilities of a change in tax law or rates is recognized in the period that includes the enactment date. A valuation allowance against deferred tax assets is recorded if it is more likely than not that all, or some portion, of the benefits related to these deferred tax assets will not be realized. The valuation allowance assessment considers tax planning strategies, where appropriate.We recognize uncertain tax positions that are determined to be more likely than not of being sustained upon examination. Recognized income tax positions are measured at the largest amount that has a greater than 50 percent likelihood of being realized. Changes in recognition or measurement are reflected in the period in which the change in judgment occurs.
Earnings per share	Earnings per shareBasic earnings per share is calculated using the weighted-average shares outstanding, including participating securities with non-forfeitable rights to dividends such as unvested restricted stock. All potentially dilutive securities, including stock options are excluded from the basic earnings per share calculation. In calculating diluted earnings per share, the weighted-average shares outstanding is increased to include all potentially dilutive securities. Basic and diluted earnings per share are calculated by dividing net income by the applicable weighted-average number of shares outstanding during the year.
Share-based compensation	Share-based compensationChubb measures and records compensation cost for all share-based payment awards at grant-date fair value. Compensation costs are recognized for vesting of share-based payment awards with only service conditions on a straight-line basis over the requisite service period for each separately vesting portion of the award as if the award were, in substance, multiple awards. For retirement-eligible participants, compensation costs for certain share-based payment awards are recognized immediately at the date of grant. Refer to Note 12 for additional information.
Chubb integration expenses	Chubb integration expensesDirect costs related to the Chubb Corp acquisition were expensed as incurred. Chubb integration expenses were nil, $23 million, and $59 million for the years ended December 31, 2020, 2019 and 2018, respectively, and include all internal and external costs directly related to the integration activities of the Chubb Corp acquisition. These expenses principally consisted of personnel-related expenses, consulting fees, and rebranding.
New accounting pronouncements	Financial Instruments – Credit Losses: Measurement of Credit Losses on Financial Instruments Effective January 1, 2020, we adopted, on a modified retrospective basis, new guidance on the accounting for credit losses of financial instruments that are measured at amortized cost, including held to maturity securities, and reinsurance recoverables, by applying an approach based on the current expected credit losses (CECL). The estimate of expected credit losses considers historical information, current information, as well as reasonable and supportable forecasts, including estimates of prepayments. In addition, the guidance also replaced the current available for sale (AFS) security other-than-temporary impairment model by requiring an estimate of the expected credit loss (ECL) only when the fair value is below the amortized cost of the asset. The length of time the fair value of an AFS security has been below its amortized cost no longer impacts the determination of whether a potential credit loss exists. The AFS security model also requires the use of a valuation allowance as compared to the previous practice of writing down the asset. In 2020, we recognized a cumulative effect adjustment and decreased beginning retained earnings by $79 million pre-tax, or $72 million after-tax, principally related to the valuation allowance for credit losses. We also adopted the required disclosures within Note 3 Investments and Note 5 Reinsurance. Results for reporting periods prior to January 1, 2020 are presented in accordance with the previous guidance. Adopted in 2021 Income Taxes - Simplifying the Accounting for Income Taxes Effective January 1, 2021, we adopted guidance which is intended to simplify the accounting for income taxes by removing several exceptions contained in existing guidance and amending other guidance. The adoption of the new guidance did not have a material effect on our results of operations or financial condition. Accounting guidance not yet adopted Effects of Reference Rate Reform on Financial Reporting In March 2020, the FASB issued guidance which provides optional expedients and exceptions for applying GAAP to investments, derivatives, or other transactions that reference the London Interbank Offered Rate (LIBOR) or another reference rate expected to be discontinued because of reference rate reform. Along with the optional expedients, the amendments include a general principle that permits an entity to consider contract modifications due to reference reform to be an event that does not require contract re-measurement at the modification date or reassessment of a previous accounting determination. Additionally, a company may make a one-time election to sell, transfer, or both sell and transfer debt securities classified as held to maturity that reference a rate affected by reference rate reform and that were classified as held to maturity before January 1, 2020. This standard may be elected over time through December 31, 2022 as reference rate reform activities occur. Our exposure to LIBOR is limited and, accordingly, we do not expect reference rate reform to have a material impact on our Consolidated Financial Statements. Targeted Improvements to the Accounting for Long-Duration Contracts In August 2018, the FASB issued guidance to improve the existing recognition, measurement, presentation, and disclosure requirements for long-duration contracts issued by an insurance entity. The amendments in this update require more frequent updating of assumptions and a standardized discount rate for the future policy benefit liability, a requirement to use the fair value measurement model for policies with market risk benefits, simplified amortization of deferred acquisition costs, and enhanced disclosures. This standard will be effective in the first quarter of 2023 with early adoption permitted. We are currently assessing the effect of adopting this guidance on our financial condition and results of operations. We will be better able to quantify the effect of adopting this standard as we progress in our implementation process and draw nearer to the date of adoption.

Summary of significant accoun_3

Summary of significant accounting policies Summary of Significant Accounting Policies (Tables) (Tables)	12 Months Ended
	Dec. 31, 2020
Cash and Cash Equivalents [Abstract]
Schedule of Cash and Cash Equivalents [Table Text Block]	The following table provides a reconciliation of cash and restricted cash reported within the Consolidated balance sheets that total to the amounts shown in the Consolidated statements of cash flows: December 31 (in millions of U.S. dollars) 2020 2019 2018 Cash $ 1,747 $ 1,537 $ 1,247 Restricted cash 89 109 93 Total cash and restricted cash shown in the Consolidated statements of cash flows $ 1,836 $ 1,646 $ 1,340

Investments (Tables)

Investments (Tables)	12 Months Ended
	Dec. 31, 2020
Investments, Debt and Equity Securities [Abstract]
Debt securities Available for sale	December 31, 2020 Amortized Cost Valuation Allowance Gross Unrealized Appreciation Gross Unrealized Depreciation Fair Value (in millions of U.S. dollars) Available for sale U.S. Treasury / Agency $ 2,471 $ — $ 199 $ — $ 2,670 Non-U.S. 24,594 (6) 1,808 (42) 26,354 Corporate and asset-backed securities 34,095 (14) 2,322 (72) 36,331 Mortgage-backed securities 17,456 — 1,022 (8) 18,470 Municipal 6,572 — 304 (2) 6,874 $ 85,188 $ (20) $ 5,655 $ (124) $ 90,699 Amortized Cost Valuation Allowance Net Carrying Value Gross Unrealized Appreciation Gross Unrealized Depreciation Fair Held to maturity U.S. Treasury / Agency $ 1,392 $ — $ 1,392 $ 60 $ — $ 1,452 Non-U.S. 1,295 (7) 1,288 118 (1) 1,405 Corporate and asset-backed securities 2,185 (35) 2,150 288 — 2,438 Mortgage-backed securities 2,000 (1) 1,999 148 (1) 2,146 Municipal 4,825 (1) 4,824 245 — 5,069 $ 11,697 $ (44) $ 11,653 $ 859 $ (2) $ 12,510 December 31, 2019 Amortized Gross Gross Fair OTTI Recognized (in millions of U.S. dollars) Available for sale U.S. Treasury / Agency $ 3,188 $ 96 $ (1) $ 3,283 $ — Non-U.S. 22,670 1,099 (62) 23,707 (25) Corporate and asset-backed securities 30,689 1,180 (78) 31,791 (5) Mortgage-backed securities 18,712 494 (14) 19,192 — Municipal 7,321 205 (11) 7,515 — $ 82,580 $ 3,074 $ (166) $ 85,488 $ (30) Held to maturity U.S. Treasury / Agency $ 1,318 $ 29 $ — $ 1,347 $ — Non-U.S. 1,423 62 — 1,485 — Corporate and asset-backed securities 2,349 121 (2) 2,468 — Mortgage-backed securities 2,331 65 — 2,396 — Municipal 5,160 150 (1) 5,309 — $ 12,581 $ 427 $ (3) $ 13,005 $ —
Debt Securities Held to Maturity	December 31, 2020 Amortized Cost Valuation Allowance Gross Unrealized Appreciation Gross Unrealized Depreciation Fair Value (in millions of U.S. dollars) Available for sale U.S. Treasury / Agency $ 2,471 $ — $ 199 $ — $ 2,670 Non-U.S. 24,594 (6) 1,808 (42) 26,354 Corporate and asset-backed securities 34,095 (14) 2,322 (72) 36,331 Mortgage-backed securities 17,456 — 1,022 (8) 18,470 Municipal 6,572 — 304 (2) 6,874 $ 85,188 $ (20) $ 5,655 $ (124) $ 90,699 Amortized Cost Valuation Allowance Net Carrying Value Gross Unrealized Appreciation Gross Unrealized Depreciation Fair Held to maturity U.S. Treasury / Agency $ 1,392 $ — $ 1,392 $ 60 $ — $ 1,452 Non-U.S. 1,295 (7) 1,288 118 (1) 1,405 Corporate and asset-backed securities 2,185 (35) 2,150 288 — 2,438 Mortgage-backed securities 2,000 (1) 1,999 148 (1) 2,146 Municipal 4,825 (1) 4,824 245 — 5,069 $ 11,697 $ (44) $ 11,653 $ 859 $ (2) $ 12,510 December 31, 2019 Amortized Gross Gross Fair OTTI Recognized (in millions of U.S. dollars) Available for sale U.S. Treasury / Agency $ 3,188 $ 96 $ (1) $ 3,283 $ — Non-U.S. 22,670 1,099 (62) 23,707 (25) Corporate and asset-backed securities 30,689 1,180 (78) 31,791 (5) Mortgage-backed securities 18,712 494 (14) 19,192 — Municipal 7,321 205 (11) 7,515 — $ 82,580 $ 3,074 $ (166) $ 85,488 $ (30) Held to maturity U.S. Treasury / Agency $ 1,318 $ 29 $ — $ 1,347 $ — Non-U.S. 1,423 62 — 1,485 — Corporate and asset-backed securities 2,349 121 (2) 2,468 — Mortgage-backed securities 2,331 65 — 2,396 — Municipal 5,160 150 (1) 5,309 — $ 12,581 $ 427 $ (3) $ 13,005 $ —
Debt Securities, Held-to-maturity, Credit Quality Indicator	The following table presents the amortized cost of our HTM securities according to S&P rating: December 31, 2020 (in millions of U.S. dollars) Amortized cost % of Total AAA $ 2,511 22 % AA 6,193 53 % A 2,138 18 % BBB 826 7 % BB 28 — % Other 1 — % Total $ 11,697 100 %
Schedule Of Fixed Maturities By Contractual Maturity	The following table presents fixed maturities by contractual maturity: December 31 December 31 2020 2019 (in millions of U.S. dollars) Net Carrying Value Fair Value Amortized Cost Fair Value Available for sale Due in 1 year or less $ 4,760 $ 4,760 $ 3,951 $ 3,973 Due after 1 year through 5 years 26,227 26,227 27,142 27,720 Due after 5 years through 10 years 27,232 27,232 23,901 24,874 Due after 10 years 14,010 14,010 8,874 9,729 72,229 72,229 63,868 66,296 Mortgage-backed securities 18,470 18,470 18,712 19,192 $ 90,699 $ 90,699 $ 82,580 $ 85,488 Held to maturity Due in 1 year or less $ 1,231 $ 1,240 $ 478 $ 479 Due after 1 year through 5 years 3,592 3,760 3,869 3,940 Due after 5 years through 10 years 3,029 3,228 3,756 3,883 Due after 10 years 1,802 2,136 2,147 2,307 9,654 10,364 10,250 10,609 Mortgage-backed securities 1,999 2,146 2,331 2,396 $ 11,653 $ 12,510 $ 12,581 $ 13,005
Schedule Of Aggregate Fair Value And Gross Unrealized Loss By Length Of Time The Security Has Continuously Been In An Unrealized Loss Position	The following table presents, for AFS fixed maturities in an unrealized loss position (including securities on loan) that are not deemed to have credit losses, the aggregate fair value and gross unrealized loss by length of time the security has continuously been in an unrealized loss position: 0 – 12 Months Over 12 Months Total December 31, 2020 Fair Value Gross Fair Value Gross Fair Value Gross (in millions of U.S. dollars) Non-U.S. $ 1,628 $ (35) $ 114 $ (5) $ 1,742 $ (40) Corporate and asset-backed securities 2,212 (33) 593 (14) 2,805 (47) Mortgage-backed securities 875 (6) 35 (2) 910 (8) Municipal 40 (1) 16 (1) 56 (2) Total AFS fixed maturities $ 4,755 $ (75) $ 758 $ (22) $ 5,513 $ (97) The following table presents, for all securities in an unrealized loss position (including securities on loan), the aggregate fair value and gross unrealized loss by length of time the security has continuously been in an unrealized loss position: 0 – 12 Months Over 12 Months Total December 31, 2019 Fair Value Gross Fair Value Gross Fair Value Gross (in millions of U.S. dollars) U.S. Treasury / Agency $ 234 $ (1) $ 339 $ — $ 573 $ (1) Non-U.S. 1,846 (34) 802 (28) 2,648 (62) Corporate and asset-backed securities 2,121 (40) 988 (40) 3,109 (80) Mortgage-backed securities 1,174 (6) 932 (8) 2,106 (14) Municipal 188 — 276 (12) 464 (12) Total fixed maturities $ 5,563 $ (81) $ 3,337 $ (88) $ 8,900 $ (169)
Schedule Of Net Realized Gains (Losses) And The Losses Included In Net Realized Gains (Losses) And OCI	The following table presents the components of Net realized gains (losses) and the change in net unrealized appreciation (depreciation) of investments: Year Ended December 31 (in millions of U.S. dollars) 2020 2019 2018 Fixed maturities: OTTI on fixed maturities, gross $ — $ (90) $ (52) OTTI on fixed maturities recognized in OCI (pre-tax) — 32 3 OTTI on fixed maturities, net — (58) (49) Gross realized gains excluding OTTI 244 203 334 Gross realized losses excluding OTTI (366) (176) (587) Recovery of expected credit losses 11 — — Impairment (1) (170) — — Total fixed maturities (281) (31) (302) Equity securities 586 104 (59) Other investments (32) (20) (5) Foreign exchange gains (losses) (483) 7 131 Investment and embedded derivative instruments 81 (435) (75) Fair value adjustments on insurance derivative (202) (4) (248) S&P futures (108) (138) (4) Other derivative instruments 1 (8) (3) Other (60) (5) (87) Net realized gains (losses) (pre-tax) $ (498) $ (530) $ (652) Change in net unrealized appreciation (depreciation) on investments (pre-tax): Fixed maturities available for sale $ 2,628 $ 3,769 $ (1,958) Fixed maturities held to maturity (24) (31) (38) Other (12) (3) — Income tax (expense) benefit (462) (647) 297 Change in net unrealized appreciation (depreciation) on investments (after-tax) $ 2,130 $ 3,088 $ (1,699)
Gain (Loss) on Securities [Table Text Block]	Realized gains and losses from Equity securities and Other investments from the table above include sales of securities and unrealized gains and losses from fair value changes as follows: Year Ended December 31, 2020 Year Ended December 31, 2019 Year Ended December 31, 2018 (in millions of U.S. dollars) Equity Securities Other Investments Total Equity Securities Other Investments Total Equity Securities Other Investments Total Net gains (losses) recognized during the period $ 586 $ (32) $ 554 $ 104 $ (20) $ 84 $ (59) $ (5) $ (64) Less: Net gains (losses) recognized from sales of securities 455 — 455 58 (5) 53 70 121 191 Unrealized gains (losses) recognized for securities still held at reporting date $ 131 $ (32) $ 99 $ 46 $ (15) $ 31 $ (129) $ (126) $ (255)
Debt Securities, Available-for-sale, Allowance for Credit Loss	The following table presents a roll-forward of valuation allowance for expected credit losses on fixed maturities: Year Ended December 31 (in millions of U.S. dollars) 2020 Available for sale Valuation allowance for expected credit losses - beginning of period $ — Impact of adoption of new accounting guidance 25 Provision for expected credit loss 188 Initial allowance for purchased securities with credit deterioration 5 Write-offs charged against the expected credit loss (5) Recovery of expected credit loss (193) Valuation allowance for expected credit losses - end of period $ 20 Held to maturity Valuation allowance for expected credit losses - beginning of period $ — Impact of adoption of new accounting guidance 44 Provision for expected credit loss 9 Recovery of expected credit loss (9) Valuation allowance for expected credit losses - end of period $ 44
Debt Securities, Held-to-maturity, Allowance for Credit Loss	The following table presents a roll-forward of valuation allowance for expected credit losses on fixed maturities: Year Ended December 31 (in millions of U.S. dollars) 2020 Available for sale Valuation allowance for expected credit losses - beginning of period $ — Impact of adoption of new accounting guidance 25 Provision for expected credit loss 188 Initial allowance for purchased securities with credit deterioration 5 Write-offs charged against the expected credit loss (5) Recovery of expected credit loss (193) Valuation allowance for expected credit losses - end of period $ 20 Held to maturity Valuation allowance for expected credit losses - beginning of period $ — Impact of adoption of new accounting guidance 44 Provision for expected credit loss 9 Recovery of expected credit loss (9) Valuation allowance for expected credit losses - end of period $ 44
Schedule Of Other Investments	December 31 (in millions of U.S. dollars) 2020 2019 Alternative investments: Partially-owned investment companies $ 5,969 $ 4,142 Limited partnerships 547 508 Investment funds 254 271 Alternative investments 6,770 4,921 Life insurance policies 438 377 Policy loans 233 247 Non-qualified separate account assets (1) 316 283 Other 188 234 Total $ 7,945 $ 6,062
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Table Text Block]	The following table presents, by investment category, the expected liquidation period, fair value, and maximum future funding commitments of alternative investments: December 31 December 31 2020 2019 (in millions of U.S. dollars) Expected Liquidation Fair Value Maximum Fair Value Maximum Financial 2 to 10 Years $ 673 $ 237 $ 611 $ 329 Real Assets 2 to 11 Years 805 598 712 422 Distressed 2 to 8 Years 358 970 263 80 Private Credit 3 to 8 Years 88 270 104 272 Traditional 2 to 14 Years 4,519 1,125 2,844 2,160 Vintage 1 to 2 Years 73 — 116 — Investment funds Not Applicable 254 — 271 — $ 6,770 $ 3,200 $ 4,921 $ 3,263
Schedule Of Sources Of Net Investment Income	Year Ended December 31 (in millions of U.S. dollars) 2020 2019 2018 Fixed maturities (1) $ 3,321 $ 3,385 $ 3,128 Short-term investments 48 84 90 Other interest income 19 25 118 Equity securities 81 26 33 Other investments 82 78 104 Gross investment income (1) 3,551 3,598 3,473 Investment expenses (176) (172) (168) Net investment income (1) $ 3,375 $ 3,426 $ 3,305 (1) Includes amortization expense related to fair value adjustment of acquired invested assets related to the Chubb Corp acquisition $ (116) $ (161) $ (248)
Schedule Of Components Of Restricted Assets	The following table presents the components of restricted assets: December 31 December 31 (in millions of U.S. dollars) 2020 2019 Trust funds $ 12,305 $ 14,004 Deposits with U.S. regulatory authorities 2,438 2,466 Deposits with non-U.S. regulatory authorities 2,905 2,709 Assets pledged under repurchase agreements 1,462 1,464 Other pledged assets 584 490 Total $ 19,694 $ 21,133

Fair value measurements (Tables

Fair value measurements (Tables)	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Schedule Of Significant Unobservable Inputs Used In Level 3 Liability Valuations	The following table presents the significant unobservable inputs used in the Level 3 liability valuations. Excluded from the table below are inputs used to determine the fair value of Level 3 assets which are based on single broker quotes and contain no quantitative unobservable inputs developed by management. The majority of our fixed maturities classified as Level 3 used external pricing when markets are less liquid due to the lack of market inputs (i.e., stale pricing, broker quotes). (in millions of U.S. dollars, except for percentages) Fair Value at December 31 2020 Valuation Significant Ranges Weighted Average (1) GLB (1) $ 1,089 Actuarial model Lapse rate 3% - 34% 4.7 % Annuitization rate 0% - 100% 3.6 % (1) The weighted average lapse and annuitization rates are determined by weighting each treaty's rates by the GLB contracts fair value.
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation	The following tables present a reconciliation of the beginning and ending balances of financial instruments measured at fair value using significant unobservable inputs (Level 3): Assets Liabilities Available-for-Sale Debt Securities Equity Short-term investments Other GLB (1) Year Ended December 31, 2020 Non-U.S. Corporate and asset-backed securities MBS (in millions of U.S. dollars) Balance, beginning of year $ 449 $ 1,451 $ 60 $ 69 $ 6 $ 10 $ 897 Transfers into Level 3 — 134 — — — — — Transfers out of Level 3 (16) (73) (1) (3) — — — Change in Net Unrealized Gains/Losses in OCI 19 (8) — — — — — Net Realized Gains/Losses (1) (30) — 1 (1) — 202 Purchases 274 708 2 23 14 — — Sales (122) (186) — (17) (2) — — Settlements (57) (423) (1) — (12) — — Other — — — — — — (10) Balance, end of year $ 546 $ 1,573 $ 60 $ 73 $ 5 $ 10 $ 1,089 Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date $ — $ (5) $ — $ 4 $ — $ — $ 202 Change in Net Unrealized Gains/Losses included in OCI at the Balance Sheet Date $ 16 $ (6) $ — $ — $ — $ — $ — (1) Our GLB reinsurance product meets the definition of a derivative instrument for accounting purposes and is accordingly carried at fair value. Assets Liabilities Available-for-Sale Debt Securities Equity Short-term investments Other GLB (1) Year Ended December 31, 2019 Non-U.S. Corporate and asset-backed securities MBS (in millions of U.S. dollars) Balance, beginning of year $ 345 $ 1,299 $ 61 $ 57 $ 1 $ 11 $ 861 Transfers into Level 3 11 23 — — — — — Transfers out of Level 3 (24) (38) (16) — — — — Change in Net Unrealized Gains/Losses in OCI 13 (2) — 1 — — — Net Realized Gains/Losses (1) (4) — (2) — — 4 Purchases 228 577 19 34 6 — — Sales (70) (125) (1) (21) — — — Settlements (53) (279) (3) — (1) (1) — Other — — — — — — 32 Balance, end of year $ 449 $ 1,451 $ 60 $ 69 $ 6 $ 10 $ 897 Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date $ — $ (2) $ — $ (3) $ — $ — $ 4 Change in Net Unrealized Gains/Losses included in OCI at the Balance Sheet Date $ 7 $ (8) $ — $ — $ — $ — $ — (1) Our GLB reinsurance product meets the definition of a derivative instrument for accounting purposes and is accordingly carried at fair value. Assets Liabilities Available-for-Sale Debt Securities Short-term investments Other GLB (1) Year Ended December 31, 2018 Non-U.S. Corporate and asset-backed securities MBS Equity Other (in millions of U.S. dollars) Balance, beginning of year $ 93 $ 1,037 $ 78 $ 44 $ — $ 263 $ 2 $ 550 Transfers into Level 3 13 24 1 — 5 — — — Transfers out of Level 3 (2) (31) (3) — — (252) — — Change in Net Unrealized Gains/Losses in OCI (12) (4) — (2) — (2) — — Net Realized Gains/Losses (3) (5) — 6 — 1 (2) 248 Purchases 334 672 5 37 9 50 — — Sales (69) (164) — (28) — — — — Settlements (9) (230) (20) — (13) (49) — — Other — — — — — — — 63 Balance, end of year $ 345 $ 1,299 $ 61 $ 57 $ 1 $ 11 $ — $ 861 Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date $ (1) $ (7) $ — $ (1) $ — $ 1 $ — $ 248
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block]	Assets Liabilities Available-for-Sale Debt Securities Equity Short-term investments Other GLB (1) Year Ended December 31, 2020 Non-U.S. Corporate and asset-backed securities MBS (in millions of U.S. dollars) Balance, beginning of year $ 449 $ 1,451 $ 60 $ 69 $ 6 $ 10 $ 897 Transfers into Level 3 — 134 — — — — — Transfers out of Level 3 (16) (73) (1) (3) — — — Change in Net Unrealized Gains/Losses in OCI 19 (8) — — — — — Net Realized Gains/Losses (1) (30) — 1 (1) — 202 Purchases 274 708 2 23 14 — — Sales (122) (186) — (17) (2) — — Settlements (57) (423) (1) — (12) — — Other — — — — — — (10) Balance, end of year $ 546 $ 1,573 $ 60 $ 73 $ 5 $ 10 $ 1,089 Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date $ — $ (5) $ — $ 4 $ — $ — $ 202 Change in Net Unrealized Gains/Losses included in OCI at the Balance Sheet Date $ 16 $ (6) $ — $ — $ — $ — $ — (1) Our GLB reinsurance product meets the definition of a derivative instrument for accounting purposes and is accordingly carried at fair value. Assets Liabilities Available-for-Sale Debt Securities Equity Short-term investments Other GLB (1) Year Ended December 31, 2019 Non-U.S. Corporate and asset-backed securities MBS (in millions of U.S. dollars) Balance, beginning of year $ 345 $ 1,299 $ 61 $ 57 $ 1 $ 11 $ 861 Transfers into Level 3 11 23 — — — — — Transfers out of Level 3 (24) (38) (16) — — — — Change in Net Unrealized Gains/Losses in OCI 13 (2) — 1 — — — Net Realized Gains/Losses (1) (4) — (2) — — 4 Purchases 228 577 19 34 6 — — Sales (70) (125) (1) (21) — — — Settlements (53) (279) (3) — (1) (1) — Other — — — — — — 32 Balance, end of year $ 449 $ 1,451 $ 60 $ 69 $ 6 $ 10 $ 897 Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date $ — $ (2) $ — $ (3) $ — $ — $ 4 Change in Net Unrealized Gains/Losses included in OCI at the Balance Sheet Date $ 7 $ (8) $ — $ — $ — $ — $ — (1) Our GLB reinsurance product meets the definition of a derivative instrument for accounting purposes and is accordingly carried at fair value. Assets Liabilities Available-for-Sale Debt Securities Short-term investments Other GLB (1) Year Ended December 31, 2018 Non-U.S. Corporate and asset-backed securities MBS Equity Other (in millions of U.S. dollars) Balance, beginning of year $ 93 $ 1,037 $ 78 $ 44 $ — $ 263 $ 2 $ 550 Transfers into Level 3 13 24 1 — 5 — — — Transfers out of Level 3 (2) (31) (3) — — (252) — — Change in Net Unrealized Gains/Losses in OCI (12) (4) — (2) — (2) — — Net Realized Gains/Losses (3) (5) — 6 — 1 (2) 248 Purchases 334 672 5 37 9 50 — — Sales (69) (164) — (28) — — — — Settlements (9) (230) (20) — (13) (49) — — Other — — — — — — — 63 Balance, end of year $ 345 $ 1,299 $ 61 $ 57 $ 1 $ 11 $ — $ 861 Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date $ (1) $ (7) $ — $ (1) $ — $ 1 $ — $ 248
Carrying Values And Fair Values Of Financial Instruments Not Measured At Fair Value	December 31, 2020 Fair Value Net Carrying Value (in millions of U.S. dollars) Level 1 Level 2 Level 3 Total Assets: Fixed maturities held to maturity U.S. Treasury / Agency $ 1,395 $ 57 $ — $ 1,452 $ 1,392 Non-U.S. — 1,405 — 1,405 1,288 Corporate and asset-backed securities — 2,438 — 2,438 2,150 Mortgage-backed securities — 2,146 — 2,146 1,999 Municipal — 5,069 — 5,069 4,824 Total assets $ 1,395 $ 11,115 $ — $ 12,510 $ 11,653 Liabilities: Repurchase agreements $ — $ 1,405 $ — $ 1,405 $ 1,405 Short-term debt — — — — — Long-term debt — 17,487 — 17,487 14,948 Trust preferred securities — 473 — 473 308 Total liabilities $ — $ 19,365 $ — $ 19,365 $ 16,661 December 31, 2019 Fair Value Carrying Value (in millions of U.S. dollars) Level 1 Level 2 Level 3 Total Assets: Fixed maturities held to maturity U.S. Treasury / Agency $ 1,292 $ 55 $ — $ 1,347 $ 1,318 Non-U.S. — 1,485 — 1,485 1,423 Corporate and asset-backed securities — 2,436 32 2,468 2,349 Mortgage-backed securities — 2,396 — 2,396 2,331 Municipal — 5,309 — 5,309 5,160 Total assets $ 1,292 $ 11,681 $ 32 $ 13,005 $ 12,581 Liabilities: Repurchase agreements $ — $ 1,416 $ — $ 1,416 $ 1,416 Short-term debt — 1,307 — 1,307 1,299 Long-term debt — 15,048 — 15,048 13,559 Trust preferred securities — 467 — 467 308 Total liabilities $ — $ 18,238 $ — $ 18,238 $ 16,582

Reinsurance (Tables)

Reinsurance (Tables)	12 Months Ended
	Dec. 31, 2020
Reinsurance Disclosures [Abstract]
Schedule of direct, assumed and ceded premiums	The following table presents direct, assumed, and ceded premiums: Year Ended December 31 (in millions of U.S. dollars) 2020 2019 2018 Premiums written Direct $ 37,749 $ 36,848 $ 34,782 Assumed 3,512 3,276 3,186 Ceded (7,441) (7,849) (7,389) Net $ 33,820 $ 32,275 $ 30,579 Premiums earned Direct $ 37,037 $ 35,876 $ 34,108 Assumed 3,323 3,107 3,175 Ceded (7,243) (7,693) (7,219) Net $ 33,117 $ 31,290 $ 30,064
Schedule of Reinsurance Recoverable on Ceded Insurance [Table Text Block]	b) Reinsurance recoverable on ceded reinsurance December 31, 2020 December 31, 2019 (in millions of U.S. dollars) Net Reinsurance Recoverable (1) Valuation allowance Net Reinsurance Recoverable (1) Valuation allowance Reinsurance recoverable on unpaid losses and loss expenses $ 14,647 $ 257 $ 14,181 $ 240 Reinsurance recoverable on paid losses and loss expenses 945 57 1,000 76 Reinsurance recoverable on losses and loss expenses $ 15,592 $ 314 $ 15,181 $ 316 Reinsurance recoverable on policy benefits $ 206 $ 5 $ 197 $ 4
Reinsurance Recoverable, Allowance for Credit Loss	The following table presents a roll-forward of valuation allowance for uncollectible reinsurance related to Reinsurance recoverable on loss and loss expenses: (in millions of U.S. dollars) Year Ended December 31, 2020 Valuation allowance for uncollectible reinsurance - beginning of period $ 316 Provision for uncollectible reinsurance 21 Write-offs charged against the valuation allowance (25) Foreign exchange revaluation 2 Valuation allowance for uncollectible reinsurance - end of period $ 314
Schedule of reinsurance recoverable and provision by category of reinsurer	December 31, 2020 Gross Reinsurance Recoverable on Loss and Loss Expenses Valuation allowance for Uncollectible Reinsurance % of Gross Reinsurance Recoverable (in millions of U.S. dollars, except for percentages) Categories Largest reinsurers $ 7,267 $ 88 1.2 % Other reinsurers rated A- or better 4,901 58 1.2 % Other reinsurers rated lower than A- or not rated 466 64 13.7 % Pools 366 14 3.8 % Structured settlements 521 11 2.1 % Captives 2,107 11 0.5 % Other 278 68 24.5 % Total $ 15,906 $ 314 2.0 %

Intangible Assets (Tables)

Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill roll-forward by business segment	The following table presents a roll-forward of Goodwill by segment: (in millions of U.S. dollars) North America Commercial P&C Insurance North America Personal P&C Insurance North America Agricultural Insurance Overseas General Insurance Global Reinsurance Life Insurance Chubb Consolidated Balance at December 31, 2018 $ 6,946 $ 2,230 $ 134 $ 4,770 $ 371 $ 820 $ 15,271 Foreign exchange revaluation and other 9 4 — 15 — (3) 25 Balance at December 31, 2019 $ 6,955 $ 2,234 $ 134 $ 4,785 $ 371 $ 817 $ 15,296 Acquisition of Banchile Seguros de Vida — — — 16 — 28 44 Foreign exchange revaluation and other 17 6 — 35 — 2 60 Balance at December 31, 2020 $ 6,972 $ 2,240 $ 134 $ 4,836 $ 371 $ 847 $ 15,400
Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block]	Associated with the Chubb Corp Acquisition For the Years Ending December 31 (in millions of U.S. dollars) Agency Fair value adjustment on Unpaid losses and loss expense (1) Total Other intangible assets Total Amortization of purchased intangibles 2021 $ 217 $ (20) $ 197 $ 89 $ 286 2022 197 (14) 183 101 284 2023 178 (7) 171 96 267 2024 160 (6) 154 90 244 2025 145 (6) 139 89 228 Total $ 897 $ (53) $ 844 $ 465 $ 1,309 (1) In connection with the Chubb Corp acquisition, we recorded an increase to Unpaid losses and loss expenses acquired to adjust the carrying value of Chubb Corp's historical Unpaid losses and loss expenses to fair value as of the acquisition date. This fair value adjustment amortizes through Amortization of purchased intangibles on the Consolidated statements of operations through the year 2032. The balance of the fair value adjustment on Unpaid losses and loss expense was $110 million and $145 million at December 31, 2020 and 2019, respectively. Refer to Note 1(h) for additional information.
VOBA	The following table presents a roll-forward of VOBA: (in millions of U.S. dollars) 2020 2019 2018 Balance, beginning of year $ 306 $ 295 $ 326 Amortization of VOBA (1) (27) (24) (25) Foreign exchange revaluation and other (16) 35 (6) Balance, end of year $ 263 $ 306 $ 295 (1) Recognized in Policy acquisition costs in the Consolidated statements of operations. The following table presents, as of December 31, 2020, the expected estimated pre-tax amortization expense related to VOBA for the next five years at current foreign exchange rates: For the Years Ending December 31 VOBA (in millions of U.S. dollars) 2021 $ 22 2022 21 2023 19 2024 17 2025 16 Total $ 95

Unpaid losses and loss expens_2

Unpaid losses and loss expenses (Tables)	12 Months Ended
	Dec. 31, 2020
Liability for Claims and Claims Adjustment Expense [Abstract]
Schedule Of Unpaid Losses And Loss Expenses Roll Forward	Chubb establishes reserves for the estimated unpaid ultimate liability for losses and loss expenses under the terms of its policies and agreements. Reserves include estimates for both claims that have been reported and for IBNR claims, and include estimates of expenses associated with processing and settling these claims. Reserves are recorded in Unpaid losses and loss expenses in the consolidated balance sheets. While we believe that our reserves for unpaid losses and loss expenses at December 31, 2020 are adequate, new information or trends may lead to future developments in incurred loss and loss expenses significantly greater or less than the reserves provided. Any such revisions could result in future changes in estimates of losses or reinsurance recoverable and would be reflected in our results of operations in the period in which the estimates are changed. The following table presents a reconciliation of beginning and ending Unpaid losses and loss expenses: Year Ended December 31 (in millions of U.S. dollars) 2020 2019 2018 Gross unpaid losses and loss expenses, beginning of year $ 62,690 $ 62,960 $ 63,179 Reinsurance recoverable on unpaid losses (1) (14,181) (14,689) (14,014) Net unpaid losses and loss expenses, beginning of year 48,509 48,271 49,165 Net losses and loss expenses incurred in respect of losses occurring in: Current year 22,124 19,575 19,048 Prior years (2) (414) (845) (981) Total 21,710 18,730 18,067 Net losses and loss expenses paid in respect of losses occurring in: Current year 7,782 7,894 7,544 Prior years 9,652 10,579 10,796 Total 17,434 18,473 18,340 Foreign currency revaluation and other 379 (19) (621) Net unpaid losses and loss expenses, end of year 53,164 48,509 48,271 Reinsurance recoverable on unpaid losses (1) 14,647 14,181 14,689 Gross unpaid losses and loss expenses, end of year $ 67,811 $ 62,690 $ 62,960 (1) Net of valuation allowance for uncollectible reinsurance.
Reconciliation of Claims Development to Liability [Table Text Block]	The following table presents a reconciliation of the loss development tables to the liability for unpaid losses and loss expenses in the consolidated balance sheet: Reconciliation of Reserve Balances to Liability for Unpaid Loss and Loss Expenses (in millions of U.S. dollars) December 31, 2020 Presented in the loss development tables: North America Commercial P&C Insurance — Workers' Compensation $ 9,600 North America Commercial P&C Insurance — Liability 17,441 North America Commercial P&C Insurance — Other Casualty 2,124 North America Commercial P&C Insurance — Non-Casualty 2,491 North America Personal P&C Insurance 3,025 Overseas General Insurance — Casualty 6,832 Overseas General Insurance — Non-Casualty 2,725 Global Reinsurance — Casualty 1,200 Global Reinsurance — Non-Casualty 312 Excluded from the loss development tables: Other 4,742 Net unpaid loss and allocated loss adjustment expense 50,492 Ceded unpaid loss and allocated loss adjustment expense: North America Commercial P&C Insurance — Workers' Compensation $ 1,461 North America Commercial P&C Insurance — Liability 5,743 North America Commercial P&C Insurance — Other Casualty 564 North America Commercial P&C Insurance — Non-Casualty 1,380 North America Personal P&C Insurance 141 Overseas General Insurance — Casualty 2,426 Overseas General Insurance — Non-Casualty 1,686 Global Reinsurance — Casualty 29 Global Reinsurance — Non-Casualty 104 Other 1,153 Ceded unpaid loss and allocated loss adjustment expense 14,687 Unpaid loss and loss expense on other than short-duration contracts (1) 1,109 Unpaid unallocated loss adjustment expenses 1,523 Unpaid losses and loss expenses $ 67,811 (1) Primarily includes the claims reserve of our International A&H business and Life Insurance segment reserves.
Claims Development tables [Table Text Block]	This product line has a substantial geographic spread and a broad mix across industries. Types of coverage include risk management business predominantly with high deductible policies, loss sensitive business (i.e., retrospectively-rated policies), business fronted for captives, as well as excess and primary guaranteed cost coverages. The triangle below shows all loss and allocated expense development for the workers' compensation product line. In our prior period development disclosure, we exclude any loss development where there is a directly related premium adjustment. For workers' compensation, changes in the exposure base due to payroll audits will drive changes in ultimate losses. In addition, we record involuntary pool assumptions (premiums and losses) on a lagged basis. Both of these items will influence the development in the triangle, particularly the first prior accident year, and are included in the reconciliation table presented on page F-58. North America Commercial P&C Insurance — Workers' Compensation — Long-tail (continued) Net Incurred Loss and Allocated Loss Adjustment Expenses Years Ended December 31 As of December 31 2020 (in millions of U.S. dollars) Unaudited Net IBNR Reserves Reported Claims (in thousands) Accident Year 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2011 $ 1,037 $ 1,030 $ 1,046 $ 1,049 $ 1,053 $ 1,022 $ 1,012 $ 1,009 $ 988 $ 973 $ 208 45 2012 1,050 1,011 1,030 1,040 1,011 989 986 977 953 234 44 2013 1,109 1,108 1,122 1,127 1,086 1,073 1,037 1,014 280 43 2014 1,207 1,201 1,217 1,215 1,163 1,100 1,073 347 45 2015 1,282 1,259 1,276 1,279 1,217 1,154 419 50 2016 1,367 1,361 1,383 1,378 1,269 530 51 2017 1,413 1,380 1,399 1,393 723 50 2018 1,359 1,361 1,379 709 51 2019 1,391 1,384 767 47 2020 1,367 1,086 24 Total $ 11,959 Net Cumulative Paid Loss and Allocated Loss Adjustment Expenses Years Ended December 31 (in millions of U.S. dollars) Unaudited Accident Year 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2011 $ 119 $ 294 $ 411 $ 484 $ 533 $ 567 $ 595 $ 616 $ 640 $ 654 2012 111 271 365 436 486 532 574 592 612 2013 107 286 422 506 553 587 616 633 2014 113 295 410 484 532 566 599 2015 116 301 418 501 564 606 2016 122 326 452 529 584 2017 120 313 437 516 2018 130 329 451 2019 143 341 2020 111 Total $ 5,107 Net Liabilities for Loss and Allocated Loss Adjustment Expenses (in millions of U.S. dollars) December 31, 2020 Accident years prior to 2011 $ 2,748 Accident years 2011 - 2020 from tables above 6,852 All Accident years $ 9,600 North America Commercial P&C Insurance — Liability — Long-tail This line consists of primary and excess liability exposures, including medical liability and professional lines, including directors and officers (D&O) liability, errors and omissions (E&O) liability, employment practices liability (EPL), fidelity bonds, and fiduciary liability. The primary and excess liability business represents the largest part of these exposures. The former includes both monoline and commercial package liability. The latter includes a substantial proportion of commercial umbrella, excess and high excess business, where loss activity can produce significant volatility in the loss triangles at later ages within an accident year (and sometimes across years) due to the size of the limits afforded and the complex nature of the underlying losses. This line includes management and professional liability products provided to a wide variety of clients, from national accounts to small firms along with private and not-for-profit organizations, distributed through brokers, agents, wholesalers and MGAs. Many of these coverages, particularly D&O and E&O, are typically written on a claims-made form. While most of the coverages are underwritten on a primary basis, there are significant amounts of excess exposure with large policy limits. Net Incurred Loss and Allocated Loss Adjustment Expenses Years Ended December 31 As of December 31 2020 (in millions of U.S. dollars) Unaudited Net IBNR Reserves Reported Claims (in thousands) Accident Year 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2011 $ 3,500 $ 3,586 $ 3,630 $ 3,665 $ 3,593 $ 3,498 $ 3,384 $ 3,316 $ 3,193 $ 3,143 $ 226 25 2012 3,552 3,628 3,613 3,565 3,524 3,426 3,331 3,235 3,235 353 25 2013 3,547 3,542 3,543 3,533 3,430 3,216 3,122 2,964 317 25 2014 3,535 3,586 3,674 3,717 3,656 3,470 3,346 572 25 2015 3,560 3,709 3,819 3,976 3,943 3,736 855 27 2016 3,534 3,595 3,692 3,805 3,799 962 27 2017 3,322 3,499 3,581 3,631 1,475 27 2018 3,375 3,494 3,696 1,737 28 2019 3,452 3,628 2,381 28 2020 4,098 3,695 24 Total $ 35,276 Net Cumulative Paid Loss and Allocated Loss Adjustment Expenses Years Ended December 31 (in millions of U.S. dollars) Unaudited Accident Year 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2011 $ 160 $ 652 $ 1,209 $ 1,805 $ 2,214 $ 2,477 $ 2,659 $ 2,741 $ 2,827 $ 2,863 2012 166 656 1,172 1,680 2,092 2,326 2,502 2,619 2,688 2013 130 548 1,192 1,597 2,007 2,232 2,374 2,465 2014 164 679 1,250 1,804 2,202 2,442 2,584 2015 138 605 1,206 1,856 2,291 2,533 2016 171 663 1,336 1,975 2,334 2017 161 617 1,162 1,701 2018 190 754 1,303 2019 176 671 2020 152 Total $ 19,294 North America Commercial P&C Insurance — Liability — Long-tail (continued) Net Liabilities for Loss and Allocated Loss Adjustment Expenses (in millions of U.S. dollars) December 31, 2020 Accident years prior to 2011 $ 1,459 Accident years 2011 - 2020 from tables above 15,982 All Accident years $ 17,441 This product line consists of the remaining commercial casualty coverages such as automobile liability and aviation. There is also a small portion of commercial multi-peril (CMP) business in accident years 2014 and prior. The paid and reported data are impacted by some catastrophe loss activity primarily on the CMP exposures just noted. Net Incurred Loss and Allocated Loss Adjustment Expenses Years Ended December 31 As of December 31 2020 (in millions of U.S. dollars) Unaudited Net IBNR Reserves Reported Claims (in thousands) Accident Year 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2011 $ 581 $ 590 $ 581 $ 549 $ 533 $ 525 $ 517 $ 511 $ 513 $ 503 $ 13 16 2012 634 606 577 561 520 519 509 507 505 2 16 2013 527 531 523 516 469 462 462 458 21 18 2014 595 583 581 597 555 539 539 25 17 2015 487 470 502 515 458 455 35 15 2016 504 502 527 524 481 61 16 2017 532 566 577 616 118 17 2018 536 564 575 198 17 2019 606 637 284 16 2020 646 517 9 Total $ 5,415 North America Commercial P&C Insurance — Other-Casualty — Long-tail (continued) Net Cumulative Paid Loss and Allocated Loss Adjustment Expenses Years Ended December 31 (in millions of U.S. dollars) Unaudited Accident Year 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2011 $ 86 $ 235 $ 341 $ 400 $ 437 $ 461 $ 466 $ 480 $ 486 $ 486 2012 69 223 320 387 435 470 487 493 502 2013 69 197 271 348 385 411 419 426 2014 80 220 318 391 455 474 501 2015 47 137 215 305 371 395 2016 52 146 246 323 374 2017 66 175 313 381 2018 74 169 270 2019 70 190 2020 53 Total $ 3,578 Net Liabilities for Loss and Allocated Loss Adjustment Expenses (in millions of U.S. dollars) December 31, 2020 Accident years prior to 2011 $ 287 Accident years 2011 - 2020 from tables above 1,837 All Accident years $ 2,124 This product line represents first party commercial product lines that are short-tailed in nature, such as property, inland marine, ocean marine, surety and A&H. There is a wide diversity of products, primary and excess coverages, and policy sizes. During this ten-year period, this product line was also impacted by natural catastrophes mainly in the 2012, 2017, and 2018 accident years. Net Incurred Loss and Allocated Loss Adjustment Expenses Years Ended December 31 As of December 31 2020 (in millions of U.S. dollars) Unaudited Net IBNR Reserves Reported Claims (in thousands) Accident Year 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2011 $ 1,960 $ 1,934 $ 1,877 $ 1,856 $ 1,835 $ 1,840 $ 1,835 $ 1,835 $ 1,835 $ 1,833 $ 4 416 2012 2,033 1,916 1,883 1,864 1,859 1,847 1,844 1,850 1,844 (8) 426 2013 1,434 1,424 1,337 1,360 1,340 1,340 1,338 1,344 7 455 2014 1,643 1,661 1,579 1,559 1,549 1,550 1,558 10 483 2015 1,736 1,745 1,650 1,638 1,605 1,589 (1) 545 2016 1,911 1,890 1,799 1,782 1,818 32 650 2017 2,704 2,608 2,505 2,522 51 763 2018 2,053 2,240 2,175 71 901 2019 2,052 2,037 166 1,036 2020 3,150 1,061 927 Total $ 19,870 Net Cumulative Paid Loss and Allocated Loss Adjustment Expenses Years Ended December 31 (in millions of U.S. dollars) Unaudited Accident Year 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2011 $ 939 $ 1,574 $ 1,718 $ 1,777 $ 1,787 $ 1,811 $ 1,816 $ 1,821 $ 1,825 $ 1,830 2012 715 1,577 1,698 1,767 1,795 1,822 1,816 1,842 1,844 2013 651 1,138 1,238 1,285 1,311 1,324 1,333 1,335 2014 820 1,374 1,484 1,506 1,532 1,546 1,554 2015 727 1,343 1,488 1,556 1,572 1,574 2016 846 1,504 1,656 1,733 1,761 2017 979 2,087 2,303 2,394 2018 1,027 1,825 2,018 2019 1,030 1,677 2020 1,396 Total $ 17,383 Net Liabilities for Loss and Allocated Loss Adjustment Expenses (in millions of U.S. dollars) December 31, 2020 Accident years prior to 2011 $ 4 Accident years 2011 - 2020 from tables above 2,487 All Accident years $ 2,491 North America Personal P&C Insurance — Short-tail Chubb provides personal lines coverages for high-net-worth individuals and families in North America including homeowners, automobile, valuable articles (including fine art), umbrella liability, and recreational marine insurance offered through independent regional agents and brokers. A portfolio acquired from Fireman’s Fund is presented on a prospective basis beginning in May of accident year 2015. Reserves associated with prior accident periods were acquired through a loss portfolio transfer, which does not allow for a retrospective presentation. During this ten-year period, this segment was also impacted by natural catastrophes, mainly in 2012, 2017 and 2018 accident years. Net Incurred Loss and Allocated Loss Adjustment Expenses Years Ended December 31 As of December 31 2020 (in millions of U.S. dollars) Unaudited Net IBNR Reserves Reported Claims (in thousands) Accident Year 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2011 $ 2,208 $ 2,210 $ 2,185 $ 2,173 $ 2,164 $ 2,161 $ 2,160 $ 2,158 $ 2,159 $ 2,157 $ 7 179 2012 2,185 2,183 2,183 2,191 2,186 2,186 2,189 2,194 2,190 18 188 2013 1,860 1,888 1,897 1,900 1,924 1,937 1,945 1,948 26 132 2014 2,205 2,206 2,192 2,146 2,160 2,147 2,141 14 144 2015 2,494 2,550 2,561 2,544 2,563 2,570 21 148 2016 2,440 2,535 2,545 2,482 2,471 45 154 2017 3,035 3,069 3,002 2,998 96 163 2018 3,010 3,037 3,103 244 169 2019 2,957 2,993 329 155 2020 2,931 1,119 100 Total $ 25,502 Net Cumulative Paid Loss and Allocated Loss Adjustment Expenses Years Ended December 31 (in millions of U.S. dollars) Unaudited Accident Year 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2011 $ 1,360 $ 1,835 $ 1,972 $ 2,052 $ 2,105 $ 2,129 $ 2,139 $ 2,146 $ 2,148 $ 2,149 2012 1,177 1,806 1,957 2,063 2,117 2,149 2,164 2,163 2,165 2013 1,043 1,504 1,688 1,787 1,843 1,885 1,895 1,917 2014 1,310 1,765 1,926 2,035 2,080 2,106 2,116 2015 1,499 2,084 2,271 2,392 2,478 2,508 2016 1,453 2,052 2,211 2,314 2,370 2017 1,698 2,520 2,668 2,799 2018 1,926 2,549 2,706 2019 1,668 2,437 2020 1,334 Total $ 22,501 North America Personal P&C Insurance — Short-tail (continued) Net Liabilities for Loss and Allocated Loss Adjustment Expenses (in millions of U.S. dollars) December 31, 2020 Accident years prior to 2011 $ 24 Accident years 2011 - 2020 from tables above 3,001 All Accident years $ 3,025 This product line is comprised of D&O liability, E&O liability, financial institutions (including crime/fidelity coverages), and non-U.S. general liability as well as aviation and political risk. Exposures are located around the world, including Europe, Latin America, and Asia. Approximately 45 percent of Chubb Overseas General business is generated by European accounts, exclusive of Lloyd's market. There is some U.S. exposure in Casualty from multinational accounts and in financial lines for Lloyd's market. The financial lines coverages are typically written on a claims-made form, while general liability coverages are typically on an occurrence basis and comprised of a mix of primary and excess businesses. Net Incurred Loss and Allocated Loss Adjustment Expenses Years Ended December 31 As of December 31 2020 (in millions of U.S. dollars) Unaudited Net IBNR Reserves Reported Claims (in thousands) Accident Year 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2011 $ 1,255 $ 1,262 $ 1,254 $ 1,244 $ 1,158 $ 1,090 $ 1,079 $ 1,027 $ 1,023 $ 1,025 $ 31 37 2012 1,290 1,261 1,326 1,346 1,343 1,337 1,315 1,304 1,272 87 38 2013 1,281 1,279 1,276 1,322 1,276 1,242 1,182 1,148 86 39 2014 1,279 1,352 1,362 1,378 1,293 1,206 1,165 151 39 2015 1,196 1,296 1,328 1,351 1,326 1,265 199 41 2016 1,232 1,337 1,407 1,437 1,425 341 43 2017 1,227 1,332 1,381 1,433 384 43 2018 1,330 1,383 1,447 671 43 2019 1,409 1,480 809 40 2020 1,810 1,493 28 Total $ 13,470 Overseas General Insurance — Casualty — Long-tail (continued) Net Cumulative Paid Loss and Allocated Loss Adjustment Expenses Years Ended December 31 (in millions of U.S. dollars) Unaudited Accident Year 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2011 $ 86 $ 243 $ 393 $ 528 $ 631 $ 713 $ 789 $ 842 $ 876 $ 901 2012 75 252 441 597 713 857 929 973 1,040 2013 85 267 428 579 725 829 899 952 2014 111 293 473 608 725 811 876 2015 86 287 497 679 802 884 2016 127 324 534 687 815 2017 98 323 535 702 2018 112 334 503 2019 126 341 2020 110 Total $ 7,124 Net Liabilities for Loss and Allocated Loss Adjustment Expenses (in millions of U.S. dollars) December 31, 2020 Accident years prior to 2011 $ 486 Accident years 2011 - 2020 from tables above 6,346 All Accident years $ 6,832 Overseas General Insurance — Non-Casualty — Short-tail (continued) Net Incurred Loss and Allocated Loss Adjustment Expenses Years Ended December 31 As of December 31 2020 (in millions of U.S. dollars) Unaudited Net IBNR Reserves Reported Claims (in thousands) Accident Year 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2011 $ 1,908 $ 1,995 $ 1,938 $ 1,898 $ 1,879 $ 1,867 $ 1,859 $ 1,849 $ 1,844 $ 1,843 $ 6 543 2012 1,712 1,702 1,661 1,605 1,599 1,590 1,575 1,570 1,562 13 555 2013 1,787 1,780 1,714 1,665 1,660 1,633 1,620 1,610 19 573 2014 1,863 1,932 1,875 1,864 1,828 1,817 1,810 7 548 2015 1,963 2,083 2,062 2,030 2,011 2,003 24 571 2016 2,070 2,071 2,058 2,036 2,040 22 581 2017 2,222 2,264 2,245 2,225 18 589 2018 2,186 2,276 2,237 48 624 2019 2,208 2,228 94 640 2020 2,571 804 518 Total $ 20,129 Net Cumulative Paid Loss and Allocated Loss Adjustment Expenses Years Ended December 31 (in millions of U.S. dollars) Unaudited Accident Year 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2011 $ 765 $ 1,486 $ 1,694 $ 1,750 $ 1,780 $ 1,795 $ 1,804 $ 1,808 $ 1,807 $ 1,806 2012 679 1,237 1,425 1,485 1,508 1,518 1,530 1,532 1,532 2013 696 1,284 1,480 1,512 1,549 1,567 1,575 1,578 2014 758 1,438 1,651 1,715 1,746 1,759 1,774 2015 857 1,560 1,793 1,875 1,897 1,927 2016 1,013 1,679 1,881 1,954 1,981 2017 1,051 1,848 2,029 2,106 2018 1,006 1,753 1,962 2019 1,050 1,747 2020 1,085 Total $ 17,498 (in millions of U.S. dollars) December 31, 2020 Accident years prior to 2011 $ 94 Accident years 2011 - 2020 from tables above 2,631 All Accident years $ 2,725 This product line includes proportional and excess coverages in general, automobile liability, professional liability, medical malpractice and workers' compensation, with exposures located around the world. In general, reinsurance exhibits less stable development patterns than primary business. In particular, general casualty reinsurance and excess coverages are long-tailed and can be very volatile. Net Incurred Loss and Allocated Loss Adjustment Expenses Years Ended December 31 As of December 31 (in millions of U.S. dollars) Unaudited Net Accident Year 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2011 $ 408 $ 415 $ 430 $ 433 $ 428 $ 418 $ 415 $ 409 $ 402 $ 389 $ 15 2012 387 384 392 395 379 373 372 374 379 11 2013 321 327 330 331 332 324 317 311 13 2014 334 335 340 343 345 348 331 16 2015 285 290 300 301 309 306 22 2016 224 228 236 236 245 27 2017 215 217 221 218 28 2018 246 249 256 48 2019 239 248 90 2020 247 153 Total $ 2,930 Net Cumulative Paid Loss and Allocated Loss Adjustment Expenses Years Ended December 31 (in millions of U.S. dollars) Unaudited Accident Year 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2011 $ 70 $ 146 $ 195 $ 236 $ 267 $ 292 $ 312 $ 325 $ 332 $ 338 2012 78 168 223 262 293 309 324 336 342 2013 65 143 186 222 242 260 269 272 2014 92 185 218 249 265 277 287 2015 90 159 192 217 233 250 2016 58 113 143 159 175 2017 47 100 122 140 2018 42 96 126 2019 40 90 2020 41 Total $ 2,061 Global Reinsurance — Casualty — Long-tail (continued) Net Liabilities for Loss and Allocated Loss Adjustment Expenses (in millions of U.S. dollars) December 31, 2020 Accident years prior to 2011 $ 331 Accident years 2011 - 2020 from tables above 869 All Accident years $ 1,200 This product line includes property, property catastrophe, marine, credit/surety, A&H and energy. This product line is impacted by natural catastrophes, particularly in the 2011, 2017 and 2018 accident years. Of the non-catastrophe book, the mixture of business varies by year with approximately 77 percent of loss on proportional treaties in treaty year 2011 and after. This percentage has increased over time with the proportion being approximately 59 percent for treaty years 2011 to 2012 growing to an average of 82 percent for treaty years 2013 to 2020, with the remainder being written on an excess of loss basis. Global Reinsurance — Non-Casualty — Short-tail (continued) Net Incurred Loss and Allocated Loss Adjustment Expenses Years Ended December 31 As of December 31 (in millions of U.S. dollars) Unaudited Net Accident Year 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2011 $ 277 $ 279 $ 276 $ 266 $ 267 $ 268 $ 267 $ 268 $ 267 $ 269 $ 1 2012 233 211 202 192 191 188 186 186 184 1 2013 162 160 148 143 144 141 141 140 — 2014 167 182 183 186 184 183 182 3 2015 147 155 162 162 155 161 4 2016 184 189 192 194 190 5 2017 397 424 454 451 10 2018 288 300 303 (8) 2019 143 141 29 2020 212 110 Total $ 2,233 Global Reinsurance — Non-Casualty — Short-tail (continued) Net Cumulative Paid Loss and Allocated Loss Adjustment Expenses Years Ended December 31 (in millions of U.S. dollars) Unaudited Accident Year 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2011 $ 87 $ 179 $ 210 $ 236 $ 254 $ 259 $ 262 $ 263 $ 264 $ 265 2012 45 130 157 167 173 178 180 181 180 2013 46 103 121 131 134 137 137 139 2014 66 131 154 165 171 173 175 2015 56 104 133 143 147 153 2016 57 133 161 172 178 2017 191 322 402 415 2018 94 258 277 2019 35 86 2020 63 Total $ 1,931 Net Liabilities for Loss and Allocated Loss Adjustment Expenses (in millions of U.S. dollars) December 31, 2020 Accident years prior to 2011 $ 10 Accident years 2011 - 2020 from tables above 302 All Accident years $ 312
Supplementary PPD [Table Text Block]	Supplementary Information: (Favorable)/ Adverse Prior Period Development (in millions of U.S. dollars) December 31, 2020 Accident years prior to 2011 $ (94) Accident years 2011 - 2020 from tables above (256) All Accident years $ (350) Supplementary Information: (Favorable)/ Adverse Prior Period Development (in millions of U.S. dollars) December 31, 2020 Accident years prior to 2011 $ (176) Accident years 2011 - 2020 from tables above (117) All Accident years $ (293) Supplementary Information: (Favorable)/ Adverse Prior Period Development (in millions of U.S. dollars) December 31, 2020 Accident years prior to 2011 $ 23 Accident years 2011 - 2020 from tables above 19 All Accident years $ 42 Supplementary Information: (Favorable)/ Adverse Prior Period Development (in millions of U.S. dollars) December 31, 2020 Accident years prior to 2011 $ 2 Accident years 2011 - 2020 from tables above (37) All Accident years $ (35) Supplementary Information: (Favorable)/ Adverse Prior Period Development (in millions of U.S. dollars) December 31, 2020 Accident years prior to 2011 $ (1) Accident years 2011 - 2020 from tables above 85 All Accident years $ 84 Supplementary Information: (Favorable)/ Adverse Prior Period Development (in millions of U.S. dollars) December 31, 2020 Accident years prior to 2011 $ (59) Accident years 2011 - 2020 from tables above 9 All Accident years $ (50) Supplementary Information: (Favorable)/ Adverse Prior Period Development (in millions of U.S. dollars) December 31, 2020 Accident years prior to 2011 $ (8) Accident years 2011 - 2020 from tables above (69) All Accident years $ (77) Supplementary Information: (Favorable)/ Adverse Prior Period Development (in millions of U.S. dollars) December 31, 2020 Accident years prior to 2011 $ (10) Accident years 2011 - 2020 from tables above (12) All Accident years $ (22) Supplementary Information: (Favorable)/ Adverse Prior Period Development (in millions of U.S. dollars) December 31, 2020 Accident years prior to 2011 $ — Accident years 2011 - 2020 from tables above (2) All Accident years $ (2)
Schedule of Historical Claims [Table Text Block]	Supplementary Information: Average Annual Percentage Payout of Net Incurred Claims by Age, as of December 31, 2020 (Unaudited) Age in Years 1 2 3 4 5 6 7 8 9 10 Percentage 10 % 16 % 10 % 7 % 5 % 4 % 3 % 2 % 2 % 1 % Supplementary Information: Average Annual Percentage Payout of Net Incurred Claims by Age, as of December 31, 2020 (Unaudited) Age in Years 1 2 3 4 5 6 7 8 9 10 Percentage 5 % 14 % 17 % 16 % 12 % 7 % 5 % 3 % 2 % 1 % Supplementary Information: Average Annual Percentage Payout of Net Incurred Claims by Age, as of December 31, 2020 (Unaudited) Age in Years 1 2 3 4 5 6 7 8 9 10 Percentage 12 % 23 % 19 % 14 % 10 % 5 % 3 % 2 % 1 % — % North America Commercial P&C Insurance — Non-Casualty — Short-tail (continued) Supplementary Information: Average Annual Percentage Payout of Net Incurred Claims by Age, as of December 31, 2020 (Unaudited) Age in Years 1 2 3 4 5 6 7 8 9 10 Percentage 46 % 38 % 8 % 3 % 1 % 1 % — % 1 % — % — % Supplementary Information: Average Annual Percentage Payout of Net Incurred Claims by Age, as of December 31, 2020 (Unaudited) Age in Years 1 2 3 4 5 6 7 8 9 10 Percentage 57 % 24 % 7 % 5 % 3 % 1 % 1 % — % — % — % Supplementary Information: Average Annual Percentage Payout of Net Incurred Claims by Age, as of December 31, 2020 (Unaudited) Age in Years 1 2 3 4 5 6 7 8 9 10 Percentage 8 % 15 % 15 % 12 % 10 % 8 % 6 % 4 % 4 % 3 % Supplementary Information: Average Annual Percentage Payout of Net Incurred Claims by Age, as of December 31, 2020 (Unaudited) Age in Years 1 2 3 4 5 6 7 8 9 10 Percentage 45 % 35 % 11 % 3 % 2 % 1 % 1 % — % — % — % Supplementary Information: Average Annual Percentage Payout of Net Incurred Claims by Age, as of December 31, 2020 (Unaudited) Age in Years 1 2 3 4 5 6 7 8 9 10 Percentage 21 % 23 % 12 % 10 % 7 % 5 % 4 % 3 % 2 % 2 % Supplementary Information: Average Annual Percentage Payout of Net Incurred Claims by Age, as of December 31, 2020 (Unaudited) Age in Years 1 2 3 4 5 6 7 8 9 10 Percentage 33 % 38 % 14 % 6 % 4 % 2 % 1 % 1 % — % — %
Supplementary PPD Reconciliation [Table Text Block]	The following table presents a reconciliation of the loss development triangles above to prior period development: Components of PPD Year Ended December 31, 2020 (in millions of U.S. dollars) 2011 - 2019 accident years (implied PPD per loss triangles) Accident years prior to 2011 Other (1) PPD on loss reserves RIPs, Expense adjustments, and earned premiums Total North America Commercial P&C Insurance Long-tail $ (354) $ (247) $ (102) $ (703) $ 31 $ (672) Short-tail (37) 2 5 (30) — (30) (391) (245) (97) (2) (733) 31 (3) (702) North America Personal P&C Insurance (Short-tail) 85 (1) (3) 81 (18) 63 Overseas General Insurance Long-tail 9 (59) 1 (49) — (49) Short-tail (69) (8) (24) (101) — (101) (60) (67) (23) (4) (150) — (150) Global Reinsurance Long-tail (12) (10) (1) (23) (2) (25) Short-tail (2) — (1) (3) (1) (4) (14) (10) (2) (26) (3) (29) Subtotal $ (380) $ (323) $ (125) $ (828) $ 10 $ (818) North America Agricultural Insurance (Short-tail) $ (19) $ 9 $ (10) Corporate (Long-tail) 433 — 433 Consolidated PPD $ (414) $ 19 $ (395) (1) Other includes the impact of foreign exchange. (2) Includes favorable development of $80 million related to our Alternative Risk Solutions business (U.S. and Bermuda) and an adjustment to exclude $15 million in unfavorable development in the workers' compensation line, associated with an increase in exposure for which additional premiums were collected; the remaining difference relates to a number of other items, none of which are individually material. (3) Includes premium returns associated with our Alternative Risk Solutions business, which is excluded from the triangles. (4) Includes favorable development of $22 million related to International A&H business; the remaining difference relates to a number of other items, none of which are individually material.
Prior Period Development, by Segment [Table Text Block]	Years Ended December 31 Long-tail Short-tail Total % of beginning net unpaid reserves (1) 2020 North America Commercial P&C Insurance $ (672) $ (30) $ (702) 1.4 % North America Personal P&C Insurance — 63 63 0.1 % North America Agricultural Insurance — (10) (10) — % Overseas General Insurance (49) (101) (150) 0.3 % Global Reinsurance (25) (4) (29) 0.1 % Corporate 433 — 433 0.9 % Total $ (313) $ (82) $ (395) 0.8 % 2019 North America Commercial P&C Insurance $ (668) $ 19 $ (649) 1.3 % North America Personal P&C Insurance — (95) (95) 0.2 % North America Agricultural Insurance — (80) (80) 0.2 % Overseas General Insurance (68) (24) (92) 0.2 % Global Reinsurance (59) 30 (29) 0.1 % Corporate 153 — 153 0.3 % Total $ (642) $ (150) $ (792) 1.6 % 2018 North America Commercial P&C Insurance $ (395) $ (215) $ (610) 1.2 % North America Personal P&C Insurance — 41 41 0.1 % North America Agricultural Insurance — (110) (110) 0.2 % Overseas General Insurance (67) (145) (212) 0.4 % Global Reinsurance (69) 19 (50) 0.1 % Corporate 45 — 45 0.1 % Total $ (486) $ (410) $ (896) 1.8 % (1) Calculated based on the beginning of period consolidated net unpaid losses and loss expenses.
Schedule Of Asbestos Environmental Loss Roll Forward and by segment	The following table presents a roll-forward of consolidated A&E loss reserves including allocated loss expense reserves for A&E exposures, and the valuation allowance for uncollectible paid and unpaid reinsurance recoverables: Asbestos Environmental Total (in millions of U.S. dollars) Gross Net Gross Net Gross Net Balance at December 31, 2017 $ 1,621 $ 1,051 $ 607 $ 476 $ 2,228 $ 1,527 Incurred activity 136 75 101 (97) 237 (22) (1) Paid activity (265) (162) (83) 104 (348) (58) Balance at December 31, 2018 1,492 964 625 483 2,117 1,447 Incurred activity 129 70 46 28 175 98 (1) Paid activity (162) (118) (142) (101) (304) (219) Balance at December 31, 2019 1,459 916 529 410 1,988 1,326 Incurred activity 150 90 79 41 229 131 (1) Paid activity (258) (133) (91) (72) (349) (205) Balance at December 31, 2020 $ 1,351 $ 873 $ 517 $ 379 $ 1,868 $ 1,252 (1) Excludes unallocated loss expenses and the net activity reflects third-party reinsurance other than the aggregate excess of loss reinsurance provided by National Indemnity Company (NICO) to Westchester Specialty (see Westchester Specialty section below). The A&E net loss reserves including allocated loss expense reserves and valuation allowance for uncollectible reinsurance at December 31, 2020 and 2019 shown in the table above is comprised of: December 31 (in millions of U.S. dollars) 2020 2019 Brandywine operations $ 736 $ 754 Westchester Specialty 103 117 Chubb Corp 333 381 Other, mainly Overseas General Insurance 80 74 Total $ 1,252 $ 1,326

Taxation (Tables)

Taxation (Tables)	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Schedule of components of income tax provision	The following table presents pre-tax income and the related provision for income taxes: Year Ended December 31 (in millions of U.S. dollars) 2020 2019 2018 Pre-tax income: Switzerland $ 350 $ 440 $ 950 Outside Switzerland 3,812 4,809 3,707 Total pre-tax income $ 4,162 $ 5,249 $ 4,657 Provision for income taxes Current tax expense: Switzerland $ 52 $ 29 $ 89 Outside Switzerland 876 879 563 Total current tax expense 928 908 652 Deferred tax expense (benefit): Switzerland 2 11 3 Outside Switzerland (301) (124) 40 Total deferred tax expense (benefit) (299) (113) 43 Provision for income taxes $ 629 $ 795 $ 695
Reconciliation schedule of the difference between the provision for income taxes and the expected tax provision at the Swiss statutory income tax rate	The following table presents a reconciliation of the difference between the provision for income taxes and the expected tax provision at the Swiss statutory income tax rate: Year Ended December 31 (in millions of U.S. dollars) 2020 2019 2018 Expected tax provision at Swiss statutory tax rate $ 880 $ 411 $ 365 Permanent differences: Taxes on earnings subject to rate other than Swiss statutory rate (337) 376 372 Tax-exempt interest and dividends received deduction, net of proration (41) (49) (75) Net withholding taxes 67 40 33 Share-based compensation (10) (12) (19) Impact of 2017 Tax Act — — (25) Other 70 29 44 Provision for income taxes $ 629 $ 795 $ 695
Schedule of the components of net deferred tax assets	The following table presents the components of net deferred tax assets and liabilities: December 31 December 31 (in millions of U.S. dollars) 2020 2019 Deferred tax assets: Loss reserve discount $ 884 $ 826 Unearned premiums reserve 496 519 Foreign tax credits 222 247 Provision for uncollectible balances 46 37 Loss carry-forwards 123 143 Debt related amounts 69 74 Compensation related amounts 281 261 Cumulative translation adjustments 120 33 Investments 75 — Lease liability 121 140 Total deferred tax assets 2,437 2,280 Deferred tax liabilities: Deferred policy acquisition costs 522 588 Other intangible assets, including VOBA 1,425 1,468 Un-remitted foreign earnings 77 73 Investments — 40 Unrealized appreciation on investments 957 470 Depreciation 123 157 Lease right-of-use asset 111 129 Other, net 31 45 Total deferred tax liabilities 3,246 2,970 Valuation allowance 83 114 Net deferred tax liabilities $ (892) $ (804)
Reconciliation schedule of unrecognized tax benefits	The following table presents a reconciliation of the beginning and ending amount of gross unrecognized tax benefits: December 31 December 31 (in millions of U.S. dollars) 2020 2019 Balance, beginning of year $ 47 $ 14 Additions based on tax positions related to the current year 5 12 Additions based on tax positions related to prior years 24 23 Reductions for the lapse of the applicable statutes of limitations — (2) Balance, end of year $ 76 $ 47
Summary of Income Tax Examinations [Table Text Block]	The following table summarizes tax years open for examination by major income tax jurisdiction: At December 31, 2020 Australia 2014 - 2020 Canada 2012 - 2020 France 2018 - 2020 Germany 2015 - 2020 Italy 2010 - 2020 Mexico 2014 - 2020 Spain 2012 - 2020 Switzerland 2016 - 2020 United Kingdom 2015 - 2020 United States 2014 - 2020

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2020
Debt Disclosure [Abstract]
Schedule of debt outstanding	December 31 December 31 (in millions of U.S. dollars) 2020 2019 Early Redemption Option Repurchase agreements (weighted average interest rate of 0.3% in 2020 and 2.2% in 2019) $ 1,405 $ 1,416 None Short-term debt Chubb INA: $1,300 million 2.3% due November 2020 $ — $ 1,298 Make-whole premium plus 15 bps Other short-term debt 2.75% due September 2020 — 1 None Total short-term debt $ — $ 1,299 Long-term debt Chubb INA: $1,000 million 2.875% senior notes due November 2022 $ 998 $ 997 Make-whole premium plus 20 bps $475 million 2.7% senior notes due March 2023 474 473 Make-whole premium plus 10 bps $700 million 3.35% senior notes due May 2024 698 697 Make-whole premium plus 15 bps €700 million 0.3% senior notes due December 2024 841 776 Make-whole premium plus 15 bps $800 million 3.15% senior notes due March 2025 797 796 Make-whole premium plus 15 bps $1,500 million 3.35% senior notes due May 2026 1,493 1,492 Make-whole premium plus 20 bps €575 million 0.875% senior notes due June 2027 691 635 Make-whole premium plus 20 bps €900 million 1.55% senior notes due March 2028 1,079 993 Make-whole premium plus 15 bps $100 million 8.875% debentures due August 2029 100 100 None €700 million 0.875% senior notes due December 2029 840 775 Make-whole premium plus 20 bps $1,000 million 1.375% senior notes due September 2030 991 — Make-whole premium plus 15 bps €575 million 1.4% senior notes due June 2031 687 633 Make-whole premium plus 25 bps $200 million 6.8% debentures due November 2031 242 246 Make-whole premium plus 25 bps $300 million 6.7% senior notes due May 2036 298 297 Make-whole premium plus 20 bps $800 million 6.0% senior notes due May 2037 945 953 Make-whole premium plus 20 bps €900 million 2.5% senior notes due March 2038 1,077 992 Make-whole premium plus 25 bps $600 million 6.5% senior notes due May 2038 743 751 Make-whole premium plus 30 bps $475 million 4.15% senior notes due March 2043 470 470 Make-whole premium plus 15 bps $1,500 million 4.35% senior notes due November 2045 1,484 1,483 Make-whole premium plus 25 bps Total long-term debt $ 14,948 $ 13,559 Trust preferred securities Chubb INA capital securities due April 2030 $ 308 $ 308 Redemption prices (1)

Commitments, contingencies, a_2

Commitments, contingencies, and guarantees (Tables)	12 Months Ended
	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Balance Sheet Locations, Fair Values In An Asset Or (Liability) Position, And Notional Values/Payment Provisions Of Derivative Instruments	The following table presents the balance sheet locations, fair values of derivative instruments in an asset or (liability) position, and notional values/payment provisions of our derivative instruments: December 31, 2020 December 31, 2019 Consolidated Fair Value Notional Fair Value Notional Derivative Asset Derivative (Liability) Derivative Asset Derivative (Liability) (in millions of U.S. dollars) Investment and embedded derivative instruments: Foreign currency forward contracts OA / (AP) $ 22 $ (49) $ 2,807 $ 11 $ (78) $ 2,579 Options/Futures contracts on notes, bonds, and equities OA / (AP) 13 (3) 1,749 13 (15) 1,615 Convertible securities (1) FM AFS / ES 9 — 11 4 — 5 $ 44 $ (52) $ 4,567 $ 28 $ (93) $ 4,199 Other derivative instruments: Futures contracts on equities (2) OA / (AP) $ — $ (17) $ 709 $ — $ (13) $ 613 Other OA / (AP) — — 16 2 — 63 $ — $ (17) $ 725 $ 2 $ (13) $ 676 GLB (3) (AP) $ — $ (1,089) $ 1,658 $ — $ (897) $ 1,510 (1) Includes fair value of embedded derivatives. (2) Related to GMDB and GLB book of business. (3) Note that the payment provision related to GLB is the net amount at risk. The concept of a notional value does not apply to the GLB reinsurance contracts.
Secured Borrowings Securities Lending Table	The following table presents the carrying value of collateral held under securities lending agreements by investment category and remaining contractual maturity of the underlying agreements: Remaining contractual maturity December 31, 2020 December 31, 2019 (in millions of U.S. dollars) Overnight and Continuous Collateral held under securities lending agreements: Cash $ 551 $ 346 U.S. Treasury / Agency 148 6 Non-U.S. 1,032 595 Corporate and asset-backed securities 30 5 Mortgage-backed securities 4 18 Equity securities 79 24 $ 1,844 $ 994 Gross amount of recognized liability for securities lending payable $ 1,844 $ 994 At December 31, 2020 and 2019, our repurchase agreement obligations of $1,405 million and $1,416 million, respectively, were fully collateralized. In contrast to securities lending programs, the use of cash received is not restricted for the repurchase obligations. The fair value of the underlying securities sold remains in Fixed maturities available for sale, and the repurchase agreement obligation is recorded in Repurchase agreements in the Consolidated balance sheets. The following table presents the carrying value of collateral pledged under repurchase agreements by investment category and remaining contractual maturity of the underlying agreements: Remaining contractual maturity December 31, 2020 December 31, 2019 30-90 Days Greater than 90 Days Up to 30 Days 30-90 Days Greater than 90 Days Total (in millions of U.S. dollars) Total Collateral pledged under repurchase agreements: Cash $ — $ 4 $ 4 $ 2 $ — $ — $ 2 U.S. Treasury / Agency — 106 106 107 — — 107 Mortgage-backed securities 481 871 1,352 399 476 480 1,355 $ 481 $ 981 $ 1,462 $ 508 $ 476 $ 480 $ 1,464 Gross amount of recognized liabilities for repurchase agreements $ 1,405 $ 1,416 Difference (1) $ 57 $ 48 (1) Per the repurchase agreements, the amount of collateral posted is required to exceed the amount of gross liability.
Derivative Instruments, Gain (Loss) [Table Text Block]	The following table presents net realized gains (losses) related to derivative instrument activity in the Consolidated statements of operations: Year Ended December 31 (in millions of U.S. dollars) 2020 2019 2018 Investment and embedded derivative instruments: Foreign currency forward contracts $ 65 $ (79) $ 3 Interest rate swaps — (270) (115) All other futures contracts, options, and equities 16 (88) 39 Convertible securities (1) — 2 (2) Total investment and embedded derivative instruments $ 81 $ (435) $ (75) GLB and other derivative instruments: GLB $ (202) $ (4) $ (248) Futures contracts on equities (2) (108) (138) (4) Other 1 (8) (3) Total GLB and other derivative instruments $ (309) $ (150) $ (255) $ (228) $ (585) $ (330) (1) Includes embedded derivatives.
Schedule of Future Minimum Rental Payments for Operating Leases	Future minimum lease payments under the operating leases are expected to be as follows: For the years ending December 31 (in millions of U.S. dollars) Undiscounted cash flows: 2021 $ 150 2022 123 2023 96 2024 68 2025 38 Thereafter 75 Total undiscounted lease payments $ 550 Less: Present value adjustment 33 Net lease liabilities reported as of December 31, 2020 $ 517

Shareholders' equity note (Tabl

Shareholders' equity note (Tables)	12 Months Ended
	Dec. 31, 2020
Stockholders' Equity Note [Abstract]
Dividends Declared [Table Text Block]	The following table presents dividend distributions per Common Share in Swiss francs (CHF) and U.S. dollars (USD): Year Ended December 31 2020 2019 2018 CHF USD CHF USD CHF USD Total dividend distributions per common share 2.89 $ 3.09 2.94 $ 2.98 2.84 $ 2.90
Schedule of changes in Common Shares issued and outstanding	Year Ended December 31 2020 2019 2018 Common Shares authorized and issued, beginning of year 479,783,864 479,783,864 479,783,864 Cancellation of treasury shares (2,178,600) — — Common Shares authorized and issued, end of year 477,605,264 479,783,864 479,783,864 Common Shares in treasury, beginning of year (at cost) (27,812,297) (20,580,486) (15,950,685) Net shares issued under employee share-based compensation plans 2,345,208 3,210,427 3,089,234 Shares repurchased (3,584,150) (10,442,238) (7,719,035) Cancellation of treasury shares 2,178,600 — — Common Shares in treasury, end of year (at cost) (26,872,639) (27,812,297) (20,580,486) Common Shares outstanding, end of year 450,732,625 451,971,567 459,203,378
Share Repurchase Program [Table Text Block]	The following table presents repurchases of Chubb's Common Shares conducted in a series of open market transactions under the Board authorizations: Year Ended December 31 January 1, 2021 through (in millions of U.S. dollars, except share data) 2020 2019 2018 February 24, 2021 Number of shares repurchased 3,584,150 10,442,238 7,719,035 1,971,000 Cost of shares repurchased (1) $ 516 $ 1,531 $ 1,021 $ 327

Share-based compensation (Table

Share-based compensation (Tables)	12 Months Ended
	Dec. 31, 2020
Share-based Payment Arrangement [Abstract]
Schedule of pre-tax and after-tax share-based compensation expense	The following table presents pre-tax and after-tax share-based compensation expense: Year Ended December 31 (in millions of U.S. dollars) 2020 2019 2018 Stock options and shares issued under ESPP: Pre-tax $ 45 $ 42 $ 50 After-tax (1) $ 38 $ 39 $ 40 Restricted stock: Pre-tax $ 210 $ 224 $ 235 After-tax (1) $ 164 $ 180 $ 178
Schedule of the weighted-average model valuation assumptions	Year Ended December 31 2020 2019 2018 Dividend yield 2.1 % 2.2 % 2.0 % Expected volatility 18.0 % 16.0 % 23.2 % Risk-free interest rate 1.2 % 2.6 % 2.7 % Expected life 5.7 years 5.7 years 5.7 years
Rollforward of the company's stock options	The following table presents a roll-forward of Chubb's stock options: (Intrinsic Value in millions of U.S. dollars) Number of Options Weighted-Average Exercise Price Weighted-Average Fair Value Total Intrinsic Value Options outstanding, December 31, 2017 10,433,316 $ 99.20 Granted 1,842,690 $ 143.07 $ 29.71 Exercised (1,065,384) $ 73.57 $ 71 Forfeited and expired (202,900) $ 133.92 Options outstanding, December 31, 2018 11,007,722 $ 108.25 Granted 2,073,940 $ 133.90 $ 18.76 Exercised (1,944,604) $ 84.13 $ 122 Forfeited and expired (251,801) $ 136.87 Options outstanding, December 31, 2019 10,885,257 $ 116.79 Granted 1,958,279 $ 150.10 $ 19.89 Exercised (1,158,633) $ 86.90 $ 76 Forfeited and expired (206,720) $ 138.77 Options outstanding, December 31, 2020 11,478,183 $ 125.09 $ 331 Options exercisable, December 31, 2020 7,792,343 $ 116.35 $ 293
Rollforward of the company's restricted stock	The following table presents a roll-forward of our restricted stock awards. Included in the roll-forward below are 27,679 restricted stock awards, 19,019 restricted stock awards, and 20,784 restricted stock awards that were granted to non-management directors during the years ended December 31, 2020, 2019, and 2018, respectively: Service-based Performance-based Number of Shares Weighted-Average Number of Shares Weighted-Average Unvested restricted stock, December 31, 2017 4,709,442 $ 121.16 975,497 $ 118.28 Granted 1,326,979 $ 142.76 180,065 $ 143.07 Vested (2,545,090) $ 114.83 (244,332) $ 103.03 Forfeited (196,482) $ 131.06 — $ — Unvested restricted stock, December 31, 2018 3,294,849 $ 134.17 911,230 $ 127.27 Granted 1,492,900 $ 134.38 212,059 $ 133.90 Vested (1,292,864) $ 129.18 (196,640) $ 115.62 Forfeited (200,875) $ 135.98 (50,437) $ 132.36 Unvested restricted stock, December 31, 2019 3,294,010 $ 136.20 876,212 $ 131.16 Granted 1,425,667 $ 148.56 186,291 $ 151.14 Vested (1,304,308) $ 134.02 (490,185) $ 125.66 Forfeited (152,074) $ 140.72 — $ — Unvested restricted stock, December 31, 2020 3,263,295 $ 142.32 572,318 $ 142.38

Postretirement benefits (Tables

Postretirement benefits (Tables)	12 Months Ended
	Dec. 31, 2020
Retirement Benefits [Abstract]
Schedule of Net Funded Status [Table Text Block]	Obligations and funded status The funded status of the pension and other postretirement benefit plans as well as the amounts recognized in Accumulated other comprehensive income at December 31, 2020 and 2019 was as follows: Pension Benefit Plans Other Postretirement 2020 2019 2020 2019 U.S. Plans Non-U.S. Plans U.S. Plans Non-U.S. Plans (in millions of U.S. dollars) Benefit obligation, beginning of year $ 3,569 $ 1,042 $ 3,092 $ 942 $ 103 $ 113 Service cost — 4 49 11 1 — Interest cost 99 22 118 27 2 4 Actuarial loss (gain) 441 135 443 124 1 3 Benefits paid (127) (31) (121) (39) (20) (17) Curtailments — (2) — (4) — — Settlements (15) — (12) (61) — — Foreign currency revaluation and other — 29 — 42 (1) — Benefit obligation, end of year $ 3,967 $ 1,199 $ 3,569 $ 1,042 $ 86 $ 103 Plan assets at fair value, beginning of year $ 3,301 $ 1,141 $ 2,784 $ 1,008 $ 152 $ 143 Actual return on plan assets 563 126 636 169 6 9 Employer contributions 17 19 14 16 1 — Benefits paid (127) (31) (121) (39) (39) — Settlements (15) — (12) (61) — — Foreign currency revaluation and other — 29 — 48 — — Plan assets at fair value, end of year $ 3,739 $ 1,284 $ 3,301 $ 1,141 $ 120 $ 152 Funded status at end of year $ (228) $ 85 $ (268) $ 99 $ 34 $ 49 Amounts recognized in Accumulated other comprehensive Net actuarial loss (gain) $ 78 $ 163 $ (21) $ 110 $ (5) $ (3) Prior service cost (benefit) — 9 — 10 (31) (114) Total $ 78 $ 172 $ (21) $ 120 $ (36) $ (117)
Schedule of Amounts Recognized in Other Comprehensive Income (Loss) [Table Text Block]	The funded status of the pension and other postretirement benefit plans as well as the amounts recognized in Accumulated other comprehensive income at December 31, 2020 and 2019 was as follows: Pension Benefit Plans Other Postretirement 2020 2019 2020 2019 U.S. Plans Non-U.S. Plans U.S. Plans Non-U.S. Plans (in millions of U.S. dollars) Benefit obligation, beginning of year $ 3,569 $ 1,042 $ 3,092 $ 942 $ 103 $ 113 Service cost — 4 49 11 1 — Interest cost 99 22 118 27 2 4 Actuarial loss (gain) 441 135 443 124 1 3 Benefits paid (127) (31) (121) (39) (20) (17) Curtailments — (2) — (4) — — Settlements (15) — (12) (61) — — Foreign currency revaluation and other — 29 — 42 (1) — Benefit obligation, end of year $ 3,967 $ 1,199 $ 3,569 $ 1,042 $ 86 $ 103 Plan assets at fair value, beginning of year $ 3,301 $ 1,141 $ 2,784 $ 1,008 $ 152 $ 143 Actual return on plan assets 563 126 636 169 6 9 Employer contributions 17 19 14 16 1 — Benefits paid (127) (31) (121) (39) (39) — Settlements (15) — (12) (61) — — Foreign currency revaluation and other — 29 — 48 — — Plan assets at fair value, end of year $ 3,739 $ 1,284 $ 3,301 $ 1,141 $ 120 $ 152 Funded status at end of year $ (228) $ 85 $ (268) $ 99 $ 34 $ 49 Amounts recognized in Accumulated other comprehensive Net actuarial loss (gain) $ 78 $ 163 $ (21) $ 110 $ (5) $ (3) Prior service cost (benefit) — 9 — 10 (31) (114) Total $ 78 $ 172 $ (21) $ 120 $ (36) $ (117)
Defined Benefit Plan, Plan with Projected Benefit Obligation in Excess of Plan Assets [Table Text Block]	The following table provides information on pension plans where the benefit obligation is in excess of plan assets at December 31, 2020 and 2019: 2020 2019 U.S. Plans Non-U.S. Plans U.S. Plans Non-U.S. Plans (in millions of U.S. dollars) Plans with projected benefit obligation in excess of plan assets: Projected benefit obligation $ 3,967 $ 629 $ 3,569 $ 236 Fair value of plan assets 3,739 568 3,301 175 Net funded status $ (228) $ (61) $ (268) $ (61) Plans with accumulated benefit obligation in excess of plan assets: Accumulated benefit obligation $ 3,967 $ 593 $ 3,569 $ 173 Fair value of plan assets $ 3,739 $ 565 $ 3,301 $ 140
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets [Table Text Block]	The following table provides information on pension plans where the benefit obligation is in excess of plan assets at December 31, 2020 and 2019: 2020 2019 U.S. Plans Non-U.S. Plans U.S. Plans Non-U.S. Plans (in millions of U.S. dollars) Plans with projected benefit obligation in excess of plan assets: Projected benefit obligation $ 3,967 $ 629 $ 3,569 $ 236 Fair value of plan assets 3,739 568 3,301 175 Net funded status $ (228) $ (61) $ (268) $ (61) Plans with accumulated benefit obligation in excess of plan assets: Accumulated benefit obligation $ 3,967 $ 593 $ 3,569 $ 173 Fair value of plan assets $ 3,739 $ 565 $ 3,301 $ 140
Defined Benefit Plan, Assumptions [Table Text Block]	The weighted-average assumptions used to determine the projected benefit obligation were as follows: Pension Benefit Plans U.S. Non-U.S. Other Postretirement Benefit Plans December 31, 2020 Discount rate 2.32 % 1.80 % 1.36 % Rate of compensation increase (1) N/A 3.24 % N/A Interest crediting rate 4.10 % December 31, 2019 Discount rate 3.20 % 2.39 % 2.70 % Rate of compensation increase (1) N/A 3.26 % N/A Interest crediting rate 4.10 %
Schedule of Net Benefit Costs [Table Text Block]	The components of net pension and other postretirement benefit costs reflected in Net income and other changes in plan assets and benefit obligations recognized in other comprehensive income were as follows: Pension Benefit Plans Other Postretirement U.S. Plans Non-U.S. Plans Year Ended December 31 2020 2019 2018 2020 2019 2018 2020 2019 2018 (in millions of U.S. dollars) Costs reflected in Net income: Service cost $ — $ 49 $ 57 $ 4 $ 11 $ 12 $ 1 $ — $ 1 Non-service cost: Interest cost 99 118 105 22 27 27 2 4 3 Expected return on plan assets (224) (189) (212) (41) (45) (50) (5) (4) (5) Amortization of net actuarial loss — — — 2 3 1 — — — Amortization of prior service cost — — — — — — (83) (84) (85) Curtailments — — — (1) (1) — — — (2) Settlements 3 2 2 — 1 3 — — — Total non-service benefit (122) (69) (105) (18) (15) (19) (86) (84) (89) Net periodic benefit $ (122) $ (20) $ (48) $ (14) $ (4) $ (7) $ (85) $ (84) $ (88) Changes in plan assets and benefit obligations recognized in other comprehensive income Net actuarial loss (gain) $ 102 $ (4) $ 214 $ 56 $ 6 $ 34 $ (2) $ (2) $ (11) Prior service cost (benefit) — — — — 1 3 — — — Amortization of net actuarial loss — — — (2) (3) (1) — — (1) Amortization of prior service cost — — — (1) — — 83 84 85 Curtailments — — — (1) (3) — — — 3 Settlements (3) (2) (2) — (1) (3) — — — Total decrease (increase) in other comprehensive income $ 99 $ (6) $ 212 $ 52 $ — $ 33 $ 81 $ 82 $ 76 The line items in which the service and non-service cost components of net periodic (benefit) cost are included in the Consolidated statements of operations were as follows: Pension Benefit Plans Other Postretirement Benefit Plans Year Ended December 31 2020 2019 2018 2020 2019 2018 (in millions of U.S. dollars) Service cost: Losses and loss expenses $ — $ 6 $ 7 $ — $ — $ — Administrative expenses 4 54 62 1 — 1 Total service cost 4 60 69 1 — 1 Non-service cost: Losses and loss expenses (12) (7) (10) (9) (8) (9) Administrative expenses (128) (77) (114) (77) (76) (80) Total non-service benefit (140) (84) (124) (86) (84) (89) Net periodic benefit $ (136) $ (24) $ (55) $ (85) $ (84) $ (88)
Schedule of assumptions used, net periodic benefit costs [Table Text Block]	he weighted-average assumptions used to determine the net periodic pension and other postretirement benefit costs were as follows: Pension Benefit Plans U.S. Plans Non-U.S. Plans Other Postretirement Benefit Plans Year Ended December 31 2020 Discount rate in effect for determining service cost N/A 6.04 % 3.00 % Discount rate in effect for determining interest cost 2.85 % 2.24 % 2.64 % Rate of compensation increase N/A 3.26 % N/A Expected long-term rate of return on plan assets 7.00 % 3.83 % 3.00 % Interest crediting rate 4.10 % N/A N/A 2019 Discount rate in effect for determining service cost 4.23 % 4.48 % 4.04 % Discount rate in effect for determining interest cost 3.94 % 2.88 % 3.69 % Rate of compensation increase 4.00 % 3.37 % N/A Expected long-term rate of return on plan assets 7.00 % 4.40 % 3.00 % Interest crediting rate 4.10 % N/A N/A 2018 Discount rate in effect for determining service cost 3.62 % 3.97 % 2.84 % Discount rate in effect for determining interest cost 3.27 % 2.55 % 2.62 % Rate of compensation increase 4.00 % 3.46 % N/A Expected long-term rate of return on plan assets 7.00 % 4.32 % 2.59 % Interest crediting rate 4.10 % N/A N/A
Schedule of Health Care Cost Trend Rates [Table Text Block]	The weighted-average healthcare cost trend rate assumptions used to measure the expected cost of healthcare benefits were as follows: U.S. Plans Non-U.S. Plans 2020 2019 2018 2020 2019 2018 Healthcare cost trend rate 5.96 % 6.32 % 6.68 % 5.04 % 5.24 % 6.29 % Rate to which the cost trend rate is assumed to decline (the ultimate trend rate) 4.50 % 4.50 % 4.50 % 4.00 % 4.00 % 4.50 % Year that the rate reaches the ultimate trend rate 2038 2038 2038 2040 2040 2029
Schedule of Allocation of Plan Assets [Table Text Block]	The following tables present the fair values of the pension plan assets, by valuation hierarchy. For additional information on how we classify these assets within the valuation hierarchy, refer to Note 4 to the Consolidated Financial Statements. December 31, 2020 Pension Benefit Plans (in millions of U.S. dollars) Level 1 Level 2 Level 3 Total U.S. Plans: Short-term investments $ 59 $ — $ — $ 59 U.S. Treasury / Agency 250 186 — 436 Non-U.S. and corporate bonds — 793 — 793 Municipal — 2 — 2 Equity securities 1,818 — — 1,818 Total U.S. Plan assets (1) $ 2,127 $ 981 $ — $ 3,108 Non-U.S. Plans: Short-term investments $ 5 $ — $ — $ 5 Non-U.S. and corporate bonds — 609 — 609 Equity securities 127 388 — 515 Total Non-U.S. Plan assets (1) $ 132 $ 997 $ — $ 1,129 (1) Excluded from the table above are $543 million and $147 million of other investments related to the U.S. Plans and Non-U.S. Plans, respectively, limited partnerships of $74 million and $8 million in U.S. Plans and Non-U.S. Plans, respectively, measured using NAV as a practical expedient, and $14 million in cash related to the U.S. Plans. December 31, 2019 Pension Benefit Plans (in millions of U.S. dollars) Level 1 Level 2 Level 3 Total U.S. Plans: Short-term investments $ 18 $ 37 $ — $ 55 U.S. Treasury / Agency 466 134 — 600 Non-U.S. and corporate bonds — 749 — 749 Municipal — 2 — 2 Equity securities 1,467 — — 1,467 Total U.S. Plan assets (1) $ 1,951 $ 922 $ — $ 2,873 Non-U.S. Plans: Short-term investments $ 2 $ — $ — $ 2 Non-U.S. and corporate bonds — 598 — 598 Equity securities 112 318 — 430 Total Non-U.S. Plan assets (1) $ 114 $ 916 $ — $ 1,030
Schedule of expected future benefit payments	At December 31, 2020, our estimated expected future benefit payments are as follows: Pension Benefit Plans Other Postretirement Benefit Plans For the years ending December 31 U.S. Non-U.S. Plans (in millions of U.S. dollars) 2021 $ 159 $ 30 $ 19 2022 166 28 20 2023 171 30 16 2024 175 32 12 2025 180 32 7 2026-2030 947 185 5

Other (income) expense (Tables)

Other (income) expense (Tables)	12 Months Ended
	Dec. 31, 2020
Other Income and Expenses [Abstract]
Schedule of the components of Other (income) expense	Year Ended December 31 (in millions of U.S. dollars) 2020 2019 2018 Equity in net income of partially-owned entities (1) $ 1,019 $ 617 $ 514 Gains (losses) from fair value changes in separate account assets (2) 58 44 (38) Federal excise and capital taxes (22) (23) (12) Other (61) (42) (30) Total $ 994 $ 596 $ 434 (1) Equity in net income of partially-owned entities includes $167 million, $74 million, and $43 million attributable to our investments in Huatai (Huatai Group, Huatai P&C, and Huatai Life) for the years ended December 31, 2020, 2019, and 2018, respectively. (2) Related to gains (losses) from fair value changes in separate account assets that do not qualify for separate account reporting under GAAP.

Segment information (Tables)

Segment information (Tables)	12 Months Ended
	Dec. 31, 2020
Segment Reporting [Abstract]
Operations By Segment	For the Year Ended December 31, 2020 (in millions of U.S. dollars) North America Commercial P&C Insurance North America Personal P&C Insurance North America Agricultural Insurance Overseas General Insurance Global Life Insurance Corporate Segment Measure Reclass Chubb Net premiums written $ 14,474 $ 4,920 $ 1,846 $ 9,335 $ 731 $ 2,514 $ — $ — $ 33,820 Net premiums earned 13,964 4,866 1,822 9,285 698 2,482 — — 33,117 Losses and loss expenses 10,129 3,187 1,544 5,255 435 724 435 1 21,710 Policy benefits — — — — — 726 — 58 784 Policy acquisition costs 1,942 974 123 2,568 174 766 — — 6,547 Administrative expenses 1,006 270 9 1,034 37 320 303 — 2,979 Underwriting income (loss) 887 435 146 428 52 (54) (738) (59) 1,097 Net investment income (loss) 2,061 260 30 534 307 385 (87) (115) 3,375 Other (income) expense 23 5 1 13 2 (74) (791) (173) (994) Amortization expense of purchased intangibles — 11 27 45 — 4 203 — 290 Segment income (loss) $ 2,925 $ 679 $ 148 $ 904 $ 357 $ 401 $ (237) $ (1) $ 5,176 Net realized gains (losses) (499) 1 (498) Interest expense 516 — 516 Income tax expense 629 — 629 Net income (loss) $ (1,881) $ — $ 3,533 For the Year Ended December 31, 2019 (in millions of U.S. dollars) North America Commercial P&C Insurance North America Personal P&C Insurance North America Agricultural Insurance Overseas General Insurance Global Life Insurance Corporate Segment Measure Reclass Chubb Net premiums written $ 13,375 $ 4,787 $ 1,810 $ 9,262 $ 649 $ 2,392 $ — $ — $ 32,275 Net premiums earned 12,922 4,694 1,795 8,882 654 2,343 — — 31,290 Losses and loss expenses 8,206 3,043 1,616 4,606 352 757 158 (8) 18,730 Policy benefits — — — — — 696 — 44 740 Policy acquisition costs 1,831 948 84 2,501 169 620 — — 6,153 Administrative expenses 1,028 286 6 1,033 35 323 319 — 3,030 Underwriting income (loss) 1,857 417 89 742 98 (53) (477) (36) 2,637 Net investment income (loss) 2,109 258 30 588 279 373 (125) (86) 3,426 Other (income) expense 24 3 1 12 1 (48) (459) (130) (596) Amortization expense of purchased intangibles — 12 28 45 — 2 218 — 305 Segment income (loss) $ 3,942 $ 660 $ 90 $ 1,273 $ 376 $ 366 $ (361) $ 8 $ 6,354 Net realized gains (losses) including OTTI (522) (8) (530) Interest expense 552 — 552 Chubb integration expenses 23 — 23 Income tax expense 795 — 795 Net income (loss) $ (2,253) $ — $ 4,454 For the Year Ended December 31, 2018 (in millions of U.S. dollars) North America Commercial P&C Insurance North America Personal P&C Insurance North America Agricultural Insurance Overseas General Insurance Global Life Insurance Corporate Segment Measure Reclass Chubb Net premiums written $ 12,485 $ 4,674 $ 1,577 $ 8,902 $ 671 $ 2,270 $ — $ — $ 30,579 Net premiums earned 12,402 4,593 1,569 8,612 670 2,218 — — 30,064 Losses and loss expenses 8,000 3,229 1,114 4,429 479 766 53 (3) 18,067 Policy benefits — — — — — 628 — (38) 590 Policy acquisition costs 1,829 939 79 2,346 162 557 — — 5,912 Administrative expenses 966 269 (9) 1,014 41 310 295 — 2,886 Underwriting income (loss) 1,607 156 385 823 (12) (43) (348) 41 2,609 Net investment income (loss) 2,061 236 28 622 289 341 (209) (63) 3,305 Other (income) expense 3 1 2 3 — (12) (406) (25) (434) Amortization expense of purchased intangibles — 13 28 41 — 2 255 — 339 Segment income (loss) $ 3,665 $ 378 $ 383 $ 1,401 $ 277 $ 308 $ (406) $ 3 $ 6,009 Net realized gains (losses) including OTTI (649) (3) (652) Interest expense 641 — 641 Chubb integration expenses 59 — 59 Income tax expense 695 — 695 Net income (loss) $ (2,450) $ — $ 3,962
Net Premiums Earned For Segment By Product	The following table presents net premiums earned for each segment by line of business: For the Year Ended December 31 (in millions of U.S. dollars) 2020 2019 2018 North America Commercial P&C Insurance Property & other short-tail lines $ 2,423 $ 1,987 $ 1,861 Casualty & all other 10,812 10,136 9,773 A&H 729 799 768 Total North America Commercial P&C Insurance 13,964 12,922 12,402 North America Personal P&C Insurance Personal automobile 822 829 803 Personal homeowners 3,327 3,183 3,127 Personal other 717 682 663 Total North America Personal P&C Insurance 4,866 4,694 4,593 North America Agricultural Insurance 1,822 1,795 1,569 Overseas General Insurance Property & other short-tail lines 2,468 2,244 2,134 Casualty & all other 2,738 2,494 2,429 Personal lines 1,981 1,896 1,784 A&H 2,098 2,248 2,265 Total Overseas General Insurance 9,285 8,882 8,612 Global Reinsurance Property 104 131 123 Property catastrophe 173 142 170 Casualty & all other 421 381 377 Total Global Reinsurance 698 654 670 Life Insurance Life 1,317 1,101 1,022 A&H 1,165 1,242 1,196 Total Life Insurance 2,482 2,343 2,218 Total net premiums earned $ 33,117 $ 31,290 $ 30,064
Net Premiums Earned by Geographic Region	North America Europe (1) Asia Pacific / Far East Latin America 2020 70 % 11 % 12 % 7 % 2019 70 % 11 % 12 % 7 % 2018 70 % 11 % 12 % 7 %

Earnings per share (Tables)

Earnings per share (Tables)	12 Months Ended
	Dec. 31, 2020
Earnings Per Share [Abstract]
Schedule Of Earnings Per Share, Basic And Diluted	Year Ended December 31 (in millions of U.S. dollars, except share and per share data) 2020 2019 2018 Numerator: Net income $ 3,533 $ 4,454 $ 3,962 Denominator: Denominator for basic earnings per share: Weighted-average shares outstanding 451,602,820 455,910,463 463,629,203 Denominator for diluted earnings per share: Share-based compensation plans 1,838,692 3,004,200 3,173,145 Weighted-average shares outstanding and assumed conversions 453,441,512 458,914,663 466,802,348 Basic earnings per share $ 7.82 $ 9.77 $ 8.55 Diluted earnings per share $ 7.79 $ 9.71 $ 8.49 Potential anti-dilutive share conversions 6,811,966 2,410,337 3,543,188

Related Party Disclosures (Tabl

Related Party Disclosures (Tables)	12 Months Ended
	Dec. 31, 2020
Related Party Transactions [Abstract]
Schedule of Related Party Transactions [Table Text Block]	Transactions generated under Starr agreements were as follows: Year Ended December 31 (in millions of U.S. dollars) 2020 2019 2018 Consolidated statement of operations Gross premiums written $ 507 $ 394 $ 411 Ceded premiums written $ 253 $ 207 $ 188 Commissions paid $ 97 $ 77 $ 84 Commissions received $ 59 $ 46 $ 42 Losses and loss expenses $ 170 $ 185 $ 188 Consolidated balance sheets Reinsurance recoverable on losses and loss expenses $ 432 $ 440 Ceded reinsurance premium payable $ 80 $ 56 ABR Re We own 15.6 percent of the common equity of ABR Reinsurance Capital Holdings Ltd. and warrants to acquire 0.5 percent of additional equity. ABR Reinsurance Capital Holdings Ltd., is the parent company of ABR Reinsurance Ltd. (ABR Re), an independent reinsurance company. Through long-term arrangements, Chubb will be the sole source of reinsurance risks ceded to ABR Re, and BlackRock, Inc. will be ABR Re’s exclusive investment management service provider. As an investor, Chubb is expected to benefit from underwriting profit generated by ABR Re’s reinsuring a wide range of Chubb’s primary insurance business and the income and capital appreciation BlackRock, Inc. seeks to deliver through its investment management services. In addition, Chubb has entered into an arrangement with BlackRock, Inc. under which both Chubb and BlackRock, Inc. will be entitled to an equal share of the aggregate amount of certain fees, including underwriting and investment management performance related fees, in connection with their respective reinsurance and investment management arrangements with ABR Re. ABR Re is a variable interest entity; however, Chubb is not the primary beneficiary and does not consolidate ABR Re because Chubb does not have the power to control and direct ABR Re’s most significant activities, including investing and underwriting. Our minority ownership interest is accounted for under the equity method of accounting. Chubb cedes premiums to ABR Re and recognizes the associated commissio ns. Transactions generated under ABR Re agreements were as follows: Year Ended December 31 (in millions of U.S. dollars) 2020 2019 2018 Consolidated statement of operations Ceded premiums written $ 350 $ 321 $ 329 Commissions received $ 100 $ 92 $ 96 Consolidated balance sheets Reinsurance recoverable on losses and loss expenses $ 806 $ 674 Ceded reinsurance premium payable $ 67 $ 62

Statutory Financial Informati_2

Statutory Financial Information (Tables)	12 Months Ended
	Dec. 31, 2020
Statutory Financial Information [Abstract]
Schedule of combined statutory capital and surplus and statutory net income (loss)	December 31 (in millions of U.S. dollars) 2020 2019 Statutory capital and surplus Property and casualty $ 45,964 $ 43,077 Life $ 1,641 $ 1,573 Year Ended December 31 (in millions of U.S. dollars) 2020 2019 2018 Statutory net income (loss) Property and casualty $ 4,294 $ 6,046 $ 7,521 Life $ (247) $ (210) $ (102)

Information provided in conne_2

Information provided in connection with outstanding debt of subsidiaries (Tables)	12 Months Ended
	Dec. 31, 2020
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Abstract]
Condensed Consolidating Balance Sheet	Condensed Consolidating Balance Sheet at December 31, 2020 (in millions of U.S. dollars) Chubb Limited Chubb INA Other Chubb Consolidating Chubb Limited Assets Investments $ — $ 197 $ 118,472 $ — $ 118,669 Cash (1) 84 1 1,934 (272) 1,747 Restricted Cash — — 89 — 89 Insurance and reinsurance balances receivable — — 13,926 (3,446) 10,480 Reinsurance recoverable on losses and loss expenses — — 25,217 (9,625) 15,592 Reinsurance recoverable on policy benefits — — 299 (93) 206 Value of business acquired — — 263 — 263 Goodwill and other intangible assets — — 21,211 — 21,211 Investments in subsidiaries 56,148 55,231 — (111,379) — Due from subsidiaries and affiliates, net 3,522 — 171 (3,693) — Other assets 10 463 23,921 (1,877) 22,517 Total assets $ 59,764 $ 55,892 $ 205,503 $ (130,385) $ 190,774 Liabilities Unpaid losses and loss expenses $ — $ — $ 77,180 $ (9,369) $ 67,811 Unearned premiums — — 18,853 (1,201) 17,652 Future policy benefits — — 5,806 (93) 5,713 Due to subsidiaries and affiliates, net — 3,008 685 (3,693) — Affiliated notional cash pooling programs (1) — 272 — (272) — Repurchase agreements — — 1,405 — 1,405 Long-term debt — 14,948 — — 14,948 Trust preferred securities — 308 — — 308 Other liabilities 323 1,418 26,133 (4,378) 23,496 Total liabilities 323 19,954 130,062 (19,006) 131,333 Total shareholders’ equity 59,441 35,938 75,441 (111,379) 59,441 Total liabilities and shareholders’ equity $ 59,764 $ 55,892 $ 205,503 $ (130,385) $ 190,774 (1) Chubb maintains two notional multicurrency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information. At December 31, 2020, the cash balance of one or more entities was negative; however, the overall Pool balances were positive. Condensed Consolidating Balance Sheet at December 31, 2019 (in millions of U.S. dollars) Chubb Limited Chubb INA Other Chubb Consolidating Chubb Limited Assets Investments $ — $ 1,013 $ 108,221 $ — $ 109,234 Cash (1) 2 442 1,093 — 1,537 Restricted Cash — — 109 — 109 Insurance and reinsurance balances receivable — — 12,920 (2,563) 10,357 Reinsurance recoverable on losses and loss expenses — — 24,780 (9,599) 15,181 Reinsurance recoverable on policy benefits — — 292 (95) 197 Value of business acquired — — 306 — 306 Goodwill and other intangible assets — — 21,359 — 21,359 Investments in subsidiaries 50,853 52,076 — (102,929) — Due from subsidiaries and affiliates, net 4,776 — — (4,776) — Other assets 12 408 20,072 (1,829) 18,663 Total assets $ 55,643 $ 53,939 $ 189,152 $ (121,791) $ 176,943 Liabilities Unpaid losses and loss expenses $ — $ — $ 71,916 $ (9,226) $ 62,690 Unearned premiums — — 17,978 (1,207) 16,771 Future policy benefits — — 5,468 (95) 5,373 Due to subsidiaries and affiliates, net — 4,446 330 (4,776) — Repurchase agreements — — 1,416 — 1,416 Short-term debt — 1,298 1 — 1,299 Long-term debt — 13,559 — — 13,559 Trust preferred securities — 308 — — 308 Other liabilities 312 1,649 21,793 (3,558) 20,196 Total liabilities 312 21,260 118,902 (18,862) 121,612 Total shareholders’ equity 55,331 32,679 70,250 (102,929) 55,331 Total liabilities and shareholders’ equity $ 55,643 $ 53,939 $ 189,152 $ (121,791) $ 176,943
Condensed Consolidating Statement Of Operations and Comprehensive Income	Condensed Consolidating Statements of Operations and Comprehensive Income For the Year Ended December 31, 2020 Chubb Limited Chubb INA Other Chubb Consolidating Chubb Limited (in millions of U.S. dollars) Net premiums written $ — $ — $ 33,820 $ — $ 33,820 Net premiums earned — — 33,117 — 33,117 Net investment income (1) 6 3,370 — 3,375 Equity in earnings of subsidiaries 3,457 2,052 — (5,509) — Net realized gains (losses) 20 (397) (121) — (498) Losses and loss expenses — — 21,710 — 21,710 Policy benefits — — 784 — 784 Policy acquisition costs and administrative 94 (130) 9,562 — 9,526 Interest (income) expense (136) 596 56 — 516 Other (income) expense (39) (24) (931) — (994) Amortization of purchased intangibles — — 290 — 290 Income tax expense (benefit) 24 (181) 786 — 629 Net income $ 3,533 $ 1,400 $ 4,109 $ (5,509) $ 3,533 Comprehensive income $ 5,783 $ 3,236 $ 6,512 $ (9,748) $ 5,783 Condensed Consolidating Statements of Operations and Comprehensive Income For the Year Ended December 31, 2019 Chubb Limited Chubb INA Other Chubb Consolidating Chubb Limited (in millions of U.S. dollars) Net premiums written $ — $ — $ 32,275 $ — $ 32,275 Net premiums earned — — 31,290 — 31,290 Net investment income 1 (15) 3,440 — 3,426 Equity in earnings of subsidiaries 4,307 3,022 — (7,329) — Net realized gains (losses) including OTTI (17) (31) (482) — (530) Losses and loss expenses — — 18,730 — 18,730 Policy benefits — — 740 — 740 Policy acquisition costs and administrative expenses 92 (26) 9,117 — 9,183 Interest (income) expense (243) 705 90 — 552 Other (income) expense (27) 6 (575) — (596) Amortization of purchased intangibles — — 305 — 305 Chubb integration expenses 1 2 20 — 23 Income tax expense (benefit) 14 (175) 956 — 795 Net income $ 4,454 $ 2,464 $ 4,865 $ (7,329) $ 4,454 Comprehensive income $ 7,521 $ 4,988 $ 7,922 $ (12,910) $ 7,521 Condensed Consolidating Statements of Operations and Comprehensive Income (Loss) For the Year Ended December 31, 2018 Chubb Limited Chubb INA Other Chubb Consolidating Chubb Limited (in millions of U.S. dollars) Net premiums written $ — $ — $ 30,579 $ — $ 30,579 Net premiums earned — — 30,064 — 30,064 Net investment income 6 13 3,286 — 3,305 Equity in earnings of subsidiaries 3,753 2,578 — (6,331) — Net realized gains (losses) including OTTI — 117 (769) — (652) Losses and loss expenses — — 18,067 — 18,067 Policy benefits — — 590 — 590 Policy acquisition costs and administrative expenses 87 (58) 8,769 — 8,798 Interest (income) expense (299) 806 134 — 641 Other (income) expense (24) 26 (436) — (434) Amortization of purchased intangibles — — 339 — 339 Chubb integration expenses 14 1 44 — 59 Income tax expense (benefit) 19 (148) 824 — 695 Net income $ 3,962 $ 2,081 $ 4,250 $ (6,331) $ 3,962 Comprehensive income (loss) $ 1,242 $ (27) $ 1,808 $ (1,781) $ 1,242
Condensed Consolidating Statement of Cash Flows	Condensed Consolidating Statement of Cash Flows For the Year Ended December 31, 2020 Chubb Limited Chubb INA Other Chubb Consolidating Chubb Limited (in millions of U.S. dollars) Net cash flows from operating activities $ 1,933 $ 274 $ 10,788 $ (3,210) $ 9,785 Cash flows from investing activities Purchases of fixed maturities available for sale — (49) (26,249) — (26,298) Purchases of fixed maturities held to maturity — — (202) — (202) Purchases of equity securities — — (6,419) — (6,419) Sales of fixed maturities available for sale — 9 11,368 — 11,377 Sales of equity securities — — 3,880 — 3,880 Maturities and redemptions of fixed maturities available for sale — 50 12,400 — 12,450 Maturities and redemptions of fixed maturities held to maturity — — 995 — 995 Net change in short-term investments — 772 (853) — (81) Net derivative instruments settlements — 55 (168) — (113) Private equity contributions — — (1,924) — (1,924) Private equity distributions — — 907 — 907 Payment, including deposit, for Huatai Group interest — — (1,623) — (1,623) Capital contribution (1,200) (72) — 1,272 — Other (2) 4 (472) — (470) Net cash flows from (used for) investing activities (1,202) 769 (8,360) 1,272 (7,521) Cash flows from financing activities Dividends paid on Common Shares (1,388) — — — (1,388) Common Shares repurchased (523) — — — (523) Proceeds from issuance of long-term debt — 988 — — 988 Proceeds from issuance of repurchase agreements — — 2,354 — 2,354 Repayment of long-term debt — (1,301) — — (1,301) Repayment of repurchase agreements — — (2,354) — (2,354) Proceeds from share-based compensation plans — — 145 — 145 Advances (to) from affiliates 1,265 (1,438) 173 — — Dividends to parent company — — (3,210) 3,210 — Capital contribution — — 1,272 (1,272) — Net proceeds from affiliated notional cash pooling programs (1) — 272 — (272) — Policyholder contract deposits and other — — 470 — 470 Policyholder contract withdrawals and other — — (386) — (386) Other — — (87) — (87) Net cash flows used for financing activities (646) (1,479) (1,623) 1,666 (2,082) Effect of foreign currency rate changes on cash and (3) (5) 16 — 8 Net increase (decrease) in cash and restricted cash 82 (441) 821 (272) 190 Cash and restricted cash – beginning of year (1) 2 442 1,202 — 1,646 Cash and restricted cash – end of year (1) $ 84 $ 1 $ 2,023 $ (272) $ 1,836 (1) Chubb maintains two notional multi-currency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information. At December 31, 2020, the cash balance of one or more entities was negative; however, the overall Pool balances were positive. Condensed Consolidating Statement of Cash Flows For the Year Ended December 31, 2019 Chubb Limited Chubb INA Other Chubb Consolidating Chubb Limited (in millions of U.S. dollars) Net cash flows from operating activities $ 412 $ 2,926 $ 6,878 $ (3,874) $ 6,342 Cash flows from investing activities Purchases of fixed maturities available for sale — (21) (25,825) — (25,846) Purchases of fixed maturities held to maturity — — (229) — (229) Purchases of equity securities — — (531) — (531) Sales of fixed maturities available for sale — 1 13,115 — 13,116 Sales of equity securities — — 611 — 611 Maturities and redemptions of fixed maturities available for sale — 41 8,998 — 9,039 Maturities and redemptions of fixed maturities held to maturity — — 946 — 946 Net change in short-term investments — (808) (309) — (1,117) Net derivative instruments settlements — (74) (629) — (703) Private equity contributions — — (1,315) — (1,315) Private equity distributions — — 1,390 — 1,390 Capital contribution (1,000) (110) — 1,110 — Acquisition of subsidiaries (net of cash acquired of $45) — — (29) — (29) Payment, including deposit, for Huatai Group interest — — (580) — (580) Other — (4) (653) — (657) Net cash flows used for investing activities (1,000) (975) (5,040) 1,110 (5,905) Cash flows from financing activities Dividends paid on Common Shares (1,354) — — — (1,354) Common Shares repurchased (327) — (1,203) — (1,530) Proceeds from issuance of long-term debt — 2,828 — — 2,828 Proceeds from issuance of repurchase agreements — — 2,817 — 2,817 Repayment of long-term debt — (500) (10) — (510) Repayment of repurchase agreements — — (2,817) — (2,817) Proceeds from share-based compensation plans — — 204 — 204 Advances (to) from affiliates 2,301 (3,223) 922 — — Dividends to parent company — — (3,874) 3,874 — Capital contribution — — 1,110 (1,110) — Net proceeds payments to affiliated notional cash pooling programs (1) (35) (617) — 652 — Policyholder contract deposits — — 514 — 514 Policyholder contract withdrawals — — (303) — (303) Net cash flows from (used for) financing activities 585 (1,512) (2,640) 3,416 (151) Effect of foreign currency rate changes on cash and restricted cash 4 1 15 — 20 Net increase (decrease) in cash and restricted cash 1 440 (787) 652 306 Cash and restricted cash – beginning of year (1) 1 2 1,989 (652) 1,340 Cash and restricted cash – end of year (1) $ 2 $ 442 $ 1,202 $ — $ 1,646 (1) Chubb maintains two notional multi-currency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information. At December 31, 2018, the cash balance of one or more entities was negative; however, the overall Pool balances were positive. Condensed Consolidating Statement of Cash Flows For the Year Ended December 31, 2018 Chubb Limited Chubb INA Other Chubb Consolidating Chubb Limited (in millions of U.S. dollars) Net cash flows from operating activities $ 256 $ 4,654 $ 5,878 $ (5,308) $ 5,480 Cash flows from investing activities Purchases of fixed maturities available for sale — (38) (24,697) — (24,735) Purchases of fixed maturities held to maturity — — (456) — (456) Purchases of equity securities — — (207) — (207) Sales of fixed maturities available for sale — 11 14,019 — 14,030 Sales of equity securities — — 315 — 315 Maturities and redemptions of fixed maturities available for sale — 17 7,335 — 7,352 Maturities and redemptions of fixed maturities held to maturity — — 1,124 — 1,124 Net change in short-term investments — 3 513 — 516 Net derivative instruments settlements — (7) 23 — 16 Private equity contributions — — (1,337) — (1,337) Private equity distributions — — 980 — 980 Capital contribution (1,475) (3,550) — 5,025 — Other — (18) (515) — (533) Net cash flows used for investing activities (1,475) (3,582) (2,903) 5,025 (2,935) Cash flows from financing activities Dividends paid on Common Shares (1,337) — — — (1,337) Common Shares repurchased — — (1,044) — (1,044) Proceeds from issuance of long-term debt — 2,171 — — 2,171 Proceeds from issuance of repurchase agreements — — 2,029 — 2,029 Repayment of long-term debt — (2,000) (1) — (2,001) Repayment of repurchase agreements — — (2,019) — (2,019) Proceeds from share-based compensation plans — — 115 — 115 Advances (to) from affiliates 2,519 (1,744) (775) — — Dividends to parent company — — (5,308) 5,308 — Capital contribution — — 5,025 (5,025) — Net payments to affiliated notional cash pooling programs (1) 35 502 — (537) — Policyholder contract deposits — — 453 — 453 Policyholder contract withdrawals — — (358) — (358) Net cash flows from (used for) financing activities 1,217 (1,071) (1,883) (254) (1,991) Effect of foreign currency rate changes on cash and restricted cash — — (65) — (65) Net increase (decrease) in cash and restricted cash (2) 1 1,027 (537) 489 Cash and restricted cash – beginning of year (1) 3 1 962 (115) 851 Cash and restricted cash – end of year (1) $ 1 $ 2 $ 1,989 $ (652) $ 1,340 (1) Chubb maintains two notional multi-currency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information. At December 31, 2018 and 2017, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.

Summary of significant accoun_4

Summary of significant accounting policies (Narrative) (Detail) - USD ($) $ in Millions	Jan. 14, 2016	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Deposit Assets		$ 107	$ 93
Unpaid losses and loss expenses		67,811	62,690	$ 62,960	$ 63,179
Deposit liabilities included in Deposit liabilities		86	88
Borrowings under Guaranteed Investment Agreements		2,200	2,000
Summary of significant accounting policies [Line Items]
Deferred Policy Acquisition Costs, Amortization Expense		6,547	6,153	5,912
Deferred Advertising Costs		$ 226	246
Deferred Marketing Costs, Amortization Period		10 years
Recoverable from unrated reinsurers, ceded reserve, default factor (percent)		34.00%
Percentage of fair value of loaned securities		102.00%
Quality assessment threshold used in goodwill impairment testing		50.00%
Net operating results of ESIS included within Administrative expenses		$ 18	47	49
Property, Plant and Equipment, Net		2,000	1,900
Chubb integration expenses		0	23	59
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity Attributable to Parent		(59,441)	(55,331)	(50,312)
The Chubb Corporation [Member] | Debt Securities [Member]
Summary of significant accounting policies [Line Items]
Assets, Fair Value Adjustment	$ 1,652	213
Selling and Marketing Expense [Member]
Summary of significant accounting policies [Line Items]
Deferred Policy Acquisition Costs, Amortization Expense		99	109	114
Fair Value Adjustment to Acquired Loss Reserves [Member] | The Chubb Corporation [Member]
Summary of significant accounting policies [Line Items]
Balance of FV adjustment on Unpaid Losses and Loss Expenses		110	145
Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity Attributable to Parent		$ (39,337)	$ (36,142)	(31,700)	(27,474)
Minimum
Liability for Future Policy Benefit, by Product Segment [Line Items]
Liability for Future Policy Benefits, Interest Rate		1.00%	1.00%
Summary of significant accounting policies [Line Items]
Reinsurance Premiums, Amortization Period		1 year
Maximum
Liability for Future Policy Benefit, by Product Segment [Line Items]
Liability for Future Policy Benefits, Interest Rate		9.00%	11.00%
Summary of significant accounting policies [Line Items]
Reinsurance Premiums, Amortization Period		3 years
Finite-Lived Intangible Asset, Useful Life		25 years
Affiliated notional cash pooling program		$ 300
Structured settlements
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Deposit Assets		26	$ 31
Unpaid losses and loss expenses		548
Reinsurance recoverables for amounts due from life insurance companies		522
Short-Duration Insurance, Other [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Unpaid losses and loss expenses		42	43
Software Development [Member]
Summary of significant accounting policies [Line Items]
Property, Plant and Equipment, Net		$ 1,300
Property, Plant and Equipment, Useful Life		15 years
Software Development [Member] | Minimum
Summary of significant accounting policies [Line Items]
Property, Plant and Equipment, Useful Life		3 years
Software Development [Member] | Maximum
Summary of significant accounting policies [Line Items]
Property, Plant and Equipment, Useful Life		5 years
Building [Member]
Summary of significant accounting policies [Line Items]
Property, Plant and Equipment, Net		$ 260
Building [Member] | Maximum
Summary of significant accounting policies [Line Items]
Property, Plant and Equipment, Useful Life		40 years
Cumulative Effect, Period of Adoption, Adjustment [Member] | Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity Attributable to Parent			72	$ 12	$ (264)
Cumulative effect on retained earnings, before tax [Member] | Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity Attributable to Parent			$ 79

Summary of significant accoun_5

Summary of significant accounting policies Summary of Significant Accounting Policies - Cash (Details) - USD ($) $ in Millions	Dec. 31, 2020		Dec. 31, 2019		Dec. 31, 2018		Dec. 31, 2017	[5]
Cash and Cash Equivalents [Line Items]
Cash	$ 1,747	[1]	$ 1,537	[2]	$ 1,247
Restricted Cash	89		109		93
Cash and restricted cash	$ 1,836	[3]	$ 1,646	[3],[4]	$ 1,340	[3],[5]	$ 851
[1]	Chubb maintains two notional multicurrency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information. At December 31, 2020, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.
[2]	Chubb maintains two notional multicurrency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information.
[3]	Chubb maintains two notional multi-currency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information. At December 31, 2020, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.
[4]	Chubb maintains two notional multi-currency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information. At December 31, 2018, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.
[5]	Chubb maintains two notional multi-currency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information. At December 31, 2018 and 2017, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.

Acquisitions (Details)

Acquisitions (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Investment [Line Items]
Payment, including deposit, for Huatai Group Interest			$ 1,623	$ 580
Banchile Seguros de Vida [Member]
Investment [Line Items]
Payments to Acquire Businesses, Gross	$ 74
Huatai Group [Member]
Investment [Line Items]
Ownership Percentage	47.10%		47.10%
Huatai Group [Member] | CHINA
Investment [Line Items]
Equity method investment, additional 7.1 percentage obtained			7.10%
Portion two of payments to acquire equity method investments			$ 493
Portion one of payments to acquire equity method investments				$ 1,100
Equity method investment, additional 15.3 ownership percentage obtained				15.30%
Equity method investment, additional 22.4 ownership percentage obtained				22.40%
Ownership Percentage	47.00%		47.00%	31.00%
Equity method investment, incremental 0.9 percent obtained	0.90%
Purchase of incremental ownership interest	$ 65
Payment, including deposit, for Huatai Group Interest			$ 1,623	$ 580	$ 0
Huatai Group [Member] | Subsequent Event [Member] | CHINA
Investment [Line Items]
Equity method investment, additional 7.1 percentage obtained		7.10%

Investments (Narrative) (Detail

Investments (Narrative) (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020USD ($)partnerships	Dec. 31, 2019USD ($)
Investment [Line Items]
Document Period End Date		Dec. 31, 2020
Limited partnerships number | partnerships		130
Restricted assets in fixed maturities and short-term investments		$ 19,600	$ 21,000
Restricted assets in cash		89	$ 109
Debt Securities, Available-for-sale, Purchased with Credit Deterioration, Amount at Purchase Price		108
Debt Securities, Available-for-sale, Purchased with Credit Deterioration, Allowance for Credit Loss at Acquisition Date		5
Debt Securities, Available-for-sale, Purchased with Credit Deterioration, Amount at Par Value		$ 144
Huatai Group [Member]
Investment [Line Items]
Ownership Percentage		47.10%
CHINA | Huatai Group [Member]
Investment [Line Items]
Ownership Percentage		47.00%	31.00%
Equity method investment, additional 15.3 ownership percentage obtained			15.30%
Equity method investment, additional 7.1 percentage obtained		7.10%
CHINA | Huatai Life Insurance Co. [Member]
Investment [Line Items]
Ownership Percentage		20.00%	20.00%
Subsequent Event [Member] | CHINA | Huatai Group [Member]
Investment [Line Items]
Equity method investment, additional 7.1 percentage obtained	7.10%
Indirect Ownership [Member] | CHINA | Huatai Life Insurance Co. [Member]
Investment [Line Items]
Ownership Percentage		37.50%
Direct Ownership [Member] | CHINA | Huatai Life Insurance Co. [Member]
Investment [Line Items]
Ownership Percentage		20.00%

Investments Investments (Schedu

Investments Investments (Schedule Of Amortized Cost and Fair Value of Available-for-sale Securities and Related OTTI Recognized in AOCI) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	$ 85,188	$ 82,580
Debt Securities, Available-for-sale, Allowance for Credit Loss	20	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	5,655	3,074
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(124)	(166)
Available for sale, Fair Value	90,699	85,488
Available for sale, OTTI recognized in AOCI		(30)
US Treasury and Government [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	2,471	3,188
Debt Securities, Available-for-sale, Allowance for Credit Loss	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	199	96
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	0	(1)
Available for sale, Fair Value	2,670	3,283
Available for sale, OTTI recognized in AOCI		0
Foreign
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	24,594	22,670
Debt Securities, Available-for-sale, Allowance for Credit Loss	(6)
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1,808	1,099
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(42)	(62)
Available for sale, Fair Value	26,354	23,707
Available for sale, OTTI recognized in AOCI		(25)
Corporate securities
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	34,095	30,689
Debt Securities, Available-for-sale, Allowance for Credit Loss	(14)
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	2,322	1,180
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(72)	(78)
Available for sale, Fair Value	36,331	31,791
Available for sale, OTTI recognized in AOCI		(5)
Collateralized Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	17,456	18,712
Debt Securities, Available-for-sale, Allowance for Credit Loss	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1,022	494
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(8)	(14)
Available for sale, Fair Value	18,470	19,192
Available for sale, OTTI recognized in AOCI		0
States, municipalities, and political subdivisions
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	6,572	7,321
Debt Securities, Available-for-sale, Allowance for Credit Loss	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	304	205
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(2)	(11)
Available for sale, Fair Value	$ 6,874	7,515
Available for sale, OTTI recognized in AOCI		$ 0

Investments (Schedule Of Amorti

Investments (Schedule Of Amortized Cost And Fair Value Of Held-to-Maturity And Related Other-Than-Temporary Impairment Recognized In Accumulated Other Comprehensive Income) (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	$ 11,697	$ 12,581
Debt Securities, Held-to-maturity, Allowance for Credit Loss	44	0
Debt securities, held to maturity, net carrying value	11,653
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	859	427
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(2)	(3)
Held to maturity, Fair Value	12,510	13,005
Held to maturity, OTTI recognized in AOCI		0
U.S. Treasury and agency
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	1,392	1,318
Debt Securities, Held-to-maturity, Allowance for Credit Loss	0
Debt securities, held to maturity, net carrying value	1,392
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	60	29
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	0	0
Held to maturity, Fair Value	1,452	1,347
Held to maturity, OTTI recognized in AOCI		0
Foreign
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	1,295	1,423
Debt Securities, Held-to-maturity, Allowance for Credit Loss	(7)
Debt securities, held to maturity, net carrying value	1,288
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	118	62
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(1)	0
Held to maturity, Fair Value	1,405	1,485
Held to maturity, OTTI recognized in AOCI		0
Corporate securities
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	2,185	2,349
Debt Securities, Held-to-maturity, Allowance for Credit Loss	(35)
Debt securities, held to maturity, net carrying value	2,150
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	288	121
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	0	(2)
Held to maturity, Fair Value	2,438	2,468
Held to maturity, OTTI recognized in AOCI		0
Mortgage-backed securities
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	2,000	2,331
Debt Securities, Held-to-maturity, Allowance for Credit Loss	(1)
Debt securities, held to maturity, net carrying value	1,999
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	148	65
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(1)	0
Held to maturity, Fair Value	2,146	2,396
Held to maturity, OTTI recognized in AOCI		0
States, municipalities, and political subdivisions
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	4,825	5,160
Debt Securities, Held-to-maturity, Allowance for Credit Loss	(1)
Debt securities, held to maturity, net carrying value	4,824
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	245	150
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	0	(1)
Held to maturity, Fair Value	$ 5,069	5,309
Held to maturity, OTTI recognized in AOCI		$ 0

Investments (Held-to-maturity c

Investments (Held-to-maturity credit quality indicator) (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Debt Securities, Held-to-maturity	$ 11,697	$ 12,581
Fixed Maturities Percent of Total Amortized cost	100.00%
Standard & Poor's, AAA Rating [Member]
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Debt Securities, Held-to-maturity	$ 2,511
Fixed Maturities Percent of Total Amortized cost	22.00%
Standard & Poor's, AA Rating [Member]
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Debt Securities, Held-to-maturity	$ 6,193
Fixed Maturities Percent of Total Amortized cost	53.00%
Standard & Poor's, A Rating [Member]
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Debt Securities, Held-to-maturity	$ 2,138
Fixed Maturities Percent of Total Amortized cost	18.00%
Standard & Poor's, BBB Rating [Member]
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Debt Securities, Held-to-maturity	$ 826
Fixed Maturities Percent of Total Amortized cost	7.00%
Standard & Poor's, BB Rating [Member]
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Debt Securities, Held-to-maturity	$ 28
Fixed Maturities Percent of Total Amortized cost	0.00%
Other [Member]
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Debt Securities, Held-to-maturity	$ 1
Fixed Maturities Percent of Total Amortized cost	0.00%

Investments (Schedule Of Fixed

Investments (Schedule Of Fixed Maturities By Contractual Maturity) (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Investments, Debt and Equity Securities [Abstract]
Available for sale, Due in 1 year or less, Amortized Cost		$ 3,951
Available for sale, Due after 1 year through 5 years, Amortized Cost		27,142
Available for sale, Due after 5 years though 10 years, Amortized Cost		23,901
Available for sale, Due after 10 years, Amortized Cost		8,874
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Amortized Cost		63,868
Available for sale, Mortgage-backed securities, Amortized Cost		18,712
Debt Securities, Available-for-sale, Amortized Cost	$ 85,188	82,580
Available for sale, Due in 1 year or less, Fair Value	4,760	3,973
Available for sale, Due after 1 year through 5 years, Fair Value	26,227	27,720
Available for sale, Due after 5 years through 10 years, Fair Value	27,232	24,874
Available for sale, Due after 10 years, Fair Value	14,010	9,729
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Fair Value	72,229	66,296
Available for sale, Mortgage backed securities, Fair Value	18,470	19,192
Available for sale, Fair Value	90,699	85,488
Held to maturity, Due in 1 year or less, Amortized Cost		478
Debt securities, Held-to-maturity, maturity, allocated and single maturity date, within on year, net carrying value	1,231
Held to maturity, Due after 1 year through 5 years, Amortized Cost		3,869
Debt securities, Held-to-maturity, maturity, allocated and single maturity date, after one through five years, net carrying value	3,592
Held to maturity, Due after 5 years through 10 years, Amortized Cost		3,756
Debt securities, Held-to-maturity, maturity, allocated and single maturity date, after five through ten years, net carrying value	3,029
Held to maturity, Due after 10 years, Amortized Cost		2,147
Debt securities, Held-to-maturity, maturity, allocated and single maturity date, after 10 years, net carrying value	1,802
Debt securities, Held-to-maturity, maturity, allocated and single maturity date, net carrying value	9,654
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, Amortized Cost		10,250
Held to maturity, Mortgage backed securities, Amortized Cost		2,331
Debt securities, Held-to-maturity, without single maturity date, net carrying value	1,999
Debt Securities, Held-to-maturity	11,697	12,581
Held to maturity, Due in 1 year or less, Fair Value	1,240	479
Held to maturity, Due after 1 year through 5, Fair Value	3,760	3,940
Held to maturity, Due after 5 years through 10 years, Fair Value	3,228	3,883
Held to maturity, Due after 10 years, Fair Value	2,136	2,307
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, Fair Value	10,364	10,609
Held to maturity, Mortgage backed securities, Fair Value	2,146	2,396
Debt securities, held to maturity, net carrying value	11,653
Held to maturity, Fair Value	$ 12,510	$ 13,005

Investments (Aggregate Fair Val

Investments (Aggregate Fair Value And Gross Unrealized Loss By Length Of Time Security Has Continuously Been In Unrealized Loss Position) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Investment [Line Items]
Document Period End Date	Dec. 31, 2020
Fixed Maturities [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 4,755	$ 5,563
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(75)	(81)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	758	3,337
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(22)	(88)
Debt Securities, Available-for-sale, Unrealized Loss Position	5,513	8,900
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(97)	(169)
U.S. Treasury and agency | Fixed Maturities [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months		234
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		(1)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer		339
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		0
Debt Securities, Available-for-sale, Unrealized Loss Position		573
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss		(1)
Foreign | Fixed Maturities [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	1,628	1,846
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(35)	(34)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	114	802
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(5)	(28)
Debt Securities, Available-for-sale, Unrealized Loss Position	1,742	2,648
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(40)	(62)
Corporate securities | Fixed Maturities [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	2,212	2,121
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(33)	(40)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	593	988
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(14)	(40)
Debt Securities, Available-for-sale, Unrealized Loss Position	2,805	3,109
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(47)	(80)
Mortgage-backed securities | Fixed Maturities [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	875	1,174
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(6)	(6)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	35	932
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(2)	(8)
Debt Securities, Available-for-sale, Unrealized Loss Position	910	2,106
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(8)	(14)
States, municipalities, and political subdivisions | Fixed Maturities [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	40	188
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(1)	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	16	276
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(1)	(12)
Debt Securities, Available-for-sale, Unrealized Loss Position	56	464
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ (2)	$ (12)

Investments (Roll-Forward Of Pr

Investments (Roll-Forward Of Pre-Tax Credit Losses Related To Fixed Maturities For Which Portion Of Other-Than-Temporary Impairment Was Recognized In Other Comprehensive Income) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Roll-Forward Of Pre-Tax Credit Losses Related To Fixed Maturities For Which Portion Of OTTI Was Recognized In OCI
Balance of credit losses related to securities still held-beginning of period	$ 34	$ 22
Additions where no OTTI was previously recorded	33	20
Additions where an OTTI was previously recorded	4	5
Reductions for securities sold during the period	(41)	(13)
Balance of credit losses related to securities still held-end of period	$ 30	$ 34

Investments (Net Realized Gains

Investments (Net Realized Gains (Losses) And Losses Included In Net Realized Gains (Losses) And Other Comprehensive Income) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Gain (Loss) on Securities [Line Items]
Other-than-temporary impairment (OTTI) losses gross		$ (90)	$ (52)
OTTI on Fixed Maturities		(58)	(49)
Debt Securities, Available-for-sale, Allowance for Credit Loss, Period Increase (Decrease)	$ 188
Debt Securities, Available-For-Sale, Credit Impairment Charges Intent to Sell	(170)	0	0
Foreign exchange gains( losses)	(483)	7	131
Fair Value adjustment on insurance derivative	(202)	(4)	(248)
Derivative, Gain (Loss) on Derivative, Net	(228)	(585)	(330)
Realized Investment Gains (Losses)	(498)	(530)	(652)
Unrealized Gain (Loss) on Investments	2,130	3,088	(1,699)
Other Comprehensive Income (Loss), Securities, Available-for-sale, Tax	(462)	(647)	297
Other derivative instruments
Gain (Loss) on Securities [Line Items]
Derivative, Gain (Loss) on Derivative, Net	1	(8)	(3)
Investment and embedded derivative instruments
Gain (Loss) on Securities [Line Items]
Derivative, Gain (Loss) on Derivative, Net	81	(435)	(75)
S&P Options and Futures
Gain (Loss) on Securities [Line Items]
Derivative, Gain (Loss) on Derivative, Net	(108)	(138)	(4)
Equity Securities [Member]
Gain (Loss) on Securities [Line Items]
Equity Securities, FV-NI, Realized Gain (Loss)	586	104	(59)	[1]
Fixed maturities held to maturity
Gain (Loss) on Securities [Line Items]
Unrealized Gain (Loss) on Investments	(24)	(31)	(38)
Other Investments [Member]
Gain (Loss) on Securities [Line Items]
Realized Investment Gains (Losses)	(32)	(20)	(5)
Available-for-sale Securities [Member]
Gain (Loss) on Securities [Line Items]
Unrealized Gain (Loss) on Investments	2,628	3,769	(1,958)
Debt Securities [Member]
Gain (Loss) on Securities [Line Items]
Other-than-temporary impairment (OTTI) losses gross		(90)	(52)
OTTI on fixed maturities recognized in OCI (pre-tax)	0	32	3
OTTI on Fixed Maturities		(58)	(49)
Fixed Maturities [Member]
Gain (Loss) on Securities [Line Items]
Debt Securities, Available-for-sale, Realized Gain (Loss), Excluding Other-than-temporary Impairment	244	203	334
Debt Securities, Available-for-sale, Realized Loss, Excluding Other-than-temporary Impairment	(366)	(176)	(587)
Debt Securities, Available-for-sale, Realized Gain (Loss)	(281)	(31)	(302)
Other [Member]
Gain (Loss) on Securities [Line Items]
Gain (Loss) on Sale of Other Investments	(60)	(5)	(87)
Unrealized Gain (Loss) on Investments	(12)	(3)	0
Accounting Standards Update 2016-01 [Member] | Equity Securities [Member]
Gain (Loss) on Securities [Line Items]
Equity Securities, FV-NI, Realized Gain (Loss)	586	104	(59)
Unrealized Gain (Loss) on Investments	131	46	(129)
Gain (Loss) on Sale of Investments	455	58	70
Accounting Standards Update 2016-01 [Member] | Other Investments [Member]
Gain (Loss) on Securities [Line Items]
Realized Investment Gains (Losses)	(32)	(20)	(5)
Unrealized Gain (Loss) on Investments	(32)	(15)	(126)
Gain (Loss) on Sale of Investments	0	(5)	121
Accounting Standards Update 2016-01 [Member] | Equity securities and other investments [Member]
Gain (Loss) on Securities [Line Items]
Realized Investment Gains (Losses)	554	84	(64)
Unrealized Gain (Loss) on Investments	99	31	(255)
Gain (Loss) on Sale of Investments	455	53	191
Accounting Standards Update 2016-13 [Member]
Gain (Loss) on Securities [Line Items]
Debt Securities, Available-for-sale, Allowance for Credit Loss, Period Increase (Decrease)	$ 11	$ 0	$ 0
[1]	Relates to certain securities we intended to sell and securities written to market entering default.

Investments Investments (Sche_2

Investments Investments (Schedule of Gains and Losses on Equity and Other Investments) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Gain (Loss) on Securities [Line Items]
Unrealized Gain (Loss) on Investments	$ 2,130	$ 3,088	$ (1,699)
Realized Investment Gains (Losses)	(498)	(530)	(652)
Equity Securities [Member]
Gain (Loss) on Securities [Line Items]
Equity Securities, FV-NI, Realized Gain (Loss)	586	104	(59)	[1]
Other Investments [Member]
Gain (Loss) on Securities [Line Items]
Realized Investment Gains (Losses)	(32)	(20)	(5)
Accounting Standards Update 2016-01 [Member] | Equity Securities [Member]
Gain (Loss) on Securities [Line Items]
Equity Securities, FV-NI, Realized Gain (Loss)	586	104	(59)
Unrealized Gain (Loss) on Investments	131	46	(129)
Gain (Loss) on Sale of Investments	455	58	70
Accounting Standards Update 2016-01 [Member] | Other Investments [Member]
Gain (Loss) on Securities [Line Items]
Unrealized Gain (Loss) on Investments	(32)	(15)	(126)
Gain (Loss) on Sale of Investments	0	(5)	121
Realized Investment Gains (Losses)	(32)	(20)	(5)
Accounting Standards Update 2016-01 [Member] | Equity securities and other investments [Member]
Gain (Loss) on Securities [Line Items]
Unrealized Gain (Loss) on Investments	99	31	(255)
Gain (Loss) on Sale of Investments	455	53	191
Realized Investment Gains (Losses)	$ 554	$ 84	$ (64)
[1]	Relates to certain securities we intended to sell and securities written to market entering default.

Investments (Schedule Of Other

Investments (Schedule Of Other Investments) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Other Investment Not Readily Marketable [Line Items]
Other Investments	$ 7,945	$ 6,062
Alternative Investment	6,770	4,921
Fair Value
Other Investment Not Readily Marketable [Line Items]
Other Investments	7,945	6,062
Alternative Investment	6,770	4,921
Other [Member] | Other Accounting Method [Member] | Fair Value
Other Investment Not Readily Marketable [Line Items]
Other Investments	188	234
Partially-owned Investment Companies [Member] | Equity Method Investments [Member] | Fair Value
Other Investment Not Readily Marketable [Line Items]
Other Investments	5,969	4,142
Limited Partner [Member] | Cost-method Investments [Member] | Fair Value
Other Investment Not Readily Marketable [Line Items]
Other Investments	547	508
Investment Funds [Member] | Cost-method Investments [Member] | Fair Value
Other Investment Not Readily Marketable [Line Items]
Other Investments	254	271
Life Insurance Product Line [Member] | Other Accounting Method [Member] | Fair Value
Other Investment Not Readily Marketable [Line Items]
Other Investments	438	377
Policy Loans [Member] | Other Accounting Method [Member] | Fair Value
Other Investment Not Readily Marketable [Line Items]
Other Investments	233	247
Non-qualified separate account assets [Member] | Other Accounting Method [Member] | Fair Value
Other Investment Not Readily Marketable [Line Items]
Other Investments	$ 316	$ 283

Investments (Rollforward of exp

Investments (Rollforward of expected credit losses AFS) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Jan. 01, 2020
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items]
Debt Securities, Available-for-sale, Allowance for Credit Loss	$ 20	$ 0
Debt Securities, Available-for-sale, Allowance for Credit Loss, Purchased with Credit Deterioration, Increase	5
Debt Securities, Available-for-sale, Allowance for Credit Loss, Period Increase (Decrease)	188
Debt Securities, Available-for-sale, Allowance for Credit Loss, Recovery	(193)
Debt Securities, Available-for-sale, Allowance for Credit Loss, Writeoff	(5)
Accounting Standards Update 2016-13 [Member]
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items]
Debt Securities, Available-for-sale, Allowance for Credit Loss				$ 25
Debt Securities, Available-for-sale, Allowance for Credit Loss, Period Increase (Decrease)	$ 11	$ 0	$ 0

Investments (Rollforward of e_2

Investments (Rollforward of expected credit losses HTM) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Jan. 01, 2020	Dec. 31, 2019
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items]
Debt Securities, Held-to-maturity, Allowance for Credit Loss	$ 44		$ 0
Debt Securities, Held-to-maturity, Allowance for Credit Loss, Period Increase (Decrease)	9
Debt Securities, Held-to-maturity, Allowance for Credit Loss, Recovery	$ (9)
Accounting Standards Update 2016-13 [Member]
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items]
Debt Securities, Held-to-maturity, Allowance for Credit Loss		$ 44

Investments Investments (Entiti

Investments Investments (Entities That Calculate Net Asset Value Per Share) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments	$ 3,200	$ 3,263
Alternative Investment	6,770	4,921
Financial [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments	237	329
Alternative Investment	$ 673	$ 611
Financial [Member] | Minimum [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Liquidating Investment, Remaining Period	2 years	2 years
Financial [Member] | Maximum
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Liquidating Investment, Remaining Period	10 years	10 years
Real Estate Funds [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments	$ 598	$ 422
Alternative Investment	$ 805	$ 712
Real Estate Funds [Member] | Minimum [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Liquidating Investment, Remaining Period	2 years	2 years
Real Estate Funds [Member] | Maximum
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Liquidating Investment, Remaining Period	11 years	11 years
Distressed Alternative Investments [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments	$ 970	$ 80
Alternative Investment	$ 358	$ 263
Distressed Alternative Investments [Member] | Minimum [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Liquidating Investment, Remaining Period	2 years	2 years
Distressed Alternative Investments [Member] | Maximum
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Liquidating Investment, Remaining Period	8 years	8 years
Private Credit Alternative Investments [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments	$ 270	$ 272
Alternative Investment	$ 88	$ 104
Private Credit Alternative Investments [Member] | Minimum [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Liquidating Investment, Remaining Period	3 years	3 years
Private Credit Alternative Investments [Member] | Maximum
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Liquidating Investment, Remaining Period	8 years	8 years
Private Equity Funds [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments	$ 1,125	$ 2,160
Alternative Investment	$ 4,519	$ 2,844
Private Equity Funds [Member] | Minimum [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Liquidating Investment, Remaining Period	2 years	2 years
Private Equity Funds [Member] | Maximum
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Liquidating Investment, Remaining Period	14 years	14 years
Vintage Alternative Investments [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments	$ 0	$ 0
Alternative Investment	$ 73	$ 116
Vintage Alternative Investments [Member] | Minimum [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Liquidating Investment, Remaining Period	1 year	1 year
Vintage Alternative Investments [Member] | Maximum
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Liquidating Investment, Remaining Period	2 years	2 years
Investment Funds Alternative Investments [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments	$ 0	$ 0
Alternative Investment	$ 254	$ 271

Investments (Schedule Of Invest

Investments (Schedule Of Investments In Partially-Owned Insurance Companies) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Investment [Line Items]
Document Period End Date	Dec. 31, 2020
Carrying Value	$ 2,813	$ 1,332
Goodwill	15,400	15,296	$ 15,271
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity	$ 1,385	527
Huatai Group [Member]
Investment [Line Items]
Ownership Percentage	47.10%
Huatai Group [Member] | CHINA
Investment [Line Items]
Carrying Value	$ 2,461	$ 1,053
Ownership Percentage	47.00%	31.00%
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity	$ 1,313	$ 460
Huatai Life Insurance Co. [Member] | CHINA
Investment [Line Items]
Carrying Value	$ 201	$ 147
Ownership Percentage	20.00%	20.00%
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity	$ 69	$ 64
Freisenbruch-Meyer | Bermuda
Investment [Line Items]
Carrying Value	$ 10	$ 10
Ownership Percentage	40.00%	40.00%
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity	$ 3	$ 3
Chubb Arabia Cooperative Insurance Company [Member] | Saudi Arabia
Investment [Line Items]
Carrying Value	$ 23	$ 20
Ownership Percentage	30.00%	30.00%
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity	$ 0	$ 0
Russian Reinsurance Company | Russia
Investment [Line Items]
Carrying Value	$ 4	$ 2
Ownership Percentage	23.00%	23.00%
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity	$ 0	$ 0
ABR Reinsurance Capital Holdings Ltd. [Member] | Bermuda
Investment [Line Items]
Carrying Value	$ 114	$ 100
Ownership Percentage	15.60%	12.00%
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity	$ 0	$ 0
Direct Ownership [Member] | Huatai Life Insurance Co. [Member] | CHINA
Investment [Line Items]
Ownership Percentage	20.00%
Indirect Ownership [Member] | Huatai Life Insurance Co. [Member] | CHINA
Investment [Line Items]
Ownership Percentage	37.50%
Total Direct and Indirect [Member] | Huatai Life Insurance Co. [Member] | CHINA
Investment [Line Items]
Ownership Percentage	57.50%

Investments (Schedule Of Source

Investments (Schedule Of Sources Of Net Investment Income) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Net Investment Income [Line Items]
Gross investment income	$ 3,551	$ 3,598	$ 3,473
Investment expenses	(176)	(172)	(168)
Net investment income	3,375	3,426	3,305
Amortization of Debt Issuance Costs and Discounts	(367)	(395)	(592)
The Chubb Corporation [Member]
Net Investment Income [Line Items]
Amortization of Debt Issuance Costs and Discounts	(116)	(161)	(248)
Fixed Maturities [Member]
Net Investment Income [Line Items]
Gross investment income	3,321	3,385	3,128
Short-term investments
Net Investment Income [Line Items]
Gross investment income	48	84	90
Other interest income [Member]
Net Investment Income [Line Items]
Gross investment income	19	25	118
Equity securities
Net Investment Income [Line Items]
Gross investment income	81	26	33
Other Investments [Member]
Net Investment Income [Line Items]
Gross investment income	$ 82	$ 78	$ 104

Investments (Schedule Of Compon

Investments (Schedule Of Components Of Restricted Assets) (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Investments, Debt and Equity Securities [Abstract]
Funds Held under Reinsurance Agreements, Asset	$ 12,305	$ 14,004
Deposits with non-U.S. regulatory authorities	2,905	2,709
Collateral pledged under repurchase agreements	1,462	1,464
Deposits with U.S. regulatory authorities	2,438	2,466
Other pledged assets	584	490
Total restricted assets	$ 19,694	$ 21,133

Fair Value Measurements (Narrat

Fair Value Measurements (Narrative) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, Gain (Loss) on Derivative, Net	$ (228)	$ (585)	$ (330)
Accounts payable, accrued expenses, and other liabilities	14,052	12,214
Guaranteed Minimum Income Benefit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, Gain (Loss) on Derivative, Net	(202)	(4)	(248)
Accounts payable, accrued expenses, and other liabilities		441	409	$ 346
Fair Value, Inputs, Level 3 [Member] | Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Period Increase (Decrease)	0	0	0
Fair Value, Inputs, Level 3 [Member] | Short-term investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Period Increase (Decrease)	0	0	0
Fair Value, Inputs, Level 3 [Member] | Other Long-term Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Period Increase (Decrease)	0	0	0
Fair Value, Inputs, Level 3 [Member] | Fixed maturities available for sale | Debt Security, Government, Non-US [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Period Increase (Decrease)	0	0	0
Fair Value, Inputs, Level 3 [Member] | Fixed maturities available for sale | Corporate securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Period Increase (Decrease)	0	0	0
Fair Value, Inputs, Level 3 [Member] | Fixed maturities available for sale | Mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Period Increase (Decrease)	0	0	0
Guaranteed Minimum Income Benefit | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Period Increase (Decrease)	$ (10)	$ 32	$ 63

Fair Value Measurements (Financ

Fair Value Measurements (Financial Instruments Measured At Fair Value On Recurring Basis) (Detail) - USD ($) $ in Millions	Dec. 31, 2020		Dec. 31, 2019
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available for sale, Fair Value	$ 90,699		$ 85,488
Equity Securities, FV-NI	4,027		812
Short-term investments	4,345		4,291
Other Investments	7,945		6,062
Securities lending collateral	1,844		994
US Treasury and Government [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available for sale, Fair Value	2,670		3,283
Foreign
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available for sale, Fair Value	26,354		23,707
Corporate securities
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available for sale, Fair Value	36,331		31,791
Mortgage-backed securities
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available for sale, Fair Value	18,470		19,192
States, municipalities, and political subdivisions
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available for sale, Fair Value	6,874		7,515
Estimate of Fair Value Measurement [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Other Investments	7,945		6,062
Investment Funds Limited Partnerships Partially Owned Investment Companies Fair Value [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Other Investments	6,770		4,921
Other Investments
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Other Investments	60		95
Policy Loans [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Other Investments	233
Fair Value, Recurring [Member] | Estimate of Fair Value Measurement [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available for sale, Fair Value	90,699		85,488
Equity Securities			812
Equity Securities, FV-NI	4,027
Short-term investments	4,345		4,291
Other Investments	882		799
Securities lending collateral	1,844		994
Investment derivative instruments, assets	35		24
Other derivative instruments, assets			2
Separate Account Asset	4,388		3,573
Total assets measured at fair value	106,220	[1]	95,983	[2]
Investment derivative instruments, liability	52		93
Liabilities Related to Investment Contracts, Fair Value Disclosure	1,158		1,003
Other derivative instruments, liability	17		13
Fair Value, Recurring [Member] | Estimate of Fair Value Measurement [Member] | US Treasury and Government [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available for sale, Fair Value	2,670		3,283
Fair Value, Recurring [Member] | Estimate of Fair Value Measurement [Member] | Foreign
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available for sale, Fair Value	26,354		23,707
Fair Value, Recurring [Member] | Estimate of Fair Value Measurement [Member] | Corporate securities
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available for sale, Fair Value	36,331		31,791
Fair Value, Recurring [Member] | Estimate of Fair Value Measurement [Member] | Mortgage-backed securities
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available for sale, Fair Value	18,470		19,192
Fair Value, Recurring [Member] | Estimate of Fair Value Measurement [Member] | States, municipalities, and political subdivisions
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available for sale, Fair Value	6,874		7,515
Fair Value, Recurring [Member] | Level 1
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available for sale, Fair Value	2,148		2,664
Equity Securities			728
Equity Securities, FV-NI	3,954
Short-term investments	2,866		2,803
Other Investments	434		412
Securities lending collateral	0		0
Investment derivative instruments, assets	35		24
Other derivative instruments, assets			2
Separate Account Asset	4,264		3,437
Total assets measured at fair value	13,701	[1]	10,070	[2]
Investment derivative instruments, liability	52		93
Liabilities Related to Investment Contracts, Fair Value Disclosure	69		106
Other derivative instruments, liability	17		13
Fair Value, Recurring [Member] | Level 1 | US Treasury and Government [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available for sale, Fair Value	2,148		2,664
Fair Value, Recurring [Member] | Level 1 | Foreign
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available for sale, Fair Value	0		0
Fair Value, Recurring [Member] | Level 1 | Corporate securities
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available for sale, Fair Value	0		0
Fair Value, Recurring [Member] | Level 1 | Mortgage-backed securities
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available for sale, Fair Value	0		0
Fair Value, Recurring [Member] | Level 1 | States, municipalities, and political subdivisions
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available for sale, Fair Value	0		0
Fair Value, Recurring [Member] | Level 2
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available for sale, Fair Value	86,372		80,864
Equity Securities			15
Equity Securities, FV-NI	0
Short-term investments	1,474		1,482
Other Investments	438		377
Securities lending collateral	1,844		994
Investment derivative instruments, assets	0		0
Other derivative instruments, assets			0
Separate Account Asset	124		136
Total assets measured at fair value	90,252	[1]	83,868	[2]
Investment derivative instruments, liability	0		0
Liabilities Related to Investment Contracts, Fair Value Disclosure	0		0
Other derivative instruments, liability	0		0
Fair Value, Recurring [Member] | Level 2 | US Treasury and Government [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available for sale, Fair Value	522		619
Fair Value, Recurring [Member] | Level 2 | Foreign
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available for sale, Fair Value	25,808		23,258
Fair Value, Recurring [Member] | Level 2 | Corporate securities
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available for sale, Fair Value	34,758		30,340
Fair Value, Recurring [Member] | Level 2 | Mortgage-backed securities
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available for sale, Fair Value	18,410		19,132
Fair Value, Recurring [Member] | Level 2 | States, municipalities, and political subdivisions
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available for sale, Fair Value	6,874		7,515
Fair Value, Recurring [Member] | Level 3
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available for sale, Fair Value	2,179		1,960
Equity Securities			69
Equity Securities, FV-NI	73
Short-term investments	5		6
Other Investments	10		10
Securities lending collateral	0		0
Investment derivative instruments, assets	0		0
Other derivative instruments, assets			0
Separate Account Asset	0		0
Total assets measured at fair value	2,267	[1]	2,045	[2]
Investment derivative instruments, liability	0		0
Liabilities Related to Investment Contracts, Fair Value Disclosure	1,089		897
Other derivative instruments, liability	0		0
Fair Value, Recurring [Member] | Level 3 | US Treasury and Government [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available for sale, Fair Value	0		0
Fair Value, Recurring [Member] | Level 3 | Foreign
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available for sale, Fair Value	546		449
Fair Value, Recurring [Member] | Level 3 | Corporate securities
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available for sale, Fair Value	1,573		1,451
Fair Value, Recurring [Member] | Level 3 | Mortgage-backed securities
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available for sale, Fair Value	60		60
Fair Value, Recurring [Member] | Level 3 | States, municipalities, and political subdivisions
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available for sale, Fair Value	0		0
Guaranteed Minimum Income Benefit | Fair Value, Recurring [Member] | Estimate of Fair Value Measurement [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Liabilities for Guarantees on Long-Duration Contracts, Guaranteed Benefit Liability, Gross	1,089		897
Guaranteed Minimum Income Benefit | Fair Value, Recurring [Member] | Level 1
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Liabilities for Guarantees on Long-Duration Contracts, Guaranteed Benefit Liability, Gross	0		0
Guaranteed Minimum Income Benefit | Fair Value, Recurring [Member] | Level 2
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Liabilities for Guarantees on Long-Duration Contracts, Guaranteed Benefit Liability, Gross	0		0
Guaranteed Minimum Income Benefit | Fair Value, Recurring [Member] | Level 3
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Liabilities for Guarantees on Long-Duration Contracts, Guaranteed Benefit Liability, Gross	$ 1,089		$ 897
[1]	Excluded from the table above are partially-owned investments, investment funds, and limited partnerships of $6,770 million, policy loans of $233 million and other investments of $60 million at December 31, 2020 measured using NAV as a practical expedient
[2]	Excluded from the table above are partially-owned investments, investment funds, and limited partnerships of $4,921 million and other investments of $95 million at December 31, 2019 measured using NAV as a practical expedient. (2) Our GLB reinsurance product meets the definition of a derivative instrument for accounting purposes and is accordingly carried at fair value.

Fair Value Measurements (Schedu

Fair Value Measurements (Schedule Of Significant Unobservable Inputs Used In Level 3 Liability Valuations) (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Minimum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Long-Duration Contracts, Assumptions by Product and Guarantee, Lapse Rate		3.00%
Annuitization rate		0.00%
Maximum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Long-Duration Contracts, Assumptions by Product and Guarantee, Lapse Rate		34.00%
Annuitization rate		100.00%
Weighted Average
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Long-Duration Contracts, Assumptions by Product and Guarantee, Lapse Rate		4.70%
Annuitization rate	[1]	3.60%
Level 3 | Other derivative instruments
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability Value					$ 0	$ 2
Settlements, liabilities					0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Period Increase (Decrease)					0
Level 3 | Equity Securities [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Settlements, assets		$ 0		$ 0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Period Increase (Decrease)		0		0	0
Level 3 | Short-term investments
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Settlements, assets		(12)		(1)	(13)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Period Increase (Decrease)		0		0	0
Level 3 | Other Long-term Investments [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Settlements, assets		0		(1)	(49)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Period Increase (Decrease)		0		0	0
Level 3 | Fixed maturities available for sale | Debt Security, Government, Non-US [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Settlements, assets		(57)		(53)	(9)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Period Increase (Decrease)		0		0	0
Level 3 | Fixed maturities available for sale | Corporate securities
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Settlements, assets		(423)		(279)	(230)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Period Increase (Decrease)		0		0	0
Level 3 | Fixed maturities available for sale | Mortgage-backed securities
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Settlements, assets		(1)		(3)	(20)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Period Increase (Decrease)		0		0	0
Guaranteed Minimum Income Benefit | Level 3
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability Value		1,089	[2]	897	861	$ 550
Settlements, liabilities		0		0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Period Increase (Decrease)		(10)		$ 32	$ 63
Guaranteed Minimum Income Benefit | Level 3 | Fair Value, Recurring [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability Value		$ 1,089
[1]	The weighted average lapse and annuitization rates are determined by weighting each treaty's rates by the GLB contracts fair value.
[2]	Our GLB reinsurance product meets the definition of a derivative instrument for accounting purposes and is accordingly carried at fair value.

Fair value measurements Fair Va

Fair value measurements Fair Value Measurements (Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation) (Details) - Level 3 - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Equity securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance- Beginning of year, assets	$ 69	$ 57	$ 44
Transfers into Level 3, assets	0	0	0
Transfers out of Level 3, assets	(3)	0	0
Change in Net Unrealized Gains (Losses) included in OCI, Assets	0	1	(2)
Net Realized Gains/Losses, Assets	1	(2)	6
Purchased, assets	23	34	37
Sales, assets	(17)	(21)	(28)
Settlements, assets	0	0	0
Balance- End of year, assets	73	69	57
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Assets	4	(3)	(1)
Change in Net Unrealized Gains/Losses included in OCI at the Balance Sheet Date, Assets	0	0
Short-term investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance- Beginning of year, assets	6	1	0
Transfers into Level 3, assets	0	0	5
Transfers out of Level 3, assets	0	0	0
Change in Net Unrealized Gains (Losses) included in OCI, Assets	0	0	0
Net Realized Gains/Losses, Assets	1	0	0
Purchased, assets	14	6	9
Sales, assets	(2)	0	0
Settlements, assets	(12)	(1)	(13)
Balance- End of year, assets	5	6	1
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Assets	0	0	0
Change in Net Unrealized Gains/Losses included in OCI at the Balance Sheet Date, Assets	0	0
Other investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance- Beginning of year, assets	10	11	263
Transfers into Level 3, assets	0	0	0
Transfers out of Level 3, assets	0	0	(252)
Change in Net Unrealized Gains (Losses) included in OCI, Assets	0	0	(2)
Net Realized Gains/Losses, Assets	0	0	1
Purchased, assets	0	0	50
Sales, assets	0	0	0
Settlements, assets	0	(1)	(49)
Balance- End of year, assets	10	10	11
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Assets	0	0	1
Change in Net Unrealized Gains/Losses included in OCI at the Balance Sheet Date, Assets	0	0
Available-for-sale Securities [Member] | Foreign
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance- Beginning of year, assets	449	345	93
Transfers into Level 3, assets	0	11	13
Transfers out of Level 3, assets	(16)	(24)	(2)
Change in Net Unrealized Gains (Losses) included in OCI, Assets	19	13	(12)
Net Realized Gains/Losses, Assets	(1)	(1)	(3)
Purchased, assets	274	228	334
Sales, assets	(122)	(70)	(69)
Settlements, assets	(57)	(53)	(9)
Balance- End of year, assets	546	449	345
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Assets	0	0	(1)
Change in Net Unrealized Gains/Losses included in OCI at the Balance Sheet Date, Assets	16	7
Available-for-sale Securities [Member] | Corporate securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance- Beginning of year, assets	1,451	1,299	1,037
Transfers into Level 3, assets	134	23	24
Transfers out of Level 3, assets	(73)	(38)	(31)
Change in Net Unrealized Gains (Losses) included in OCI, Assets	(8)	(2)	(4)
Net Realized Gains/Losses, Assets	(30)	(4)	(5)
Purchased, assets	708	577	672
Sales, assets	(186)	(125)	(164)
Settlements, assets	(423)	(279)	(230)
Balance- End of year, assets	1,573	1,451	1,299
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Assets	(5)	(2)	(7)
Change in Net Unrealized Gains/Losses included in OCI at the Balance Sheet Date, Assets	(6)	(8)
Available-for-sale Securities [Member] | Mortgage-backed securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance- Beginning of year, assets	60	61	78
Transfers into Level 3, assets	0	0	1
Transfers out of Level 3, assets	(1)	(16)	(3)
Change in Net Unrealized Gains (Losses) included in OCI, Assets	0	0	0
Net Realized Gains/Losses, Assets	0	0	0
Purchased, assets	2	19	5
Sales, assets	0	(1)	0
Settlements, assets	(1)	(3)	(20)
Balance- End of year, assets	60	60	61
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Assets	0	0	$ 0
Change in Net Unrealized Gains/Losses included in OCI at the Balance Sheet Date, Assets	$ 0	$ 0

Fair value measurements Fair _2

Fair value measurements Fair Value Measurements (Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation) (Details) - Level 3 - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020		Dec. 31, 2019	Dec. 31, 2018
Guaranteed Minimum Income Benefit
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance - Beginning of year, liabilities	$ 897		$ 861	$ 550
Transfers Into Level 3, liabilities	0		0	0
Transfers out of Level 3, liabilities	0		0	0
Change in Net Unrealized Gains (Losses) included in OCI, Liabilities	0		0	0
Net Realized Gains/Losses, Liabilities	202		4	248
Purchased, liabilities	0		0	0
Sales, liabilities	0		0	0
Settlements, liabilities	0		0	0
Balance - End of year, liabilities	1,089	[1]	897	861
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Liabilities	202		4	248
Fair Value, Liability, Recurring Basis, Still Held, Unrealized Gain (Loss), OCI	$ 0		0
Other derivative instruments
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance - Beginning of year, liabilities			$ 0	2
Transfers Into Level 3, liabilities				0
Transfers out of Level 3, liabilities				0
Change in Net Unrealized Gains (Losses) included in OCI, Liabilities				0
Net Realized Gains/Losses, Liabilities				(2)
Purchased, liabilities				0
Sales, liabilities				0
Settlements, liabilities				0
Balance - End of year, liabilities				0
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Liabilities				$ 0
[1]	Our GLB reinsurance product meets the definition of a derivative instrument for accounting purposes and is accordingly carried at fair value.

Fair Value Measurements (Carryi

Fair Value Measurements (Carrying Values And Fair Values Of Financial Instruments Not Measured At Fair Value) (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt Securities, Held-to-maturity, Fair Value	$ 12,510	$ 13,005
Debt Securities, Held-to-maturity	11,697	12,581
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Repurchase agreements	1,405	1,416
Short-term debt	0	1,299
Long-term debt	14,948	13,559
Trust preferred securities	308	308
Total liabilities	131,333	121,612
US Treasury and Government [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt Securities, Held-to-maturity, Fair Value	1,452	1,347
Debt Securities, Held-to-maturity	1,392	1,318
Foreign
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt Securities, Held-to-maturity, Fair Value	1,405	1,485
Debt Securities, Held-to-maturity	1,295	1,423
Corporate securities
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt Securities, Held-to-maturity, Fair Value	2,438	2,468
Debt Securities, Held-to-maturity	2,185	2,349
Mortgage-backed securities
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt Securities, Held-to-maturity, Fair Value	2,146	2,396
Debt Securities, Held-to-maturity	2,000	2,331
States, municipalities, and political subdivisions
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt Securities, Held-to-maturity, Fair Value	5,069	5,309
Debt Securities, Held-to-maturity	4,825	5,160
Estimate of Fair Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Repurchase agreements	1,405	1,416
Short-term debt, Fair Value	0	1,307
Long-term debt, Fair Value	17,487	15,048
Trust preferred securities	473	467
Total liabilities	19,365	18,238
Reported Value Measurement
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt Securities, Held-to-maturity	11,653	12,581
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Repurchase agreements	1,405	1,416
Short-term debt	0	1,299
Long-term debt	14,948	13,559
Trust preferred securities	308	308
Total liabilities	16,661	16,582
Reported Value Measurement | US Treasury and Government [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt Securities, Held-to-maturity	1,392	1,318
Reported Value Measurement | Foreign
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt Securities, Held-to-maturity	1,288	1,423
Reported Value Measurement | Corporate securities
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt Securities, Held-to-maturity	2,150	2,349
Reported Value Measurement | Mortgage-backed securities
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt Securities, Held-to-maturity	1,999	2,331
Reported Value Measurement | States, municipalities, and political subdivisions
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt Securities, Held-to-maturity	4,824	5,160
Level 1
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt Securities, Held-to-maturity, Fair Value	1,395	1,292
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Repurchase agreements	0	0
Short-term debt, Fair Value	0	0
Long-term debt, Fair Value	0	0
Trust preferred securities	0	0
Total liabilities	0	0
Level 1 | US Treasury and Government [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt Securities, Held-to-maturity, Fair Value	1,395	1,292
Level 1 | Foreign
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt Securities, Held-to-maturity, Fair Value	0	0
Level 1 | Corporate securities
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt Securities, Held-to-maturity, Fair Value	0	0
Level 1 | Mortgage-backed securities
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt Securities, Held-to-maturity, Fair Value	0	0
Level 1 | States, municipalities, and political subdivisions
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt Securities, Held-to-maturity, Fair Value	0	0
Level 2
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt Securities, Held-to-maturity, Fair Value	11,115	11,681
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Repurchase agreements	1,405	1,416
Short-term debt, Fair Value	0	1,307
Long-term debt, Fair Value	17,487	15,048
Trust preferred securities	473	467
Total liabilities	19,365	18,238
Level 2 | US Treasury and Government [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt Securities, Held-to-maturity, Fair Value	57	55
Level 2 | Foreign
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt Securities, Held-to-maturity, Fair Value	1,405	1,485
Level 2 | Corporate securities
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt Securities, Held-to-maturity, Fair Value	2,438	2,436
Level 2 | Mortgage-backed securities
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt Securities, Held-to-maturity, Fair Value	2,146	2,396
Level 2 | States, municipalities, and political subdivisions
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt Securities, Held-to-maturity, Fair Value	5,069	5,309
Level 3
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt Securities, Held-to-maturity, Fair Value	0	32
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Repurchase agreements	0	0
Short-term debt, Fair Value	0	0
Long-term debt, Fair Value	0	0
Trust preferred securities	0	0
Total liabilities	0	0
Level 3 | US Treasury and Government [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt Securities, Held-to-maturity, Fair Value	0	0
Level 3 | Foreign
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt Securities, Held-to-maturity, Fair Value	0	0
Level 3 | Corporate securities
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt Securities, Held-to-maturity, Fair Value	0	32
Level 3 | Mortgage-backed securities
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt Securities, Held-to-maturity, Fair Value	0	0
Level 3 | States, municipalities, and political subdivisions
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt Securities, Held-to-maturity, Fair Value	$ 0	$ 0

Reinsurance (Consolidated Reins

Reinsurance (Consolidated Reinsurance) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Premiums written [Abstract]
Direct	$ 37,749	$ 36,848	$ 34,782
Assumed	3,512	3,276	3,186
Ceded	(7,441)	(7,849)	(7,389)
Net	33,820	32,275	30,579
Premiums earned [Abstract]
Direct	37,037	35,876	34,108
Assumed	3,323	3,107	3,175
Ceded	(7,243)	(7,693)	(7,219)
Net premiums earned	33,117	31,290	30,064
Reinsurance recoveries on losses and loss expenses incurred	$ 5,000	$ 4,900	$ 5,600

Reinsurance (Reinsurance Recove

Reinsurance (Reinsurance Recoverable on Ceded Reinsurance) (Details) - USD ($) $ in Millions		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reinsurance Disclosures [Abstract]
Reinsurance recoverable on unpaid losses	[1]	$ 14,647	$ 14,181	$ 14,689	$ 14,014
Reinsurance Recoverables on Unpaid Losses, Allowance		257	240
Reinsurance recoverable on paid losses and loss expenses		945	1,000
Reinsurance Recoverables on Paid Losses, Allowance		57	76
Net reinsurance recoverable on losses and loss expenses	[2]	15,592	15,181
Reinsurance Recoverable, Allowance for Credit Loss		314	316
Reinsurance Recoverable Future Policy Benefits		206	197
Reinsurance Recoverables on Future Policy Benefits, Allowance		$ 5	$ 4
[1]	Net of valuation allowance for uncollectible reinsurance.
[2]	Net of valuation allowance for uncollectible reinsurance.

Reinsurance, Allowance (Details

Reinsurance, Allowance (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Reinsurance Disclosures [Abstract]
Reinsurance Recoverable, Allowance for Credit Loss	$ 314	$ 316
Reinsurance Recoverable, Credit Loss Expense (Reversal)	21
Reinsurance, Loss on Uncollectible Accounts in Period, Amount	(25)
Reinsurance Recoverable, Allowance for Credit Loss, Other	$ 2

Reinsurance (Reinsurance Reco_2

Reinsurance (Reinsurance Recoverable by Category and Listing of Largest Reinsurers) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Ceded Credit Risk [Line Items]
Gross reinsurance recoverable	$ 15,906
Provision	$ 314	$ 316
% of Gross	2.00%
Largest reinsurers
Ceded Credit Risk [Line Items]
Gross reinsurance recoverable	$ 7,267
Provision	$ 88
% of Gross	1.20%
Other reinsurers balances rated A- or better
Ceded Credit Risk [Line Items]
Gross reinsurance recoverable	$ 4,901
Provision	$ 58
% of Gross	1.20%
Other reinsurers balances with ratings lower than A- or not rated
Ceded Credit Risk [Line Items]
Gross reinsurance recoverable	$ 466
Provision	$ 64
% of Gross	13.70%
Other pools and government agencies
Ceded Credit Risk [Line Items]
Gross reinsurance recoverable	$ 366
Provision	$ 14
% of Gross	3.80%
Structured settlements
Ceded Credit Risk [Line Items]
Gross reinsurance recoverable	$ 521
Provision	$ 11
% of Gross	2.10%
Other captives
Ceded Credit Risk [Line Items]
Gross reinsurance recoverable	$ 2,107
Provision	$ 11
% of Gross	0.50%
Other
Ceded Credit Risk [Line Items]
Gross reinsurance recoverable	$ 278
Provision	$ 68
% of Gross	24.50%

Intangible Assets (Narrative) (

Intangible Assets (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Other intangible assets	$ 5,811	$ 6,063
Intangible assets subject to amortization	2,846	3,114
Intangible assets not subject to amortization	2,965	2,949
Amortization of Purchased Intangibles	$ 290	$ 305	$ 339

Intangible Assets (Roll-forward

Intangible Assets (Roll-forward of Goodwill by Business Segment) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Goodwill [Roll Forward]
Balance at beginning of period	$ 15,296	$ 15,271
Foreign exchange revaluation and other	60	25
Balance at end of period	15,400	15,296
North America Commercial P&C Insurance
Goodwill [Roll Forward]
Balance at beginning of period	6,955	6,946
Foreign exchange revaluation and other	17	9
Balance at end of period	6,972	6,955
Segment Insurance North American Personal P&C [Member] [Member]
Goodwill [Roll Forward]
Balance at beginning of period	2,234	2,230
Foreign exchange revaluation and other	6	4
Balance at end of period	2,240	2,234
North America Agricultural Insurance
Goodwill [Roll Forward]
Balance at beginning of period	134	134
Foreign exchange revaluation and other	0	0
Balance at end of period	134	134
Overseas General Insurance
Goodwill [Roll Forward]
Balance at beginning of period	4,785	4,770
Foreign exchange revaluation and other	35	15
Balance at end of period	4,836	4,785
Segment Global Reinsurance [Member]
Goodwill [Roll Forward]
Balance at beginning of period	371	371
Foreign exchange revaluation and other	0	0
Balance at end of period	371	371
Life Insurance
Goodwill [Roll Forward]
Balance at beginning of period	817	820
Foreign exchange revaluation and other	2	(3)
Balance at end of period	847	$ 817
Banchile Seguros de Vida [Member]
Goodwill [Roll Forward]
Goodwill, Acquired During Period	44
Banchile Seguros de Vida [Member] | North America Commercial P&C Insurance
Goodwill [Roll Forward]
Goodwill, Acquired During Period	0
Banchile Seguros de Vida [Member] | Segment Insurance North American Personal P&C [Member] [Member]
Goodwill [Roll Forward]
Goodwill, Acquired During Period	0
Banchile Seguros de Vida [Member] | North America Agricultural Insurance
Goodwill [Roll Forward]
Goodwill, Acquired During Period	0
Banchile Seguros de Vida [Member] | Overseas General Insurance
Goodwill [Roll Forward]
Goodwill, Acquired During Period	16
Banchile Seguros de Vida [Member] | Segment Global Reinsurance [Member]
Goodwill [Roll Forward]
Goodwill, Acquired During Period	0
Banchile Seguros de Vida [Member] | Life Insurance
Goodwill [Roll Forward]
Goodwill, Acquired During Period	$ 28

Intangible Assets (Estimated Am

Intangible Assets (Estimated Amortization Expense Over Next Five Years) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
2021, Other intangible assets	$ 286
2022, Other intangible assets	284
2023, Other intangible assets	267
2024, Other intangible assets	244
2025, Other intangible assets	228
Total, Other intangible assets	1,309
Other Intangible Assets [Member]
Finite-Lived Intangible Assets [Line Items]
2021, Other intangible assets	89
2022, Other intangible assets	101
2023, Other intangible assets	96
2024, Other intangible assets	90
2025, Other intangible assets	89
Total, Other intangible assets	465
The Chubb Corporation [Member]
Finite-Lived Intangible Assets [Line Items]
2021, Other intangible assets	197
2022, Other intangible assets	183
2023, Other intangible assets	171
2024, Other intangible assets	154
2025, Other intangible assets	139
Total, Other intangible assets	844
The Chubb Corporation [Member] | Agency distribution relationships and renewal rights [Member]
Finite-Lived Intangible Assets [Line Items]
2021, Other intangible assets	217
2022, Other intangible assets	197
2023, Other intangible assets	178
2024, Other intangible assets	160
2025, Other intangible assets	145
Total, Other intangible assets	897
The Chubb Corporation [Member] | Fair Value Adjustment to Acquired Loss Reserves [Member]
Finite-Lived Intangible Assets [Line Items]
2021, Other intangible assets	(20)
2022, Other intangible assets	(14)
2023, Other intangible assets	(7)
2024, Other intangible assets	(6)
2025, Other intangible assets	(6)
Total, Other intangible assets	(53)
Balance of FV adjustment on Unpaid Losses and Loss Expenses	$ 110	$ 145
Maximum
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	25 years

Intangible Assets (VOBA) (Detai

Intangible Assets (VOBA) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
VOBA Roll Forward
VOBA balance, beginning of year	$ 306	$ 295	$ 326
Amortization of Value of Business Acquired (VOBA)	(27)	(24)	(25)
VOBA Foreign exchange revaluation	(16)	35	(6)
VOBA balance, end of year	263	$ 306	$ 295
Present Value of Future Insurance Profits, Amortization Expense, Next Five Years [Abstract]
2021, VOBA	22
2022, VOBA	21
2023, VOBA	19
2024, VOBA	17
2025, VOBA	16
Total, VOBA	$ 95

Unpaid losses and loss expens_3

Unpaid losses and loss expenses (Unpaid Losses and Loss Expenses Rollforward) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Unpaid Losses and Loss Expenses [Roll Forward]
Gross unpaid losses and loss expenses, beginning of year		$ 62,690	$ 62,960	$ 63,179
Reinsurance recoverable on unpaid losses, beginning of year	[1]	(14,181)	(14,689)	(14,014)
Net unpaid losses and loss expenses, beginning of year		48,509	48,271	49,165
Net losses and loss expenses incurred in respect of losses incurring in Current Year		22,124	19,575	19,048
Prior Year Claims and Claims Adjustment Expense	[2]	(414)	(845)	(981)
Total		21,710	18,730	18,067
Net losses and loss expenses paid in Current Year		7,782	7,894	7,544
Net losses and loss expenses paid in Prior Year		9,652	10,579	10,796
Total		17,434	18,473	18,340
Foreign currency revaluation and other		379	(19)	(621)
Net unpaid losses and loss expenses, end of year		53,164	48,509	48,271
Reinsurance recoverable on unpaid losses, end of year	[1]	14,647	14,181	14,689
Gross unpaid losses and loss expenses, end of year		67,811	62,690	62,960
Prior Period Development, net adjustments		$ 19	$ 53	$ 85
[1]	Net of valuation allowance for uncollectible reinsurance.
[2]	Relates to prior period loss reserve development only and excludes prior period development related to reinstatement premiums, expense adjustments and earned premiums totaling $19 million, $53 million, and $85 million for 2020, 2019, and 2018, respectively.

Unpaid losses and loss expens_4

Unpaid losses and loss expenses Unpaid losses and loss expenses (Reconciliation of reserve Balances to Liability for Unpaid Loss)(Details) (Details) - USD ($) $ in Millions		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Unpaid Loss and Allocated Loss Adjustment Expenses, Net		$ 50,492
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments		14,687
Short-duration Insurance Contracts, Liability for Unpaid Claims and Claim Adjustment Expense, Aggregate Reconciling Items	[1]	1,109
Unpaid unallocated loss adjustment expenses		1,523
Unpaid losses and loss expenses		67,811	$ 62,690	$ 62,960	$ 63,179
North America Commercial P&C Insurance - Workers' Compensation [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Unpaid Loss and Allocated Loss Adjustment Expenses, Net		9,600
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments		1,461
North America Commercial P&C Insurance - Liability [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Unpaid Loss and Allocated Loss Adjustment Expenses, Net		17,441
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments		5,743
North America Commercial P&C Insurance - Other Casualty [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Unpaid Loss and Allocated Loss Adjustment Expenses, Net		2,124
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments		564
North America Commercial P&C Insurance - Non-Casualty [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Unpaid Loss and Allocated Loss Adjustment Expenses, Net		2,491
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments		1,380
North America Personal P&C Insurance [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Unpaid Loss and Allocated Loss Adjustment Expenses, Net		3,025
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments		141
Overseas General Insurance - Casualty [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Unpaid Loss and Allocated Loss Adjustment Expenses, Net		6,832
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments		2,426
Overseas General Insurance - Non-Casualty [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Unpaid Loss and Allocated Loss Adjustment Expenses, Net		2,725
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments		1,686
Global Reinsurance - Casualty [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Unpaid Loss and Allocated Loss Adjustment Expenses, Net		1,200
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments		29
Global Reinsurance - Non-Casualty [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Unpaid Loss and Allocated Loss Adjustment Expenses, Net		312
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments		104
Other Segments [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Unpaid Loss and Allocated Loss Adjustment Expenses, Net		4,742
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments		$ 1,153
[1]	Primarily includes the claims reserve of our International A&H business and Life Insurance segment reserves.

Unpaid losses and loss expens_5

Unpaid losses and loss expenses Unpaid Losses and loss expenses, claims development (Cumulative Net incurred Loss and Allocated Loss Adjustment Expense) (Details) $ in Millions	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)	Dec. 31, 2012USD ($)	Dec. 31, 2011USD ($)
Claims Development [Line Items]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net	$ 50,492
North America Commercial P&C Insurance - Workers' Compensation [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	11,959
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	5,107
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net	9,600
North America Commercial P&C Insurance - Liability [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	35,276
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	19,294
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net	17,441
North America Commercial P&C Insurance - Other Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	5,415
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	3,578
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net	2,124
North America Commercial P&C Insurance - Non-Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	19,870
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	17,383
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net	2,491
North America Personal P&C Insurance [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	25,502
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	22,501
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net	3,025
Overseas General Insurance - Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	13,470
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	7,124
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net	6,832
Overseas General Insurance - Non-Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	20,129
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	17,498
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net	2,725
Global Reinsurance - Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	2,930
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	2,061
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net	1,200
Global Reinsurance - Non-Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	2,233
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	1,931
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net	312
Short-duration Insurance Contracts, Accident Year 2010 [Member] | North America Commercial P&C Insurance - Workers' Compensation [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	973	$ 988	$ 1,009	$ 1,012	$ 1,022	$ 1,053	$ 1,049	$ 1,046	$ 1,030	$ 1,037
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	208
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 654	640	616	595	567	533	484	411	294	119
Cumulative Number of Reported Claims	45,000
Short-duration Insurance Contracts, Accident Year 2010 [Member] | North America Commercial P&C Insurance - Liability [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 3,143	3,193	3,316	3,384	3,498	3,593	3,665	3,630	3,586	3,500
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	226
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 2,863	2,827	2,741	2,659	2,477	2,214	1,805	1,209	652	160
Cumulative Number of Reported Claims	25,000
Short-duration Insurance Contracts, Accident Year 2010 [Member] | North America Commercial P&C Insurance - Other Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 503	513	511	517	525	533	549	581	590	581
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	13
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 486	486	480	466	461	437	400	341	235	86
Cumulative Number of Reported Claims	16,000
Short-duration Insurance Contracts, Accident Year 2010 [Member] | North America Commercial P&C Insurance - Non-Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 1,833	1,835	1,835	1,835	1,840	1,835	1,856	1,877	1,934	1,960
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	4
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 1,830	1,825	1,821	1,816	1,811	1,787	1,777	1,718	1,574	939
Cumulative Number of Reported Claims	416,000
Short-duration Insurance Contracts, Accident Year 2010 [Member] | North America Personal P&C Insurance [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 2,157	2,159	2,158	2,160	2,161	2,164	2,173	2,185	2,210	2,208
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	7
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 2,149	2,148	2,146	2,139	2,129	2,105	2,052	1,972	1,835	1,360
Cumulative Number of Reported Claims	179,000
Short-duration Insurance Contracts, Accident Year 2010 [Member] | Overseas General Insurance - Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 1,025	1,023	1,027	1,079	1,090	1,158	1,244	1,254	1,262	1,255
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	31
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 901	876	842	789	713	631	528	393	243	86
Cumulative Number of Reported Claims	37,000
Short-duration Insurance Contracts, Accident Year 2010 [Member] | Overseas General Insurance - Non-Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 1,843	1,844	1,849	1,859	1,867	1,879	1,898	1,938	1,995	1,908
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	6
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 1,806	1,807	1,808	1,804	1,795	1,780	1,750	1,694	1,486	765
Cumulative Number of Reported Claims	543,000
Short-duration Insurance Contracts, Accident Year 2010 [Member] | Global Reinsurance - Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 389	402	409	415	418	428	433	430	415	408
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	15
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	338	332	325	312	292	267	236	195	146	70
Short-duration Insurance Contracts, Accident Year 2010 [Member] | Global Reinsurance - Non-Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	269	267	268	267	268	267	266	276	279	277
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	1
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	265	264	263	262	259	254	236	210	179	$ 87
Short-duration Insurance Contracts, Accident Year 2011 [Member] | North America Commercial P&C Insurance - Workers' Compensation [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	953	977	986	989	1,011	1,040	1,030	1,011	1,050
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	234
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 612	592	574	532	486	436	365	271	111
Cumulative Number of Reported Claims	44,000
Short-duration Insurance Contracts, Accident Year 2011 [Member] | North America Commercial P&C Insurance - Liability [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 3,235	3,235	3,331	3,426	3,524	3,565	3,613	3,628	3,552
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	353
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 2,688	2,619	2,502	2,326	2,092	1,680	1,172	656	166
Cumulative Number of Reported Claims	25,000
Short-duration Insurance Contracts, Accident Year 2011 [Member] | North America Commercial P&C Insurance - Other Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 505	507	509	519	520	561	577	606	634
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	2
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 502	493	487	470	435	387	320	223	69
Cumulative Number of Reported Claims	16,000
Short-duration Insurance Contracts, Accident Year 2011 [Member] | North America Commercial P&C Insurance - Non-Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 1,844	1,850	1,844	1,847	1,859	1,864	1,883	1,916	2,033
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	(8)
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 1,844	1,842	1,816	1,822	1,795	1,767	1,698	1,577	715
Cumulative Number of Reported Claims	426,000
Short-duration Insurance Contracts, Accident Year 2011 [Member] | North America Personal P&C Insurance [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 2,190	2,194	2,189	2,186	2,186	2,191	2,183	2,183	2,185
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	18
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 2,165	2,163	2,164	2,149	2,117	2,063	1,957	1,806	1,177
Cumulative Number of Reported Claims	188,000
Short-duration Insurance Contracts, Accident Year 2011 [Member] | Overseas General Insurance - Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 1,272	1,304	1,315	1,337	1,343	1,346	1,326	1,261	1,290
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	87
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 1,040	973	929	857	713	597	441	252	75
Cumulative Number of Reported Claims	38,000
Short-duration Insurance Contracts, Accident Year 2011 [Member] | Overseas General Insurance - Non-Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 1,562	1,570	1,575	1,590	1,599	1,605	1,661	1,702	1,712
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	13
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 1,532	1,532	1,530	1,518	1,508	1,485	1,425	1,237	679
Cumulative Number of Reported Claims	555,000
Short-duration Insurance Contracts, Accident Year 2011 [Member] | Global Reinsurance - Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 379	374	372	373	379	395	392	384	387
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	11
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	342	336	324	309	293	262	223	168	78
Short-duration Insurance Contracts, Accident Year 2011 [Member] | Global Reinsurance - Non-Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	184	186	186	188	191	192	202	211	233
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	1
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	180	181	180	178	173	167	157	130	$ 45
Short-duration Insurance Contracts, Accident Year 2012 [Member] | North America Commercial P&C Insurance - Workers' Compensation [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	1,014	1,037	1,073	1,086	1,127	1,122	1,108	1,109
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	280
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 633	616	587	553	506	422	286	107
Cumulative Number of Reported Claims	43,000
Short-duration Insurance Contracts, Accident Year 2012 [Member] | North America Commercial P&C Insurance - Liability [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 2,964	3,122	3,216	3,430	3,533	3,543	3,542	3,547
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	317
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 2,465	2,374	2,232	2,007	1,597	1,192	548	130
Cumulative Number of Reported Claims	25,000
Short-duration Insurance Contracts, Accident Year 2012 [Member] | North America Commercial P&C Insurance - Other Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 458	462	462	469	516	523	531	527
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	21
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 426	419	411	385	348	271	197	69
Cumulative Number of Reported Claims	18,000
Short-duration Insurance Contracts, Accident Year 2012 [Member] | North America Commercial P&C Insurance - Non-Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 1,344	1,338	1,340	1,340	1,360	1,337	1,424	1,434
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	7
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 1,335	1,333	1,324	1,311	1,285	1,238	1,138	651
Cumulative Number of Reported Claims	455,000
Short-duration Insurance Contracts, Accident Year 2012 [Member] | North America Personal P&C Insurance [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 1,948	1,945	1,937	1,924	1,900	1,897	1,888	1,860
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	26
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 1,917	1,895	1,885	1,843	1,787	1,688	1,504	1,043
Cumulative Number of Reported Claims	132,000
Short-duration Insurance Contracts, Accident Year 2012 [Member] | Overseas General Insurance - Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 1,148	1,182	1,242	1,276	1,322	1,276	1,279	1,281
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	86
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 952	899	829	725	579	428	267	85
Cumulative Number of Reported Claims	39,000
Short-duration Insurance Contracts, Accident Year 2012 [Member] | Overseas General Insurance - Non-Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 1,610	1,620	1,633	1,660	1,665	1,714	1,780	1,787
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	19
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 1,578	1,575	1,567	1,549	1,512	1,480	1,284	696
Cumulative Number of Reported Claims	573,000
Short-duration Insurance Contracts, Accident Year 2012 [Member] | Global Reinsurance - Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 311	317	324	332	331	330	327	321
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	13
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	272	269	260	242	222	186	143	65
Short-duration Insurance Contracts, Accident Year 2012 [Member] | Global Reinsurance - Non-Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	140	141	141	144	143	148	160	162
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	0
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	139	137	137	134	131	121	103	$ 46
Short-duration Insurance Contracts, Accident Year 2013 [Member] | North America Commercial P&C Insurance - Workers' Compensation [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	1,073	1,100	1,163	1,215	1,217	1,201	1,207
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	347
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 599	566	532	484	410	295	113
Cumulative Number of Reported Claims	45,000
Short-duration Insurance Contracts, Accident Year 2013 [Member] | North America Commercial P&C Insurance - Liability [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 3,346	3,470	3,656	3,717	3,674	3,586	3,535
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	572
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 2,584	2,442	2,202	1,804	1,250	679	164
Cumulative Number of Reported Claims	25,000
Short-duration Insurance Contracts, Accident Year 2013 [Member] | North America Commercial P&C Insurance - Other Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 539	539	555	597	581	583	595
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	25
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 501	474	455	391	318	220	80
Cumulative Number of Reported Claims	17,000
Short-duration Insurance Contracts, Accident Year 2013 [Member] | North America Commercial P&C Insurance - Non-Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 1,558	1,550	1,549	1,559	1,579	1,661	1,643
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	10
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 1,554	1,546	1,532	1,506	1,484	1,374	820
Cumulative Number of Reported Claims	483,000
Short-duration Insurance Contracts, Accident Year 2013 [Member] | North America Personal P&C Insurance [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 2,141	2,147	2,160	2,146	2,192	2,206	2,205
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	14
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 2,116	2,106	2,080	2,035	1,926	1,765	1,310
Cumulative Number of Reported Claims	144,000
Short-duration Insurance Contracts, Accident Year 2013 [Member] | Overseas General Insurance - Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 1,165	1,206	1,293	1,378	1,362	1,352	1,279
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	151
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 876	811	725	608	473	293	111
Cumulative Number of Reported Claims	39,000
Short-duration Insurance Contracts, Accident Year 2013 [Member] | Overseas General Insurance - Non-Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 1,810	1,817	1,828	1,864	1,875	1,932	1,863
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	7
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 1,774	1,759	1,746	1,715	1,651	1,438	758
Cumulative Number of Reported Claims	548,000
Short-duration Insurance Contracts, Accident Year 2013 [Member] | Global Reinsurance - Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 331	348	345	343	340	335	334
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	16
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	287	277	265	249	218	185	92
Short-duration Insurance Contracts, Accident Year 2013 [Member] | Global Reinsurance - Non-Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	182	183	184	186	183	182	167
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	3
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	175	173	171	165	154	131	$ 66
Short-duration Insurance Contracts, Accident Year 2014 [Member] | North America Commercial P&C Insurance - Workers' Compensation [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	1,154	1,217	1,279	1,276	1,259	1,282
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	419
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 606	564	501	418	301	116
Cumulative Number of Reported Claims	50,000
Short-duration Insurance Contracts, Accident Year 2014 [Member] | North America Commercial P&C Insurance - Liability [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 3,736	3,943	3,976	3,819	3,709	3,560
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	855
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 2,533	2,291	1,856	1,206	605	138
Cumulative Number of Reported Claims	27,000
Short-duration Insurance Contracts, Accident Year 2014 [Member] | North America Commercial P&C Insurance - Other Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 455	458	515	502	470	487
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	35
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 395	371	305	215	137	47
Cumulative Number of Reported Claims	15,000
Short-duration Insurance Contracts, Accident Year 2014 [Member] | North America Commercial P&C Insurance - Non-Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 1,589	1,605	1,638	1,650	1,745	1,736
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	(1)
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 1,574	1,572	1,556	1,488	1,343	727
Cumulative Number of Reported Claims	545,000
Short-duration Insurance Contracts, Accident Year 2014 [Member] | North America Personal P&C Insurance [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 2,570	2,563	2,544	2,561	2,550	2,494
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	21
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 2,508	2,478	2,392	2,271	2,084	1,499
Cumulative Number of Reported Claims	148,000
Short-duration Insurance Contracts, Accident Year 2014 [Member] | Overseas General Insurance - Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 1,265	1,326	1,351	1,328	1,296	1,196
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	199
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 884	802	679	497	287	86
Cumulative Number of Reported Claims	41,000
Short-duration Insurance Contracts, Accident Year 2014 [Member] | Overseas General Insurance - Non-Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 2,003	2,011	2,030	2,062	2,083	1,963
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	24
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 1,927	1,897	1,875	1,793	1,560	857
Cumulative Number of Reported Claims	571,000
Short-duration Insurance Contracts, Accident Year 2014 [Member] | Global Reinsurance - Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 306	309	301	300	290	285
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	22
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	250	233	217	192	159	90
Short-duration Insurance Contracts, Accident Year 2014 [Member] | Global Reinsurance - Non-Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	161	155	162	162	155	147
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	4
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	153	147	143	133	104	$ 56
Short-duration Insurance Contracts, Accident Year 2015 [Member] | North America Commercial P&C Insurance - Workers' Compensation [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	1,269	1,378	1,383	1,361	1,367
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	530
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 584	529	452	326	122
Cumulative Number of Reported Claims	51,000
Short-duration Insurance Contracts, Accident Year 2015 [Member] | North America Commercial P&C Insurance - Liability [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 3,799	3,805	3,692	3,595	3,534
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	962
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 2,334	1,975	1,336	663	171
Cumulative Number of Reported Claims	27,000
Short-duration Insurance Contracts, Accident Year 2015 [Member] | North America Commercial P&C Insurance - Other Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 481	524	527	502	504
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	61
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 374	323	246	146	52
Cumulative Number of Reported Claims	16,000
Short-duration Insurance Contracts, Accident Year 2015 [Member] | North America Commercial P&C Insurance - Non-Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 1,818	1,782	1,799	1,890	1,911
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	32
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 1,761	1,733	1,656	1,504	846
Cumulative Number of Reported Claims	650,000
Short-duration Insurance Contracts, Accident Year 2015 [Member] | North America Personal P&C Insurance [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 2,471	2,482	2,545	2,535	2,440
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	45
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 2,370	2,314	2,211	2,052	1,453
Cumulative Number of Reported Claims	154,000
Short-duration Insurance Contracts, Accident Year 2015 [Member] | Overseas General Insurance - Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 1,425	1,437	1,407	1,337	1,232
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	341
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 815	687	534	324	127
Cumulative Number of Reported Claims	43,000
Short-duration Insurance Contracts, Accident Year 2015 [Member] | Overseas General Insurance - Non-Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 2,040	2,036	2,058	2,071	2,070
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	22
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 1,981	1,954	1,881	1,679	1,013
Cumulative Number of Reported Claims	581,000
Short-duration Insurance Contracts, Accident Year 2015 [Member] | Global Reinsurance - Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 245	236	236	228	224
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	27
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	175	159	143	113	58
Short-duration Insurance Contracts, Accident Year 2015 [Member] | Global Reinsurance - Non-Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	190	194	192	189	184
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	5
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	178	172	161	133	$ 57
Short-duration Insurance Contracts, Accident Year 2016 [Member] | North America Commercial P&C Insurance - Workers' Compensation [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	1,393	1,399	1,380	1,413
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	723
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 516	437	313	120
Cumulative Number of Reported Claims	50,000
Short-duration Insurance Contracts, Accident Year 2016 [Member] | North America Commercial P&C Insurance - Liability [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 3,631	3,581	3,499	3,322
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	1,475
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 1,701	1,162	617	161
Cumulative Number of Reported Claims	27,000
Short-duration Insurance Contracts, Accident Year 2016 [Member] | North America Commercial P&C Insurance - Other Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 616	577	566	532
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	118
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 381	313	175	66
Cumulative Number of Reported Claims	17,000
Short-duration Insurance Contracts, Accident Year 2016 [Member] | North America Commercial P&C Insurance - Non-Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 2,522	2,505	2,608	2,704
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	51
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 2,394	2,303	2,087	979
Cumulative Number of Reported Claims	763,000
Short-duration Insurance Contracts, Accident Year 2016 [Member] | North America Personal P&C Insurance [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 2,998	3,002	3,069	3,035
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	96
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 2,799	2,668	2,520	1,698
Cumulative Number of Reported Claims	163,000
Short-duration Insurance Contracts, Accident Year 2016 [Member] | Overseas General Insurance - Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 1,433	1,381	1,332	1,227
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	384
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 702	535	323	98
Cumulative Number of Reported Claims	43,000
Short-duration Insurance Contracts, Accident Year 2016 [Member] | Overseas General Insurance - Non-Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 2,225	2,245	2,264	2,222
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	18
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 2,106	2,029	1,848	1,051
Cumulative Number of Reported Claims	589,000
Short-duration Insurance Contracts, Accident Year 2016 [Member] | Global Reinsurance - Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 218	221	217	215
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	28
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	140	122	100	47
Short-duration Insurance Contracts, Accident Year 2016 [Member] | Global Reinsurance - Non-Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	451	454	424	397
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	10
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	415	402	322	$ 191
Short-duration Insurance Contracts, Accident Year 2017 [Member] | North America Commercial P&C Insurance - Workers' Compensation [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	1,379	1,361	1,359
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	709
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 451	329	130
Cumulative Number of Reported Claims	51,000
Short-duration Insurance Contracts, Accident Year 2017 [Member] | North America Commercial P&C Insurance - Liability [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 3,696	3,494	3,375
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	1,737
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 1,303	754	190
Cumulative Number of Reported Claims	28,000
Short-duration Insurance Contracts, Accident Year 2017 [Member] | North America Commercial P&C Insurance - Other Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 575	564	536
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	198
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 270	169	74
Cumulative Number of Reported Claims	17,000
Short-duration Insurance Contracts, Accident Year 2017 [Member] | North America Commercial P&C Insurance - Non-Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 2,175	2,240	2,053
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	71
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 2,018	1,825	1,027
Cumulative Number of Reported Claims	901,000
Short-duration Insurance Contracts, Accident Year 2017 [Member] | North America Personal P&C Insurance [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 3,103	3,037	3,010
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	244
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 2,706	2,549	1,926
Cumulative Number of Reported Claims	169,000
Short-duration Insurance Contracts, Accident Year 2017 [Member] | Overseas General Insurance - Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 1,447	1,383	1,330
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	671
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 503	334	112
Cumulative Number of Reported Claims	43,000
Short-duration Insurance Contracts, Accident Year 2017 [Member] | Overseas General Insurance - Non-Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 2,237	2,276	2,186
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	48
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 1,962	1,753	1,006
Cumulative Number of Reported Claims	624,000
Short-duration Insurance Contracts, Accident Year 2017 [Member] | Global Reinsurance - Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 256	249	246
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	48
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	126	96	42
Short-duration Insurance Contracts, Accident Year 2017 [Member] | Global Reinsurance - Non-Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	303	300	288
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	(8)
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	277	258	$ 94
Short-duration Insurance Contracts, Accident Year 2018 [Member] | North America Commercial P&C Insurance - Workers' Compensation [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	1,384	1,391
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	767
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 341	143
Cumulative Number of Reported Claims	47,000
Short-duration Insurance Contracts, Accident Year 2018 [Member] | North America Commercial P&C Insurance - Liability [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 3,628	3,452
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	2,381
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 671	176
Cumulative Number of Reported Claims	28,000
Short-duration Insurance Contracts, Accident Year 2018 [Member] | North America Commercial P&C Insurance - Other Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 637	606
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	284
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 190	70
Cumulative Number of Reported Claims	16,000
Short-duration Insurance Contracts, Accident Year 2018 [Member] | North America Commercial P&C Insurance - Non-Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 2,037	2,052
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	166
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 1,677	1,030
Cumulative Number of Reported Claims	1,036,000
Short-duration Insurance Contracts, Accident Year 2018 [Member] | North America Personal P&C Insurance [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 2,993	2,957
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	329
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 2,437	1,668
Cumulative Number of Reported Claims	155,000
Short-duration Insurance Contracts, Accident Year 2018 [Member] | Overseas General Insurance - Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 1,480	1,409
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	809
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 341	126
Cumulative Number of Reported Claims	40,000
Short-duration Insurance Contracts, Accident Year 2018 [Member] | Overseas General Insurance - Non-Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 2,228	2,208
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	94
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 1,747	1,050
Cumulative Number of Reported Claims	640,000
Short-duration Insurance Contracts, Accident Year 2018 [Member] | Global Reinsurance - Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 248	239
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	90
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	90	40
Short-duration Insurance Contracts, Accident Year 2018 [Member] | Global Reinsurance - Non-Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	141	143
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	29
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	86	$ 35
Short-Duration Insurance Contract, Accident Year 2019 [Member] | North America Commercial P&C Insurance - Workers' Compensation [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	1,367
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	1,086
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 111
Cumulative Number of Reported Claims	24,000
Short-Duration Insurance Contract, Accident Year 2019 [Member] | North America Commercial P&C Insurance - Liability [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 4,098
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	3,695
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 152
Cumulative Number of Reported Claims	24,000
Short-Duration Insurance Contract, Accident Year 2019 [Member] | North America Commercial P&C Insurance - Other Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 646
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	517
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 53
Cumulative Number of Reported Claims	9,000
Short-Duration Insurance Contract, Accident Year 2019 [Member] | North America Commercial P&C Insurance - Non-Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 3,150
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	1,061
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 1,396
Cumulative Number of Reported Claims	927,000
Short-Duration Insurance Contract, Accident Year 2019 [Member] | North America Personal P&C Insurance [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 2,931
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	1,119
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 1,334
Cumulative Number of Reported Claims	100,000
Short-Duration Insurance Contract, Accident Year 2019 [Member] | Overseas General Insurance - Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 1,810
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	1,493
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 110
Cumulative Number of Reported Claims	28,000
Short-Duration Insurance Contract, Accident Year 2019 [Member] | Overseas General Insurance - Non-Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 2,571
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	804
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 1,085
Cumulative Number of Reported Claims	518,000
Short-Duration Insurance Contract, Accident Year 2019 [Member] | Global Reinsurance - Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 247
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	153
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	41
Short-Duration Insurance Contract, Accident Year 2019 [Member] | Global Reinsurance - Non-Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	212
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	110
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	63
prior to 2011 | North America Commercial P&C Insurance - Workers' Compensation [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net, Not Separately Presented	2,748
prior to 2011 | North America Commercial P&C Insurance - Liability [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net, Not Separately Presented	1,459
prior to 2011 | North America Commercial P&C Insurance - Other Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net, Not Separately Presented	287
prior to 2011 | North America Commercial P&C Insurance - Non-Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net, Not Separately Presented	4
prior to 2011 | North America Personal P&C Insurance [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net, Not Separately Presented	24
prior to 2011 | Overseas General Insurance - Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net, Not Separately Presented	486
prior to 2011 | Overseas General Insurance - Non-Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net, Not Separately Presented	94
prior to 2011 | Global Reinsurance - Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net, Not Separately Presented	331
prior to 2011 | Global Reinsurance - Non-Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net, Not Separately Presented	10
2011 - 2020 | North America Commercial P&C Insurance - Workers' Compensation [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net, Not Separately Presented	6,852
2011 - 2020 | North America Commercial P&C Insurance - Liability [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net, Not Separately Presented	15,982
2011 - 2020 | North America Commercial P&C Insurance - Other Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net, Not Separately Presented	1,837
2011 - 2020 | North America Commercial P&C Insurance - Non-Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net, Not Separately Presented	2,487
2011 - 2020 | North America Personal P&C Insurance [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net, Not Separately Presented	3,001
2011 - 2020 | Overseas General Insurance - Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net, Not Separately Presented	6,346
2011 - 2020 | Overseas General Insurance - Non-Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net, Not Separately Presented	2,631
2011 - 2020 | Global Reinsurance - Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net, Not Separately Presented	869
2011 - 2020 | Global Reinsurance - Non-Casualty [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net, Not Separately Presented	$ 302

Unpaid losses and loss expens_6

Unpaid losses and loss expenses Unpaid losses and loss expenses (Details) (Supplementary PPD) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020USD ($)
North America Commercial P&C Insurance - Workers' Compensation [Member]
Supplementary PPD [Line Items]
Short-Duration PPD	$ (350)
North America Commercial P&C Insurance - Workers' Compensation [Member] | prior to 2011
Supplementary PPD [Line Items]
Short-Duration PPD	(94)
North America Commercial P&C Insurance - Workers' Compensation [Member] | 2011 - 2020
Supplementary PPD [Line Items]
Short-Duration PPD	(256)
North America Commercial P&C Insurance - Liability [Member]
Supplementary PPD [Line Items]
Short-Duration PPD	(293)
North America Commercial P&C Insurance - Liability [Member] | prior to 2011
Supplementary PPD [Line Items]
Short-Duration PPD	(176)
North America Commercial P&C Insurance - Liability [Member] | 2011 - 2020
Supplementary PPD [Line Items]
Short-Duration PPD	(117)
North America Commercial P&C Insurance - Other Casualty [Member]
Supplementary PPD [Line Items]
Short-Duration PPD	42
North America Commercial P&C Insurance - Other Casualty [Member] | prior to 2011
Supplementary PPD [Line Items]
Short-Duration PPD	23
North America Commercial P&C Insurance - Other Casualty [Member] | 2011 - 2020
Supplementary PPD [Line Items]
Short-Duration PPD	19
North America Commercial P&C Insurance - Non-Casualty [Member]
Supplementary PPD [Line Items]
Short-Duration PPD	(35)
North America Commercial P&C Insurance - Non-Casualty [Member] | prior to 2011
Supplementary PPD [Line Items]
Short-Duration PPD	2
North America Commercial P&C Insurance - Non-Casualty [Member] | 2011 - 2020
Supplementary PPD [Line Items]
Short-Duration PPD	(37)
North America Personal P&C Insurance [Member]
Supplementary PPD [Line Items]
Short-Duration PPD	84
North America Personal P&C Insurance [Member] | prior to 2011
Supplementary PPD [Line Items]
Short-Duration PPD	(1)
North America Personal P&C Insurance [Member] | 2011 - 2020
Supplementary PPD [Line Items]
Short-Duration PPD	85
Overseas General Insurance - Casualty [Member]
Supplementary PPD [Line Items]
Short-Duration PPD	(50)
Overseas General Insurance - Casualty [Member] | prior to 2011
Supplementary PPD [Line Items]
Short-Duration PPD	(59)
Overseas General Insurance - Casualty [Member] | 2011 - 2020
Supplementary PPD [Line Items]
Short-Duration PPD	9
Overseas General Insurance - Non-Casualty [Member]
Supplementary PPD [Line Items]
Short-Duration PPD	(77)
Overseas General Insurance - Non-Casualty [Member] | prior to 2011
Supplementary PPD [Line Items]
Short-Duration PPD	(8)
Overseas General Insurance - Non-Casualty [Member] | 2011 - 2020
Supplementary PPD [Line Items]
Short-Duration PPD	(69)
Global Reinsurance - Casualty [Member]
Supplementary PPD [Line Items]
Short-Duration PPD	(22)
Global Reinsurance - Casualty [Member] | prior to 2011
Supplementary PPD [Line Items]
Short-Duration PPD	(10)
Global Reinsurance - Casualty [Member] | 2011 - 2020
Supplementary PPD [Line Items]
Short-Duration PPD	(12)
Global Reinsurance - Non-Casualty [Member]
Supplementary PPD [Line Items]
Short-Duration PPD	(2)
Global Reinsurance - Non-Casualty [Member] | prior to 2011
Supplementary PPD [Line Items]
Short-Duration PPD	0
Global Reinsurance - Non-Casualty [Member] | 2011 - 2020
Supplementary PPD [Line Items]
Short-Duration PPD	$ (2)

Unpaid losses and loss expens_7

Unpaid losses and loss expenses Unpaid losses and loss expenses (Average Annual Payout) (Details)	Dec. 31, 2020
North America Commercial P&C Insurance - Workers' Compensation [Member]
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Short-duration Insurance Contracts, Historical Claims Duration, Year One	10.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two	16.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three	10.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four	7.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five	5.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Six	4.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Seven	3.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Eight	2.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Nine	2.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Ten	1.00%
North America Commercial P&C Insurance - Liability [Member]
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Short-duration Insurance Contracts, Historical Claims Duration, Year One	5.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two	14.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three	17.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four	16.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five	12.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Six	7.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Seven	5.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Eight	3.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Nine	2.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Ten	1.00%
North America Commercial P&C Insurance - Other Casualty [Member]
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Short-duration Insurance Contracts, Historical Claims Duration, Year One	12.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two	23.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three	19.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four	14.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five	10.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Six	5.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Seven	3.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Eight	2.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Nine	1.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Ten	0.00%
North America Commercial P&C Insurance - Non-Casualty [Member]
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Short-duration Insurance Contracts, Historical Claims Duration, Year One	46.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two	38.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three	8.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four	3.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five	1.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Six	1.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Seven	0.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Eight	1.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Nine	0.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Ten	0.00%
North America Personal P&C Insurance [Member]
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Short-duration Insurance Contracts, Historical Claims Duration, Year One	57.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two	24.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three	7.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four	5.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five	3.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Six	1.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Seven	1.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Eight	0.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Nine	0.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Ten	0.00%
Overseas General Insurance - Casualty [Member]
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Short-duration Insurance Contracts, Historical Claims Duration, Year One	8.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two	15.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three	15.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four	12.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five	10.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Six	8.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Seven	6.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Eight	4.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Nine	4.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Ten	3.00%
Overseas General Insurance - Non-Casualty [Member]
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Short-duration Insurance Contracts, Historical Claims Duration, Year One	45.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two	35.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three	11.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four	3.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five	2.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Six	1.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Seven	1.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Eight	0.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Nine	0.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Ten	0.00%
Global Reinsurance - Casualty [Member]
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Short-duration Insurance Contracts, Historical Claims Duration, Year One	21.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two	23.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three	12.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four	10.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five	7.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Six	5.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Seven	4.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Eight	3.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Nine	2.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Ten	2.00%
Global Reinsurance - Non-Casualty [Member]
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Short-duration Insurance Contracts, Historical Claims Duration, Year One	33.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two	38.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three	14.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four	6.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five	4.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Six	2.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Seven	1.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Eight	1.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Nine	0.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Ten	0.00%

Unpaid losses and loss expens_8

Unpaid losses and loss expenses Unpaid losses and loss expenses (Details) (Supplementary PPD Reconciliation) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense	[1]	$ (414)	$ (845)	$ (981)
Prior Period Development, net Adjustments		19	53	85
Net Prior Period Development		(395)	(792)	(896)
Alternative Risk Solutions [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense		80
North America Workers' Compensation [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense		15
Long Tail [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		(313)	(642)	(486)
Short Tail [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		(82)	(150)	(410)
Segments included in loss triangles [Domain]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense		(828)
Other PPD adjustments	[2]	(125)
Prior Period Development, net Adjustments		10
Net Prior Period Development		(818)
Segments included in loss triangles [Domain] | 2011 - 2019
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense		(380)
Segments included in loss triangles [Domain] | prior to 2011
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense		(323)
North America Commercial P&C Insurance
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense		(733)
Other PPD adjustments	[2],[3]	(97)
Prior Period Development, net Adjustments		31
Net Prior Period Development		(702)	(649)	(610)
North America Commercial P&C Insurance | 2011 - 2019
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense		(391)
North America Commercial P&C Insurance | prior to 2011
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense		(245)
North America Commercial P&C Insurance | Long Tail [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense		(703)
Other PPD adjustments	[2]	(102)
Prior Period Development, net Adjustments		31
Net Prior Period Development		(672)	(668)	(395)
North America Commercial P&C Insurance | Long Tail [Member] | North America Workers' Compensation [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development			(303)
North America Commercial P&C Insurance | Long Tail [Member] | 2011 - 2019
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense		(354)
North America Commercial P&C Insurance | Long Tail [Member] | prior to 2011
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense		(247)
North America Commercial P&C Insurance | Short Tail [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense		(30)
Other PPD adjustments	[2]	5
Prior Period Development, net Adjustments		0
Net Prior Period Development		(30)	19	(215)
North America Commercial P&C Insurance | Short Tail [Member] | 2011 - 2019
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense		(37)
North America Commercial P&C Insurance | Short Tail [Member] | prior to 2011
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense		2
North America Personal P&C Insurance [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		63	(95)	41
North America Personal P&C Insurance [Member] | Long Tail [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		0	0	0
North America Personal P&C Insurance [Member] | Short Tail [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense		81
Other PPD adjustments	[2]	(3)
Prior Period Development, net Adjustments		(18)
Net Prior Period Development		63	(95)	41
North America Personal P&C Insurance [Member] | Short Tail [Member] | 2011 - 2019
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense		85
North America Personal P&C Insurance [Member] | Short Tail [Member] | prior to 2011
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense		(1)
Overseas General Insurance
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense		(150)
Other PPD adjustments	[2],[4]	(23)
Prior Period Development, net Adjustments		0
Net Prior Period Development		(150)	(92)	(212)
Overseas General Insurance | International A&H [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense		22
Overseas General Insurance | 2011 - 2019
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense		(60)
Overseas General Insurance | prior to 2011
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense		(67)
Overseas General Insurance | Long Tail [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense		(49)
Other PPD adjustments	[2]	1
Prior Period Development, net Adjustments		0
Net Prior Period Development		(49)	(68)	(67)
Overseas General Insurance | Long Tail [Member] | 2011 - 2019
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense		9
Overseas General Insurance | Long Tail [Member] | prior to 2011
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense		(59)
Overseas General Insurance | Short Tail [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense		(101)
Other PPD adjustments	[2]	(24)
Prior Period Development, net Adjustments		0
Net Prior Period Development		(101)	(24)	(145)
Overseas General Insurance | Short Tail [Member] | 2011 - 2019
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense		(69)
Overseas General Insurance | Short Tail [Member] | prior to 2011
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense		(8)
Segment Global Reinsurance [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense		(26)
Other PPD adjustments	[2]	(2)
Prior Period Development, net Adjustments		(3)
Net Prior Period Development		(29)	(29)	(50)
Segment Global Reinsurance [Member] | 2011 - 2019
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense		(14)
Segment Global Reinsurance [Member] | prior to 2011
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense		(10)
Segment Global Reinsurance [Member] | Long Tail [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense		(23)
Other PPD adjustments	[2]	(1)
Prior Period Development, net Adjustments		(2)
Net Prior Period Development		(25)	(59)	(69)
Segment Global Reinsurance [Member] | Long Tail [Member] | 2011 - 2019
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense		(12)
Segment Global Reinsurance [Member] | Long Tail [Member] | prior to 2011
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense		(10)
Segment Global Reinsurance [Member] | Short Tail [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense		(3)
Other PPD adjustments	[2]	(1)
Prior Period Development, net Adjustments		(1)
Net Prior Period Development		(4)	30	19
Segment Global Reinsurance [Member] | Short Tail [Member] | 2011 - 2019
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense		(2)
Segment Global Reinsurance [Member] | Short Tail [Member] | prior to 2011
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense		0
North America Agricultural Insurance
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		(10)	(80)	(110)
North America Agricultural Insurance | Long Tail [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		0	0	0
North America Agricultural Insurance | Short Tail [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense		(19)
Prior Period Development, net Adjustments		9
Net Prior Period Development		(10)	(80)	(110)
Corporate Segment [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		433	153	45
Corporate Segment [Member] | Long Tail [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Prior Year Claims and Claims Adjustment Expense		433
Prior Period Development, net Adjustments		0
Net Prior Period Development		433	153	45
Corporate Segment [Member] | Short Tail [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		$ 0	$ 0	$ 0
[1]	Relates to prior period loss reserve development only and excludes prior period development related to reinstatement premiums, expense adjustments and earned premiums totaling $19 million, $53 million, and $85 million for 2020, 2019, and 2018, respectively.
[2]	Other includes the impact of foreign exchange.
[3]	Includes favorable development of $80 million related to our Alternative Risk Solutions business (U.S. and Bermuda) and an adjustment to exclude $15 million in unfavorable development in the workers' compensation line, associated with an increase in exposure for which additional premiums were collected; the remaining difference relates to a number of other items, none of which are individually material. (3) Includes premium returns associated with our Alternative Risk Solutions business, which is excluded from the triangles.
[4]	Includes favorable development of $22 million related to International A&H business; the remaining difference relates to a number of other items, none of which are individually material.

Unpaid losses and loss expens_9

Unpaid losses and loss expenses Unpaid losses and loss expenses (PPD table) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		$ (395)	$ (792)	$ (896)
Prior Period Development Percentage Opening Net Unpaid Reserves	[1]	0.80%	1.60%	1.80%
Long Tail [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		$ (313)	$ (642)	$ (486)
Short Tail [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		(82)	(150)	(410)
North America Commercial P&C Insurance
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		$ (702)	$ (649)	$ (610)
Prior Period Development Percentage Opening Net Unpaid Reserves	[1]	1.40%	1.30%	1.20%
North America Commercial P&C Insurance | Long Tail [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		$ (672)	$ (668)	$ (395)
North America Commercial P&C Insurance | Short Tail [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		(30)	19	(215)
North America Personal P&C Insurance [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		$ 63	$ (95)	$ 41
Prior Period Development Percentage Opening Net Unpaid Reserves	[1]	0.10%	0.20%	0.10%
North America Personal P&C Insurance [Member] | Long Tail [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		$ 0	$ 0	$ 0
North America Personal P&C Insurance [Member] | Short Tail [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		63	(95)	41
North America Agricultural Insurance
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		$ (10)	$ (80)	$ (110)
Prior Period Development Percentage Opening Net Unpaid Reserves	[1]	0.00%	0.20%	0.20%
North America Agricultural Insurance | Long Tail [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		$ 0	$ 0	$ 0
North America Agricultural Insurance | Short Tail [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		(10)	(80)	(110)
Overseas General Insurance
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		$ (150)	$ (92)	$ (212)
Prior Period Development Percentage Opening Net Unpaid Reserves	[1]	0.30%	0.20%	0.40%
Overseas General Insurance | Long Tail [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		$ (49)	$ (68)	$ (67)
Overseas General Insurance | Short Tail [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		(101)	(24)	(145)
Segment Global Reinsurance [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		$ (29)	$ (29)	$ (50)
Prior Period Development Percentage Opening Net Unpaid Reserves	[1]	0.10%	0.10%	0.10%
Segment Global Reinsurance [Member] | Long Tail [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		$ (25)	$ (59)	$ (69)
Segment Global Reinsurance [Member] | Short Tail [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		(4)	30	19
Corporate Segment [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		$ 433	$ 153	$ 45
Prior Period Development Percentage Opening Net Unpaid Reserves	[1]	0.90%	0.30%	0.10%
Corporate Segment [Member] | Long Tail [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		$ 433	$ 153	$ 45
Corporate Segment [Member] | Short Tail [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		$ 0	$ 0	$ 0
[1]	Calculated based on the beginning of period consolidated net unpaid losses and loss expenses.

Unpaid losses and loss expen_10

Unpaid losses and loss expenses (A&E Loss Roll-forward) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Liability For Asbestos And Environmental Claims Net Roll Forward
Balance (gross) at beginning of year		$ 1,988	$ 2,117	$ 2,228
Balance (net) at beginning of year		1,326	1,447	1,527
Incurred activity, gross		229	175	237
Incurred activity, net	[1]	131	98	(22)
Paid activity, gross		(349)	(304)	(348)
Paid activity, net		(205)	(219)	(58)
Balance (gross) at end of year		1,868	1,988	2,117
Balance (net) at end of year		1,252	1,326	1,447
Asbestos Issue [Member]
Liability For Asbestos And Environmental Claims Net Roll Forward
Balance (gross) at beginning of year		1,459	1,492	1,621
Balance (net) at beginning of year		916	964	1,051
Incurred activity, gross		150	129	136
Incurred activity, net		90	70	75
Paid activity, gross		(258)	(162)	(265)
Paid activity, net		(133)	(118)	(162)
Balance (gross) at end of year		1,351	1,459	1,492
Balance (net) at end of year		873	916	964
Environmental Issue [Member]
Liability For Asbestos And Environmental Claims Net Roll Forward
Balance (gross) at beginning of year		529	625	607
Balance (net) at beginning of year		410	483	476
Incurred activity, gross		79	46	101
Incurred activity, net		41	28	(97)
Paid activity, gross		(91)	(142)	(83)
Liability for Unpaid Claims and Claims Adjustment Expense, Period Increase (Decrease)		(72)	(101)	104
Balance (gross) at end of year		517	529	625
Balance (net) at end of year		379	410	$ 483
Brandywine [Member]
Liability For Asbestos And Environmental Claims Net Roll Forward
Balance (net) at beginning of year		754
Balance (net) at end of year		736	754
Westchester Specialty [Member]
Liability For Asbestos And Environmental Claims Net Roll Forward
Balance (net) at beginning of year		117
Balance (net) at end of year		103	117
Other Segments [Member]
Liability For Asbestos And Environmental Claims Net Roll Forward
Balance (net) at beginning of year		74
Balance (net) at end of year		80	74
The Chubb Corporation [Member]
Liability For Asbestos And Environmental Claims Net Roll Forward
Balance (net) at beginning of year		381
Balance (net) at end of year		$ 333	$ 381
[1]	Excludes unallocated loss expenses and the net activity reflects third-party reinsurance other than the aggregate excess of loss reinsurance provided by National Indemnity Company (NICO) to Westchester Specialty (see Westchester Specialty section below)

Unpaid losses and loss expen_11

Unpaid losses and loss expenses (Narrative) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2004
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		$ (395)	$ (792)	$ (896)
Prior Period Development, net Adjustments		$ 19	$ 53	$ 85
Prior Period Development Percentage Opening Net Unpaid Reserves	[1]	0.80%	1.60%	1.80%
Incurred activity		$ 21,710	$ 18,730	$ 18,067
Liability for Claims and Claims Adjustment Expense		67,811	62,690	62,960	$ 63,179
Brandywine Run-off [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred activity		573
Reinsurance coverage to Century provided by ACE INA under XOL		800
Statutory capital and surplus		25
Dividend retention fund established by INA Financial Corporation		50
Required minimum balance under the dividend retention fund		50
Contributions to the dividend retention fund		250	90	50		$ 35	$ 15
Minimum contribution from the dividend retention fund to Century not required for XOL agreement		200
Dividend Retention Fund Contribution to XOL		302	64
Aggregate reinsurance balances ceded by active ACE companies to Century		1,600	1,500
Liability for Claims and Claims Adjustment Expense		$ 2,100	1,800
Surplus note								$ 100
Westchester and Brandywine Run-off [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
NICO pro-rata share of reinsurance protection (percent)		75.00%
NICO retention for losses and loss expenses incurred on or before 12/31/1996		$ 721
NICO reinsurance protection on losses and loss expenses incurred on or before 12/31/1996, net of retenion		1,000
NICO reinsurance protection on losses and loss expenses		372
Long Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		(313)	(642)	(486)
Short Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		(82)	(150)	(410)
North America Commercial P&C Insurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		(702)	$ (649)	$ (610)
Prior Period Development, net Adjustments		$ 31
Prior Period Development Percentage Opening Net Unpaid Reserves	[1]	1.40%	1.30%	1.20%
North America Commercial P&C Insurance | Long Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		$ (672)	$ (668)	$ (395)
Prior Period Development, net Adjustments		31
North America Commercial P&C Insurance | Short Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		(30)	19	(215)
Prior Period Development, net Adjustments		0
North America Commercial P&C Insurance | North America Commercial P&C Insurance - Workers' Compensation [Member] | Long Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development			(303)
North America Commercial P&C Insurance | Multi-Line [Member] | Long Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		(26)	(34)
North America Commercial P&C Insurance | Other [Member] | Long Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		77	26
North America Commercial P&C Insurance | Management Liability [Member] | Long Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development			(217)
North America Commercial P&C Insurance | Professional Liability [Member] | Long Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development			(60)
North America Commercial P&C Insurance | Workers' Compensation Insurance [Member] | Long Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		(363)
North America Commercial P&C Insurance | Property and Inland Marine | Short Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development			108
North America Commercial P&C Insurance | Catastrophe [Member] | Property and Inland Marine | Short Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development			(36)
North America Commercial P&C Insurance | Accident years 2014 and prior [Member] | Commercial Excess and Umbrella [Member] | Long Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		(83)
North America Commercial P&C Insurance | Short-duration Insurance Contracts, Accident Year 2015 [Member] | Political [Member] | Long Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development			(23)
North America Commercial P&C Insurance | Accident Year 2013 and prior [Member] | Commercial Excess and Umbrella [Member] | Long Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development			(41)
North America Commercial P&C Insurance | Short-duration Insurance Contracts, Accident Year 2016 [Member] | Foreign Casualty Line [Member] | Long Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		(40)
North America Commercial P&C Insurance | Short-duration Insurance Contracts, Accident Year 2017 [Member] | Surety Product Line [Member] | Short Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development			(49)
North America Commercial P&C Insurance | Short-duration Insurance Contracts, Accident Year 2018 [Member] | North America Commercial P&C Insurance - Workers' Compensation [Member] | Long Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development			(61)
North America Commercial P&C Insurance | Short-duration Insurance Contracts, Accident Year 2018 [Member] | Surety Product Line [Member] | Short Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		(31)
North America Commercial P&C Insurance | Short-duration Insurance Contracts, Accident Year 2018 [Member] | Property and Inland Marine | Short Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development			152
North America Commercial P&C Insurance | Accident years 2016 and prior [Member] | Professional Errors and Omissions Insurance [Member] | Long Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		(67)
North America Commercial P&C Insurance | Accident years 2016 and prior [Member] | Multi-Line [Member] | Long Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		(41)
North America Commercial P&C Insurance | Accident years 2016 and prior [Member] | Environmental lines [Member] | Long Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		(43)
North America Commercial P&C Insurance | Accident Year 2015 and prior [Member] | Foreign Casualty Line [Member] | Long Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development			(39)
North America Commercial P&C Insurance | Accident Year 2015 and prior [Member] | Medical Portfolios [Member] | Long Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development			(24)
North America Commercial P&C Insurance | Accident Year 2015 and prior [Member] | Multi-Line [Member] | Long Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development			(36)
North America Commercial P&C Insurance | Accident Year 2015 and prior [Member] | Management Liability [Member] | Long Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		(231)
North America Commercial P&C Insurance | Accident years 2016 - 2019 [Member] | Medical Portfolios [Member] | Long Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		64
North America Commercial P&C Insurance | Accident years 2018 - 2019 [Member] | Accident and Health [Member] | Short Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		(37)
North America Commercial P&C Insurance | Short-Duration Insurance Contract, Accident Year 2019 [Member] | Workers' Compensation Insurance [Member] | Long Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		(62)
North America Commercial P&C Insurance | Short-Duration Insurance Contract, Accident Year 2019 [Member] | Property and Inland Marine | Short Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		21
North America Commercial P&C Insurance | Accident years 2014 - 2018 [Member] | Auto Liability Excess Lines [Member] | Long Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development			38
North America Commercial P&C Insurance | Accident years 2017 - 2019 | General Liability Coverages | Long Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		48
North America Commercial P&C Insurance | Accident year 2017 and prior | Non-catastrophe [Member] | Property and Inland Marine | Short Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development			(44)
North America Commercial P&C Insurance | Accident year 2017 - 2018 | Catastrophe [Member] | Property and Inland Marine | Short Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development			(41)
North America Personal P&C Insurance [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		$ 63	$ (95)	$ 41
Prior Period Development Percentage Opening Net Unpaid Reserves	[1]	0.10%	0.20%	0.10%
North America Personal P&C Insurance [Member] | Long Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		$ 0	$ 0	$ 0
North America Personal P&C Insurance [Member] | Short Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		63	(95)	41
Prior Period Development, net Adjustments		(18)
North America Personal P&C Insurance [Member] | Personal Excess [Member] | Short Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		(22)
North America Personal P&C Insurance [Member] | Accident years 2017 - 2018 [Member] | Catastrophe [Member] | Short Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development			(132)
North America Personal P&C Insurance [Member] | Short-duration Insurance Contracts, Accident Year 2016 [Member] | Personal Excess [Member] | Short Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development			(26)
North America Personal P&C Insurance [Member] | Short-duration Insurance Contracts, Accident Year 2018 [Member] | Homeowners and Valuables [Member] | Short Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development			82
North America Personal P&C Insurance [Member] | Accident Year 2017 to 2019 [Member] | Homeowners and Valuables [Member] | Short Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		84
North America Agricultural Insurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		$ (10)	$ (80)	$ (110)
Prior Period Development Percentage Opening Net Unpaid Reserves	[1]	0.00%	0.20%	0.20%
North America Agricultural Insurance | Long Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		$ 0	$ 0	$ 0
North America Agricultural Insurance | Short Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		(10)	(80)	(110)
Prior Period Development, net Adjustments		9
Overseas General Insurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		(150)	$ (92)	$ (212)
Prior Period Development, net Adjustments		$ 0
Prior Period Development Percentage Opening Net Unpaid Reserves	[1]	0.30%	0.20%	0.40%
Overseas General Insurance | Long Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		$ (49)	$ (68)	$ (67)
Prior Period Development, net Adjustments		0
Overseas General Insurance | Short Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		(101)	(24)	(145)
Prior Period Development, net Adjustments		0
Overseas General Insurance | Casualty Lines [Member] | Long Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		(94)	(101)
Overseas General Insurance | Financial [Member] | Long Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		80	52
Overseas General Insurance | Accident years 2017 - 2018 [Member] | Surety Product Line [Member] | Short Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development			27
Overseas General Insurance | Accident years 2017 - 2018 [Member] | Accident and Health [Member] | Short Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development			(45)
Overseas General Insurance | Short-duration Insurance Contracts, Accident Year 2018 [Member] | Construction [Member] | Short Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development			23
Overseas General Insurance | Accident years 2016 and prior [Member] | Casualty Lines [Member] | Long Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		(143)
Overseas General Insurance | Accident years 2016 and prior [Member] | Marine [Member] | Short Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development			(36)
Overseas General Insurance | Accident Year 2015 and prior [Member] | Casualty Lines [Member] | Long Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development			(123)
Overseas General Insurance | Accident Year 2015 and prior [Member] | Financial [Member] | Long Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		(61)	(75)
Overseas General Insurance | Accident years 2016 - 2018 [Member] | Casualty Lines [Member] | Long Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development			22
Overseas General Insurance | Accident years 2016 - 2018 [Member] | Financial [Member] | Long Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development			127
Overseas General Insurance | Accident Year 2017 to 2019 [Member] | Casualty Lines [Member] | Long Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		49
Overseas General Insurance | Accident years 2016 - 2019 [Member] | Financial [Member] | Long Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		141
Overseas General Insurance | Accident years 2018 - 2019 [Member] | Accident and Health [Member] | Short Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		(21)
Overseas General Insurance | Accident years 2018 - 2019 [Member] | Political Risk | Long Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		(22)
Overseas General Insurance | Accident years 2012 through 2019 | Marine [Member] | Short Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		$ (69)
Overseas General Insurance - Casualty [Member] | Europe [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Loss by Geographic Percentage		45.00%
Overseas General Insurance - Non-Casualty [Member] | Latin America [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Loss by Geographic Percentage		30.00%
Global Reinsurance Non-Casualty [Member] | Accident year 2013 to 2020
Liability for Claims and Claims Adjustment Expense [Line Items]
Loss by Geographic Percentage		82.00%
Global Reinsurance Non-Casualty [Member] | Accident years 2011 to 2012
Liability for Claims and Claims Adjustment Expense [Line Items]
Loss by Geographic Percentage		59.00%
Global Reinsurance Non-Casualty [Member] | accident year 2011 and after
Liability for Claims and Claims Adjustment Expense [Line Items]
Loss by Geographic Percentage		77.00%
Segment Global Reinsurance [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		$ (29)	$ (29)	$ (50)
Prior Period Development, net Adjustments		$ (3)
Prior Period Development Percentage Opening Net Unpaid Reserves	[1]	0.10%	0.10%	0.10%
Segment Global Reinsurance [Member] | Long Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		$ (25)	$ (59)	$ (69)
Prior Period Development, net Adjustments		(2)
Segment Global Reinsurance [Member] | Short Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		(4)	30	19
Prior Period Development, net Adjustments		(1)
Segment Global Reinsurance [Member] | Accident Year 2013 and prior [Member] | Other [Member] | Long Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development			(59)
Segment Global Reinsurance [Member] | Accident years 2017 - 2018 [Member] | Catastrophe [Member] | Short Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development			44
Corporate Segment [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		$ 433	$ 153	$ 45
Prior Period Development Percentage Opening Net Unpaid Reserves	[1]	0.90%	0.30%	0.10%
Corporate Segment [Member] | Discontinued Operations [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		$ 38	$ 37
Corporate Segment [Member] | Long Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		433	153	$ 45
Prior Period Development, net Adjustments		0
Corporate Segment [Member] | Short Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		0	0	$ 0
Corporate Segment [Member] | Other [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		254
Corporate Segment [Member] | Other [Member] | Other [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		27
Corporate Segment [Member] | Asbestos & Environmental [Member] | Long Tail [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Prior Period Development		$ 106	$ 116
[1]	Calculated based on the beginning of period consolidated net unpaid losses and loss expenses.

Taxation (Narrative) (Details)

Taxation (Narrative) (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Jan. 30, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Examination [Line Items]
Unrecognized Tax Benefits		$ 76	$ 47	$ 14
Income Tax Credits and Adjustments		31	19
Valuation allowance		83	114
Unrecognized tax benefits that would affect the effective tax rate		45	28
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense		8	5
Liabilities recorded for tax-related interest and penalties		16	$ 8
Subsequent Event [Member]
Income Tax Examination [Line Items]
Tax Adjustments, Settlements, and Unusual Provisions	$ 23
Domestic Tax Authority [Member]
Income Tax Examination [Line Items]
Net operating loss carry-forwards		$ 407
Switzerland
Income Tax Examination [Line Items]
Applicable income tax rates		21.20%	7.83%	7.83%
Foreign Tax Authority [Member]
Income Tax Examination [Line Items]
Foreign tax credit carry-forward		$ 222
Bermuda
Income Tax Examination [Line Items]
Applicable income tax rates		0.00%
UNITED STATES
Income Tax Examination [Line Items]
Applicable income tax rates		21.00%
UNITED KINGDOM
Income Tax Examination [Line Items]
Applicable income tax rates		19.00%

Taxation (Provision For Income

Taxation (Provision For Income Taxes) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Examination [Line Items]
Income (Loss) from Continuing Operations before Income Taxes, Domestic	$ 350	$ 440	$ 950
Income (Loss) from Continuing Operations before Income Taxes, Foreign	3,812	4,809	3,707
Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	4,162	5,249	4,657
Current tax expense	928	908	652
Deferred tax expense	(299)	(113)	43
Provision for income taxes	629	795	695
Domestic Tax Authority [Member]
Income Tax Examination [Line Items]
Current tax expense	52	29	89
Deferred tax expense	2	11	3
Foreign Tax Authority [Member]
Income Tax Examination [Line Items]
Current tax expense	876	879	563
Deferred tax expense	$ (301)	$ (124)	$ 40

Taxation (Reconciliation Of The

Taxation (Reconciliation Of The Difference Between The Provision for Income Taxes and the Expected Tax Provision at Swiss Statutory Income Tax Rate) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Expected tax provision at Swiss statutory rate	$ 880	$ 411	$ 365
Taxes on earnings subject to rates other that Swiss statutory rate	(337)	376	372
Tax exempt interest and dividends received deduction, net of proration	(41)	(49)	(75)
Net witholding taxes	67	40	33
Effective Income Tax Rate Reconciliation, Tax Expense (Benefit), Share-based Payment Arrangement, Amount	(10)	(12)	(19)
Income tax benefit related to 2017 Tax Act	0	0	(25)
Other	70	29	44
Provision for income taxes	$ 629	$ 795	$ 695

Taxation (Components Of Net Def

Taxation (Components Of Net Deferred Tax Assets) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Deferred Tax Assets, Gross [Abstract]
Loss reserve discount	$ 884	$ 826
Unearned premium reserve	496	519
Foreign tax credits	222	247
Provision for uncollectible balances	46	37
Loss carry-forwards	123	143
Debt related amounts	69	74
Compensation related amounts	281	261
Cumulative translation adjustments	120	33
Unrealized depreciation on investments	75	0
Deferred Tax Asset, Lease Liability	121	140
Total deferred tax assets	2,437	2,280
Deferred Tax Liabilities, Gross [Abstract]
Deferred policy acquisition costs	522	588
VOBA and other intangible assets	1,425	1,468
Un-remitted foreign earnings	77	73
Investments	0	40
Unrealized appreciation on investments	957	470
Depreciation	123	157
Leasing Arrangements	111	129
Deferred Tax Liabilities, Other	31	45
Deferred Tax Liabilities, Gross	3,246	2,970
Valuation allowance	83	114
Deferred Tax Liabilities, Net	$ (892)	$ (804)

Taxation (Reconciliation of Unr

Taxation (Reconciliation of Unrecognized Tax Benefits) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits, beginning of year	$ 47	$ 14
Additions based on tax provisions related to the current year	5	12
Additions based on tax positions related to prior years	24	23
Reductions for the lapse of the applicable statutes of limitations	0	(2)
Unrecognized Tax Benefits, end of year	$ 76	$ 47

Taxation Taxation (Summary Of I

Taxation Taxation (Summary Of Income Tax Examinations) (Details)	12 Months Ended
	Dec. 31, 2020
Earliest Tax Year [Member] | Switzerland
Income Tax Examination [Line Items]
Open Tax Year	2016
Earliest Tax Year [Member] | AUSTRALIA
Income Tax Examination [Line Items]
Open Tax Year	2014
Earliest Tax Year [Member] | CANADA
Income Tax Examination [Line Items]
Open Tax Year	2012
Earliest Tax Year [Member] | FRANCE
Income Tax Examination [Line Items]
Open Tax Year	2018
Earliest Tax Year [Member] | GERMANY
Income Tax Examination [Line Items]
Open Tax Year	2015
Earliest Tax Year [Member] | ITALY
Income Tax Examination [Line Items]
Open Tax Year	2010
Earliest Tax Year [Member] | MEXICO
Income Tax Examination [Line Items]
Open Tax Year	2014
Earliest Tax Year [Member] | SPAIN
Income Tax Examination [Line Items]
Open Tax Year	2012
Earliest Tax Year [Member] | UNITED KINGDOM
Income Tax Examination [Line Items]
Open Tax Year	2015
Earliest Tax Year [Member] | UNITED STATES
Income Tax Examination [Line Items]
Open Tax Year	2014
Latest Tax Year [Member] | Switzerland
Income Tax Examination [Line Items]
Open Tax Year	2020
Latest Tax Year [Member] | AUSTRALIA
Income Tax Examination [Line Items]
Open Tax Year	2020
Latest Tax Year [Member] | CANADA
Income Tax Examination [Line Items]
Open Tax Year	2020
Latest Tax Year [Member] | FRANCE
Income Tax Examination [Line Items]
Open Tax Year	2020
Latest Tax Year [Member] | GERMANY
Income Tax Examination [Line Items]
Open Tax Year	2020
Latest Tax Year [Member] | ITALY
Income Tax Examination [Line Items]
Open Tax Year	2020
Latest Tax Year [Member] | MEXICO
Income Tax Examination [Line Items]
Open Tax Year	2020
Latest Tax Year [Member] | SPAIN
Income Tax Examination [Line Items]
Open Tax Year	2020
Latest Tax Year [Member] | UNITED KINGDOM
Income Tax Examination [Line Items]
Open Tax Year	2020
Latest Tax Year [Member] | UNITED STATES
Income Tax Examination [Line Items]
Open Tax Year	2020

Debt (Narrative) (Details)

Debt (Narrative) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Mar. 31, 2000
INA Senior Notes Due November 2020 [Member] | Senior Notes
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 1,300
Long-term debt stated interest rate	2.30%
Senior Notes | INA Senior Notes Due September 2030
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 1,000
Long-term debt stated interest rate	1.375%
Trust Preferred Securities | INA capital securities due 2030
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 309	$ 300
ACE Capital Trust II common securities purchased		$ 9.2
Long-term debt stated interest rate	9.70%	9.70%
Unsecured Debt | INA Senior Notes Due August 2029 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 100
Long-term debt stated interest rate	8.875%

Debt (Schedule of Debt Outstand

Debt (Schedule of Debt Outstanding) (Details) € in Millions, $ in Millions	Dec. 31, 2020USD ($)	Dec. 31, 2020EUR (€)	Dec. 31, 2019USD ($)	Mar. 31, 2000USD ($)
Debt Instrument [Line Items]
Short-term debt	$ 0		$ 1,299
Long-term debt	14,948		13,559
Trust preferred securities	308		308
Senior Notes
Debt Instrument [Line Items]
Long-term debt	14,948		13,559
Senior Notes | INA Senior Notes Due November 2022 [Member]
Debt Instrument [Line Items]
Long-term debt	998		997
Debt Instrument, Face Amount	$ 1,000
Long-term debt stated interest rate	2.875%	2.875%
Make Whole Premium Additional Percent	20.00%	20.00%
Senior Notes | INA Senior Notes Due March 2023 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 474		473
Debt Instrument, Face Amount	$ 475
Long-term debt stated interest rate	2.70%	2.70%
Make Whole Premium Additional Percent	10.00%	10.00%
Senior Notes | INA Senior Notes Due May 2024 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 698		697
Debt Instrument, Face Amount	$ 700
Long-term debt stated interest rate	3.35%	3.35%
Make Whole Premium Additional Percent	15.00%	15.00%
Senior Notes | INA Senior Notes Due December 2024 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 841		776
Debt Instrument, Face Amount | €		€ 700
Long-term debt stated interest rate	0.30%	0.30%
Make Whole Premium Additional Percent	15.00%	15.00%
Senior Notes | INA Senior Notes Due March 2025 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 797		796
Debt Instrument, Face Amount	$ 800
Long-term debt stated interest rate	3.15%	3.15%
Make Whole Premium Additional Percent	15.00%	15.00%
Senior Notes | INA Senior Notes Due May 2026 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 1,493		1,492
Debt Instrument, Face Amount	$ 1,500
Long-term debt stated interest rate	3.35%	3.35%
Make Whole Premium Additional Percent	20.00%	20.00%
Senior Notes | INA Senior Notes Due June 2027 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 691		635
Debt Instrument, Face Amount | €		€ 575
Long-term debt stated interest rate	0.875%	0.875%
Make Whole Premium Additional Percent	20.00%	20.00%
Senior Notes | INA Senior Notes Due March 2028 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 1,079		993
Debt Instrument, Face Amount | €		€ 900
Long-term debt stated interest rate	1.55%	1.55%
Make Whole Premium Additional Percent	15.00%	15.00%
Senior Notes | INA Senior Notes Due December 2029 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 840		775
Debt Instrument, Face Amount | €		€ 700
Long-term debt stated interest rate	0.875%	0.875%
Make Whole Premium Additional Percent	20.00%	20.00%
Senior Notes | INA Senior Notes Due September 2030
Debt Instrument [Line Items]
Long-term debt	$ 991		0
Debt Instrument, Face Amount	$ 1,000
Long-term debt stated interest rate	1.375%	1.375%
Make Whole Premium Additional Percent	15.00%	15.00%
Senior Notes | INA Senior Notes Due June 2031 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 687		633
Debt Instrument, Face Amount | €		€ 575
Long-term debt stated interest rate	1.40%	1.40%
Make Whole Premium Additional Percent	25.00%	25.00%
Senior Notes | INA Senior Notes Due November 2031
Debt Instrument [Line Items]
Make Whole Premium Additional Percent	25.00%	25.00%
Senior Notes | INA Senior Notes Due May 2036 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 298		297
Debt Instrument, Face Amount	$ 300
Long-term debt stated interest rate	6.70%	6.70%
Make Whole Premium Additional Percent	20.00%	20.00%
Senior Notes | INA Senior Notes Due May 2037 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 945		953
Debt Instrument, Face Amount	$ 800
Long-term debt stated interest rate	6.00%	6.00%
Make Whole Premium Additional Percent	20.00%	20.00%
Senior Notes | INA Senior Notes Due March 2038 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 1,077		992
Debt Instrument, Face Amount | €		€ 900
Long-term debt stated interest rate	2.50%	2.50%
Make Whole Premium Additional Percent	25.00%	25.00%
Senior Notes | INA Senior Notes Due May 2038 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 743		751
Debt Instrument, Face Amount	$ 600
Long-term debt stated interest rate	6.50%	6.50%
Make Whole Premium Additional Percent	30.00%	30.00%
Senior Notes | INA Senior Notes Due March 2043 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 470		470
Debt Instrument, Face Amount	$ 475
Long-term debt stated interest rate	4.15%	4.15%
Make Whole Premium Additional Percent	15.00%	15.00%
Senior Notes | INA Senior Notes Due November 2045 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 1,484		1,483
Debt Instrument, Face Amount	$ 1,500
Long-term debt stated interest rate	4.35%	4.35%
Make Whole Premium Additional Percent	25.00%	25.00%
Trust Preferred Securities | INA capital securities due 2030
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 309			$ 300
Long-term debt stated interest rate	9.70%	9.70%		9.70%
Trust preferred securities	$ 308		308
Unsecured Debt | INA Senior Notes Due August 2029 [Member]
Debt Instrument [Line Items]
Long-term debt	100		100
Debt Instrument, Face Amount	$ 100
Long-term debt stated interest rate	8.875%	8.875%
Unsecured Debt | INA Senior Notes Due November 2031
Debt Instrument [Line Items]
Long-term debt	$ 242		246
Debt Instrument, Face Amount	$ 200
Long-term debt stated interest rate	6.80%	6.80%
Repurchase agreements
Debt Instrument [Line Items]
Short-term debt	$ 1,405		$ 1,416
Weighted average interest rate on short-term debt	0.30%	0.30%	2.20%
Senior Notes | INA Senior Notes Due November 2020 [Member]
Debt Instrument [Line Items]
Short-term debt	$ 0		$ 1,298
Debt Instrument, Face Amount	$ 1,300
Long-term debt stated interest rate	2.30%	2.30%
Make Whole Premium Additional Percent	15.00%	15.00%
Senior Notes | Other Short Term Debt due September 2020 [Member]
Debt Instrument [Line Items]
Short-term debt	$ 0		$ 1
Long-term debt stated interest rate	2.75%	2.75%

Commitments, contingencies, a_3

Commitments, contingencies, and guarantees (Narrative) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2010
Financial Instruments Owned and Pledged as Collateral [Line Items]
Derivative Liability, Fair Value, Amount Subject to a Master Netting Agreement	$ 30	$ 75
Securities Sold under Agreements to Repurchase	$ 1,405	$ 1,416
Concentration Risk Percentage Marsh	12.00%	12.00%	10.00%
Purchase Commitment, Remaining Minimum Amount Committed	$ 605
Carrying value of limited partnerships and partially-owned investment companies included in other investments	6,500	$ 4,700
Funding commitments relating to limited partnerships and partially-owned investment companies	3,200	3,300
Line of Credit Facility, Current Borrowing Capacity				$ 4,000
Line of Credit Facility, Capacity Available for Specific Purpose Other than for Trade Purchases	1,900
Operating Lease, Right-of-Use Asset	473	551
Operating Lease, Liability	$ 517	603
Operating Lease, Weighted Average Remaining Lease Term	4 years 10 months 24 days
Operating Lease, Weighted Average Discount Rate, Percent	2.60%
Total rental expense related to operating leases	$ 152	171	$ 169
Deposit Assets	$ 107	$ 93
Operating Lease, Liability, Statement of Financial Position [Extensible List]	us-gaap:OtherLiabilities	us-gaap:OtherLiabilities
Repurchase agreements	$ 1,405	$ 1,416
Letter of Credit [Member]
Financial Instruments Owned and Pledged as Collateral [Line Items]
Line of Credit Facility, Amount Outstanding	$ 1,700
Huatai Group [Member]
Financial Instruments Owned and Pledged as Collateral [Line Items]
Ownership Percentage	47.10%
CHINA | Huatai Group [Member]
Financial Instruments Owned and Pledged as Collateral [Line Items]
Equity method investment, additional 22.4 ownership percentage obtained		22.40%
Ownership Percentage	47.00%	31.00%

Commitments, contingencies, a_4

Commitments, contingencies, and guarantees (Balance Sheet Locations, Fair Values In Asset Or (Liability) Position, And Notional Values/Payment Provisions Of Derivative Instruments) (Detail) - USD ($) $ in Millions		Dec. 31, 2020	Dec. 31, 2019
Derivatives, Fair Value [Line Items]
Future policy benefits		$ 5,713	$ 5,373
Derivative, Notional Amount		4,567	4,199
Foreign currency forward contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount		2,807	2,579
Futures contracts on notes and bonds [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount		1,749	1,615
Convertible Securities [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount		11	5
Futures contracts on equities
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount		709	613
Other
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount		16	63
Other Derivative Instruments [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount		725	676
Guaranteed Minimum Income Benefit
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount		1,658	1,510
Accounts Payable and Accrued Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability		(52)	(93)
Accounts Payable and Accrued Liabilities [Member] | Foreign currency forward contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability		(49)	(78)
Accounts Payable and Accrued Liabilities [Member] | Futures contracts on notes and bonds [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability		(3)	(15)
Accounts Payable and Accrued Liabilities [Member] | Convertible Securities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability	[1]	0	0
Accounts Payable and Accrued Liabilities [Member] | Futures contracts on equities
Derivatives, Fair Value [Line Items]
Derivative Liability	[2]	(17)	(13)
Accounts Payable and Accrued Liabilities [Member] | Other
Derivatives, Fair Value [Line Items]
Derivative Liability		0	0
Accounts Payable and Accrued Liabilities [Member] | Other Derivative Instruments [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability		(17)	(13)
Other Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset		44	28
Other Assets [Member] | Foreign currency forward contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset		22	11
Other Assets [Member] | Futures contracts on notes and bonds [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset		13	13
Other Assets [Member] | Futures contracts on equities
Derivatives, Fair Value [Line Items]
Derivative Asset	[2]	0	0
Other Assets [Member] | Other
Derivatives, Fair Value [Line Items]
Derivative Asset		0	2
Other Assets [Member] | Other Derivative Instruments [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset		0	2
Other Assets [Member] | Guaranteed Minimum Income Benefit
Derivatives, Fair Value [Line Items]
Derivative Asset		0	0
Accounts Payable Future Policy Benefits [Member] | Guaranteed Minimum Income Benefit
Derivatives, Fair Value [Line Items]
Derivative Liability		(1,089)	(897)
Available-for-sale Securities [Member] | Convertible Securities [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	[1]	9	4
Guaranteed Minimum Income Benefit | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Derivatives, Fair Value [Line Items]
Liabilities for Guarantees on Long-Duration Contracts, Guaranteed Benefit Liability, Gross		$ 1,089	$ 897
[1]	Includes fair value of embedded derivatives.
[2]	Related to GMDB and GLB book of business. (3) Note that the payment provision related to GLB is the net amount at risk. The concept of a notional value does not apply to the GLB reinsurance contracts.

Commitments, contingencies, a_5

Commitments, contingencies, and guarantees Commitments, Contingencies, And Guarantees (Transactions accounted for as secured borrowings) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending collateral	$ 1,844	$ 994
Collateral held under securities lending agreements	1,844	994
Maturity Overnight [Member] | Cash
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending collateral	551	346
Maturity Overnight [Member] | U.S. Treasury and agency
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending collateral	148	6
Maturity Overnight [Member] | Foreign [Member]
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending collateral	1,032	595
Maturity Overnight [Member] | Corporate securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending collateral	30	5
Maturity Overnight [Member] | Mortgage-backed securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending collateral	4	18
Maturity Overnight [Member] | Equity securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities lending collateral	$ 79	$ 24

Commitments, contingencies, a_6

Commitments, contingencies, and guarantees Commitments, contingencies, and guarantees (Collateral pledged under repurchase agreements) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Collateral pledged under repurchase agreements	$ 1,462	$ 1,464
Securities Sold under Agreements to Repurchase	1,405	1,416
Cash
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Collateral pledged under repurchase agreements	4	2
US Treasury and Government [Member]
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Collateral pledged under repurchase agreements	106	107
Mortgage-backed securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Collateral pledged under repurchase agreements	1,352	1,355
Repurchase Agreements [Member]
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Secured Borrowings, Gross, Difference, Amount	57	48
Maturity Less than 30 Days [Member]
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Collateral pledged under repurchase agreements		508
Maturity Less than 30 Days [Member] | Cash
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Collateral pledged under repurchase agreements		2
Maturity Less than 30 Days [Member] | US Treasury and Government [Member]
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Collateral pledged under repurchase agreements		107
Maturity Less than 30 Days [Member] | Mortgage-backed securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Collateral pledged under repurchase agreements		399
Maturity 30 to 90 Days [Member]
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Collateral pledged under repurchase agreements	481	476
Maturity 30 to 90 Days [Member] | Cash
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Collateral pledged under repurchase agreements	0	0
Maturity 30 to 90 Days [Member] | US Treasury and Government [Member]
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Collateral pledged under repurchase agreements	0	0
Maturity 30 to 90 Days [Member] | Mortgage-backed securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Collateral pledged under repurchase agreements	481	476
Maturity Greater than 90 Days [Member]
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Collateral pledged under repurchase agreements	981	480
Maturity Greater than 90 Days [Member] | Cash
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Collateral pledged under repurchase agreements	4	0
Maturity Greater than 90 Days [Member] | US Treasury and Government [Member]
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Collateral pledged under repurchase agreements	106	0
Maturity Greater than 90 Days [Member] | Mortgage-backed securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Collateral pledged under repurchase agreements	$ 871	$ 480

Commitments, contingencies, a_7

Commitments, contingencies, and guarantees (Net Realized Gains (Losses) Of Derivative Instrument Activity In Consolidated Statement Of Operations) (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net		$ (228)	$ (585)	$ (330)
Foreign currency forward contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net		65	(79)	3
Interest Rate Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net		0	(270)	(115)
All Other Futures Contracts And Options [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net		16	(88)	39
Convertible Securities [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	[1]	0	2	(2)
Investment And Embedded Derivative Instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net		81	(435)	(75)
GLB
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net		(202)	(4)	(248)
Futures contracts on equities
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	[2]	(108)	(138)	(4)
Other Derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net		1	(8)	(3)
Guaranteed Living Benefit And Other Derivative Instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net		$ (309)	$ (150)	$ (255)
[1]	Includes embedded derivatives.
[2]	Related to GMDB and GLB book of business.

Commitments, contingencies, a_8

Commitments, contingencies, and guarantees (Future Minimum Lease Payments) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
2020	$ 150
2021	123
2022	96
2023	68
2024	38
Thereafter	75
Total undiscounted lease payments	550
Present value adjustment	33
Operating Lease, Liability	$ 517	$ 603

Shareholders' equity (Detail)

Shareholders' equity (Detail) $ / shares in Units, $ in Millions

12 Months Ended

Dec. 31, 2020SFr / sharesshares

Dec. 31, 2019SFr / sharesshares

Dec. 31, 2018shares

Feb. 01, 2021USD ($)

Nov. 19, 2020USD ($)

May 31, 2020$ / shares

May 20, 2020$ / shares

Nov. 21, 2019USD ($)

May 31, 2019$ / shares

Dec. 01, 2018USD ($)

May 31, 2018$ / shares

Dec. 31, 2017shares

Dec. 21, 2017USD ($)

Stockholders' Equity Note [Abstract]

Common Stock, Dividend Rate Approved | $ / shares

$ 0.78

$ 0.75

$ 0.73

The number of votes associated with one Common Share

one

Annual dividend per share approved by shareholders | $ / shares

$ 3.12

$ 3

$ 2.92

Authorized Share Capital [Line Items]

Common Shares, par value | SFr / shares

SFr 24.15

SFr 24.15

Common Shares, shares issued | shares

477,605,264

479,783,864

479,783,864

479,783,864

Treasury Stock, Shares, Retired | shares

2,178,600

0

0

The maximum ownership percentage for voting allowed for any one shareholder

10.00%

General Purpose

Authorized Share Capital [Line Items]

Authorized share capital for future issuance | shares

200,000,000

Issuance of Debt

Authorized Share Capital [Line Items]

Authorized share capital for future issuance | shares

33,000,000

Employee Benefit Plans

Authorized Share Capital [Line Items]

Authorized share capital for future issuance | shares

25,410,929

2018 Stock Repurchase Plan [Member] [Domain]

Authorized Share Capital [Line Items]

Stock repurchase program authorized amount

$ 1,000

2019 Stock Repurchase Plan [Member]

Authorized Share Capital [Line Items]

Stock repurchase program authorized amount

$ 1,500

Nov 2019 Stock Repurchase Plan [Member]

Authorized Share Capital [Line Items]

Stock repurchase program authorized amount

$ 1,500

Nov 2020 Stock Repurchase Plan [Member]

Authorized Share Capital [Line Items]

Stock repurchase program authorized amount

$ 1,500

Subsequent Event [Member] | Nov 2020 Stock Repurchase Plan [Member]

Authorized Share Capital [Line Items]

Stock repurchase program authorized amount

$ 2,500

CB_Increase(Decrease)StockRepurchaseProgramAuthorizedAmount

$ 1,000

Shareholders' equity Schedule o

Shareholders' equity Schedule of Dividends Declared (Details)	12 Months Ended
	Dec. 31, 2020SFr / shares	Dec. 31, 2020$ / shares	Dec. 31, 2019SFr / shares	Dec. 31, 2019$ / shares	Dec. 31, 2018SFr / shares	Dec. 31, 2018$ / shares
Switzerland, Francs
Dividends Declared [Line Items]
Total dividend distributions per common share | SFr / shares	SFr 2.89		SFr 2.94		SFr 2.84
United States of America, Dollars
Dividends Declared [Line Items]
Total dividend distributions per common share | $ / shares		$ 3.09		$ 2.98		$ 2.90

Shareholders' equity (Rollforwa

Shareholders' equity (Rollforward Of Changes In Common Stock Shares Issued And Outstanding) (Details) - shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Class of Stock [Line Items]
Shares issued, Beginning of year	479,783,864	479,783,864	479,783,864
Treasury Stock, Shares, Retired	(2,178,600)	0	0
Shares issued, End of year	477,605,264	479,783,864	479,783,864
Common Shares in treasury, end of year	(26,872,639)	(27,812,297)	(20,580,486)	(15,950,685)
Stock Issued During Period, Shares, New Issues	2,345,208	3,210,427	3,089,234
Treasury Stock, Shares, Acquired	(3,584,150)	(10,442,238)	(7,719,035)
Shares issued and outstanding, end of year	450,732,625	451,971,567	459,203,378

Shareholders' equity Repurchase

Shareholders' equity Repurchase of Common Shares (Details) - USD ($) $ in Millions	2 Months Ended	12 Months Ended
	Feb. 24, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Equity, Class of Treasury Stock [Line Items]
Number of shares repurchased		3,584,150	10,442,238	7,719,035
Common Shares repurchased		$ 516	$ 1,531	$ 1,021
Subsequent Event [Member]
Equity, Class of Treasury Stock [Line Items]
Number of shares repurchased	1,971,000
Common Shares repurchased	$ 327

Share-based compensation (Narra

Share-based compensation (Narrative) (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense related to the unvested share-based awards	$ 199,000,000
Weighted-average expected recognition period for the unrecognized compensation expense	1 year
Weighted average remaining contractual term for stock options outstanding	6 years
Weighted-average remaining contractual term for stock options exercisable	4 years 9 months 18 days
Cash received from exercise of stock options	$ 100,000,000
Restricted stock awards granted to non-management directors	27,679	19,019	20,784
Amounts paid during period by employees for the purchase of shares under the ESPP	$ 45,000,000	$ 41,000,000	$ 37,000,000
Number of shares purchased during period by employees pursuant to the provisions of the ESPP	383,751	321,800	347,116
Discounted purchase price from market price for the ESPP	85.00%
Share-based Compensation Arrangement by Share-based Payment Award, Maximum Employee Subscription Rate for the ESPP	10.00%
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee Stock Purchase Plan Authorized Amount	$ 25,000
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of award	3 years
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of award	3 years
Stock option term in years	10 years
Restricted stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of award	4 years
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of award	1 year
Number of deferred restricted stock units	166,624
Restricted Stock Units (RSUs) | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of award	1 year
Restricted Stock Units (RSUs) | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of award	3 years
ACE Limited 2004 Long-Term Incentive Plan [Member] | Restricted stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of award	4 years
Common shares | Employee Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common shares authorized for issuance under plan	6,500,000
Common Stock, Capital Shares Reserved for Future Issuance	1,402,017
Common shares | Chubb Limited 2016 Long-Term Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common shares authorized for issuance under plan	19,500,000
Common Stock, Capital Shares Reserved for Future Issuance	7,576,239

Share-based compensation (Pre-t

Share-based compensation (Pre-tax and After-tax Share-based Compensation Expense) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based Payment Arrangement, Expense, Tax Benefit		$ 10	$ 12	$ 19
Restricted stock
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation expense, pre-tax		210	224	235
Share-based compensation expense, after-tax		164	180	178
Stock options
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation expense, pre-tax		45	42	50
Share-based compensation expense, after-tax	[1]	$ 38	$ 39	$ 40
[1]	The windfall tax benefit recorded to Income tax expense in the Consolidated statement of operations was $10 million, $12 million, and $19 million for the years ended December 31, 2020, 2019, and 2018, respectively.

Share-based compensation (Weigh

Share-based compensation (Weighted Average Assumptions for Option Grants) (Details) - Options	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend yield	2.10%	2.20%	2.00%
Expected volatility	18.00%	16.00%	23.20%
Risk-free interest rate	1.20%	2.60%	2.70%
Expected life	5 years 8 months 12 days	5 years 8 months 12 days	5 years 8 months 12 days

Share-based compensation (Rollf

Share-based compensation (Rollforward Of Company's Stock Options) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Options, Weighted-Average Fair Value and Total Intrinsic Value [Abstract]
Weighted-average fair value of stock options granted (US$ per share)	$ 19.89	$ 18.76	$ 29.71
Total intrinsic value of options exercised	$ 76	$ 122	$ 71
Total intrinsic value of options outstanding	331
Total intrinsic value of options exercisable	$ 293
Number of Options [Roll Forward]
Number of option outstanding, beginning of period	10,885,257	11,007,722	10,433,316
Number of options granted	1,958,279	2,073,940	1,842,690
Number of options exercised	(1,158,633)	(1,944,604)	(1,065,384)
Number of options forfeited	(206,720)	(251,801)	(202,900)
Number of option outstanding, end of period	11,478,183	10,885,257	11,007,722
Number of options exercisable	7,792,343
Weighted-Average Exercise Price [Roll Forward]
Weighted-average exercise price of options outstanding, beginning of period (US$ oer share)	$ 116.79	$ 108.25	$ 99.20
Weighted-average exercise price of options granted (US$ per share)	150.10	133.90	143.07
Weighted-average exercise price of options exercised (US$ per share)	86.90	84.13	73.57
Weighted average exercise price of options forfeited (US$ per share)	138.77	136.87	133.92
Weighted-average exercise price of options outstanding, end of period (US$ oer share	125.09	$ 116.79	$ 108.25
Weighted average exercise price of options exercisable (US$ per share)	$ 116.35

Share-based compensation (Rol_2

Share-based compensation (Rollforward Of Company's Restricted Stock) (Details) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Restricted stock
Number of Restricted Stock [Roll Forward]
Number of unvested restricted stock, beginning of period	3,294,010	3,294,849	4,709,442
Number of restricted stock, granted	1,425,667	1,492,900	1,326,979
Number of restricted stock, vested and issued	(1,304,308)	(1,292,864)	(2,545,090)
Number of restricted stock, forfeited	(152,074)	(200,875)	(196,482)
Number of unvested restricted stock, end of period	3,263,295	3,294,010	3,294,849
Weighted-Average Grant-Day Fair Value [Roll Forward]
Weighted average grant-day fair value of unvested restricted stock outstanding, beginning of period (US$ per share)	$ 136.20	$ 134.17	$ 121.16
Weighted average grant-day fair value of restricted stock, granted (US$ per share)	148.56	134.38	142.76
Weighted average grant-day fair value of restricted stock, vested and issued (US$ per share)	134.02	129.18	114.83
Weighted average grant-day fair value of restricted stock, forfeited (US$ per share)	140.72	135.98	131.06
Weighted average grant-day fair value of unvested restricted stock outstanding, end of period (US$ per share)	$ 142.32	$ 136.20	$ 134.17
Performance Shares
Number of Restricted Stock [Roll Forward]
Number of unvested restricted stock, beginning of period	876,212	911,230	975,497
Number of restricted stock, granted	186,291	212,059	180,065
Number of restricted stock, vested and issued	(490,185)	(196,640)	(244,332)
Number of restricted stock, forfeited	0	(50,437)	0
Number of unvested restricted stock, end of period	572,318	876,212	911,230
Weighted-Average Grant-Day Fair Value [Roll Forward]
Weighted average grant-day fair value of unvested restricted stock outstanding, beginning of period (US$ per share)	$ 131.16	$ 127.27	$ 118.28
Weighted average grant-day fair value of restricted stock, granted (US$ per share)	151.14	133.90	143.07
Weighted average grant-day fair value of restricted stock, vested and issued (US$ per share)	125.66	115.62	103.03
Weighted average grant-day fair value of restricted stock, forfeited (US$ per share)	0	132.36	0
Weighted average grant-day fair value of unvested restricted stock outstanding, end of period (US$ per share)	$ 142.38	$ 131.16	$ 127.27

Postretirement benefits (Narrat

Postretirement benefits (Narrative) (Details) - USD ($) $ in Millions	Oct. 31, 2016	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Expenses recognized during period under the defined contributions plans		$ 211	$ 171	$ 171
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Accumulated Benefit Obligation		5,100	4,600
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year		20
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		120	152	143
Actuarial Loss (gain)		1	3
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Accumulated Benefit Obligation		23	25
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year		1
Defined Benefit Plan, Plan Amendment [Abstract]
(Increase) decrease in other comprehensive income, curtailment		0	0	3
Amortization of Prior Service Cost (Credit)		$ 83	84	85
Defined Benefit Plan, Equity Securities [Member] | Minimum
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Percentage		55.00%
Defined Benefit Plan, Equity Securities [Member] | Maximum
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Percentage		65.00%
UNITED STATES | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		$ 3,739	3,301	2,784
Actuarial Loss (gain)		441	443
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Accumulated Benefit Obligation		3,967	3,569
Defined Benefit Plan, Plan Amendment [Abstract]
(Increase) decrease in other comprehensive income, curtailment		0	0	0
Amortization of Prior Service Cost (Credit)		0	0	0
UNITED STATES | Postretirement Health Coverage [Member]
Defined Benefit Plan, Plan Amendment [Abstract]
Effect of Plan Amendment on Accumulated Benefit Obligation	$ 383
Amortization of Prior Service Cost (Credit)		79	79	80
Remaining Balance of Change in Benefit Obligation For Plan Amendment		26
UNITED STATES | Postretirement Health Coverage [Member] | Subject to Amortization [Member]
Defined Benefit Plan, Plan Amendment [Abstract]
Effect of Plan Amendment on Accumulated Benefit Obligation	$ 410
Non - U.S. | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount		1,284	1,141	1,008
Actuarial Loss (gain)		135	124
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Accumulated Benefit Obligation		593	173
Defined Benefit Plan, Plan Amendment [Abstract]
(Increase) decrease in other comprehensive income, curtailment		(1)	(3)	0
Amortization of Prior Service Cost (Credit)		$ 0	$ 0	$ 0

Postretirement benefits Schedul

Postretirement benefits Schedule of Net Funded Status (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Pension Plan [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Service Cost	$ 4	$ 60	$ 69
Pension Plan [Member] | Non - U.S.
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligation, beginning of year	1,042	942
Service Cost	4	11	12
Interest Cost	22	27	27
Actuarial Loss (gain)	135	124
Defined Benefit Plan, Benefit Obligation, Benefits Paid	(31)	(39)
Curtailments	(2)	(4)
Settlements, Benefit obligations	0	(61)
Foreign currency revaluation, benefit obligations	29	42
Benefit Obligation, end of year	1,199	1,042	942
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Plan assets at fair value, beginning of year	1,141	1,008
Actual Return on Plan Assets	126	169
Employer Contributions	19	16
Benefits Paid	(31)	(39)
Settlements	0	(61)
Foreign currency revaluation, Plan Assets	29	48
Plan assets at fair value, end of year	1,284	1,141	1,008
Defined Benefit Plan, Funded (Unfunded) Status of Plan	85	99
Pension Plan [Member] | UNITED STATES
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligation, beginning of year	3,569	3,092
Service Cost	0	49	57
Interest Cost	99	118	105
Actuarial Loss (gain)	441	443
Defined Benefit Plan, Benefit Obligation, Benefits Paid	(127)	(121)
Curtailments	0	0
Settlements, Benefit obligations	(15)	(12)
Foreign currency revaluation, benefit obligations	0	0
Benefit Obligation, end of year	3,967	3,569	3,092
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Plan assets at fair value, beginning of year	3,301	2,784
Actual Return on Plan Assets	563	636
Employer Contributions	17	14
Benefits Paid	(127)	(121)
Settlements	(15)	(12)
Foreign currency revaluation, Plan Assets	0	0
Plan assets at fair value, end of year	3,739	3,301	2,784
Defined Benefit Plan, Funded (Unfunded) Status of Plan	(228)	(268)
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligation, beginning of year	103	113
Service Cost	1	0	1
Interest Cost	2	4	3
Actuarial Loss (gain)	1	3
Defined Benefit Plan, Benefit Obligation, Benefits Paid	(20)	(17)
Curtailments	0	0
Settlements, Benefit obligations	0	0
Foreign currency revaluation, benefit obligations	(1)	0
Benefit Obligation, end of year	86	103	113
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Plan assets at fair value, beginning of year	152	143
Actual Return on Plan Assets	6	9
Employer Contributions	1	0
Benefits Paid	(39)	0
Settlements	0	0
Foreign currency revaluation, Plan Assets	0	0
Plan assets at fair value, end of year	120	152	$ 143
Defined Benefit Plan, Funded (Unfunded) Status of Plan	$ 34	$ 49

Postretirement benefits Sched_2

Postretirement benefits Schedule of amounts recognized in AOCI on a pretax basis (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Pension Plan [Member] | Non - U.S.
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net actuarial loss (gain)	$ 163	$ 110
Prior Service Cost (benefit)	9	10
Total	172	120
Pension Plan [Member] | UNITED STATES
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net actuarial loss (gain)	78	(21)
Prior Service Cost (benefit)	0	0
Total	78	(21)
Other Postretirement Benefits Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net actuarial loss (gain)	(5)	(3)
Prior Service Cost (benefit)	(31)	(114)
Total	$ (36)	$ (117)

Postretirement benefits Sched_3

Postretirement benefits Schedule of Benefit Obligation in Excess of FV (Details) - Pension Plan [Member] - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
UNITED STATES
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Pension Plan with Projected Benefit Obligation in Excess of Plan Assets, Projected Benefit Obligation	$ 3,967	$ 3,569
Defined Benefit Plan, Pension Plan with Projected Benefit Obligation in Excess of Plan Assets, Plan Assets	3,739	3,301
Net Funded Status With PBO in Excess Of Plan Assets	(228)	(268)
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Accumulated Benefit Obligation	3,967	3,569
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Plan Assets	3,739	3,301
Non - U.S.
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Pension Plan with Projected Benefit Obligation in Excess of Plan Assets, Projected Benefit Obligation	629	236
Defined Benefit Plan, Pension Plan with Projected Benefit Obligation in Excess of Plan Assets, Plan Assets	568	175
Net Funded Status With PBO in Excess Of Plan Assets	(61)	(61)
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Accumulated Benefit Obligation	593	173
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Plan Assets	$ 565	$ 140

Postretirement benefits Sched_4

Postretirement benefits Schedule of assumptions used to determine benefit obligation (Details)	Dec. 31, 2020	Dec. 31, 2019
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract]
Benefit Obligation, Discount Rate	1.36%	2.70%
Non - U.S. | Pension Plan [Member]
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract]
Benefit Obligation, Discount Rate	1.80%	2.39%
Benefit Obligation, Rate of Compensation Increase	3.24%	3.26%
UNITED STATES | Pension Plan [Member]
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract]
Benefit Obligation, Discount Rate	2.32%	3.20%
Interest crediting rate	4.10%	4.10%

Postretirement benefits Sched_5

Postretirement benefits Schedule of net periodic benefit costs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan, Amount Recognized in Net Periodic Benefit Cost (Credit) and Other Comprehensive (Income) Loss, before Tax [Abstract]
Total (increase) decrease in other comprehensive (Income) Loss	$ 232	$ 76	$ 321
Pension Plan [Member]
Defined Benefit Plan, Amount Recognized in Net Periodic Benefit Cost (Credit) and Other Comprehensive (Income) Loss, before Tax [Abstract]
Service Cost	4	60	69
Defined Benefit Plan, Non Service (Benefit) Cost	(140)	(84)	(124)
Net Periodic Benefit Cost	(136)	(24)	(55)
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan, Amount Recognized in Net Periodic Benefit Cost (Credit) and Other Comprehensive (Income) Loss, before Tax [Abstract]
Service Cost	1	0	1
Interest Cost	2	4	3
Expected Return on Plan Assets	(5)	(4)	(5)
Amortization of (Gains) Losses	0	0	0
Amortization of Prior Service Cost (Credit)	(83)	(84)	(85)
Recognized Net (Gain) Loss Due to Curtailments	0	0	(2)
Recognized Net (Gain) Loss Due to Settlements	0	0	0
Defined Benefit Plan, Non Service (Benefit) Cost	(86)	(84)	(89)
Net Periodic Benefit Cost	(85)	(84)	(88)
(Increase) decrease in Other Comprehensive Income (Loss), Net Actuarial (Gain) Loss)	(2)	(2)	(11)
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), before Tax	0	0	0
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax	0	0	(1)
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, before Tax	83	84	85
(Increase) decrease in other comprehensive income, curtailment	0	0	3
(Increase) decrease in other comprehensive income, settlement	0	0	0
Total (increase) decrease in other comprehensive (Income) Loss	81	82	76
Losses and loss expenses [Member] | Pension Plan [Member]
Defined Benefit Plan, Amount Recognized in Net Periodic Benefit Cost (Credit) and Other Comprehensive (Income) Loss, before Tax [Abstract]
Service Cost	0	6	7
Defined Benefit Plan, Non Service (Benefit) Cost	(12)	(7)	(10)
Losses and loss expenses [Member] | Other Postretirement Benefits Plan [Member]
Defined Benefit Plan, Amount Recognized in Net Periodic Benefit Cost (Credit) and Other Comprehensive (Income) Loss, before Tax [Abstract]
Service Cost	0	0	0
Defined Benefit Plan, Non Service (Benefit) Cost	(9)	(8)	(9)
General and Administrative Expense [Member] | Pension Plan [Member]
Defined Benefit Plan, Amount Recognized in Net Periodic Benefit Cost (Credit) and Other Comprehensive (Income) Loss, before Tax [Abstract]
Service Cost	4	54	62
Defined Benefit Plan, Non Service (Benefit) Cost	(128)	(77)	(114)
General and Administrative Expense [Member] | Other Postretirement Benefits Plan [Member]
Defined Benefit Plan, Amount Recognized in Net Periodic Benefit Cost (Credit) and Other Comprehensive (Income) Loss, before Tax [Abstract]
Service Cost	1	0	1
Defined Benefit Plan, Non Service (Benefit) Cost	(77)	(76)	(80)
Non - U.S. | Pension Plan [Member]
Defined Benefit Plan, Amount Recognized in Net Periodic Benefit Cost (Credit) and Other Comprehensive (Income) Loss, before Tax [Abstract]
Service Cost	4	11	12
Interest Cost	22	27	27
Expected Return on Plan Assets	(41)	(45)	(50)
Amortization of (Gains) Losses	2	3	1
Amortization of Prior Service Cost (Credit)	0	0	0
Recognized Net (Gain) Loss Due to Curtailments	(1)	(1)	0
Recognized Net (Gain) Loss Due to Settlements	0	1	3
Defined Benefit Plan, Non Service (Benefit) Cost	(18)	(15)	(19)
Net Periodic Benefit Cost	(14)	(4)	(7)
(Increase) decrease in Other Comprehensive Income (Loss), Net Actuarial (Gain) Loss)	56	6	34
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), before Tax	0	1	3
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax	(2)	(3)	(1)
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, before Tax	(1)	0	0
(Increase) decrease in other comprehensive income, curtailment	(1)	(3)	0
(Increase) decrease in other comprehensive income, settlement	0	(1)	(3)
Total (increase) decrease in other comprehensive (Income) Loss	52	0	33
UNITED STATES | Pension Plan [Member]
Defined Benefit Plan, Amount Recognized in Net Periodic Benefit Cost (Credit) and Other Comprehensive (Income) Loss, before Tax [Abstract]
Service Cost	0	49	57
Interest Cost	99	118	105
Expected Return on Plan Assets	(224)	(189)	(212)
Amortization of (Gains) Losses	0	0	0
Amortization of Prior Service Cost (Credit)	0	0	0
Recognized Net (Gain) Loss Due to Curtailments	0	0	0
Recognized Net (Gain) Loss Due to Settlements	3	2	2
Defined Benefit Plan, Non Service (Benefit) Cost	(122)	(69)	(105)
Net Periodic Benefit Cost	(122)	(20)	(48)
(Increase) decrease in Other Comprehensive Income (Loss), Net Actuarial (Gain) Loss)	102	(4)	214
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), before Tax	0	0	0
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax	0	0	0
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, before Tax	0	0	0
(Increase) decrease in other comprehensive income, curtailment	0	0	0
(Increase) decrease in other comprehensive income, settlement	(3)	(2)	(2)
Total (increase) decrease in other comprehensive (Income) Loss	$ 99	$ (6)	$ 212

Postretirement benefits Weighte

Postretirement benefits Weighted Average Assumption used to determine the net periodic cost of benefit (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Pension Plan [Member] | UNITED STATES
Defined Benefit Plan Disclosure [Line Items]
Rate of Compensation Increase		4.00%	4.00%
Expected Long-term Return on Assets	7.00%	7.00%	7.00%
Interest crediting rate, net periodic benefit costs	4.10%	4.10%	4.10%
Pension Plan [Member] | UNITED STATES | Interest Cost [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate	2.85%	3.94%	3.27%
Pension Plan [Member] | UNITED STATES | Service Cost [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate		4.23%	3.62%
Pension Plan [Member] | Non - U.S.
Defined Benefit Plan Disclosure [Line Items]
Rate of Compensation Increase	3.26%	3.37%	3.46%
Expected Long-term Return on Assets	3.83%	4.40%	4.32%
Pension Plan [Member] | Non - U.S. | Interest Cost [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate	2.24%	2.88%	2.55%
Pension Plan [Member] | Non - U.S. | Service Cost [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate	6.04%	4.48%	3.97%
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected Long-term Return on Assets	3.00%	3.00%	2.59%
Other Postretirement Benefits Plan [Member] | Interest Cost [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate	2.64%	3.69%	2.62%
Other Postretirement Benefits Plan [Member] | Service Cost [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate	3.00%	4.04%	2.84%

Postretirement benefits Sched_6

Postretirement benefits Schedule of Health Care Cost Trend Rates (Details) - Pension Plan [Member]	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
UNITED STATES
Defined Benefit Plan, Assumed Health Care Cost Trend Rates [Abstract]
Health Care Cost Trend Rate	5.96%	6.32%	6.68%
Ultimate Health Care Cost Trend Rate	4.50%	4.50%	4.50%
Year that Rate Reaches Ultimate Trend Rate	2038	2038	2038
Non - U.S.
Defined Benefit Plan, Assumed Health Care Cost Trend Rates [Abstract]
Health Care Cost Trend Rate	5.04%	5.24%	6.29%
Ultimate Health Care Cost Trend Rate	4.00%	4.00%	4.50%
Year that Rate Reaches Ultimate Trend Rate	2040	2040	2029

Postretirement benefits Sched_7

Postretirement benefits Schedule of Allocation of Plan Assets (Details) - USD ($) $ in Millions	Dec. 31, 2020		Dec. 31, 2019		Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Other Investments	$ 7,945		$ 6,062
Cash	1,747	[1]	1,537	[2]	$ 1,247
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	120		152		143
Fair Value, Recurring [Member] | Level 1
Defined Benefit Plan Disclosure [Line Items]
Other Investments	434		412
Fair Value, Recurring [Member] | Level 2
Defined Benefit Plan Disclosure [Line Items]
Other Investments	438		377
Fair Value, Recurring [Member] | Level 3
Defined Benefit Plan Disclosure [Line Items]
Other Investments	10		10
Other Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Other Investments	60		95
Investment Funds Limited Partnerships Partially Owned Investment Companies Fair Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Other Investments	6,770		4,921
UNITED STATES | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets excluding measured using NAV	3,108		2,873
Defined Benefit Plan, Plan Assets, Amount	3,739		3,301		2,784
Cash	14
UNITED STATES | Pension Plan [Member] | Level 1
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets excluding measured using NAV	2,127		1,951
UNITED STATES | Pension Plan [Member] | Level 2
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets excluding measured using NAV	981		922
UNITED STATES | Pension Plan [Member] | Level 3
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets excluding measured using NAV	0		0
UNITED STATES | Pension Plan [Member] | Short-term investments
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets excluding measured using NAV	59		55
UNITED STATES | Pension Plan [Member] | Short-term investments | Level 1
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets excluding measured using NAV	59		18
UNITED STATES | Pension Plan [Member] | Short-term investments | Level 2
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets excluding measured using NAV	0		37
UNITED STATES | Pension Plan [Member] | Short-term investments | Level 3
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets excluding measured using NAV	0		0
UNITED STATES | Pension Plan [Member] | US Treasury and Government [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets excluding measured using NAV	436		600
UNITED STATES | Pension Plan [Member] | US Treasury and Government [Member] | Level 1
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets excluding measured using NAV	250		466
UNITED STATES | Pension Plan [Member] | US Treasury and Government [Member] | Level 2
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets excluding measured using NAV	186		134
UNITED STATES | Pension Plan [Member] | US Treasury and Government [Member] | Level 3
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets excluding measured using NAV	0		0
UNITED STATES | Pension Plan [Member] | Debt Security, Government, Non-US [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets excluding measured using NAV	793		749
UNITED STATES | Pension Plan [Member] | Debt Security, Government, Non-US [Member] | Level 1
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets excluding measured using NAV	0		0
UNITED STATES | Pension Plan [Member] | Debt Security, Government, Non-US [Member] | Level 2
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets excluding measured using NAV	793		749
UNITED STATES | Pension Plan [Member] | Debt Security, Government, Non-US [Member] | Level 3
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets excluding measured using NAV	0		0
UNITED STATES | Pension Plan [Member] | States, municipalities, and political subdivisions
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets excluding measured using NAV	2		2
UNITED STATES | Pension Plan [Member] | States, municipalities, and political subdivisions | Level 1
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets excluding measured using NAV	0		0
UNITED STATES | Pension Plan [Member] | States, municipalities, and political subdivisions | Level 2
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets excluding measured using NAV	2		2
UNITED STATES | Pension Plan [Member] | States, municipalities, and political subdivisions | Level 3
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets excluding measured using NAV	0		0
UNITED STATES | Pension Plan [Member] | Defined Benefit Plan, Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets excluding measured using NAV	1,818		1,467
UNITED STATES | Pension Plan [Member] | Defined Benefit Plan, Equity Securities [Member] | Level 1
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets excluding measured using NAV	1,818		1,467
UNITED STATES | Pension Plan [Member] | Defined Benefit Plan, Equity Securities [Member] | Level 2
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets excluding measured using NAV	0		0
UNITED STATES | Pension Plan [Member] | Defined Benefit Plan, Equity Securities [Member] | Level 3
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets excluding measured using NAV	0		0
UNITED STATES | Other Investments [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Other Investments	543		428
UNITED STATES | Investment Funds Limited Partnerships Partially Owned Investment Companies Fair Value [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Other Investments	74
Non - U.S. | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets excluding measured using NAV	1,129		1,030
Defined Benefit Plan, Plan Assets, Amount	1,284		1,141		$ 1,008
Non - U.S. | Pension Plan [Member] | Level 1
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets excluding measured using NAV	132		114
Non - U.S. | Pension Plan [Member] | Level 2
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets excluding measured using NAV	997		916
Non - U.S. | Pension Plan [Member] | Level 3
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets excluding measured using NAV	0		0
Non - U.S. | Pension Plan [Member] | Short-term investments
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets excluding measured using NAV	5		2
Non - U.S. | Pension Plan [Member] | Short-term investments | Level 1
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets excluding measured using NAV	5		2
Non - U.S. | Pension Plan [Member] | Short-term investments | Level 2
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets excluding measured using NAV	0		0
Non - U.S. | Pension Plan [Member] | Short-term investments | Level 3
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets excluding measured using NAV	0		0
Non - U.S. | Pension Plan [Member] | Debt Security, Government, Non-US [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets excluding measured using NAV	609		598
Non - U.S. | Pension Plan [Member] | Debt Security, Government, Non-US [Member] | Level 1
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets excluding measured using NAV	0		0
Non - U.S. | Pension Plan [Member] | Debt Security, Government, Non-US [Member] | Level 2
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets excluding measured using NAV	609		598
Non - U.S. | Pension Plan [Member] | Debt Security, Government, Non-US [Member] | Level 3
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets excluding measured using NAV	0		0
Non - U.S. | Pension Plan [Member] | Defined Benefit Plan, Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets excluding measured using NAV	515		430
Non - U.S. | Pension Plan [Member] | Defined Benefit Plan, Equity Securities [Member] | Level 1
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets excluding measured using NAV	127		112
Non - U.S. | Pension Plan [Member] | Defined Benefit Plan, Equity Securities [Member] | Level 2
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets excluding measured using NAV	388		318
Non - U.S. | Pension Plan [Member] | Defined Benefit Plan, Equity Securities [Member] | Level 3
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets excluding measured using NAV	0		0
Non - U.S. | Other Investments [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Other Investments	147		107
Non - U.S. | Investment Funds Limited Partnerships Partially Owned Investment Companies Fair Value [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Other Investments	$ 8		$ 4
[1]	Chubb maintains two notional multicurrency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information. At December 31, 2020, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.
[2]	Chubb maintains two notional multicurrency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information.

Postretirement benefits (Schedu

Postretirement benefits (Schedule of Expected Future Benefit Payments) (Details) $ in Millions	Dec. 31, 2020USD ($)
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
2021	$ 19
2022	20
2023	16
2024	12
2025	7
2026-2030	5
Non - U.S. | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
2021	30
2022	28
2023	30
2024	32
2025	32
2026-2030	185
UNITED STATES | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
2021	159
2022	166
2023	171
2024	175
2025	180
2026-2030	$ 947

Other (income) expense (Details

Other (income) expense (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Equity in net income of partially-owned entities	[1]	$ 1,019	$ 617	$ 514
Gains (losses) from fair value changes in separate account assets	[2]	58	44	(38)
Federal excise and capital taxes		(22)	(23)	(12)
Other		(61)	(42)	(30)
Total		994	596	434
Huatai Group [Member]
Equity in net income of partially-owned entities	[1]	$ 167	$ 74	$ 43
[1]	Equity in net income of partially-owned entities includes $167 million, $74 million, and $43 million attributable to our investments in Huatai (Huatai Group, Huatai P&C, and Huatai Life) for the years ended December 31, 2020, 2019, and 2018, respectively.
[2]	Related to gains (losses) from fair value changes in separate account assets that do not qualify for separate account reporting under GAAP.

Segment Information (Operations

Segment Information (Operations By Segment) (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Net premiums written		$ 33,820	$ 32,275	$ 30,579
Net premiums earned		33,117	31,290	30,064
Losses and loss expenses		21,710	18,730	18,067
Policy benefits		784	740	590
Policy Acquisition Costs		6,547	6,153	5,912
Administrative expenses		2,979	3,030	2,886
Underwriting income (loss)		1,097	2,637	2,609
Net Investment Income		3,375	3,426	3,305
Other (Income) Expense		(994)	(596)	(434)
Amortization of Purchased Intangibles		290	305	339
Segment Underwriting Income Loss and Net Investment Income Loss		5,176	6,354	6,009
Interest expense		516	552	641
Chubb integration expenses		0	23	59
Income tax expense (benefit)		629	795	695
Net income		3,533	4,454	3,962
Derivative, Gain (Loss) on Derivative, Net		228	585	330
Other (income) expense		(994)	(596)	(434)
(Gains) losses from fair value changes in separate account assets	[1]	58	44	(38)
Realized Investment Gains (Losses)		(498)	(530)	(652)
Interest Income (Expense), Net		516	552	641
Segment Reconciling Items [Member]
Segment Reporting Information [Line Items]
Net premiums written		0	0	0
Net premiums earned		0	0	0
Losses and loss expenses		1	(8)	(3)
Policy benefits		58	44	(38)
Policy Acquisition Costs		0	0	0
Administrative expenses		0	0	0
Net Investment Income		(115)	(86)	(63)
Other (Income) Expense		(173)	(130)	(25)
Amortization of Purchased Intangibles		0	0	0
Segment Underwriting Income Loss and Net Investment Income Loss		(1)	8	3
Chubb integration expenses			0	0
Income tax expense (benefit)		0	0	0
Net income		0	0	0
Realized Investment Gains (Losses)		1	(8)	(3)
Underwriting Income (Loss)		(59)	(36)	41
Interest Income (Expense), Net		0	0	0
North America Commercial P&C Insurance
Segment Reporting Information [Line Items]
Net premiums written		14,474	13,375	12,485
Net premiums earned		13,964	12,922	12,402
Losses and loss expenses		10,129	8,206	8,000
Policy benefits		0	0	0
Policy Acquisition Costs		1,942	1,831	1,829
Administrative expenses		1,006	1,028	966
Underwriting income (loss)		887	1,857	1,607
Net Investment Income		2,061	2,109	2,061
Other (Income) Expense		23	24	3
Amortization of Purchased Intangibles		0	0	0
Segment Underwriting Income Loss and Net Investment Income Loss		2,925	3,942	3,665
Segment Insurance North American Personal P&C [Member] [Member]
Segment Reporting Information [Line Items]
Net premiums written		4,920	4,787	4,674
Net premiums earned		4,866	4,694	4,593
Losses and loss expenses		3,187	3,043	3,229
Policy benefits		0	0	0
Policy Acquisition Costs		974	948	939
Administrative expenses		270	286	269
Underwriting income (loss)		435	417	156
Net Investment Income		260	258	236
Other (Income) Expense		5	3	1
Amortization of Purchased Intangibles		11	12	13
Segment Underwriting Income Loss and Net Investment Income Loss		679	660	378
North America Agricultural Insurance
Segment Reporting Information [Line Items]
Net premiums written		1,846	1,810	1,577
Net premiums earned		1,822	1,795	1,569
Losses and loss expenses		1,544	1,616	1,114
Policy benefits		0	0	0
Policy Acquisition Costs		123	84	79
Administrative expenses		9	6	(9)
Underwriting income (loss)		146	89	385
Net Investment Income		30	30	28
Other (Income) Expense		1	1	2
Amortization of Purchased Intangibles		27	28	28
Segment Underwriting Income Loss and Net Investment Income Loss		148	90	383
Overseas General Insurance
Segment Reporting Information [Line Items]
Net premiums written		9,335	9,262	8,902
Net premiums earned		9,285	8,882	8,612
Losses and loss expenses		5,255	4,606	4,429
Policy benefits		0	0	0
Policy Acquisition Costs		2,568	2,501	2,346
Administrative expenses		1,034	1,033	1,014
Underwriting income (loss)		428	742	823
Net Investment Income		534	588	622
Other (Income) Expense		13	12	3
Amortization of Purchased Intangibles		45	45	41
Segment Underwriting Income Loss and Net Investment Income Loss		904	1,273	1,401
Segment Global Reinsurance [Member]
Segment Reporting Information [Line Items]
Net premiums written		731	649	671
Net premiums earned		698	654	670
Losses and loss expenses		435	352	479
Policy benefits		0	0	0
Policy Acquisition Costs		174	169	162
Administrative expenses		37	35	41
Underwriting income (loss)		52	98	(12)
Net Investment Income		307	279	289
Other (Income) Expense		2	1	0
Amortization of Purchased Intangibles		0	0	0
Segment Underwriting Income Loss and Net Investment Income Loss		357	376	277
Life Insurance
Segment Reporting Information [Line Items]
Net premiums written		2,514	2,392	2,270
Net premiums earned		2,482	2,343	2,218
Losses and loss expenses		724	757	766
Policy benefits		726	696	628
Policy Acquisition Costs		766	620	557
Administrative expenses		320	323	310
Underwriting income (loss)		(54)	(53)	(43)
Net Investment Income		385	373	341
Other (Income) Expense		(74)	(48)	(12)
Amortization of Purchased Intangibles		4	2	2
Segment Underwriting Income Loss and Net Investment Income Loss		401	366	308
Corporate and Other
Segment Reporting Information [Line Items]
Net premiums written		0	0	0
Net premiums earned		0	0	0
Losses and loss expenses		435	158	53
Policy benefits		0	0	0
Policy Acquisition Costs		0	0	0
Administrative expenses		303	319	295
Underwriting income (loss)		(738)	(477)	(348)
Net Investment Income		(87)	(125)	(209)
Other (Income) Expense		(791)	(459)	(406)
Amortization of Purchased Intangibles		203	218	255
Segment Underwriting Income Loss and Net Investment Income Loss		(237)	(361)	(406)
Interest expense		516	552	641
Chubb integration expenses			23	59
Income tax expense (benefit)		629	795	695
Net income		(1,881)	(2,253)	(2,450)
Realized Investment Gains (Losses)		$ (499)	$ (522)	$ (649)
[1]	Related to gains (losses) from fair value changes in separate account assets that do not qualify for separate account reporting under GAAP.

Segment Information (Net Premiu

Segment Information (Net Premiums Earned For Segment By Product) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Net premiums earned	$ 33,117	$ 31,290	$ 30,064
North America Commercial P&C Insurance
Segment Reporting Information [Line Items]
Net premiums earned	13,964	12,922	12,402
North America Commercial P&C Insurance | Property and other short-tail [Member]
Segment Reporting Information [Line Items]
Net premiums earned	2,423	1,987	1,861
North America Commercial P&C Insurance | Casualty and all other [Member]
Segment Reporting Information [Line Items]
Net premiums earned	10,812	10,136	9,773
North America Commercial P&C Insurance | Accident and Health [Member]
Segment Reporting Information [Line Items]
Net premiums earned	729	799	768
North American Personal P&C [Member]
Segment Reporting Information [Line Items]
Net premiums earned	4,866	4,694	4,593
North American Personal P&C [Member] | Automobiles [Member]
Segment Reporting Information [Line Items]
Net premiums earned	822	829	803
North American Personal P&C [Member] | Personal homeowner [Member]
Segment Reporting Information [Line Items]
Net premiums earned	3,327	3,183	3,127
North American Personal P&C [Member] | Insurance, Other [Member]
Segment Reporting Information [Line Items]
Net premiums earned	717	682	663
North America Agricultural Insurance
Segment Reporting Information [Line Items]
Net premiums earned	1,822	1,795	1,569
Overseas General Insurance
Segment Reporting Information [Line Items]
Net premiums earned	9,285	8,882	8,612
Overseas General Insurance | Property and other short-tail [Member]
Segment Reporting Information [Line Items]
Net premiums earned	2,468	2,244	2,134
Overseas General Insurance | Casualty and all other [Member]
Segment Reporting Information [Line Items]
Net premiums earned	2,738	2,494	2,429
Overseas General Insurance | Accident and Health [Member]
Segment Reporting Information [Line Items]
Net premiums earned	2,098	2,248	2,265
Overseas General Insurance | Personal lines [Member]
Segment Reporting Information [Line Items]
Net premiums earned	1,981	1,896	1,784
Segment Global Reinsurance [Member]
Segment Reporting Information [Line Items]
Net premiums earned	698	654	670
Segment Global Reinsurance [Member] | Property and other short-tail [Member]
Segment Reporting Information [Line Items]
Net premiums earned	104	131	123
Segment Global Reinsurance [Member] | Casualty and all other [Member]
Segment Reporting Information [Line Items]
Net premiums earned	421	381	377
Segment Global Reinsurance [Member] | Property catastrophe [Member]
Segment Reporting Information [Line Items]
Net premiums earned	173	142	170
Life Insurance
Segment Reporting Information [Line Items]
Net premiums earned	2,482	2,343	2,218
Life Insurance | Accident and Health [Member]
Segment Reporting Information [Line Items]
Net premiums earned	1,165	1,242	1,196
Life Insurance | Life Insurance Product Line [Member]
Segment Reporting Information [Line Items]
Net premiums earned	$ 1,317	$ 1,101	$ 1,022

Segment Information (Net Prem_2

Segment Information (Net Premiums Earned By Geographic Region) (Details)		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
North America [Member]
Segment Reporting Information [Line Items]
Percentage of net premiums earned by geographic region		70.00%	70.00%	70.00%
Europe [Member]
Segment Reporting Information [Line Items]
Percentage of net premiums earned by geographic region	[1]	11.00%	11.00%	11.00%
Asia Pacific and Far East [Member]
Segment Reporting Information [Line Items]
Percentage of net premiums earned by geographic region		12.00%	12.00%	12.00%
Latin America [Member]
Segment Reporting Information [Line Items]
Percentage of net premiums earned by geographic region		7.00%	7.00%	7.00%
[1]	(1) Europe includes Eurasia and Africa regions.

Earnings Per Share (Detail)

Earnings Per Share (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Earnings Per Share [Abstract]
Net income	$ 3,533	$ 4,454	$ 3,962
Weighted-average shares outstanding	451,602,820	455,910,463	463,629,203
Share-based compensation plans	1,838,692	3,004,200	3,173,145
Adjusted weighted-average shares outstanding and assumed conversions	453,441,512	458,914,663	466,802,348
Basic earnings per share	$ 7.82	$ 9.77	$ 8.55
Diluted earnings per share	$ 7.79	$ 9.71	$ 8.49
Potential anti-dilutive share conversions	6,811,966	2,410,337	3,543,188

Related party transaction (Deta

Related party transaction (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Related Party Transaction [Line Items]
Ceded Premiums Written	$ 7,441	$ 7,849	$ 7,389
Losses and loss expenses	21,710	18,730	18,067
Insurance and reinsurance balances payable	6,708	6,184
Net premiums written	$ 33,820	$ 32,275	30,579
Bermuda | ABR Reinsurance Capital Holdings Ltd. [Member]
Related Party Transaction [Line Items]
Ownership Percentage	15.60%	12.00%
Starr Technical Risk Agency and Affiliates [Member]
Related Party Transaction [Line Items]
Premiums Written, Gross	$ 507	$ 394	411
Ceded Premiums Written	253	207	188
Paid commissions	97	77	84
Commissions received	59	46	42
Losses and loss expenses	170	185	188
Reinsurance Recoverable on Losses and Loss Expenses	432	440
Insurance and reinsurance balances payable	80	56
Minimum Amount of Program Business to be Written to Earn Profit Sharing	20
ABR Reinsurance Capital Holdings Ltd. [Member]
Related Party Transaction [Line Items]
Ceded Premiums Written	350	321	329
Commissions received	100	92	$ 96
Reinsurance Recoverable on Losses and Loss Expenses	806	674
Insurance and reinsurance balances payable	$ 67	$ 62
Warrants & Rights Outstanding	0.50%

Statutory Financial Informati_3

Statutory Financial Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statutory Accounting Practices [Line Items]
Dividends available to be paid	$ 6,400
Approximate increase in statutory capital and surplus resulting from discount of certain A&E liabilities	140	$ 147
Minimum statutory capital and surplus required to satisfy regulatory requirements	29,400	26,700
Statutory Accounting Practices, Permitted Practice, Amount	55	54
PropertyAndCasualtySubsidiaries [Member]
Statutory Accounting Practices [Line Items]
Statutory capital and surplus	45,964	43,077
Statutory net income	4,294	6,046	$ 7,521
LifeSubsidiaries [Member] [Member]
Statutory Accounting Practices [Line Items]
Statutory capital and surplus	1,641	1,573
Statutory net income	$ (247)	$ (210)	$ (102)

Information provided in conne_3

Information provided in connection with outstanding debt of subsidiaries (Condensed Consolidating Balance Sheet) (Detail) - USD ($) $ in Millions	Dec. 31, 2020		Dec. 31, 2019		Dec. 31, 2018	Dec. 31, 2017
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Investments	$ 118,669		$ 109,234
Cash	1,747	[1]	1,537	[2]	$ 1,247
Restricted Cash	89		109		93
Insurance and reinsurance balances receivable, net of valuation allowance - $44 and $44	10,480		10,357
Reinsurance recoverable on losses and loss expenses, net of valuation allowance - $314 and $316	15,592		15,181
Reinsurance Recoverable Future Policy Benefits	206		197
Value of business acquired	263		306		295	$ 326
Goodwill	21,211		21,359
Investments in subsidiaries	0		0
Due from subsidiaries and affiliates, net	0		0
Other assets	22,517		18,663
Total assets	190,774		176,943
Unpaid losses and loss expenses	67,811		62,690		62,960	63,179
Unearned premiums	17,652		16,771
Future policy benefits	5,713		5,373
Due to subsidiaries and affiliates, net	0		0
Affiliated notional cash pooling programs	0
Repurchase agreements	1,405		1,416
Short-term debt	0		1,299
Long-term debt	14,948		13,559
Trust preferred securities	308		308
Other liabilities	23,496		20,196
Total liabilities	131,333		121,612
Total shareholders' equity	59,441		55,331
Total liabilities and shareholders’ equity	190,774		176,943
Consolidating Adjustments
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Investments	0		0
Cash	(272)	[1]	0	[2]
Restricted Cash	0		0
Insurance and reinsurance balances receivable, net of valuation allowance - $44 and $44	(3,446)		(2,563)
Reinsurance recoverable on losses and loss expenses, net of valuation allowance - $314 and $316	(9,625)		(9,599)
Reinsurance Recoverable Future Policy Benefits	(93)		(95)
Value of business acquired	0		0
Goodwill	0		0
Investments in subsidiaries	(111,379)		(102,929)
Due from subsidiaries and affiliates, net	(3,693)		(4,776)
Other assets	(1,877)		(1,829)
Total assets	(130,385)		(121,791)
Unpaid losses and loss expenses	(9,369)		(9,226)
Unearned premiums	(1,201)		(1,207)
Future policy benefits	(93)		(95)
Due to subsidiaries and affiliates, net	(3,693)		(4,776)
Affiliated notional cash pooling programs	(272)
Repurchase agreements	0		0
Short-term debt			0
Long-term debt	0		0
Trust preferred securities	0		0
Other liabilities	(4,378)		(3,558)
Total liabilities	(19,006)		(18,862)
Total shareholders' equity	(111,379)		(102,929)
Total liabilities and shareholders’ equity	(130,385)		(121,791)
Chubb limited (Parent Guarantor)
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Investments	0		0
Cash	84	[1]	2	[2]	$ 1	$ 3
Restricted Cash	0		0
Insurance and reinsurance balances receivable, net of valuation allowance - $44 and $44	0		0
Reinsurance recoverable on losses and loss expenses, net of valuation allowance - $314 and $316	0		0
Reinsurance Recoverable Future Policy Benefits	0		0
Value of business acquired	0		0
Goodwill	0		0
Investments in subsidiaries	56,148		50,853
Due from subsidiaries and affiliates, net	3,522		4,776
Other assets	10		12
Total assets	59,764		55,643
Unpaid losses and loss expenses	0		0
Unearned premiums	0		0
Future policy benefits	0		0
Due to subsidiaries and affiliates, net	0		0
Affiliated notional cash pooling programs	0
Repurchase agreements	0		0
Short-term debt			0
Long-term debt	0		0
Trust preferred securities	0		0
Other liabilities	323		312
Total liabilities	323		312
Total shareholders' equity	59,441		55,331
Total liabilities and shareholders’ equity	59,764		55,643
Chubb INA Holdings Inc. (Subsidiary Issuer)
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Investments	197		1,013
Cash	1	[1]	442	[2]
Restricted Cash	0		0
Insurance and reinsurance balances receivable, net of valuation allowance - $44 and $44	0		0
Reinsurance recoverable on losses and loss expenses, net of valuation allowance - $314 and $316	0		0
Reinsurance Recoverable Future Policy Benefits	0		0
Value of business acquired	0		0
Goodwill	0		0
Investments in subsidiaries	55,231		52,076
Due from subsidiaries and affiliates, net	0		0
Other assets	463		408
Total assets	55,892		53,939
Unpaid losses and loss expenses	0		0
Unearned premiums	0		0
Future policy benefits	0		0
Due to subsidiaries and affiliates, net	3,008		4,446
Affiliated notional cash pooling programs	272
Repurchase agreements	0		0
Short-term debt			1,298
Long-term debt	14,948		13,559
Trust preferred securities	308		308
Other liabilities	1,418		1,649
Total liabilities	19,954		21,260
Total shareholders' equity	35,938		32,679
Total liabilities and shareholders’ equity	55,892		53,939
Other Chubb Limited Subsidiaries and Eliminations
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Investments	118,472		108,221
Cash	1,934	[1]	1,093	[2]
Restricted Cash	89		109
Insurance and reinsurance balances receivable, net of valuation allowance - $44 and $44	13,926		12,920
Reinsurance recoverable on losses and loss expenses, net of valuation allowance - $314 and $316	25,217		24,780
Reinsurance Recoverable Future Policy Benefits	299		292
Value of business acquired	263		306
Goodwill	21,211		21,359
Investments in subsidiaries	0		0
Due from subsidiaries and affiliates, net	171		0
Other assets	23,921		20,072
Total assets	205,503		189,152
Unpaid losses and loss expenses	77,180		71,916
Unearned premiums	18,853		17,978
Future policy benefits	5,806		5,468
Due to subsidiaries and affiliates, net	685		330
Affiliated notional cash pooling programs	0
Repurchase agreements	1,405		1,416
Short-term debt			1
Long-term debt	0		0
Trust preferred securities	0		0
Other liabilities	26,133		21,793
Total liabilities	130,062		118,902
Total shareholders' equity	75,441		70,250
Total liabilities and shareholders’ equity	$ 205,503		$ 189,152
[1]	Chubb maintains two notional multicurrency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information. At December 31, 2020, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.
[2]	Chubb maintains two notional multicurrency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information.

Information provided in conne_4

Information provided in connection with outstanding debt of subsidiaries (Condensed Consolidating Statement Of Operations and Comprehensive Income) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net premiums written	$ 33,820	$ 32,275	$ 30,579
Net premiums earned	33,117	31,290	30,064
Net Investment Income	3,375	3,426	3,305
Equity in earnings of subsidiaries	0	0	0
Realized Investment Gains (Losses)	(498)	(530)	(652)
Losses and loss expenses	21,710	18,730	18,067
Policy benefits	784	740	590
Policy acquisition costs and administrative expenses	9,526	9,183	8,798
Interest (income) expense	516	552	641
Other (Income) Expense	(994)	(596)	(434)
Amortization of Purchased Intangibles	290	305	339
Chubb integration expenses	0	23	59
Income tax expense (benefit)	629	795	695
Net income	3,533	4,454	3,962
Comprehensive income	5,783	7,521	1,242
Chubb limited (Parent Guarantor)
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net premiums written	0	0	0
Net premiums earned	0	0	0
Net Investment Income	(1)	1	6
Equity in earnings of subsidiaries	3,457	4,307	3,753
Realized Investment Gains (Losses)	20	(17)	0
Losses and loss expenses	0	0	0
Policy benefits	0	0	0
Policy acquisition costs and administrative expenses	94	92	87
Interest (income) expense	(136)	(243)	(299)
Other (Income) Expense	(39)	(27)	(24)
Amortization of Purchased Intangibles	0	0	0
Chubb integration expenses	0	1	14
Income tax expense (benefit)	24	14	19
Net income	3,533	4,454	3,962
Comprehensive income	5,783	7,521	1,242
Chubb INA Holdings Inc. (Subsidiary Issuer)
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net premiums written	0	0	0
Net premiums earned	0	0	0
Net Investment Income	6	(15)	13
Equity in earnings of subsidiaries	2,052	3,022	2,578
Realized Investment Gains (Losses)	(397)	(31)	117
Losses and loss expenses	0	0	0
Policy benefits	0	0	0
Policy acquisition costs and administrative expenses	(130)	(26)	(58)
Interest (income) expense	596	705	806
Other (Income) Expense	(24)	6	26
Amortization of Purchased Intangibles	0	0	0
Chubb integration expenses		2	1
Income tax expense (benefit)	(181)	(175)	(148)
Net income	1,400	2,464	2,081
Comprehensive income	3,236	4,988	(27)
Other Chubb Limited Subsidiaries and Eliminations
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net premiums written	33,820	32,275	30,579
Net premiums earned	33,117	31,290	30,064
Net Investment Income	3,370	3,440	3,286
Equity in earnings of subsidiaries	0	0	0
Realized Investment Gains (Losses)	(121)	(482)	(769)
Losses and loss expenses	21,710	18,730	18,067
Policy benefits	784	740	590
Policy acquisition costs and administrative expenses	9,562	9,117	8,769
Interest (income) expense	56	90	134
Other (Income) Expense	(931)	(575)	(436)
Amortization of Purchased Intangibles	290	305	339
Chubb integration expenses		20	44
Income tax expense (benefit)	786	956	824
Net income	4,109	4,865	4,250
Comprehensive income	6,512	7,922	1,808
Consolidating Adjustments
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net premiums written	0	0	0
Net premiums earned	0	0	0
Net Investment Income	0	0	0
Equity in earnings of subsidiaries	(5,509)	(7,329)	(6,331)
Realized Investment Gains (Losses)	0	0	0
Losses and loss expenses	0	0	0
Policy benefits	0	0	0
Policy acquisition costs and administrative expenses	0	0	0
Interest (income) expense	0	0	0
Other (Income) Expense	0	0	0
Amortization of Purchased Intangibles	0	0	0
Chubb integration expenses		0	0
Income tax expense (benefit)	0	0	0
Net income	(5,509)	(7,329)	(6,331)
Comprehensive income	$ (9,748)	$ (12,910)	$ (1,781)

Information provided in conne_5

Information provided in connection with outstanding debt of subsidiaries (Condensed Consolidating Statement Of Cash Flows) (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020		Dec. 31, 2019		Dec. 31, 2018
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net cash flows from operating activities		$ 9,785		$ 6,342		$ 5,480
Payments To Acquire Available For Sale Securities Debt Condensed		(26,298)		(25,846)		(24,735)
Purchases of fixed maturities held to maturity		(202)		(229)		(456)
Purchases of equity securities		(6,419)		(531)		(207)
Proceeds From Sale Of Available For Sale Securities Debt Condensed		11,377		13,116		14,030
Sales of equity securities		3,880		611		315
Maturities and redemptions of fixed maturities available for sale		12,450		9,039		7,352
Maturities and redemptions of fixed maturities held to maturity		995		946		1,124
Net change in short-term investments		(81)		(1,117)		516
Net derivative instruments settlements		(113)		(703)		16
Private equity contributions		(1,924)		(1,315)		(1,337)
Private equity distributions		907		1,390		980
Payment, including deposit, for Huatai Group Interest		(1,623)		(580)
Payments to Acquire Businesses, Net of Cash Acquired		0		(29)		0
Payment Of Contributions To Subsidiary		0		0		0
Other		(470)		(657)		(533)
Net Cash Provided by (Used in) Investing Activities		(7,521)		(5,905)		(2,935)
Dividends paid on Common Shares		(1,388)		(1,354)		(1,337)
Common Shares repurchased		(523)		(1,530)		(1,044)
Proceeds from issuance of long-term debt		988		2,828		2,171
Proceeds from (Payments for) in Securities Sold under Agreements to Repurchase		2,354		2,817		2,029
Repayments of Long-term Debt		(1,301)		(510)		(2,001)
Payments for Securities Purchased under Agreements to Resell		(2,354)		(2,817)		(2,019)
Proceeds from share-based compensation plans		145		204		115
Advances from (to) affiliates		0		0		0
Dividends to parent company		0		0		0
Proceeds from Contributions from Parent		0		0		0
Net proceeds from (Repayments to) affiliated notional cash pooling program		0		0	[1]	0
Policyholder contract deposits		470		514		453
Policyholder contract withdrawals		(386)		(303)		(358)
Other		(87)		0		0
Net cash flows (used for) from financing activities		(2,082)		(151)		(1,991)
Effect of foreign currency rate changes on cash and restricted cash		8		20		(65)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect		190		306		489
Cash and restricted cash - beginning of year		1,646	[1],[2]	1,340	[2],[3]	851	[3]
Cash and restricted cash - end of year	[2]	1,836		1,646	[1]	1,340	[3]
Cash Acquired from Acquisition		0		45		0
Parent Company Only
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net cash flows from operating activities		1,933		412		256
Payments To Acquire Available For Sale Securities Debt Condensed		0		0		0
Purchases of fixed maturities held to maturity		0		0		0
Purchases of equity securities		0		0		0
Proceeds From Sale Of Available For Sale Securities Debt Condensed		0		0		0
Sales of equity securities		0		0		0
Maturities and redemptions of fixed maturities available for sale		0		0		0
Maturities and redemptions of fixed maturities held to maturity		0		0		0
Net change in short-term investments		0		0		0
Net derivative instruments settlements		0		0		0
Private equity contributions		0		0		0
Private equity distributions		0		0		0
Payment, including deposit, for Huatai Group Interest		0		0
Payments to Acquire Businesses, Net of Cash Acquired				0
Payment Of Contributions To Subsidiary		(1,200)		(1,000)		(1,475)
Other		2		0		0
Net Cash Provided by (Used in) Investing Activities		(1,202)		(1,000)		(1,475)
Dividends paid on Common Shares		(1,388)		(1,354)		(1,337)
Common Shares repurchased		(523)		(327)		0
Proceeds from issuance of long-term debt		0		0		0
Proceeds from (Payments for) in Securities Sold under Agreements to Repurchase		0		0		0
Repayments of Long-term Debt		0		0		0
Payments for Securities Purchased under Agreements to Resell		0		0		0
Proceeds from share-based compensation plans		0		0		0
Advances from (to) affiliates		1,265		2,301		2,519
Dividends to parent company		0		0		0
Proceeds from Contributions from Parent		0		0		0
Net proceeds from (Repayments to) affiliated notional cash pooling program	[4]	0		(35)		35
Policyholder contract deposits		0		0		0
Policyholder contract withdrawals		0		0		0
Other		0
Net cash flows (used for) from financing activities		(646)		585		1,217
Effect of foreign currency rate changes on cash and restricted cash		(3)		4		0
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect		82		1		(2)
Cash and restricted cash - beginning of year		2	[1],[2]	1	[2],[3]	3	[3]
Cash and restricted cash - end of year	[2]	84		2	[1]	1	[3]
Chubb INA Holdings Inc. (Subsidiary Issuer)
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net cash flows from operating activities		274		2,926		4,654
Payments To Acquire Available For Sale Securities Debt Condensed		(49)		(21)		(38)
Purchases of fixed maturities held to maturity		0		0		0
Purchases of equity securities		0		0		0
Proceeds From Sale Of Available For Sale Securities Debt Condensed		9		1		11
Sales of equity securities		0		0		0
Maturities and redemptions of fixed maturities available for sale		50		41		17
Maturities and redemptions of fixed maturities held to maturity		0		0		0
Net change in short-term investments		772		(808)		3
Net derivative instruments settlements		55		(74)		(7)
Private equity contributions		0		0		0
Private equity distributions		0		0		0
Payment, including deposit, for Huatai Group Interest		0		0
Payments to Acquire Businesses, Net of Cash Acquired				0
Payment Of Contributions To Subsidiary		(72)		(110)		(3,550)
Other		4		(4)		(18)
Net Cash Provided by (Used in) Investing Activities		769		(975)		(3,582)
Dividends paid on Common Shares		0		0		0
Common Shares repurchased		0		0		0
Proceeds from issuance of long-term debt		988		2,828		2,171
Proceeds from (Payments for) in Securities Sold under Agreements to Repurchase		0		0		0
Repayments of Long-term Debt		(1,301)		(500)		(2,000)
Payments for Securities Purchased under Agreements to Resell		0		0		0
Proceeds from share-based compensation plans		0		0		0
Advances from (to) affiliates		(1,438)		(3,223)		(1,744)
Dividends to parent company		0		0		0
Proceeds from Contributions from Parent		0		0		0
Net proceeds from (Repayments to) affiliated notional cash pooling program		272		(617)		502
Policyholder contract deposits		0		0		0
Policyholder contract withdrawals		0		0		0
Other		0
Net cash flows (used for) from financing activities		(1,479)		(1,512)		(1,071)
Effect of foreign currency rate changes on cash and restricted cash		(5)		1		0
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect		(441)		440		1
Cash and restricted cash - beginning of year		442	[1],[2]	2	[2],[3]	1	[3]
Cash and restricted cash - end of year	[2]	1		442	[1]	2	[3]
Other Chubb Limited Subsidiaries and Eliminations
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net cash flows from operating activities		10,788		6,878		5,878
Payments To Acquire Available For Sale Securities Debt Condensed		(26,249)		(25,825)		(24,697)
Purchases of fixed maturities held to maturity		(202)		(229)		(456)
Purchases of equity securities		(6,419)		(531)		(207)
Proceeds From Sale Of Available For Sale Securities Debt Condensed		11,368		13,115		14,019
Sales of equity securities		3,880		611		315
Maturities and redemptions of fixed maturities available for sale		12,400		8,998		7,335
Maturities and redemptions of fixed maturities held to maturity		995		946		1,124
Net change in short-term investments		(853)		(309)		513
Net derivative instruments settlements		(168)		(629)		23
Private equity contributions		(1,924)		(1,315)		(1,337)
Private equity distributions		907		1,390		980
Payment, including deposit, for Huatai Group Interest		(1,623)		(580)
Payments to Acquire Businesses, Net of Cash Acquired				(29)
Payment Of Contributions To Subsidiary		0		0		0
Other		(472)		(653)		(515)
Net Cash Provided by (Used in) Investing Activities		(8,360)		(5,040)		(2,903)
Dividends paid on Common Shares		0		0		0
Common Shares repurchased		0		(1,203)		(1,044)
Proceeds from issuance of long-term debt		0		0		0
Proceeds from (Payments for) in Securities Sold under Agreements to Repurchase		2,354		2,817		2,029
Repayments of Long-term Debt		0		(10)		(1)
Payments for Securities Purchased under Agreements to Resell		(2,354)		(2,817)		(2,019)
Proceeds from share-based compensation plans		145		204		115
Advances from (to) affiliates		173		922		(775)
Dividends to parent company		(3,210)		(3,874)		(5,308)
Proceeds from Contributions from Parent		1,272		1,110		5,025
Net proceeds from (Repayments to) affiliated notional cash pooling program		0		0		0
Policyholder contract deposits		470		514		453
Policyholder contract withdrawals		(386)		(303)		(358)
Other		(87)
Net cash flows (used for) from financing activities		(1,623)		(2,640)		(1,883)
Effect of foreign currency rate changes on cash and restricted cash		16		15		(65)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect		821		(787)		1,027
Cash and restricted cash - beginning of year		1,202	[1],[2]	1,989	[3]	962	[3]
Cash and restricted cash - end of year		2,023	[2]	1,202	[1],[2]	1,989	[3]
Consolidating Adjustments
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net cash flows from operating activities		(3,210)		(3,874)		(5,308)
Payments To Acquire Available For Sale Securities Debt Condensed		0		0		0
Purchases of fixed maturities held to maturity		0		0		0
Purchases of equity securities		0		0		0
Proceeds From Sale Of Available For Sale Securities Debt Condensed		0		0		0
Sales of equity securities		0		0		0
Maturities and redemptions of fixed maturities available for sale		0		0		0
Maturities and redemptions of fixed maturities held to maturity		0		0		0
Net change in short-term investments		0		0		0
Net derivative instruments settlements		0		0		0
Private equity contributions		0		0		0
Private equity distributions		0		0		0
Payment, including deposit, for Huatai Group Interest		0		0
Payments to Acquire Businesses, Net of Cash Acquired				0
Payment Of Contributions To Subsidiary		1,272		1,110		5,025
Other		0		0		0
Net Cash Provided by (Used in) Investing Activities		1,272		1,110		5,025
Dividends paid on Common Shares		0		0		0
Common Shares repurchased		0		0		0
Proceeds from issuance of long-term debt		0		0		0
Proceeds from (Payments for) in Securities Sold under Agreements to Repurchase		0		0		0
Repayments of Long-term Debt		0		0		0
Payments for Securities Purchased under Agreements to Resell		0		0		0
Proceeds from share-based compensation plans		0		0		0
Advances from (to) affiliates		0		0		0
Dividends to parent company		3,210		3,874		5,308
Proceeds from Contributions from Parent		(1,272)		(1,110)		(5,025)
Net proceeds from (Repayments to) affiliated notional cash pooling program		(272)		652	[1]	(537)
Policyholder contract deposits		0		0		0
Policyholder contract withdrawals		0		0		0
Other		0
Net cash flows (used for) from financing activities		1,666		3,416		(254)
Effect of foreign currency rate changes on cash and restricted cash		0		0		0
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect		(272)		652		(537)
Cash and restricted cash - beginning of year		0	[1],[2]	(652)	[2],[3]	(115)	[3]
Cash and restricted cash - end of year	[2]	$ (272)		$ 0	[1]	$ (652)	[3]
[1]	Chubb maintains two notional multi-currency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information. At December 31, 2018, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.
[2]	Chubb maintains two notional multi-currency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information. At December 31, 2020, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.
[3]	Chubb maintains two notional multi-currency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information. At December 31, 2018 and 2017, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.
[4]	Chubb maintains two notional multicurrency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information.

Schedule I (Details)

Schedule I (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Other Investments	$ 7,945	$ 6,062
Cost or Amortized Cost	113,023
Fair Value	119,407
Amount at Which Shown in the Balance Sheet	118,550
All Related Party [Member]
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Other Investments	119
Fixed maturities available for sale
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost	85,168
Fair Value	90,699
Amount at Which Shown in the Balance Sheet	90,699
Fixed maturities available for sale | U.S. Treasury and agency
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost	2,471
Fair Value	2,670
Amount at Which Shown in the Balance Sheet	2,670
Fixed maturities available for sale | Foreign
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost	24,588
Fair Value	26,354
Amount at Which Shown in the Balance Sheet	26,354
Fixed maturities available for sale | Corporate securities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost	34,081
Fair Value	36,331
Amount at Which Shown in the Balance Sheet	36,331
Fixed maturities available for sale | Mortgage-backed securities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost	17,456
Fair Value	18,470
Amount at Which Shown in the Balance Sheet	18,470
Fixed maturities available for sale | States, municipalities, and political subdivisions
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost	6,572
Fair Value	6,874
Amount at Which Shown in the Balance Sheet	6,874
Fixed maturities held to maturity
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost	11,653
Fair Value	12,510
Amount at Which Shown in the Balance Sheet	11,653
Fixed maturities held to maturity | U.S. Treasury and agency
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost	1,392
Fair Value	1,452
Amount at Which Shown in the Balance Sheet	1,392
Fixed maturities held to maturity | Foreign
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost	1,288
Fair Value	1,405
Amount at Which Shown in the Balance Sheet	1,288
Fixed maturities held to maturity | Corporate securities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost	2,150
Fair Value	2,438
Amount at Which Shown in the Balance Sheet	2,150
Fixed maturities held to maturity | Mortgage-backed securities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost	1,999
Fair Value	2,146
Amount at Which Shown in the Balance Sheet	1,999
Fixed maturities held to maturity | States, municipalities, and political subdivisions
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost	4,824
Fair Value	5,069
Amount at Which Shown in the Balance Sheet	4,824
Industrial, miscellaneous, and all others
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost	4,027
Fair Value	4,027
Amount at Which Shown in the Balance Sheet	4,027
Short-term investments
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost	4,349
Fair Value	4,345
Amount at Which Shown in the Balance Sheet	4,345
Other investments
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost or Amortized Cost	7,826
Fair Value	7,826
Amount at Which Shown in the Balance Sheet	$ 7,826

Schedule II (BALANCE SHEETS - P

Schedule II (BALANCE SHEETS - Parent Company Only) (Details) - USD ($) $ in Millions	Dec. 31, 2020		Dec. 31, 2019		Dec. 31, 2018	Dec. 31, 2017
Assets
Investments in subsidiaries and affiliates on equity basis	$ 0		$ 0
Cash	1,747	[1]	1,537	[2]	$ 1,247
Due from subsidiaries and affiliates, net	0		0
Other assets	8,822		7,581
Total assets	190,774		176,943
Liabilities
Accounts payable, accrued expenses, and other liabilities	14,052		12,214
Total liabilities	131,333		121,612
Stockholders' Equity Attributable to Parent [Abstract]
Common Shares	11,064		11,121
Common Shares in treasury (26,872,639 and 27,812,297 shares)	(3,644)		(3,754)
Retained earnings	39,337		36,142
Accumulated other comprehensive income	2,869		619
Total shareholders' equity	59,441		55,331		50,312
Total liabilities and shareholders’ equity	190,774		176,943
Parent Company Only
Assets
Investments in subsidiaries and affiliates on equity basis	56,148		50,853
Total investments	56,148		50,853
Cash	84	[1]	2	[2]	$ 1	$ 3
Due from subsidiaries and affiliates, net	3,522		4,776
Other assets	10		12
Total assets	59,764		55,643
Liabilities
Accounts payable, accrued expenses, and other liabilities	323		312
Total liabilities	323		312
Stockholders' Equity Attributable to Parent [Abstract]
Common Shares	11,064		11,121
Common Shares in treasury (26,872,639 and 27,812,297 shares)	(3,644)		(3,754)
Additional paid-in capital	9,815		11,203
Retained earnings	39,337		36,142
Accumulated other comprehensive income	2,869		619
Total shareholders' equity	59,441		55,331
Total liabilities and shareholders’ equity	$ 59,764		$ 55,643
[1]	Chubb maintains two notional multicurrency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information. At December 31, 2020, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.
[2]	Chubb maintains two notional multicurrency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information.

Schedule II Schedule II (STATEM

Schedule II Schedule II (STATEMENTS OF OPERATIONS - Parent Company Only) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Condensed Financial Statements, Captions [Line Items]
Equity in net income of subsidiaries and affiliates	[1]	$ 1,019	$ 617	$ 514
Total revenues		35,994	34,186	32,717
Administrative and other (income) expense		2,979	3,030	2,886
Business Combination, Integration Related Costs		0	23	59
Income tax expense (benefit)		629	795	695
Total expenses		31,832	28,937	28,060
Net income		3,533	4,454	3,962
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest		5,783	7,521	1,242
Chubb limited (Parent Guarantor)
Condensed Financial Statements, Captions [Line Items]
Investment income, including intercompany interest income		155	227	305
Equity in net income of subsidiaries and affiliates		3,457	4,307	3,753
Total revenues		3,612	4,534	4,058
Administrative and other (income) expense		55	65	63
Business Combination, Integration Related Costs		0	1	14
Income tax expense (benefit)		24	14	19
Total expenses		79	80	96
Net income		3,533	4,454	3,962
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest		$ 5,783	$ 7,521	$ 1,242
[1]	Equity in net income of partially-owned entities includes $167 million, $74 million, and $43 million attributable to our investments in Huatai (Huatai Group, Huatai P&C, and Huatai Life) for the years ended December 31, 2020, 2019, and 2018, respectively.

Schedule II (STATEMENTS OF CASH

Schedule II (STATEMENTS OF CASH FLOWS - Parent Company Only) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020		Dec. 31, 2019		Dec. 31, 2018
Condensed Financial Statements, Captions [Line Items]
Net cash flows from operating activities		$ 9,785		$ 6,342		$ 5,480
Payment Of Contributions To Subsidiary		0		0		0
Dividends paid on Common Shares		(1,388)		(1,354)		(1,337)
Common Shares repurchased		(523)		(1,530)		(1,044)
Net proceeds from (payments to) affiliated notional cash pooling programs		0		0	[1]	0
Net cash flows (used for) from financing activities		(2,082)		(151)		(1,991)
Effect of foreign currency rate changes on cash and restricted cash		8		20		(65)
Cash and restricted cash – beginning of year		1,537	[2]	1,247
Cash and restricted cash – end of year		1,747	[3]	1,537	[2]	1,247
Payments for (Proceeds from) Other Investing Activities		470		657		533
Chubb limited (Parent Guarantor)
Condensed Financial Statements, Captions [Line Items]
Net cash flows from operating activities		1,933		412		256
Payment Of Contributions To Subsidiary		(1,200)		(1,000)		(1,475)
Net cash flows used for investing activities		(1,202)		(1,000)		(1,475)
Dividends paid on Common Shares		(1,388)		(1,354)		(1,337)
Common Shares repurchased		(523)		(327)		0
Payments To From Affiliates		1,265		2,301		2,519
Net proceeds from (payments to) affiliated notional cash pooling programs	[4]	0		(35)		35
Net cash flows (used for) from financing activities		(646)		585		1,217
Effect of foreign currency rate changes on cash and restricted cash		(3)		4		0
Net increase (decrease) in cash and restricted cash		82		1		(2)
Cash and restricted cash – beginning of year		2	[2]	1		3
Cash and restricted cash – end of year		84	[3]	2	[2]	1
Cash dividend paid by Affiliates	[5]	2,000		200		75
Payments for (Proceeds from) Other Investing Activities		$ (2)		$ 0		$ 0
[1]	Chubb maintains two notional multi-currency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information. At December 31, 2018, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.
[2]	Chubb maintains two notional multicurrency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information.
[3]	Chubb maintains two notional multicurrency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information. At December 31, 2020, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.
[4]	Chubb maintains two notional multicurrency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information.
[5]	Includes cash dividends received from subsidiaries of $2.0 billion, $200 million, and $75 million in 2020, 2019, and 2018, respectively.

Schedule IV (SUPPLEMENTAL INFOR

Schedule IV (SUPPLEMENTAL INFORMATION CONCERNING REINSURANCE) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Direct Amount	$ 37,037	$ 35,876	$ 34,108
Ceded To Other Companies	7,243	7,693	7,219
Assumed From Other Companies	3,323	3,107	3,175
Net Amount	$ 33,117	$ 31,290	$ 30,064
Percentage of Amount Assumed to Net	10.00%	10.00%	11.00%
Property and Casualty [Member]
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Direct Amount	$ 31,546	$ 30,339	$ 28,793
Ceded To Other Companies	6,782	7,236	6,792
Assumed From Other Companies	3,044	2,797	2,812
Net Amount	$ 27,808	$ 25,900	$ 24,813
Percentage of Amount Assumed to Net	11.00%	11.00%	11.00%
Accident and Health [Member]
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Direct Amount	$ 4,249	$ 4,546	$ 4,409
Ceded To Other Companies	368	376	342
Assumed From Other Companies	111	119	162
Net Amount	$ 3,992	$ 4,289	$ 4,229
Percentage of Amount Assumed to Net	3.00%	3.00%	4.00%
Life [Member]
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Direct Amount	$ 1,242	$ 991	$ 906
Ceded To Other Companies	93	81	85
Assumed From Other Companies	168	191	201
Net Amount	$ 1,317	$ 1,101	$ 1,022
Percentage of Amount Assumed to Net	13.00%	17.00%	20.00%

Schedule VI (SUPPLEMENTARY INFO

Schedule VI (SUPPLEMENTARY INFORMATION CONCERNING PROPERTY AND CASUALTY OPERATIONS) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
SEC Schedule, 12-18, Supplemental Information, Property-Casualty Insurance Underwriters [Abstract]
Deferred Policy Acquisition Costs		$ 4,244	$ 4,161	$ 3,926
Net Reserves for Unpaid Losses		53,164	48,509	48,271
Unearned Premiums		17,652	16,771	15,532
Net Premiums Earned		31,800	30,189	29,042
Net Investment Income		3,074	3,141	3,047
Current Year Claim and Claim Adjustment Expense		22,124	19,575	19,048
Prior Year Claim and Claim Adjustment Expense		(414)	(845)	(981)
Net Losses and Loss Expenses Incurred Related to Prior Year	[1]	(414)	(845)	(981)
Amortization of Deferred Policy Acquisition Costs		6,076	5,831	5,630
Net Paid Losses and Loss Expenses		17,434	18,473	18,340
Net Premiums Written		$ 32,471	$ 31,126	$ 29,505
[1]	Relates to prior period loss reserve development only and excludes prior period development related to reinstatement premiums, expense adjustments and earned premiums totaling $19 million, $53 million, and $85 million for 2020, 2019, and 2018, respectively.