The Travelers Companies, Inc. (TRV) 10-Q 20 Apr 21 2021 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2021	Apr. 15, 2021
Document and Entity Information
Document type	10-Q
Document quarterly report	true
Document period end date	Mar. 31, 2021
Document transition report	false
Entity file number	001-10898
Registrant name	Travelers Companies, Inc.
Entity incorporation, state	MN
Entity tax identification number	41-0518860
Entity address, address line one	485 Lexington Avenue
Entity address, city	New York
Entity address, state	NY
Entity address, postal zip code	10017
City area code	917
Local phone number	778-6000
Title of 12(b) security	Common stock, without par value
Trading symbol	TRV
Security exchange name	NYSE
Entity current reporting status	Yes
Entity interactive data current	Yes
Filer category	Large Accelerated Filer
Entity small business	false
Entity emerging growth company	false
Entity shell company	false
Common stock shares outstanding		251,465,267
Central index key	0000086312
Amendment flag	false
Current fiscal year end date	--12-31
Document fiscal year focus	2021
Document fiscal period focus	Q1

Consolidated Statement of Incom

Consolidated Statement of Income (Unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Revenues
Premiums	$ 7,386	$ 7,229
Net investment income	701	611
Fee income	101	108
Net realized investment gains (losses)	44	(98)
Other revenues	81	58
Total revenues	8,313	7,908
Claims and expenses
Claims and claim adjustment expenses	4,970	4,789
Amortization of deferred acquisition costs	1,207	1,178
General and administrative expenses	1,163	1,137
Interest expense	82	84
Total claims and expenses	7,422	7,188
Income before income taxes	891	720
Income tax expense	158	120
Net income	$ 733	$ 600
Net income per share
Basic (in dollars per share)	$ 2.89	$ 2.34
Diluted (in dollars per share)	$ 2.87	$ 2.33
Weighted average number of common shares outstanding
Basic (in shares)	252.1	254.4
Diluted (in shares)	254.1	255.9
Cash dividends declared per common share (in dollars per share)	$ 0.85	$ 0.82

Consolidated Statement of Compr

Consolidated Statement of Comprehensive Income (Loss) (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Statement of Comprehensive Income [Abstract]
Net income	$ 733	$ 600
Other comprehensive loss:
Changes in net unrealized gains on investment securities having no credit losses recognized in the consolidated statement of income	(1,596)	(575)
Changes in net unrealized gains on investment securities having credit losses recognized in the consolidated statement of income	0	(6)
Net changes in benefit plan assets and obligations	25	23
Net changes in unrealized foreign currency translation	26	(268)
Other comprehensive loss before income taxes	(1,545)	(826)
Income tax benefit	(334)	(137)
Other comprehensive loss, net of taxes	(1,211)	(689)
Comprehensive loss	$ (478)	$ (89)

Consolidated Balance Sheet (Una

Consolidated Balance Sheet (Unaudited at March 31, 2021) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Assets
Fixed maturities, available for sale, at fair value (amortized cost $70,286 and $68,830; allowance for expected credit losses of $2 and $2)	$ 73,861	$ 74,003
Equity securities, at fair value (cost $387 and $387)	477	453
Real estate investments	1,018	1,026
Short-term securities	4,987	5,511
Other investments	3,544	3,430
Total investments	83,887	84,423
Cash	663	721
Investment income accrued	569	603
Premiums receivable (net of allowance for expected credit losses of $110 and $105)	8,167	7,829
Reinsurance recoverables (net of allowance for estimated uncollectible reinsurance of $142 and $146)	8,345	8,350
Ceded unearned premiums	1,165	772
Deferred acquisition costs	2,411	2,358
Contractholder receivables (net of allowance for expected credit losses of $19 and $19)	4,271	4,242
Goodwill	4,017	3,976
Other intangible assets	318	317
Other assets	3,219	3,173
Total assets	117,032	116,764
Liabilities
Claims and claim adjustment expense reserves	55,340	54,521
Unearned premium reserves	15,742	15,222
Contractholder payables	4,290	4,261
Payables for reinsurance premiums	702	356
Deferred taxes	293	558
Debt	6,550	6,550
Other liabilities	5,846	6,095
Total liabilities	88,763	87,563
Shareholders’ equity
Common stock (1,750.0 shares authorized; 251.5 and 252.4 shares issued and outstanding)	23,905	23,743
Retained earnings	39,285	38,771
Accumulated other comprehensive income	1,291	2,502
Treasury stock, at cost (530.0 and 527.3 shares)	(36,212)	(35,815)
Total shareholders’ equity	28,269	29,201
Total liabilities and shareholders’ equity	$ 117,032	$ 116,764

Consolidated Balance Sheet Pare

Consolidated Balance Sheet Parentheticals (Unaudited at March 31, 2021) - USD ($) shares in Millions, $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Fixed maturities, available for sale, amortized cost	$ 70,286	$ 68,830
Fixed maturities, available for sale, allowance for expected credit losses	2	2
Equity securities, cost	387	387
Premiums receivable, allowance for expected credit losses	110	105
Reinsurance recoverables, allowance for estimated uncollectible reinsurance	142	146
Contractholder receivables, allowance for expected credit losses	$ 19	$ 19
Common stock, shares authorized (in shares)	1,750	1,750
Common stock, shares issued (in shares)	251.5	252.4
Common stock, shares outstanding (in shares)	251.5	252.4
Treasury stock, at cost (in shares)	530	527.3

Consolidated Statement of Chang

Consolidated Statement of Changes in Shareholders' Equity (Unaudited) - USD ($) shares in Millions, $ in Millions	Total	Common stock [Member]	Retained earnings [Member]	Retained earnings [Member]Cumulative Effect, Period of Adoption, Adjustment [Member]	Accumulated other comprehensive income (loss), net of tax [Member]	Treasury stock, at cost [Member]	Common shares outstanding [Member]
Shareholders' Equity [Roll Forward]
Shareholders' equity		$ 23,469	$ 36,977	$ (43)	$ 640	$ (35,143)
Balance, beginning of period at Dec. 31, 2019		23,469	36,977	(43)	640	(35,143)
Shareholders' Equity [Roll Forward]
Employee share-based compensation		27
Compensation amortization under share-based plans and other changes		46
Shareholders' equity	$ 25,204	23,542	37,325	$ (43)	(49)	(35,614)
Net income	600		600
Dividends			(210)
Other			1
Other comprehensive loss	(689)				(689)
Treasury stock acquired — share repurchase authorization						(425)
Net shares acquired related to employee share-based compensation plans						(46)
Balance, end of period at Mar. 31, 2020	25,204	23,542	37,325		(49)	(35,614)
Balance, beginning of year (in shares) at Dec. 31, 2019							255.5
Common shares outstanding
Treasury stock acquired - share repurchase authorization (in shares)							(3.5)
Net shares issued under employee share-based compensation plans (in shares)							0.8
Balance, end of period (in shares) at Mar. 31, 2020							252.8
Shareholders' Equity [Roll Forward]
Shareholders' equity	25,204	23,542	37,325		(49)	(35,614)
Shareholders' equity	29,201	23,743	38,771		2,502	(35,815)
Balance, beginning of period at Dec. 31, 2020	29,201	23,743	38,771		2,502	(35,815)
Shareholders' Equity [Roll Forward]
Employee share-based compensation		108
Compensation amortization under share-based plans and other changes		54
Shareholders' equity	29,201	23,905	39,285		2,502	(36,212)
Net income	733		733
Dividends			(216)
Other			(3)
Other comprehensive loss	(1,211)				(1,211)
Treasury stock acquired — share repurchase authorization	(356)					(356)
Net shares acquired related to employee share-based compensation plans	(41)					(41)
Balance, end of period at Mar. 31, 2021	$ 28,269	23,905	39,285		1,291	(36,212)
Balance, beginning of year (in shares) at Dec. 31, 2020	252.4						252.4
Common shares outstanding
Treasury stock acquired - share repurchase authorization (in shares)	(2.4)						(2.4)
Net shares issued under employee share-based compensation plans (in shares)							1.5
Balance, end of period (in shares) at Mar. 31, 2021	251.5						251.5
Shareholders' Equity [Roll Forward]
Shareholders' equity	$ 28,269	$ 23,905	$ 39,285		$ 1,291	$ (36,212)

Consolidated Statement of Cash

Consolidated Statement of Cash Flows (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash flows from operating activities
Net income	$ 733	$ 600
Adjustments to reconcile net income to net cash provided by operating activities:
Net realized investment (gains) losses	(44)	98
Depreciation and amortization	235	203
Deferred federal income tax expense	56	6
Amortization of deferred acquisition costs	1,207	1,178
Equity in income from other investments	(200)	(67)
Premiums receivable	(333)	(326)
Reinsurance recoverables	12	(15)
Deferred acquisition costs	(1,258)	(1,215)
Claims and claim adjustment expense reserves	777	388
Unearned premium reserves	509	414
Other operating activities	(504)	(636)
Net cash provided by operating activities	1,190	628
Cash flows from investing activities
Proceeds from maturities of fixed maturities	2,064	1,461
Proceeds from sales of investments:
Fixed maturities	1,238	388
Equity securities	25	33
Other investments	79	64
Purchases of investments:
Fixed maturities	(4,754)	(2,630)
Equity securities	(19)	(35)
Real estate investments	(5)	(16)
Other investments	(97)	(103)
Net sales of short-term securities	524	906
Securities transactions in course of settlement	269	85
Acquisition, net of cash acquired	(38)	0
Other investing activities	(60)	(69)
Net cash provided by (used in) investing activities	(774)	84
Cash flows from financing activities
Treasury stock acquired — share repurchase authorization	(356)	(425)
Treasury stock acquired — net employee share-based compensation	(41)	(46)
Dividends paid to shareholders	(214)	(210)
Issuance of common stock — employee share options	134	31
Net cash used in financing activities	(477)	(650)
Effect of exchange rate changes on cash	3	(12)
Net increase (decrease) in cash	(58)	50
Cash at beginning of year	721	494
Cash at end of period	663	544
Supplemental disclosure of cash flow information
Income taxes paid	58	15
Interest paid	$ 59	$ 60

Basis of Presentation and Accou

Basis of Presentation and Accounting Policies	3 Months Ended
	Mar. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation and Accounting Policies	BASIS OF PRESENTATION AND ACCOUNTING POLICIES Basis of Presentation The interim consolidated financial statements include the accounts of The Travelers Companies, Inc. (together with its subsidiaries, the Company). These financial statements are prepared in conformity with U.S. generally accepted accounting principles (GAAP) and are unaudited. In the opinion of the Company’s management, all adjustments necessary for a fair presentation have been reflected. Certain financial information that is normally included in annual financial statements prepared in accordance with GAAP, but that is not required for interim reporting purposes, has been omitted. All material intercompany transactions and balances have been eliminated. The accompanying interim consolidated financial statements and related notes should be read in conjunction with the Company’s consolidated financial statements and related notes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2020 (the Company’s 2020 Annual Report). The preparation of the interim consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the interim consolidated financial statements and the reported amounts of revenues and claims and expenses during the reporting period. Actual results could differ from those estimates. Adoption of Accounting Standards Income Taxes - Simplifying the Accounting for Income Taxes In December 2019, the Financial Accounting Standards Board (FASB) issued updated guidance for the accounting for income taxes. The updated guidance is intended to simplify the accounting for income taxes by removing several exceptions contained in existing guidance and amending other existing guidance to simplify several other income tax accounting matters. The Company adopted the updated guidance for the quarter ended March 31, 2021. The adoption of this guidance did not have a material effect on the Company’s results of operations, financial position or liquidity. For additional information regarding accounting standards that the Company adopted during the periods presented, see note 1 of notes to the consolidated financial statements in the Company’s 2020 Annual Report.

Segment Information

Segment Information	3 Months Ended
	Mar. 31, 2021
Segment Reporting [Abstract]
Segment Information	SEGMENT INFORMATION Nature of Operations The Company’s results are reported in the following three business segments — Business Insurance, Bond & Specialty Insurance and Personal Insurance. These segments reflect the manner in which the Company’s businesses are currently managed and represent an aggregation of products and services based on the type of customer, how the business is marketed and the manner in which risks are underwritten. For more information regarding the Company’s nature of operations, see the “Nature of Operations ” section of note 1 of notes to the consolidated financial statements in the Company’s 2020 Annual Report. The following tables summarize the components of the Company’s revenues, income and total assets by reportable business segments: (For the three months ended March 31, in millions) Business Bond & Specialty Personal Total 2021 Premiums $ 3,799 $ 743 $ 2,844 $ 7,386 Net investment income 523 59 119 701 Fee income 95 — 6 101 Other revenues 53 5 23 81 Total segment revenues (1) $ 4,470 $ 807 $ 2,992 $ 8,269 Segment income (1) $ 317 $ 137 $ 314 $ 768 2020 Premiums $ 3,864 $ 667 $ 2,698 $ 7,229 Net investment income 453 55 103 611 Fee income 102 — 6 108 Other revenues 31 5 22 58 Total segment revenues (1) $ 4,450 $ 727 $ 2,829 $ 8,006 Segment income (1) $ 289 $ 122 $ 336 $ 747 _________________________________________________________ (1) Segment revenues for reportable business segments exclude net realized investment gains (losses) and revenues included in "interest expense and other." Segment income for reportable business segments equals net income excluding the after-tax impact of net realized investment gains (losses) and income (loss) from "interest expense and other." Business Segment Reconciliations Three Months Ended (in millions) 2021 2020 Revenue reconciliation Earned premiums Business Insurance: Domestic: Workers’ compensation $ 811 $ 899 Commercial automobile 695 684 Commercial property 531 508 General liability 607 601 Commercial multi-peril 870 886 Other 14 12 Total Domestic 3,528 3,590 International 271 274 Total Business Insurance 3,799 3,864 Bond & Specialty Insurance: Domestic: Fidelity and surety 266 257 General liability 331 287 Other 56 58 Total Domestic 653 602 International 90 65 Total Bond & Specialty Insurance 743 667 Personal Insurance: Domestic: Automobile 1,370 1,351 Homeowners and Other 1,308 1,176 Total Domestic 2,678 2,527 International 166 171 Total Personal Insurance 2,844 2,698 Total earned premiums 7,386 7,229 Net investment income 701 611 Fee income 101 108 Other revenues 81 58 Total segment revenues 8,269 8,006 Other revenues — — Net realized investment gains (losses) 44 (98) Total revenues $ 8,313 $ 7,908 Income reconciliation, net of tax Total segment income $ 768 $ 747 Interest Expense and Other (1) (69) (71) Core income 699 676 Net realized investment gains (losses) 34 (76) Net income $ 733 $ 600 _________________________________________________________ (1) The primary component of Interest Expense and Other was after-tax interest expense of $65 million and $66 million for the three months ended March 31, 2021 and 2020, respectively. (in millions) March 31, December 31, Asset reconciliation Business Insurance $ 88,657 $ 88,422 Bond & Specialty Insurance 9,488 9,420 Personal Insurance 18,279 18,328 Total assets by reportable segment 116,424 116,170 Other assets (1) 608 594 Total consolidated assets $ 117,032 $ 116,764 _________________________________________________________

Investments

Investments	3 Months Ended
	Mar. 31, 2021
Investments [Abstract]
Investments	INVESTMENTS Fixed Maturities The amortized cost and fair value of investments in fixed maturities classified as available for sale were as follows: Amortized Cost Allowance for Expected Credit Losses Gross Unrealized Fair Value (at March 31, 2021, in millions) Gains Losses U.S. Treasury securities and obligations of U.S. government and government agencies and authorities $ 2,530 $ — $ 32 $ 18 $ 2,544 Obligations of states, municipalities and political subdivisions: Local general obligation 17,719 — 1,079 84 18,714 Revenue 11,748 — 699 44 12,403 State general obligation 1,337 — 81 4 1,414 Pre-refunded 3,365 — 204 — 3,569 Total obligations of states, municipalities and political subdivisions 34,169 — 2,063 132 36,100 Debt securities issued by foreign governments 962 — 18 4 976 Mortgage-backed securities, collateralized mortgage obligations and pass-through securities 1,939 — 107 1 2,045 All other corporate bonds 30,663 2 1,651 141 32,171 Redeemable preferred stock 23 — 2 — 25 Total $ 70,286 $ 2 $ 3,873 $ 296 $ 73,861 Amortized Cost Allowance for Expected Credit Losses Gross Unrealized Fair Value (at December 31, 2020, in millions) Gains Losses U.S. Treasury securities and obligations of U.S. government and government agencies and authorities $ 2,111 $ — $ 38 $ — $ 2,149 Obligations of states, municipalities and political subdivisions: Local general obligation 17,289 — 1,370 2 18,657 Revenue 11,806 — 909 — 12,715 State general obligation 1,343 — 101 — 1,444 Pre-refunded 3,325 — 219 — 3,544 Total obligations of states, municipalities and political subdivisions 33,763 — 2,599 2 36,360 Debt securities issued by foreign governments 1,028 — 26 — 1,054 Mortgage-backed securities, collateralized mortgage obligations and pass-through securities 2,222 — 139 — 2,361 All other corporate bonds 29,683 2 2,382 9 32,054 Redeemable preferred stock 23 — 2 — 25 Total $ 68,830 $ 2 $ 5,186 $ 11 $ 74,003 Pre-refunded bonds of $3.57 billion and $3.54 billion at March 31, 2021 and December 31, 2020, respectively, were bonds for which states or municipalities have established irrevocable trusts, almost exclusively comprised of U.S. Treasury securities and obligations of U.S. government and government agencies and authorities. These trusts were created to fund the payment of principal and interest due under the bonds. Proceeds from sales of fixed maturities classified as available for sale were $1.24 billion and $388 million during the three months ended March 31, 2021 and 2020, respectively. Gross gains of $15 million and gross losses of $1 million were realized on those sales during each of the three months ended March 31, 2021 and 2020. Equity Securities The cost and fair value of investments in equity securities were as follows: Fair (at March 31, 2021, in millions) Cost Gross Gains Gross Losses Value Public common stock $ 352 $ 87 $ 7 $ 432 Non-redeemable preferred stock 35 10 — 45 Total $ 387 $ 97 $ 7 $ 477 Fair (at December 31, 2020, in millions) Cost Gross Gains Gross Losses Value Public common stock $ 352 $ 70 $ 12 $ 410 Non-redeemable preferred stock 35 8 — 43 Total $ 387 $ 78 $ 12 $ 453 For the three months ended March 31, 2021 and 2020, the Company recognized $23 million and $(79) million of net gains (losses) on equity securities still held as of March 31, 2021 and 2020, respectively. Net realized losses on equity securities still held for the first quarter of 2020 were driven by the impact of changes in fair value attributable to the disruption in global financial markets associated with the global pandemic beginning in March 2020. Unrealized Investment Losses The following tables summarize, for all fixed maturities classified as available for sale in an unrealized loss position at March 31, 2021 and December 31, 2020, the aggregate fair value and gross unrealized loss by length of time those securities have been continuously in an unrealized loss position. The fair value amounts reported in the tables are estimates that are prepared using the process described in note 4 herein and in note 4 of notes to the consolidated financial statements in the Company’s 2020 Annual Report. The Company also relies upon estimates of several factors in its review and evaluation of individual investments, using the process described in note 1 of notes to the consolidated financial statements in the Company’s 2020 Annual Report to determine whether a credit loss impairment exists. Less than 12 months 12 months or longer Total (at March 31, 2021, in millions) Fair Gross Fair Gross Fair Gross Fixed maturities U.S. Treasury securities and obligations of U.S. government and government agencies and authorities $ 854 $ 18 $ — $ — $ 854 $ 18 Obligations of states, municipalities and political subdivisions 4,654 132 — — 4,654 132 Debt securities issued by foreign governments 158 4 — — 158 4 Mortgage-backed securities, collateralized mortgage obligations and pass-through securities 50 1 1 — 51 1 All other corporate bonds 3,494 137 125 4 3,619 141 Total $ 9,210 $ 292 $ 126 $ 4 $ 9,336 $ 296 Less than 12 months 12 months or longer Total (at December 31, 2020, in millions) Fair Gross Fair Gross Fair Gross Fixed maturities U.S. Treasury securities and obligations of U.S. government and government agencies and authorities $ 92 $ — $ — $ — $ 92 $ — Obligations of states, municipalities and political subdivisions 245 2 — — 245 2 Debt securities issued by foreign governments 7 — — — 7 — Mortgage-backed securities, collateralized mortgage obligations and pass-through securities 20 — 1 — 21 — All other corporate bonds 681 6 97 3 778 9 Total $ 1,045 $ 8 $ 98 $ 3 $ 1,143 $ 11 At March 31, 2021, the amount of gross unrealized losses for all fixed maturity investments reported at fair value for which fair value was less than 80% of amortized cost was not significant. Credit Impairment Charges The following tables present changes in the allowance for expected credit losses on fixed maturities classified as available for sale: Fixed Maturities (for the three months ended March 31, 2021, in millions) Mortgage-Backed Securities, Collateralized Mortgage Obligations and Pass-Through Securities All Other Corporate Bonds Total Balance, December 31, 2020 $ — $ 2 $ 2 Additions for expected credit losses on securities where no credit losses were previously recognized — — — Additions (reductions) for expected credit losses on securities where credit losses were previously recognized — — — Reductions due to sales/defaults of credit-impaired securities — — — Reductions for impairments of securities which the Company intends to sell or more likely than not will be required to sell (1) — — — Balance, March 31, 2021 $ — $ 2 $ 2 (1) Credit impairment charges recognized in net realized investment gains (losses) for the three months ended March 31, 2021 included no credit losses on fixed maturity securities which the Company had the intent to sell. Fixed Maturities (for the twelve months ended December 31, 2020, in millions) Mortgage-Backed Securities, Collateralized Mortgage Obligations and Pass-Through Securities All Other Corporate Bonds Total Balance, January 1, 2020 $ — $ — $ — Additions for expected credit losses on securities where no credit losses were previously recognized — 10 10 Additions (reductions) for expected credit losses on securities where credit losses were previously recognized — (6) (6) Reductions due to sales/defaults of credit-impaired securities — (2) (2) Reductions for impairments of securities which the Company intends to sell or more likely than not will be required to sell (1) — — — Balance, December 31, 2020 $ — $ 2 $ 2 (1) Credit impairment charges recognized in net realized investment gains for the twelve months ended December 31, 2020 included $13 million of credit losses on fixed maturity securities which the Company had the intent to sell. An allowance for expected credit losses was not previously recorded for these securities. Total net credit impairment charges (recoveries) included in net realized investment gains (losses) in the consolidated statement of income were $0 million and $16 million for the three months ended March 31, 2021 and 2020, respectively. Credit losses related to the fixed maturity portfolio for the three months ended March 31, 2021 and 2020 represented less than 1% of the fixed maturity portfolio on a pre-tax basis and less than 1% of shareholders’ equity on an after-tax basis.

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2021
Fair Value Disclosures [Abstract]
Fair Value Measurements	FAIR VALUE MEASUREMENTS The Company’s estimates of fair value for financial assets and financial liabilities are based on the framework established in the fair value accounting guidance. The framework is based on the inputs used in valuation, gives the highest priority to quoted prices in active markets and requires that observable inputs be used in the valuations when available. The disclosure of fair value estimates in the fair value accounting guidance hierarchy is based on whether the significant inputs into the valuation are observable. In determining the level of the hierarchy in which the estimate is disclosed, the highest priority is given to unadjusted quoted prices in active markets and the lowest priority to unobservable inputs that reflect the Company’s significant market assumptions. The level in the fair value hierarchy within which the fair value measurement is reported is based on the lowest level input that is significant to the measurement in its entirety. The three levels of the hierarchy are as follows: • Level 1 - Unadjusted quoted market prices for identical assets or liabilities in active markets that the Company has the ability to access. • Level 2 - Quoted prices for similar assets or liabilities in active markets; quoted prices for identical or similar assets or liabilities in inactive markets; or valuations based on models where the significant inputs are observable (e.g., interest rates, yield curves, prepayment speeds, default rates, loss severities, etc.) or can be corroborated by observable market data. • Level 3 - Valuations based on models where significant inputs are not observable. The unobservable inputs reflect the Company’s own assumptions about the inputs that market participants would use. Valuation of Investments Reported at Fair Value in Financial Statements The Company utilized a pricing service to estimate fair value measurements for approximately 99% of its fixed maturities at both March 31, 2021 and December 31, 2020. While the vast majority of the Company’s fixed maturities are included in Level 2, the Company holds a number of municipal bonds and corporate bonds which are not valued by the pricing service and estimates the fair value of these bonds using either another internal pricing matrix, a present value income approach, or a broker quote (collectively, the other methodologies). The other methodologies include some unobservable inputs that are significant to the valuation. Due to the limited amount of observable market information available in the estimation of fair value, the Company includes the fair value estimates for bonds that are valued using the other methodologies in Level 3. For more information regarding the valuation of the Company’s fixed maturities, equity securities and other investments, see note 4 of notes to the consolidated financial statements in the Company’s 2020 Annual Report. Other Liabilities The Company has a put/call option that was entered into in connection with a business acquisition that allows the Company to acquire the remaining shares of the acquired company at a future date. The fair value of the put/call option at both March 31, 2021 and December 31, 2020 was $5 million, which was determined using an internal model and is based on the acquired company's financial performance, adjusted for a risk margin and discounted to present value. The Company includes the fair value estimate of the put/call option in Level 3. Fair Value Hierarchy The following tables present the level within the fair value hierarchy at which the Company’s financial assets and financial liabilities are measured on a recurring basis. (at March 31, 2021, in millions) Total Level 1 Level 2 Level 3 Invested assets: Fixed maturities U.S. Treasury securities and obligations of U.S. government and government agencies and authorities $ 2,544 $ 2,544 $ — $ — Obligations of states, municipalities and political subdivisions 36,100 — 36,089 11 Debt securities issued by foreign governments 976 — 976 — Mortgage-backed securities, collateralized mortgage obligations and pass-through securities 2,045 — 2,045 — All other corporate bonds 32,171 4 32,009 158 Redeemable preferred stock 25 3 22 — Total fixed maturities 73,861 2,551 71,141 169 Equity securities Public common stock 432 432 — — Non-redeemable preferred stock 45 38 7 — Total equity securities 477 470 7 — Other investments 52 17 — 35 Total $ 74,390 $ 3,038 $ 71,148 $ 204 Other liabilities $ 5 $ — $ — $ 5 (at December 31, 2020, in millions) Total Level 1 Level 2 Level 3 Invested assets: Fixed maturities U.S. Treasury securities and obligations of U.S. government and government agencies and authorities $ 2,149 $ 2,149 $ — $ — Obligations of states, municipalities and political subdivisions 36,360 — 36,349 11 Debt securities issued by foreign governments 1,054 — 1,054 — Mortgage-backed securities, collateralized mortgage obligations and pass-through securities 2,361 — 2,361 — All other corporate bonds 32,054 — 31,899 155 Redeemable preferred stock 25 3 22 — Total fixed maturities 74,003 2,152 71,685 166 Equity securities Public common stock 410 410 — — Non-redeemable preferred stock 43 18 25 — Total equity securities 453 428 25 — Other investments 52 17 — 35 Total $ 74,508 $ 2,597 $ 71,710 $ 201 Other liabilities $ 5 $ — $ — $ 5 There was no significant activity in Level 3 of the hierarchy during the three months ended March 31, 2021 or the year ended December 31, 2020. Financial Instruments Disclosed, But Not Carried, At Fair Value The following tables present the carrying value and fair value of the Company’s financial assets and financial liabilities disclosed, but not carried, at fair value, and the level within the fair value hierarchy at which such assets and liabilities are categorized. (at March 31, 2021, in millions) Carrying Fair Level 1 Level 2 Level 3 Financial assets Short-term securities $ 4,987 $ 4,987 $ 630 $ 4,306 $ 51 Financial liabilities Debt $ 6,450 $ 7,994 $ — $ 7,994 $ — Commercial paper $ 100 $ 100 $ — $ 100 $ — (at December 31, 2020, in millions) Carrying Fair Level 1 Level 2 Level 3 Financial assets Short-term securities $ 5,511 $ 5,511 $ 630 $ 4,829 $ 52 Financial liabilities Debt $ 6,450 $ 8,976 $ — $ 8,976 $ — Commercial paper $ 100 $ 100 $ — $ 100 $ — The Company had no material assets or liabilities that were measured at fair value on a non-recurring basis during the three months ended March 31, 2021 or the year ended December 31, 2020.

Allowance for Expected Credit L

Allowance for Expected Credit Losses	3 Months Ended
	Mar. 31, 2021
Credit Loss [Abstract]
Allowance for Expected Credit Losses	ALLOWANCE FOR EXPECTED CREDIT LOSSES Premiums Receivable The following table presents the balances of premiums receivable, net of the allowance for expected credit losses, at March 31, 2021 and December 31, 2020, and the changes in the allowance for expected credit losses for the three months ended March 31, 2021 and the twelve months ended December 31, 2020. At and For the Three Months Ended March 31, 2021 At and For the Twelve Months Ended December 31, 2020 (in millions) Premiums Receivable, Net of Allowance for Expected Credit Losses Allowance for Expected Credit Losses Premiums Receivable, Net of Allowance for Expected Credit Losses Allowance for Expected Credit Losses Balance, beginning of period $ 7,829 $ 105 $ 7,909 $ 49 Current period change for expected credit losses 16 103 Write-offs of uncollectible premiums receivable 11 47 Balance, end of period $ 8,167 $ 110 $ 7,829 $ 105 Reinsurance Recoverables The following table presents the balances of reinsurance recoverables, net of the allowance for estimated uncollectible reinsurance, at March 31, 2021 and December 31, 2020, and the changes in the allowance for estimated uncollectible reinsurance for the three months ended March 31, 2021 and the twelve months ended December 31, 2020. At and For the Three Months Ended March 31, 2021 At and For the Twelve Months Ended December 31, 2020 (in millions) Reinsurance Recoverables, Net of Allowance for Estimated Uncollectible Reinsurance Allowance for Estimated Uncollectible Reinsurance Reinsurance Recoverables, Net of Allowance for Estimated Uncollectible Reinsurance Allowance for Estimated Uncollectible Reinsurance Balance, beginning of period $ 8,350 $ 146 $ 8,235 $ 92 Cumulative effect of adoption of updated accounting guidance for credit losses at January 1, 2020 — 53 Current period change for estimated uncollectible reinsurance (4) 1 Write-offs of uncollectible reinsurance recoverables — — Balance, end of period $ 8,345 $ 142 $ 8,350 $ 146 Of the total reinsurance recoverables at March 31, 2021, after deducting mandatory pools and associations and before allowances for estimated uncollectible reinsurance, $5.83 billion, or 87%, were rated by A.M. Best Company. The Company utilizes updated A.M. Best credit ratings on a quarterly basis when determining the allowance. Of the total rated by A.M. Best Company, 94% were rated A- or better. The remaining 13% of reinsurance recoverables were comprised of the following: 6% related to captive insurance companies, 1% related to the Company’s participation in voluntary pools, and 6% related to balances of companies not rated by A.M. Best Company. Certain of the Company's reinsurance recoverables are collateralized by letters of credit, funds held or trust agreements. Contractholder Receivables The following table presents the balances of contractholder receivables, net of the allowance for expected credit losses, at March 31, 2021 and December 31, 2020, and the changes in the allowance for expected credit losses for the three months ended March 31, 2021 and the twelve months ended December 31, 2020. At and For the Three Months Ended March 31, 2021 At and For the Twelve Months Ended December 31, 2020 (in millions) Contractholder Receivables, Net of Allowance for Expected Credit Losses Allowance for Expected Credit Losses Contractholder Receivables, Net of Allowance for Expected Credit Losses Allowance for Expected Credit Losses Balance, beginning of period $ 4,242 $ 19 $ 4,599 $ 20 Current period change for expected credit losses — 1 Write-offs of uncollectible contractholder receivables — 2 Balance, end of period $ 4,271 $ 19 $ 4,242 $ 19

Goodwill and Other Intangible A

Goodwill and Other Intangible Assets	3 Months Ended
	Mar. 31, 2021
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Other Intangible Assets	GOODWILL AND OTHER INTANGIBLE ASSETS Goodwill The following table presents the carrying amount of the Company’s goodwill by segment. Each reportable segment includes goodwill associated with the Company’s international business which is subject to the impact of changes in foreign currency exchange rates. (in millions) March 31, December 31, Business Insurance $ 2,618 $ 2,613 Bond & Specialty Insurance 550 550 Personal Insurance (1) 823 787 Other 26 26 Total $ 4,017 $ 3,976 _________________________________________________________ (1) Goodwill at March 31, 2021 included approximately $33 million associated with a business acquired in the first quarter of 2021, which is deductible for tax purposes. Other Intangible Assets The following tables present a summary of the Company’s other intangible assets by major asset class. (at March 31, 2021, in millions) Gross Accumulated Net Subject to amortization Customer-related $ 105 $ 34 $ 71 Contract-based (1) 205 185 20 Total subject to amortization 310 219 91 Not subject to amortization 227 — 227 Total $ 537 $ 219 $ 318 (at December 31, 2020, in millions) Gross Accumulated Net Subject to amortization Customer-related $ 101 $ 31 $ 70 Contract-based (1) 205 184 21 Total subject to amortization 306 215 91 Not subject to amortization 226 — 226 Total $ 532 $ 215 $ 317 _________________________________________________________ (1) Contract-based intangible assets subject to amortization are comprised of fair value adjustments on claims and claim adjustment expense reserves, reinsurance recoverables and other contract-related intangible assets. Fair value adjustments recorded in connection with insurance acquisitions were based on management’s estimate of nominal claims and claim adjustment expense reserves and reinsurance recoverables. The method used calculated a risk adjustment to a risk-free discounted reserve that would, if reserves ran off as expected, produce results that yielded the assumed cost-of-capital on the capital supporting the loss reserves. The fair value adjustments are reported as other intangible assets on the consolidated balance sheet, and the amounts measured in accordance with the acquirer’s accounting policies for insurance contracts have been reported as part of the claims and claim adjustment expense reserves and reinsurance recoverables. The intangible assets are being recognized into income over the expected payment pattern. Because the time value of money and the risk adjustment (cost of capital) components of the intangible assets run off at different rates, the amount recognized in income may be a net benefit in some periods and a net expense in other periods. Amortization expense of intangible assets was $4 million for each of the three months ended March 31, 2021 and 2020. Amortization expense for all intangible assets subject to amortization is estimated to be $11 million for the remainder of 2021, $14 million in 2022, $13 million in 2023, $13 million in 2024 and $12 million in 2025. Amortization expense for intangible assets arising from insurance contracts acquired in a business combination is estimated to be $3 million for the remainder of 2021, $3 million in 2022, $3 million in 2023, $2 million in 2024 and $2 million in 2025.

Insurance Claim Reserves

Insurance Claim Reserves	3 Months Ended
	Mar. 31, 2021
Insurance Loss Reserves [Abstract]
Insurance Claim Reserves	Claims and claim adjustment expense reserves were as follows: (in millions) March 31, December 31, Property-casualty $ 55,330 $ 54,510 Accident and health 10 11 Total $ 55,340 $ 54,521 The following table presents a reconciliation of beginning and ending property casualty reserve balances for claims and claim adjustment expenses: Three Months Ended March 31, (in millions) 2021 2020 Claims and claim adjustment expense reserves at beginning of year $ 54,510 $ 51,836 Less reinsurance recoverables on unpaid losses 8,153 8,035 Cumulative effect of adoption of updated accounting guidance for credit losses at January 1, 2020 — 53 Net reserves at beginning of year 46,357 43,854 Estimated claims and claim adjustment expenses for claims arising in the current year 5,242 4,763 Estimated decrease in claims and claim adjustment expenses for claims arising in prior years (294) (3) Total increases 4,948 4,760 Claims and claim adjustment expense payments for claims arising in: Current year 1,059 947 Prior years 3,012 3,439 Total payments 4,071 4,386 Unrealized foreign exchange (gain) loss 28 (210) Net reserves at end of period 47,262 44,018 Plus reinsurance recoverables on unpaid losses 8,068 7,926 Claims and claim adjustment expense reserves at end of period $ 55,330 $ 51,944 Gross claims and claim adjustment expense reserves at March 31, 2021 increased by $820 million from December 31, 2020, primarily reflecting the impacts of (i) catastrophe losses in the first three months of 2021, (ii) loss cost trends for the current accident year and (iii) reduced claim settlement activity largely due to the disruptions in the judicial system related to COVID-19. Reinsurance recoverables on unpaid losses at March 31, 2021 decreased by $85 million from December 31, 2020, primarily reflecting the impacts of cash collections in the first three months of 2021, partially offset by catastrophe losses in the same period. Prior Year Reserve Development The following disclosures regarding reserve development are on a “net of reinsurance” basis. For the three months ended March 31, 2021 and 2020, estimated claims and claim adjustment expenses incurred included $294 million and $3 million, respectively, of net favorable development for claims arising in prior years, including $317 million and $27 million, respectively, of net favorable prior year reserve development, and $12 million of accretion of discount in each period that impacted the Company's results of operations. Business Insurance. Net favorable prior year reserve development in the first quarter of 2021 totaled $134 million, primarily driven by better than expected loss experience in domestic operations in the workers' compensation product line for multiple accident years, partially offset by an increase to environmental reserves. Net favorable prior year reserve development in the first quarter of 2021 included a subrogation benefit of $10 million from Southern California Edison Company related to the 2018 Woolsey wildfire in California. Net favorable prior year reserve development in the first quarter of 2020 totaled $5 million, primarily driven by better than expected loss experience in domestic operations in the workers' compensation and commercial property product lines for multiple accident years, largely offset by higher than expected loss experience in the commercial automobile product line for recent accident years. Bond & Specialty Insurance. Net favorable prior year reserve development in the first quarter of 2021 totaled $15 million, primarily driven by better than expected loss experience in the domestic surety product line for multiple accident years, partially offset by higher than expected loss experience in the domestic general liability product line for management liability coverages for multiple accident years. There was no net prior year reserve development in the first quarter of 2020.

Other Comprehensive Income and

Other Comprehensive Income and Accumulated Other Comprehensive Income	3 Months Ended
	Mar. 31, 2021
Other Comprehensive Income And Accumulated Other Comprehensive Income Disclosure [Abstract]
Other Comprehensive Income and Accumulated Other Comprehensive Income	OTHER COMPREHENSIVE INCOME AND ACCUMULATED OTHER COMPREHENSIVE INCOME The following table presents the changes in the Company’s accumulated other comprehensive income (AOCI) for the three months ended March 31, 2021. Changes in Net Unrealized Gains on Investment Securities (in millions) Having No Credit Having Credit Net Benefit Plan Assets and Net Unrealized Total Accumulated Balance, December 31, 2020 $ 3,892 $ 182 $ (832) $ (740) $ 2,502 Other comprehensive income (loss) (OCI) before reclassifications, net of tax (1,246) — — 26 (1,220) Amounts reclassified from AOCI, net of tax (11) — 20 — 9 Net OCI, current period (1,257) — 20 26 (1,211) Balance, March 31, 2021 $ 2,635 $ 182 $ (812) $ (714) $ 1,291 The following table presents the pre-tax components of the Company’s other comprehensive loss and the related income tax expense (benefit). Three Months Ended (in millions) 2021 2020 Changes in net unrealized gains on investment securities: Having no credit losses recognized in the consolidated statement of income $ (1,596) $ (575) Income tax benefit (339) (118) Net of taxes (1,257) (457) Having credit losses recognized in the consolidated statement of income — (6) Income tax benefit — (2) Net of taxes — (4) Net changes in benefit plan assets and obligations 25 23 Income tax expense 5 5 Net of taxes 20 18 Net changes in unrealized foreign currency translation 26 (268) Income tax benefit — (22) Net of taxes 26 (246) Total other comprehensive loss (1,545) (826) Total income tax benefit (334) (137) Total other comprehensive loss, net of taxes $ (1,211) $ (689) The following table presents the pre-tax and related income tax (expense) benefit components of the amounts reclassified from the Company’s AOCI to the Company’s consolidated statement of income. Three Months Ended (in millions) 2021 2020 Reclassification adjustments related to unrealized gains on investment securities: Having no credit losses recognized in the consolidated statement of income (1) $ (14) $ 2 Income tax expense (2) (3) — Net of taxes (11) 2 Having credit losses recognized in the consolidated statement of income (1) — — Income tax benefit (2) — — Net of taxes — — Reclassification adjustment related to benefit plan assets and obligations: Claims and claim adjustment expenses (3) 10 9 General and administrative expenses (3) 15 12 Total 25 21 Income tax benefit (2) 5 4 Net of taxes 20 17 Reclassification adjustment related to foreign currency translation (1) — — Income tax benefit (2) — — Net of taxes — — Total reclassifications 11 23 Total income tax benefit 2 4 Total reclassifications, net of taxes $ 9 $ 19 _________________________________________________________ (1) (Increases) decreases net realized investment gains (losses) on the consolidated statement of income. (2) (Increases) decreases income tax expense on the consolidated statement of income. (3) Increases (decreases) expenses on the consolidated statement of income.

Common Share Repurchases

Common Share Repurchases	3 Months Ended
	Mar. 31, 2021
Treasury Stock Transactions, Excluding Value of Shares Reissued [Abstract]
Common Share Repurchases	COMMON SHARE REPURCHASES During the three months ended March 31, 2021, the Company repurchased 2.4 million common shares under its share repurchase authorization for total cost of $356 million. The average cost per share repurchased was $147.87.  In addition, the Company acquired 0.3 million shares for a total cost of approximately $41 million during the three months ended March 31, 2021 that were not part of the publicly announced share repurchase authorization.  These shares consisted of shares retained to cover payroll withholding taxes in connection with the vesting of restricted stock unit awards and performance share awards, and shares used by employees to cover the price of certain stock options that were exercised. On April 20, 2021, the Board of Directors approved a share repurchase authorization that added an additional $5.0 billion of repurchase capacity to the $805 million of capacity remaining at March 31, 2021.

Earnings per Share

Earnings per Share	3 Months Ended
	Mar. 31, 2021
Earnings Per Share Reconciliation [Abstract]
Earnings per Share	EARNINGS PER SHARE The following is a reconciliation of the income and share data used in the basic and diluted earnings per share computations for the periods presented: Three Months Ended (in millions, except per share amounts) 2021 2020 Basic and Diluted Net income, as reported $ 733 $ 600 Participating share-based awards — allocated income (5) (5) Net income available to common shareholders — basic and diluted $ 728 $ 595 Common Shares Basic Weighted average shares outstanding 252.1 254.4 Diluted Weighted average shares outstanding 252.1 254.4 Weighted average effects of dilutive securities — stock options and performance shares 2.0 1.5 Total 254.1 255.9 Net Income per Common Share Basic $ 2.89 $ 2.34 Diluted $ 2.87 $ 2.33

Share-Based Incentive Compensat

Share-Based Incentive Compensation	3 Months Ended
	Mar. 31, 2021
Share-based Payment Arrangement [Abstract]
Share-Based Incentive Compensation	SHARE-BASED INCENTIVE COMPENSATION The following information relates to fully vested stock option awards at March 31, 2021: Stock Options Number Weighted Weighted Aggregate Vested at end of period (1) 8,045,981 $ 122.61 6.5 years $ 224 Exercisable at end of period 4,930,089 $ 116.37 5.0 years $ 168 _________________________________________________________ (1) Represents awards for which the requisite service has been rendered, including those that are retirement eligible. The total compensation cost for all share-based incentive compensation awards recognized in earnings was $53 million and $46 million for the three months ended March 31, 2021 and 2020, respectively. The related tax benefits recognized in earnings were $9 million and $8 million for the three months ended March 31, 2021 and 2020, respectively. The total unrecognized compensation cost related to all nonvested share-based incentive compensation awards at March 31, 2021 was $240 million, which is expected to be recognized over a weighted-average period of 2.2 years.

Pension Plans, Retirement Benef

Pension Plans, Retirement Benefits and Savings Plans	3 Months Ended
	Mar. 31, 2021
Retirement Benefits [Abstract]
Pension Plans, Retirement Benefits and Savings Plans	PENSION PLANS, RETIREMENT BENEFITS AND SAVINGS PLANS The following table summarizes the components of net periodic benefit cost (benefit) for the Company’s pension and postretirement benefit plans recognized in the consolidated statement of income for the three months ended March 31, 2021 and 2020. Pension Plans Postretirement Benefit Plans (for the three months ended March 31, in millions) 2021 2020 2021 2020 Net Periodic Benefit Cost (Benefit): Service cost $ 35 $ 33 $ — $ — Non-service cost (benefit): Interest cost on benefit obligation $ 21 $ 29 $ 1 $ 1 Expected return on plan assets (69) (69) — — Amortization of unrecognized: Prior service benefit — — (1) (2) Net actuarial (gain) loss 27 23 (1) — Total non-service cost (benefit) (21) (17) (1) (1) Net periodic benefit cost (benefit) $ 14 $ 16 $ (1) $ (1) The following table indicates the line items in which the respective service cost and non-service cost (benefit) are presented in the consolidated statement of income for the three months ended March 31, 2021 and 2020. Pension Plans Postretirement Benefit Plans (for the three months ended March 31, in millions) 2021 2020 2021 2020 Service Cost: Claims and claim adjustment expenses $ 14 $ 14 $ — $ — General and administrative expenses 21 19 — — Total service cost 35 33 — — Non-Service Cost (Benefit): Claims and claim adjustment expenses (9) (7) — — General and administrative expenses (12) (10) (1) (1) Total non-service cost (benefit) (21) (17) (1) (1) Net periodic benefit cost (benefit) $ 14 $ 16 $ (1) $ (1)

Leases

Leases	3 Months Ended
	Mar. 31, 2021
Leases [Abstract]
Leases	LEASES The Company enters into lease agreements for real estate that is primarily used for office space in the ordinary course of business. These leases are accounted for as operating leases, whereby lease expense is recognized on a straight-line basis over the term of the lease, and a right-of-use asset and lease liability is recognized as part of other assets and other liabilities, respectively, in the consolidated balance sheet. Most leases include an option to extend or renew the lease term. The exercise of the renewal option is at the Company's discretion. The operating lease liability includes lease payments related to options to extend or renew the lease term if the Company is reasonably certain of exercising those options. The Company, in determining the present value of lease payments, utilizes either the rate implicit in the lease, if that rate is readily determinable, or the Company’s incremental secured borrowing rate commensurate with the term of the underlying lease. Lease expense is included in general and administrative expenses in the consolidated statement of income. Additional information regarding the Company’s real estate operating leases is as follows: Three Months Ended (in millions) 2021 2020 Lease cost Operating leases $ 23 $ 24 Short-term leases (1) — — Lease expense 23 24 Less: sublease income (2) — — Net lease cost $ 23 $ 24 Other information on operating leases Cash payments to settle a lease liability reported in cash flows $ 26 $ 27 Right-of-use assets obtained in exchange for new lease liabilities $ 12 $ 14 Weighted average discount rate 2.46 % 2.97 % Weighted average remaining lease term 4.9 years 5.0 years _________________________________________________________ (1) Leases with a term of twelve months or less are not recorded on the consolidated balance sheet.

Contingencies, Commitments and

Contingencies, Commitments and Guarantees	3 Months Ended
	Mar. 31, 2021
Contingencies, Commitments and Guarantees [Abstract]
Contingencies, Commitments and Guarantees	CONTINGENCIES, COMMITMENTS AND GUARANTEES Contingencies The major pending legal proceedings, other than ordinary routine litigation incidental to the business, to which the Company or any of its subsidiaries is a party or to which any of the Company’s properties is subject are described below. Asbestos and Environmental Claims and Litigation In the ordinary course of its insurance business, the Company has received and continues to receive claims for insurance arising under policies issued by the Company asserting alleged injuries and damages from asbestos- and environmental-related exposures that are the subject of related coverage litigation. The Company is defending asbestos- and environmental-related litigation vigorously and believes that it has meritorious defenses; however, the outcomes of these disputes are uncertain. In this regard, the Company employs dedicated specialists and comprehensive resolution strategies to manage asbestos and environmental loss exposure, including settling litigation under appropriate circumstances. Currently, it is not possible to predict legal outcomes and their impact on future loss development for claims and litigation relating to asbestos and environmental claims. Any such development could be affected by future court decisions and interpretations, as well as future changes, if any, in applicable legislation. Because of these uncertainties, additional liabilities may arise for amounts in excess of the Company’s current insurance reserves. In addition, the Company’s estimate of ultimate claims and claim adjustment expenses may change. These additional liabilities or changes in estimates, or a range of either, cannot now be reasonably estimated and could result in income statement charges that could be material to the Company’s results of operations in future periods. Other Proceedings Not Arising Under Insurance Contracts or Reinsurance Agreements The Company is involved in other lawsuits, including lawsuits alleging extra-contractual damages relating to insurance contracts or reinsurance agreements, that do not arise under insurance contracts or reinsurance agreements. The legal costs associated with such lawsuits are expensed in the period in which the costs are incurred. Based upon currently available information, the Company does not believe it is reasonably possible that any such lawsuit or related lawsuits would be material to the Company’s results of operations or would have a material adverse effect on the Company’s financial position or liquidity. Other Commitments and Guarantees Commitments Investment Commitments — The Company has unfunded commitments to private equity limited partnerships, real estate partnerships and others. These commitments totaled $1.66 billion and $1.76 billion at March 31, 2021 and December 31, 2020, respectively. Guarantees The maximum amount of the Company’s contingent obligation for indemnifications related to the sale of businesses that are quantifiable was $351 million at March 31, 2021. The maximum amount of the Company’s obligation related to the guarantee of certain insurance policy obligations of a former insurance subsidiary was $480 million at March 31, 2021, all of which is indemnified by a third party. For more information regarding Company guarantees, see note 17 of notes to the consolidated financial statements in the Company’s 2020 Annual Report.

Basis of Presentation and Acc_2

Basis of Presentation and Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation [Policy Text Block]	Basis of Presentation The interim consolidated financial statements include the accounts of The Travelers Companies, Inc. (together with its subsidiaries, the Company). These financial statements are prepared in conformity with U.S. generally accepted accounting principles (GAAP) and are unaudited. In the opinion of the Company’s management, all adjustments necessary for a fair presentation have been reflected. Certain financial information that is normally included in annual financial statements prepared in accordance with GAAP, but that is not required for interim reporting purposes, has been omitted. All material intercompany transactions and balances have been eliminated. The accompanying interim consolidated financial statements and related notes should be read in conjunction with the Company’s consolidated financial statements and related notes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2020 (the Company’s 2020 Annual Report).
Adoption of Accounting Standards [Policy Text Block]	Adoption of Accounting Standards Income Taxes - Simplifying the Accounting for Income Taxes In December 2019, the Financial Accounting Standards Board (FASB) issued updated guidance for the accounting for income taxes. The updated guidance is intended to simplify the accounting for income taxes by removing several exceptions contained in existing guidance and amending other existing guidance to simplify several other income tax accounting matters. The Company adopted the updated guidance for the quarter ended March 31, 2021. The adoption of this guidance did not have a material effect on the Company’s results of operations, financial position or liquidity. For additional information regarding accounting standards that the Company adopted during the periods presented, see note 1 of notes to the consolidated financial statements in the Company’s 2020 Annual Report.

Segment Information (Tables)

Segment Information (Tables)	3 Months Ended
	Mar. 31, 2021
Segment Reporting [Abstract]
Company's revenues and income by segment [Table Text Block]	(For the three months ended March 31, in millions) Business Bond & Specialty Personal Total 2021 Premiums $ 3,799 $ 743 $ 2,844 $ 7,386 Net investment income 523 59 119 701 Fee income 95 — 6 101 Other revenues 53 5 23 81 Total segment revenues (1) $ 4,470 $ 807 $ 2,992 $ 8,269 Segment income (1) $ 317 $ 137 $ 314 $ 768 2020 Premiums $ 3,864 $ 667 $ 2,698 $ 7,229 Net investment income 453 55 103 611 Fee income 102 — 6 108 Other revenues 31 5 22 58 Total segment revenues (1) $ 4,450 $ 727 $ 2,829 $ 8,006 Segment income (1) $ 289 $ 122 $ 336 $ 747 _________________________________________________________ (1) Segment revenues for reportable business segments exclude net realized investment gains (losses) and revenues included in "interest expense and other." Segment income for reportable business segments equals net income excluding the after-tax impact of net realized investment gains (losses) and income (loss) from "interest expense and other."
Business segment reconciliations of revenue and income, net of tax [Table Text Block]	Business Segment Reconciliations Three Months Ended (in millions) 2021 2020 Revenue reconciliation Earned premiums Business Insurance: Domestic: Workers’ compensation $ 811 $ 899 Commercial automobile 695 684 Commercial property 531 508 General liability 607 601 Commercial multi-peril 870 886 Other 14 12 Total Domestic 3,528 3,590 International 271 274 Total Business Insurance 3,799 3,864 Bond & Specialty Insurance: Domestic: Fidelity and surety 266 257 General liability 331 287 Other 56 58 Total Domestic 653 602 International 90 65 Total Bond & Specialty Insurance 743 667 Personal Insurance: Domestic: Automobile 1,370 1,351 Homeowners and Other 1,308 1,176 Total Domestic 2,678 2,527 International 166 171 Total Personal Insurance 2,844 2,698 Total earned premiums 7,386 7,229 Net investment income 701 611 Fee income 101 108 Other revenues 81 58 Total segment revenues 8,269 8,006 Other revenues — — Net realized investment gains (losses) 44 (98) Total revenues $ 8,313 $ 7,908 Income reconciliation, net of tax Total segment income $ 768 $ 747 Interest Expense and Other (1) (69) (71) Core income 699 676 Net realized investment gains (losses) 34 (76) Net income $ 733 $ 600 _________________________________________________________ (1) The primary component of Interest Expense and Other was after-tax interest expense of $65 million and $66 million for the three months ended March 31, 2021 and 2020, respectively.
Asset reconciliation [Table Text Block]	(in millions) March 31, December 31, Asset reconciliation Business Insurance $ 88,657 $ 88,422 Bond & Specialty Insurance 9,488 9,420 Personal Insurance 18,279 18,328 Total assets by reportable segment 116,424 116,170 Other assets (1) 608 594 Total consolidated assets $ 117,032 $ 116,764 _________________________________________________________ (1) The primary components of other assets at both March 31, 2021 and December 31, 2020 were accrued over-funded benefit plan assets related to the Company’s qualified domestic pension plan and other intangible assets.

Investments (Tables)

Investments (Tables)	3 Months Ended
	Mar. 31, 2021
Investments [Abstract]
Amortized cost and fair value of investments in fixed maturities [Table Text Block]	The amortized cost and fair value of investments in fixed maturities classified as available for sale were as follows: Amortized Cost Allowance for Expected Credit Losses Gross Unrealized Fair Value (at March 31, 2021, in millions) Gains Losses U.S. Treasury securities and obligations of U.S. government and government agencies and authorities $ 2,530 $ — $ 32 $ 18 $ 2,544 Obligations of states, municipalities and political subdivisions: Local general obligation 17,719 — 1,079 84 18,714 Revenue 11,748 — 699 44 12,403 State general obligation 1,337 — 81 4 1,414 Pre-refunded 3,365 — 204 — 3,569 Total obligations of states, municipalities and political subdivisions 34,169 — 2,063 132 36,100 Debt securities issued by foreign governments 962 — 18 4 976 Mortgage-backed securities, collateralized mortgage obligations and pass-through securities 1,939 — 107 1 2,045 All other corporate bonds 30,663 2 1,651 141 32,171 Redeemable preferred stock 23 — 2 — 25 Total $ 70,286 $ 2 $ 3,873 $ 296 $ 73,861 Amortized Cost Allowance for Expected Credit Losses Gross Unrealized Fair Value (at December 31, 2020, in millions) Gains Losses U.S. Treasury securities and obligations of U.S. government and government agencies and authorities $ 2,111 $ — $ 38 $ — $ 2,149 Obligations of states, municipalities and political subdivisions: Local general obligation 17,289 — 1,370 2 18,657 Revenue 11,806 — 909 — 12,715 State general obligation 1,343 — 101 — 1,444 Pre-refunded 3,325 — 219 — 3,544 Total obligations of states, municipalities and political subdivisions 33,763 — 2,599 2 36,360 Debt securities issued by foreign governments 1,028 — 26 — 1,054 Mortgage-backed securities, collateralized mortgage obligations and pass-through securities 2,222 — 139 — 2,361 All other corporate bonds 29,683 2 2,382 9 32,054 Redeemable preferred stock 23 — 2 — 25 Total $ 68,830 $ 2 $ 5,186 $ 11 $ 74,003
Cost and fair value of investments in equity securities [Table Text Block]	The cost and fair value of investments in equity securities were as follows: Fair (at March 31, 2021, in millions) Cost Gross Gains Gross Losses Value Public common stock $ 352 $ 87 $ 7 $ 432 Non-redeemable preferred stock 35 10 — 45 Total $ 387 $ 97 $ 7 $ 477 Fair (at December 31, 2020, in millions) Cost Gross Gains Gross Losses Value Public common stock $ 352 $ 70 $ 12 $ 410 Non-redeemable preferred stock 35 8 — 43 Total $ 387 $ 78 $ 12 $ 453
Unrealized investment losses [Table Text Block]	The following tables summarize, for all fixed maturities classified as available for sale in an unrealized loss position at March 31, 2021 and December 31, 2020, the aggregate fair value and gross unrealized loss by length of time those securities have been continuously in an unrealized loss position. The fair value amounts reported in the tables are estimates that are prepared using the process described in note 4 herein and in note 4 of notes to the consolidated financial statements in the Company’s 2020 Annual Report. The Company also relies upon estimates of several factors in its review and evaluation of individual investments, using the process described in note 1 of notes to the consolidated financial statements in the Company’s 2020 Annual Report to determine whether a credit loss impairment exists. Less than 12 months 12 months or longer Total (at March 31, 2021, in millions) Fair Gross Fair Gross Fair Gross Fixed maturities U.S. Treasury securities and obligations of U.S. government and government agencies and authorities $ 854 $ 18 $ — $ — $ 854 $ 18 Obligations of states, municipalities and political subdivisions 4,654 132 — — 4,654 132 Debt securities issued by foreign governments 158 4 — — 158 4 Mortgage-backed securities, collateralized mortgage obligations and pass-through securities 50 1 1 — 51 1 All other corporate bonds 3,494 137 125 4 3,619 141 Total $ 9,210 $ 292 $ 126 $ 4 $ 9,336 $ 296 Less than 12 months 12 months or longer Total (at December 31, 2020, in millions) Fair Gross Fair Gross Fair Gross Fixed maturities U.S. Treasury securities and obligations of U.S. government and government agencies and authorities $ 92 $ — $ — $ — $ 92 $ — Obligations of states, municipalities and political subdivisions 245 2 — — 245 2 Debt securities issued by foreign governments 7 — — — 7 — Mortgage-backed securities, collateralized mortgage obligations and pass-through securities 20 — 1 — 21 — All other corporate bonds 681 6 97 3 778 9 Total $ 1,045 $ 8 $ 98 $ 3 $ 1,143 $ 11
Changes in the allowance for expected credit losses on fixed maturities classified as available for sale [Table Text Block]	The following tables present changes in the allowance for expected credit losses on fixed maturities classified as available for sale: Fixed Maturities (for the three months ended March 31, 2021, in millions) Mortgage-Backed Securities, Collateralized Mortgage Obligations and Pass-Through Securities All Other Corporate Bonds Total Balance, December 31, 2020 $ — $ 2 $ 2 Additions for expected credit losses on securities where no credit losses were previously recognized — — — Additions (reductions) for expected credit losses on securities where credit losses were previously recognized — — — Reductions due to sales/defaults of credit-impaired securities — — — Reductions for impairments of securities which the Company intends to sell or more likely than not will be required to sell (1) — — — Balance, March 31, 2021 $ — $ 2 $ 2 (1) Credit impairment charges recognized in net realized investment gains (losses) for the three months ended March 31, 2021 included no credit losses on fixed maturity securities which the Company had the intent to sell. Fixed Maturities (for the twelve months ended December 31, 2020, in millions) Mortgage-Backed Securities, Collateralized Mortgage Obligations and Pass-Through Securities All Other Corporate Bonds Total Balance, January 1, 2020 $ — $ — $ — Additions for expected credit losses on securities where no credit losses were previously recognized — 10 10 Additions (reductions) for expected credit losses on securities where credit losses were previously recognized — (6) (6) Reductions due to sales/defaults of credit-impaired securities — (2) (2) Reductions for impairments of securities which the Company intends to sell or more likely than not will be required to sell (1) — — — Balance, December 31, 2020 $ — $ 2 $ 2 (1) Credit impairment charges recognized in net realized investment gains for the twelve months ended December 31, 2020 included $13 million of credit losses on fixed maturity securities which the Company had the intent to sell. An allowance for expected credit losses was not previously recorded for these securities.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2021
Fair Value Disclosures [Abstract]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured on a recurring basis [Table Text Block]	The following tables present the level within the fair value hierarchy at which the Company’s financial assets and financial liabilities are measured on a recurring basis. (at March 31, 2021, in millions) Total Level 1 Level 2 Level 3 Invested assets: Fixed maturities U.S. Treasury securities and obligations of U.S. government and government agencies and authorities $ 2,544 $ 2,544 $ — $ — Obligations of states, municipalities and political subdivisions 36,100 — 36,089 11 Debt securities issued by foreign governments 976 — 976 — Mortgage-backed securities, collateralized mortgage obligations and pass-through securities 2,045 — 2,045 — All other corporate bonds 32,171 4 32,009 158 Redeemable preferred stock 25 3 22 — Total fixed maturities 73,861 2,551 71,141 169 Equity securities Public common stock 432 432 — — Non-redeemable preferred stock 45 38 7 — Total equity securities 477 470 7 — Other investments 52 17 — 35 Total $ 74,390 $ 3,038 $ 71,148 $ 204 Other liabilities $ 5 $ — $ — $ 5 (at December 31, 2020, in millions) Total Level 1 Level 2 Level 3 Invested assets: Fixed maturities U.S. Treasury securities and obligations of U.S. government and government agencies and authorities $ 2,149 $ 2,149 $ — $ — Obligations of states, municipalities and political subdivisions 36,360 — 36,349 11 Debt securities issued by foreign governments 1,054 — 1,054 — Mortgage-backed securities, collateralized mortgage obligations and pass-through securities 2,361 — 2,361 — All other corporate bonds 32,054 — 31,899 155 Redeemable preferred stock 25 3 22 — Total fixed maturities 74,003 2,152 71,685 166 Equity securities Public common stock 410 410 — — Non-redeemable preferred stock 43 18 25 — Total equity securities 453 428 25 — Other investments 52 17 — 35 Total $ 74,508 $ 2,597 $ 71,710 $ 201 Other liabilities $ 5 $ — $ — $ 5
Carrying value and fair value of the Company's financial assets and financial liabilities disclosed, but not carried, at fair value, and the level within the fair value hierarchy at which such assets and liabilities are categorized [Table Text Block]	The following tables present the carrying value and fair value of the Company’s financial assets and financial liabilities disclosed, but not carried, at fair value, and the level within the fair value hierarchy at which such assets and liabilities are categorized. (at March 31, 2021, in millions) Carrying Fair Level 1 Level 2 Level 3 Financial assets Short-term securities $ 4,987 $ 4,987 $ 630 $ 4,306 $ 51 Financial liabilities Debt $ 6,450 $ 7,994 $ — $ 7,994 $ — Commercial paper $ 100 $ 100 $ — $ 100 $ — (at December 31, 2020, in millions) Carrying Fair Level 1 Level 2 Level 3 Financial assets Short-term securities $ 5,511 $ 5,511 $ 630 $ 4,829 $ 52 Financial liabilities Debt $ 6,450 $ 8,976 $ — $ 8,976 $ — Commercial paper $ 100 $ 100 $ — $ 100 $ —

Allowance for Expected Credit_2

Allowance for Expected Credit Losses (Tables)	3 Months Ended
	Mar. 31, 2021
Credit Loss [Abstract]
Changes in the allowance for expected credit losses on premiums receivable [Table Text Block]	The following table presents the balances of premiums receivable, net of the allowance for expected credit losses, at March 31, 2021 and December 31, 2020, and the changes in the allowance for expected credit losses for the three months ended March 31, 2021 and the twelve months ended December 31, 2020. At and For the Three Months Ended March 31, 2021 At and For the Twelve Months Ended December 31, 2020 (in millions) Premiums Receivable, Net of Allowance for Expected Credit Losses Allowance for Expected Credit Losses Premiums Receivable, Net of Allowance for Expected Credit Losses Allowance for Expected Credit Losses Balance, beginning of period $ 7,829 $ 105 $ 7,909 $ 49 Current period change for expected credit losses 16 103 Write-offs of uncollectible premiums receivable 11 47 Balance, end of period $ 8,167 $ 110 $ 7,829 $ 105
Changes in the allowance for estimated uncollectible reinsurance [Table Text Block]	The following table presents the balances of reinsurance recoverables, net of the allowance for estimated uncollectible reinsurance, at March 31, 2021 and December 31, 2020, and the changes in the allowance for estimated uncollectible reinsurance for the three months ended March 31, 2021 and the twelve months ended December 31, 2020. At and For the Three Months Ended March 31, 2021 At and For the Twelve Months Ended December 31, 2020 (in millions) Reinsurance Recoverables, Net of Allowance for Estimated Uncollectible Reinsurance Allowance for Estimated Uncollectible Reinsurance Reinsurance Recoverables, Net of Allowance for Estimated Uncollectible Reinsurance Allowance for Estimated Uncollectible Reinsurance Balance, beginning of period $ 8,350 $ 146 $ 8,235 $ 92 Cumulative effect of adoption of updated accounting guidance for credit losses at January 1, 2020 — 53 Current period change for estimated uncollectible reinsurance (4) 1 Write-offs of uncollectible reinsurance recoverables — — Balance, end of period $ 8,345 $ 142 $ 8,350 $ 146
Changes in the allowance for expected credit losses on contractholder receivables [Table Text Block]	The following table presents the balances of contractholder receivables, net of the allowance for expected credit losses, at March 31, 2021 and December 31, 2020, and the changes in the allowance for expected credit losses for the three months ended March 31, 2021 and the twelve months ended December 31, 2020. At and For the Three Months Ended March 31, 2021 At and For the Twelve Months Ended December 31, 2020 (in millions) Contractholder Receivables, Net of Allowance for Expected Credit Losses Allowance for Expected Credit Losses Contractholder Receivables, Net of Allowance for Expected Credit Losses Allowance for Expected Credit Losses Balance, beginning of period $ 4,242 $ 19 $ 4,599 $ 20 Current period change for expected credit losses — 1 Write-offs of uncollectible contractholder receivables — 2 Balance, end of period $ 4,271 $ 19 $ 4,242 $ 19

Goodwill and Other Intangible_2

Goodwill and Other Intangible Assets (Tables)	3 Months Ended
	Mar. 31, 2021
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill by segment [Table Text Block]	The following table presents the carrying amount of the Company’s goodwill by segment. Each reportable segment includes goodwill associated with the Company’s international business which is subject to the impact of changes in foreign currency exchange rates. (in millions) March 31, December 31, Business Insurance $ 2,618 $ 2,613 Bond & Specialty Insurance 550 550 Personal Insurance (1) 823 787 Other 26 26 Total $ 4,017 $ 3,976 _________________________________________________________
Other intangible assets subject to amortization [Table Text Block]	The following tables present a summary of the Company’s other intangible assets by major asset class. (at March 31, 2021, in millions) Gross Accumulated Net Subject to amortization Customer-related $ 105 $ 34 $ 71 Contract-based (1) 205 185 20 Total subject to amortization 310 219 91 Not subject to amortization 227 — 227 Total $ 537 $ 219 $ 318 (at December 31, 2020, in millions) Gross Accumulated Net Subject to amortization Customer-related $ 101 $ 31 $ 70 Contract-based (1) 205 184 21 Total subject to amortization 306 215 91 Not subject to amortization 226 — 226 Total $ 532 $ 215 $ 317 _________________________________________________________ (1) Contract-based intangible assets subject to amortization are comprised of fair value adjustments on claims and claim adjustment expense reserves, reinsurance recoverables and other contract-related intangible assets. Fair value adjustments recorded in connection with insurance acquisitions were based on management’s estimate of nominal claims and claim adjustment expense reserves and reinsurance recoverables. The method used calculated a risk adjustment to a risk-free discounted reserve that would, if reserves ran off as expected, produce results that yielded the assumed cost-of-capital on the capital supporting the loss reserves. The fair value adjustments are reported as other intangible assets on the consolidated balance sheet, and the amounts measured in accordance with the acquirer’s accounting policies for insurance contracts have been reported as part of the claims and claim adjustment expense reserves and reinsurance recoverables. The intangible assets are being recognized into income over the expected payment pattern. Because the time value of money and the risk adjustment (cost of capital) components of the intangible assets run off at different rates, the amount recognized in income may be a net benefit in some periods and a net expense in other periods.
Other intangible assets not subject to amortization [Table Text Block]	The following tables present a summary of the Company’s other intangible assets by major asset class. (at March 31, 2021, in millions) Gross Accumulated Net Subject to amortization Customer-related $ 105 $ 34 $ 71 Contract-based (1) 205 185 20 Total subject to amortization 310 219 91 Not subject to amortization 227 — 227 Total $ 537 $ 219 $ 318 (at December 31, 2020, in millions) Gross Accumulated Net Subject to amortization Customer-related $ 101 $ 31 $ 70 Contract-based (1) 205 184 21 Total subject to amortization 306 215 91 Not subject to amortization 226 — 226 Total $ 532 $ 215 $ 317 _________________________________________________________ (1) Contract-based intangible assets subject to amortization are comprised of fair value adjustments on claims and claim adjustment expense reserves, reinsurance recoverables and other contract-related intangible assets. Fair value adjustments recorded in connection with insurance acquisitions were based on management’s estimate of nominal claims and claim adjustment expense reserves and reinsurance recoverables. The method used calculated a risk adjustment to a risk-free discounted reserve that would, if reserves ran off as expected, produce results that yielded the assumed cost-of-capital on the capital supporting the loss reserves. The fair value adjustments are reported as other intangible assets on the consolidated balance sheet, and the amounts measured in accordance with the acquirer’s accounting policies for insurance contracts have been reported as part of the claims and claim adjustment expense reserves and reinsurance recoverables. The intangible assets are being recognized into income over the expected payment pattern. Because the time value of money and the risk adjustment (cost of capital) components of the intangible assets run off at different rates, the amount recognized in income may be a net benefit in some periods and a net expense in other periods.

Insurance Claim Reserves (Table

Insurance Claim Reserves (Tables)	3 Months Ended
	Mar. 31, 2021
Insurance Loss Reserves [Abstract]
Claims and claim adjustment expense reserves [Table Text Block]	Claims and claim adjustment expense reserves were as follows: (in millions) March 31, December 31, Property-casualty $ 55,330 $ 54,510 Accident and health 10 11 Total $ 55,340 $ 54,521
Reconciliation of beginning and ending property casualty reserve balances for claims and claim adjustment expenses [Table Text Block]	The following table presents a reconciliation of beginning and ending property casualty reserve balances for claims and claim adjustment expenses: Three Months Ended March 31, (in millions) 2021 2020 Claims and claim adjustment expense reserves at beginning of year $ 54,510 $ 51,836 Less reinsurance recoverables on unpaid losses 8,153 8,035 Cumulative effect of adoption of updated accounting guidance for credit losses at January 1, 2020 — 53 Net reserves at beginning of year 46,357 43,854 Estimated claims and claim adjustment expenses for claims arising in the current year 5,242 4,763 Estimated decrease in claims and claim adjustment expenses for claims arising in prior years (294) (3) Total increases 4,948 4,760 Claims and claim adjustment expense payments for claims arising in: Current year 1,059 947 Prior years 3,012 3,439 Total payments 4,071 4,386 Unrealized foreign exchange (gain) loss 28 (210) Net reserves at end of period 47,262 44,018 Plus reinsurance recoverables on unpaid losses 8,068 7,926 Claims and claim adjustment expense reserves at end of period $ 55,330 $ 51,944

Other Comprehensive Income an_2

Other Comprehensive Income and Accumulated Other Comprehensive Income (Tables)	3 Months Ended
	Mar. 31, 2021
Other Comprehensive Income And Accumulated Other Comprehensive Income Disclosure [Abstract]
Changes in accumulated other comprehensive income (AOCI) [Table Text Block]	The following table presents the changes in the Company’s accumulated other comprehensive income (AOCI) for the three months ended March 31, 2021. Changes in Net Unrealized Gains on Investment Securities (in millions) Having No Credit Having Credit Net Benefit Plan Assets and Net Unrealized Total Accumulated Balance, December 31, 2020 $ 3,892 $ 182 $ (832) $ (740) $ 2,502 Other comprehensive income (loss) (OCI) before reclassifications, net of tax (1,246) — — 26 (1,220) Amounts reclassified from AOCI, net of tax (11) — 20 — 9 Net OCI, current period (1,257) — 20 26 (1,211) Balance, March 31, 2021 $ 2,635 $ 182 $ (812) $ (714) $ 1,291
Pre-tax components of other comprehensive loss and the related income tax expense (benefit) for each component [Table Text Block]	The following table presents the pre-tax components of the Company’s other comprehensive loss and the related income tax expense (benefit). Three Months Ended (in millions) 2021 2020 Changes in net unrealized gains on investment securities: Having no credit losses recognized in the consolidated statement of income $ (1,596) $ (575) Income tax benefit (339) (118) Net of taxes (1,257) (457) Having credit losses recognized in the consolidated statement of income — (6) Income tax benefit — (2) Net of taxes — (4) Net changes in benefit plan assets and obligations 25 23 Income tax expense 5 5 Net of taxes 20 18 Net changes in unrealized foreign currency translation 26 (268) Income tax benefit — (22) Net of taxes 26 (246) Total other comprehensive loss (1,545) (826) Total income tax benefit (334) (137) Total other comprehensive loss, net of taxes $ (1,211) $ (689)
Pre-tax and related income tax (expense) benefit components of the amounts reclassified from accumulated other comprehensive income to the consolidated statement of income [Table Text Block]	The following table presents the pre-tax and related income tax (expense) benefit components of the amounts reclassified from the Company’s AOCI to the Company’s consolidated statement of income. Three Months Ended (in millions) 2021 2020 Reclassification adjustments related to unrealized gains on investment securities: Having no credit losses recognized in the consolidated statement of income (1) $ (14) $ 2 Income tax expense (2) (3) — Net of taxes (11) 2 Having credit losses recognized in the consolidated statement of income (1) — — Income tax benefit (2) — — Net of taxes — — Reclassification adjustment related to benefit plan assets and obligations: Claims and claim adjustment expenses (3) 10 9 General and administrative expenses (3) 15 12 Total 25 21 Income tax benefit (2) 5 4 Net of taxes 20 17 Reclassification adjustment related to foreign currency translation (1) — — Income tax benefit (2) — — Net of taxes — — Total reclassifications 11 23 Total income tax benefit 2 4 Total reclassifications, net of taxes $ 9 $ 19 _________________________________________________________ (1) (Increases) decreases net realized investment gains (losses) on the consolidated statement of income. (2) (Increases) decreases income tax expense on the consolidated statement of income. (3) Increases (decreases) expenses on the consolidated statement of income.

Earnings per Share (Table)

Earnings per Share (Table)	3 Months Ended
	Mar. 31, 2021
Earnings Per Share Reconciliation [Abstract]
Earnings per share reconciliation [Table Text Block]	The following is a reconciliation of the income and share data used in the basic and diluted earnings per share computations for the periods presented: Three Months Ended (in millions, except per share amounts) 2021 2020 Basic and Diluted Net income, as reported $ 733 $ 600 Participating share-based awards — allocated income (5) (5) Net income available to common shareholders — basic and diluted $ 728 $ 595 Common Shares Basic Weighted average shares outstanding 252.1 254.4 Diluted Weighted average shares outstanding 252.1 254.4 Weighted average effects of dilutive securities — stock options and performance shares 2.0 1.5 Total 254.1 255.9 Net Income per Common Share Basic $ 2.89 $ 2.34 Diluted $ 2.87 $ 2.33

Share-Based Incentive Compens_2

Share-Based Incentive Compensation (Table)	3 Months Ended
	Mar. 31, 2021
Share-based Payment Arrangement [Abstract]
Information for fully vested stock option awards [Table Text Block]	The following information relates to fully vested stock option awards at March 31, 2021: Stock Options Number Weighted Weighted Aggregate Vested at end of period (1) 8,045,981 $ 122.61 6.5 years $ 224 Exercisable at end of period 4,930,089 $ 116.37 5.0 years $ 168 _________________________________________________________ (1) Represents awards for which the requisite service has been rendered, including those that are retirement eligible.

Pension Plans, Retirement Ben_2

Pension Plans, Retirement Benefits and Savings Plans (Tables)	3 Months Ended
	Mar. 31, 2021
Retirement Benefits [Abstract]
Summary of the components of net periodic benefit cost (benefit) for the Company's pension and postretirement benefit plans recognized in the consolidated statement of income [Table Text Block]	The following table summarizes the components of net periodic benefit cost (benefit) for the Company’s pension and postretirement benefit plans recognized in the consolidated statement of income for the three months ended March 31, 2021 and 2020. Pension Plans Postretirement Benefit Plans (for the three months ended March 31, in millions) 2021 2020 2021 2020 Net Periodic Benefit Cost (Benefit): Service cost $ 35 $ 33 $ — $ — Non-service cost (benefit): Interest cost on benefit obligation $ 21 $ 29 $ 1 $ 1 Expected return on plan assets (69) (69) — — Amortization of unrecognized: Prior service benefit — — (1) (2) Net actuarial (gain) loss 27 23 (1) — Total non-service cost (benefit) (21) (17) (1) (1) Net periodic benefit cost (benefit) $ 14 $ 16 $ (1) $ (1)
Consolidated statement of income line items impacted by service costs and non-service cost (benefit) [Table Text Block]	The following table indicates the line items in which the respective service cost and non-service cost (benefit) are presented in the consolidated statement of income for the three months ended March 31, 2021 and 2020. Pension Plans Postretirement Benefit Plans (for the three months ended March 31, in millions) 2021 2020 2021 2020 Service Cost: Claims and claim adjustment expenses $ 14 $ 14 $ — $ — General and administrative expenses 21 19 — — Total service cost 35 33 — — Non-Service Cost (Benefit): Claims and claim adjustment expenses (9) (7) — — General and administrative expenses (12) (10) (1) (1) Total non-service cost (benefit) (21) (17) (1) (1) Net periodic benefit cost (benefit) $ 14 $ 16 $ (1) $ (1)

Leases (Table)

Leases (Table)	3 Months Ended
	Mar. 31, 2021
Leases [Abstract]
Additional information regarding real estate operating leases	Lease expense is included in general and administrative expenses in the consolidated statement of income. Additional information regarding the Company’s real estate operating leases is as follows: Three Months Ended (in millions) 2021 2020 Lease cost Operating leases $ 23 $ 24 Short-term leases (1) — — Lease expense 23 24 Less: sublease income (2) — — Net lease cost $ 23 $ 24 Other information on operating leases Cash payments to settle a lease liability reported in cash flows $ 26 $ 27 Right-of-use assets obtained in exchange for new lease liabilities $ 12 $ 14 Weighted average discount rate 2.46 % 2.97 % Weighted average remaining lease term 4.9 years 5.0 years _________________________________________________________ (1) Leases with a term of twelve months or less are not recorded on the consolidated balance sheet.

Segment Information (Details)

Segment Information (Details) $ in Millions	3 Months Ended
	Mar. 31, 2021USD ($)segment	Mar. 31, 2020USD ($)
Segment reporting information
Number of reportable business segments | segment	3
Premiums	$ 7,386	$ 7,229
Net investment income	701	611
Fee income	101	108
Other revenues	81	58
Net realized investment gains (losses)	44	(98)
Total revenues	8,313	7,908
Core income (loss)	699	676
Net realized investment gains (losses), net of tax	34	(76)
Net income	733	600
Reportable Segments [Member]
Segment reporting information
Premiums	7,386	7,229
Net investment income	701	611
Fee income	101	108
Other revenues	81	58
Total segment revenues	8,269	8,006
Core income (loss)	768	747
Reportable Segments [Member] | Business Insurance [Member]
Segment reporting information
Premiums	3,799	3,864
Net investment income	523	453
Fee income	95	102
Other revenues	53	31
Total segment revenues	4,470	4,450
Core income (loss)	317	289
Reportable Segments [Member] | Business Insurance [Member] | Domestic [Member]
Segment reporting information
Premiums	3,528	3,590
Reportable Segments [Member] | Business Insurance [Member] | Domestic [Member] | Workers' compensation [Member]
Segment reporting information
Premiums	811	899
Reportable Segments [Member] | Business Insurance [Member] | Domestic [Member] | Automobile [Member]
Segment reporting information
Premiums	695	684
Reportable Segments [Member] | Business Insurance [Member] | Domestic [Member] | Commercial property [Member]
Segment reporting information
Premiums	531	508
Reportable Segments [Member] | Business Insurance [Member] | Domestic [Member] | General liability [Member]
Segment reporting information
Premiums	607	601
Reportable Segments [Member] | Business Insurance [Member] | Domestic [Member] | Commercial multi-peril [Member]
Segment reporting information
Premiums	870	886
Reportable Segments [Member] | Business Insurance [Member] | Domestic [Member] | Other [Member]
Segment reporting information
Premiums	14	12
Reportable Segments [Member] | Business Insurance [Member] | International [Member]
Segment reporting information
Premiums	271	274
Reportable Segments [Member] | Bond & Specialty Insurance [Member]
Segment reporting information
Premiums	743	667
Net investment income	59	55
Fee income	0	0
Other revenues	5	5
Total segment revenues	807	727
Core income (loss)	137	122
Reportable Segments [Member] | Bond & Specialty Insurance [Member] | Domestic [Member]
Segment reporting information
Premiums	653	602
Reportable Segments [Member] | Bond & Specialty Insurance [Member] | Domestic [Member] | General liability [Member]
Segment reporting information
Premiums	331	287
Reportable Segments [Member] | Bond & Specialty Insurance [Member] | Domestic [Member] | Fidelity and surety [Member]
Segment reporting information
Premiums	266	257
Reportable Segments [Member] | Bond & Specialty Insurance [Member] | Domestic [Member] | Other [Member]
Segment reporting information
Premiums	56	58
Reportable Segments [Member] | Bond & Specialty Insurance [Member] | International [Member]
Segment reporting information
Premiums	90	65
Reportable Segments [Member] | Personal Insurance [Member]
Segment reporting information
Premiums	2,844	2,698
Net investment income	119	103
Fee income	6	6
Other revenues	23	22
Total segment revenues	2,992	2,829
Core income (loss)	314	336
Reportable Segments [Member] | Personal Insurance [Member] | Domestic [Member]
Segment reporting information
Premiums	2,678	2,527
Reportable Segments [Member] | Personal Insurance [Member] | Domestic [Member] | Automobile [Member]
Segment reporting information
Premiums	1,370	1,351
Reportable Segments [Member] | Personal Insurance [Member] | Domestic [Member] | Homeowners and Other [Member]
Segment reporting information
Premiums	1,308	1,176
Reportable Segments [Member] | Personal Insurance [Member] | International [Member]
Segment reporting information
Premiums	166	171
Other [Member]
Segment reporting information
Other revenues	0	0
Core income (loss)	(69)	(71)
After-tax interest expense	$ 65	$ 66

Segment Information (Details) -

Segment Information (Details) - Assets by Segment - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Assets by segment
Total assets	$ 117,032	$ 116,764
Reportable Segments [Member]
Assets by segment
Total assets	116,424	116,170
Reportable Segments [Member] | Business Insurance [Member]
Assets by segment
Total assets	88,657	88,422
Reportable Segments [Member] | Bond & Specialty Insurance [Member]
Assets by segment
Total assets	9,488	9,420
Reportable Segments [Member] | Personal Insurance [Member]
Assets by segment
Total assets	18,279	18,328
Other assets [Member]
Assets by segment
Total assets	$ 608	$ 594

Investments (Details) - Investm

Investments (Details) - Investment Information, Debt Securities - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020	Dec. 31, 2019
Investment disclosure details
Fixed maturities, amortized cost	$ 70,286		$ 68,830
Allowance for expected credit losses	2		2	$ 0
Gross unrealized gains	3,873		5,186
Gross unrealized losses	296		11
Fixed maturities, at fair value	73,861		74,003
Proceeds from sales of fixed maturities classified as available for sale	1,238	$ 388
Gross realized gains	15	15
Gross realized losses	1	$ 1
U.S. Treasury securities and obligations of U.S. government and government agencies and authorities [Member]
Investment disclosure details
Fixed maturities, amortized cost	2,530		2,111
Allowance for expected credit losses	0		0
Gross unrealized gains	32		38
Gross unrealized losses	18		0
Fixed maturities, at fair value	2,544		2,149
Obligations of states, municipalities and political subdivisions [Member]
Investment disclosure details
Fixed maturities, amortized cost	34,169		33,763
Allowance for expected credit losses	0		0
Gross unrealized gains	2,063		2,599
Gross unrealized losses	132		2
Fixed maturities, at fair value	36,100		36,360
Obligations of states, municipalities and political subdivisions, local general obligation [Member]
Investment disclosure details
Fixed maturities, amortized cost	17,719		17,289
Allowance for expected credit losses	0		0
Gross unrealized gains	1,079		1,370
Gross unrealized losses	84		2
Fixed maturities, at fair value	18,714		18,657
Obligations of states, municipalities and political subdivisions, revenue [Member]
Investment disclosure details
Fixed maturities, amortized cost	11,748		11,806
Allowance for expected credit losses	0		0
Gross unrealized gains	699		909
Gross unrealized losses	44		0
Fixed maturities, at fair value	12,403		12,715
Obligations of states, municipalities and political subdivisions, state general obligation [Member]
Investment disclosure details
Fixed maturities, amortized cost	1,337		1,343
Allowance for expected credit losses	0		0
Gross unrealized gains	81		101
Gross unrealized losses	4		0
Fixed maturities, at fair value	1,414		1,444
Obligations of states, municipalities and political subdivisions, pre-refunded [Member]
Investment disclosure details
Fixed maturities, amortized cost	3,365		3,325
Allowance for expected credit losses	0		0
Gross unrealized gains	204		219
Gross unrealized losses	0		0
Fixed maturities, at fair value	3,569		3,544
Debt securities issued by foreign governments [Member]
Investment disclosure details
Fixed maturities, amortized cost	962		1,028
Allowance for expected credit losses	0		0
Gross unrealized gains	18		26
Gross unrealized losses	4		0
Fixed maturities, at fair value	976		1,054
Mortgage-backed securities, collateralized mortgage obligations and pass-through securities [Member]
Investment disclosure details
Fixed maturities, amortized cost	1,939		2,222
Allowance for expected credit losses	0		0	0
Gross unrealized gains	107		139
Gross unrealized losses	1		0
Fixed maturities, at fair value	2,045		2,361
All other corporate bonds [Member]
Investment disclosure details
Fixed maturities, amortized cost	30,663		29,683
Allowance for expected credit losses	2		2	$ 0
Gross unrealized gains	1,651		2,382
Gross unrealized losses	141		9
Fixed maturities, at fair value	32,171		32,054
Redeemable preferred stock [Member]
Investment disclosure details
Fixed maturities, amortized cost	23		23
Allowance for expected credit losses	0		0
Gross unrealized gains	2		2
Gross unrealized losses	0		0
Fixed maturities, at fair value	$ 25		$ 25

Investments (Details) - Inves_2

Investments (Details) - Investment Information, Equity Securities - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Investment disclosure details
Equity securities, cost	$ 387		$ 387
Gross gains	97		78
Gross losses	7		12
Equity securities, at fair value	477		453
Net recognized gains (losses) on equity securities still held	23	$ (79)
Public common stock [Member]
Investment disclosure details
Equity securities, cost	352		352
Gross gains	87		70
Gross losses	7		12
Equity securities, at fair value	432		410
Non-redeemable preferred stock [Member]
Investment disclosure details
Equity securities, cost	35		35
Gross gains	10		8
Gross losses	0		0
Equity securities, at fair value	$ 45		$ 43

Investments (Details) - Inves_3

Investments (Details) - Investment Information, Losses - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Investment disclosure details
Continuous unrealized loss position, less than 12 months, fair value	$ 9,210	$ 1,045
Continuous unrealized loss position, less than 12 months, gross unrealized losses	292	8
Continuous unrealized loss position, 12 months or longer, fair value	126	98
Continuous unrealized loss position, 12 months or longer, gross unrealized losses	4	3
Continuous unrealized loss position, total, fair value	9,336	1,143
Continuous unrealized loss position, total, gross unrealized losses	296	11
U.S. Treasury securities and obligations of U.S. government and government agencies and authorities [Member]
Investment disclosure details
Continuous unrealized loss position, less than 12 months, fair value	854	92
Continuous unrealized loss position, less than 12 months, gross unrealized losses	18	0
Continuous unrealized loss position, 12 months or longer, fair value	0	0
Continuous unrealized loss position, 12 months or longer, gross unrealized losses	0	0
Continuous unrealized loss position, total, fair value	854	92
Continuous unrealized loss position, total, gross unrealized losses	18	0
Obligations of states, municipalities and political subdivisions [Member]
Investment disclosure details
Continuous unrealized loss position, less than 12 months, fair value	4,654	245
Continuous unrealized loss position, less than 12 months, gross unrealized losses	132	2
Continuous unrealized loss position, 12 months or longer, fair value	0	0
Continuous unrealized loss position, 12 months or longer, gross unrealized losses	0	0
Continuous unrealized loss position, total, fair value	4,654	245
Continuous unrealized loss position, total, gross unrealized losses	132	2
Debt securities issued by foreign governments [Member]
Investment disclosure details
Continuous unrealized loss position, less than 12 months, fair value	158	7
Continuous unrealized loss position, less than 12 months, gross unrealized losses	4	0
Continuous unrealized loss position, 12 months or longer, fair value	0	0
Continuous unrealized loss position, 12 months or longer, gross unrealized losses	0	0
Continuous unrealized loss position, total, fair value	158	7
Continuous unrealized loss position, total, gross unrealized losses	4	0
Mortgage-backed securities, collateralized mortgage obligations and pass-through securities [Member]
Investment disclosure details
Continuous unrealized loss position, less than 12 months, fair value	50	20
Continuous unrealized loss position, less than 12 months, gross unrealized losses	1	0
Continuous unrealized loss position, 12 months or longer, fair value	1	1
Continuous unrealized loss position, 12 months or longer, gross unrealized losses	0	0
Continuous unrealized loss position, total, fair value	51	21
Continuous unrealized loss position, total, gross unrealized losses	1	0
All other corporate bonds [Member]
Investment disclosure details
Continuous unrealized loss position, less than 12 months, fair value	3,494	681
Continuous unrealized loss position, less than 12 months, gross unrealized losses	137	6
Continuous unrealized loss position, 12 months or longer, fair value	125	97
Continuous unrealized loss position, 12 months or longer, gross unrealized losses	4	3
Continuous unrealized loss position, total, fair value	3,619	778
Continuous unrealized loss position, total, gross unrealized losses	$ 141	$ 9

Investments (Details) - Allowan

Investments (Details) - Allowance for Expected Credit Losses - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Allowance for expected credit losses [Roll Forward]
Allowance for expected credit losses on fixed maturities classified as available-for-sale, balance, beginning of period	$ 2	$ 0	$ 0
Additions for expected credit losses on securities where no credit losses were previously recognized	0		10
Additions (reductions) for expected credit losses on securities where credit losses were previously recognized	0		(6)
Reductions due to sales/defaults of credit-impaired securities	0		(2)
Reductions for impairments of securities which the Company intends to sell or more likely than not will be required to sell	0		0
Allowance for expected credit losses on fixed maturities classified as available-for-sale, balance, end of period	2		2
Credit impairment charges recognized in net realized investment gains (losses) on securities which the Company intends to sell and for which an allowance for credit loss was not previously recorded	0		13
Total net credit impairment charges included in net realized investment gains (losses) in the consolidated statement of income	$ 0	$ 16
Credit losses on fixed maturities recognized in the consolidated statement of income, as a percentage of the fixed maturity portfolio on a pre-tax basis (less than)	1.00%	1.00%
Credit losses on fixed maturities recognized in the consolidated statement of income, as a percentage of shareholders' equity on an after-tax basis (less than)	1.00%	1.00%
Mortgage-backed securities, collateralized mortgage obligations and pass-through securities [Member]
Allowance for expected credit losses [Roll Forward]
Allowance for expected credit losses on fixed maturities classified as available-for-sale, balance, beginning of period	$ 0	$ 0	0
Additions for expected credit losses on securities where no credit losses were previously recognized	0		0
Additions (reductions) for expected credit losses on securities where credit losses were previously recognized	0		0
Reductions due to sales/defaults of credit-impaired securities	0		0
Reductions for impairments of securities which the Company intends to sell or more likely than not will be required to sell	0		0
Allowance for expected credit losses on fixed maturities classified as available-for-sale, balance, end of period	0		0
All other corporate bonds [Member]
Allowance for expected credit losses [Roll Forward]
Allowance for expected credit losses on fixed maturities classified as available-for-sale, balance, beginning of period	2	$ 0	0
Additions for expected credit losses on securities where no credit losses were previously recognized	0		10
Additions (reductions) for expected credit losses on securities where credit losses were previously recognized	0		(6)
Reductions due to sales/defaults of credit-impaired securities	0		(2)
Reductions for impairments of securities which the Company intends to sell or more likely than not will be required to sell	0		0
Allowance for expected credit losses on fixed maturities classified as available-for-sale, balance, end of period	$ 2		$ 2

Investments (Details) - Other I

Investments (Details) - Other Investments	3 Months Ended
	Mar. 31, 2021
Investments [Abstract]
Availability of financial information provided by hedge funds following the date of the reporting	1 month
Availability of financial information provided by private equity and real estate partnerships following the date of the reporting, maximum	3 months

Fair Value Measurements (Detail

Fair Value Measurements (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Percent of fixed maturities for which a pricing service estimates fair value	99.00%	99.00%
Estimated fair value of put/call option	$ 5	$ 5

Fair Value Measurements (Deta_2

Fair Value Measurements (Details) - Fair Value Hierarchy - Recurring basis [Member] - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	$ 74,390	$ 74,508
Other liabilities measured on a recurring basis	5	5
Fixed maturities [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	73,861	74,003
U.S. Treasury securities and obligations of U.S. government and government agencies and authorities [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	2,544	2,149
Obligations of states, municipalities and political subdivisions [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	36,100	36,360
Debt securities issued by foreign governments [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	976	1,054
Mortgage-backed securities, collateralized mortgage obligations and pass-through securities [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	2,045	2,361
All other corporate bonds [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	32,171	32,054
Redeemable preferred stock [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	25	25
Equity securities [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	477	453
Public common stock [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	432	410
Non-redeemable preferred stock [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	45	43
Other Investments [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	52	52
Level 1 [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	3,038	2,597
Other liabilities measured on a recurring basis	0	0
Level 1 [Member] | Fixed maturities [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	2,551	2,152
Level 1 [Member] | U.S. Treasury securities and obligations of U.S. government and government agencies and authorities [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	2,544	2,149
Level 1 [Member] | Obligations of states, municipalities and political subdivisions [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	0	0
Level 1 [Member] | Debt securities issued by foreign governments [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	0	0
Level 1 [Member] | Mortgage-backed securities, collateralized mortgage obligations and pass-through securities [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	0	0
Level 1 [Member] | All other corporate bonds [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	4	0
Level 1 [Member] | Redeemable preferred stock [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	3	3
Level 1 [Member] | Equity securities [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	470	428
Level 1 [Member] | Public common stock [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	432	410
Level 1 [Member] | Non-redeemable preferred stock [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	38	18
Level 1 [Member] | Other Investments [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	17	17
Level 2 [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	71,148	71,710
Other liabilities measured on a recurring basis	0	0
Level 2 [Member] | Fixed maturities [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	71,141	71,685
Level 2 [Member] | U.S. Treasury securities and obligations of U.S. government and government agencies and authorities [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	0	0
Level 2 [Member] | Obligations of states, municipalities and political subdivisions [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	36,089	36,349
Level 2 [Member] | Debt securities issued by foreign governments [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	976	1,054
Level 2 [Member] | Mortgage-backed securities, collateralized mortgage obligations and pass-through securities [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	2,045	2,361
Level 2 [Member] | All other corporate bonds [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	32,009	31,899
Level 2 [Member] | Redeemable preferred stock [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	22	22
Level 2 [Member] | Equity securities [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	7	25
Level 2 [Member] | Public common stock [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	0	0
Level 2 [Member] | Non-redeemable preferred stock [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	7	25
Level 2 [Member] | Other Investments [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	0	0
Level 3 [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	204	201
Other liabilities measured on a recurring basis	5	5
Level 3 [Member] | Fixed maturities [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	169	166
Level 3 [Member] | U.S. Treasury securities and obligations of U.S. government and government agencies and authorities [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	0	0
Level 3 [Member] | Obligations of states, municipalities and political subdivisions [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	11	11
Level 3 [Member] | Debt securities issued by foreign governments [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	0	0
Level 3 [Member] | Mortgage-backed securities, collateralized mortgage obligations and pass-through securities [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	0	0
Level 3 [Member] | All other corporate bonds [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	158	155
Level 3 [Member] | Redeemable preferred stock [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	0	0
Level 3 [Member] | Equity securities [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	0	0
Level 3 [Member] | Public common stock [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	0	0
Level 3 [Member] | Non-redeemable preferred stock [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	0	0
Level 3 [Member] | Other Investments [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	$ 35	$ 35

Fair Value Measurements (Deta_3

Fair Value Measurements (Details) - Financial Instruments - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Financial Instruments
Short-term securities	$ 4,987	$ 5,511
Carrying Value [Member]
Financial Instruments
Short-term securities	4,987	5,511
Debt	6,450	6,450
Commercial paper	100	100
Fair Value [Member]
Financial Instruments
Short-term securities	4,987	5,511
Debt	7,994	8,976
Commercial paper	100	100
Fair Value [Member] | Level 1 [Member]
Financial Instruments
Short-term securities	630	630
Debt	0	0
Commercial paper	0	0
Fair Value [Member] | Level 2 [Member]
Financial Instruments
Short-term securities	4,306	4,829
Debt	7,994	8,976
Commercial paper	100	100
Fair Value [Member] | Level 3 [Member]
Financial Instruments
Short-term securities	51	52
Debt	0	0
Commercial paper	$ 0	$ 0

Allowance for Expected Credit_3

Allowance for Expected Credit Losses (Details) - Changes in the Allowance for Expected Credit Losses on Premiums Receivable - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Credit Loss [Abstract]
Premiums receivable (net of allowance for expected credit losses), balance, beginning of period	$ 7,829	$ 7,909
Premiums receivable (net of allowance for expected credit losses), balance, end of period	8,167	7,829
Premiums receivable, allowance for expected credit losses [Roll Forward]
Premiums receivable, allowance for expected credit losses, beginning balance	105	49
Current period change for expected credit losses	16	103
Write-offs of uncollectible premiums receivable	11	47
Premiums receivable, allowance for expected credit losses, ending balance	$ 110	$ 105

Allowance for Expected Credit_4

Allowance for Expected Credit Losses (Details) - Changes in the Allowance for Estimated Uncollectible Reinsurance - USD ($) $ in Millions	Dec. 31, 2019	Mar. 31, 2021	Dec. 31, 2020
Reinsurance recoverables, allowance for uncollectible reinsurance
Reinsurance recoverables (net of allowance for estimated uncollectible reinsurance), balance, beginning of period		$ 8,350	$ 8,235
Reinsurance recoverables (net of allowance for estimated uncollectible reinsurance), balance, end of period	$ 8,235	8,345	8,350
Reinsurance recoverables, allowance for uncollectible reinsurance [Roll Forward]
Reinsurance recoverables, allowance for uncollectible reinsurance, beginning balance		146	92
Reinsurance recoverables, allowance for estimated uncollectible reinsurance	$ 92	146	146
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member
Current period change for estimated uncollectible reinsurance		(4)	1
Write-offs of uncollectible reinsurance recoverables		0	0
Reinsurance recoverables, allowance for uncollectible reinsurance, ending balance	$ 92	$ 142	146
Cumulative Effect, Period of Adoption, Adjustment [Member]
Reinsurance recoverables, allowance for uncollectible reinsurance [Roll Forward]
Reinsurance recoverables, allowance for uncollectible reinsurance, beginning balance			53
Reinsurance recoverables, allowance for estimated uncollectible reinsurance	53		$ 53
Reinsurance recoverables, allowance for uncollectible reinsurance, ending balance	$ 53

Allowance for Expected Credit_5

Allowance for Expected Credit Losses (Details) - Narrative - Reinsurer Concentration Risk [Member] $ in Millions	3 Months Ended
	Mar. 31, 2021USD ($)
Reinsurance Recoverables [Member] | Reinsurer Group Rated by A.M. Best [Member] | A.M. Best, Rating Provided [Member]
Reinsurance recoverables, credit quality indicator
Reinsurance recoverables, after deducting mandatory pools and associations and before allowances for expected credit losses	$ 5,830
Concentration risk percentage	87.00%
Reinsurance Recoverables [Member] | Reinsurer Group Not Rated by A.M. Best [Member]
Reinsurance recoverables, credit quality indicator
Concentration risk percentage	13.00%
Reinsurance Recoverables [Member] | Captive Insurance Companies [Member]
Reinsurance recoverables, credit quality indicator
Concentration risk percentage	6.00%
Reinsurance Recoverables [Member] | Voluntary Pools [Member]
Reinsurance recoverables, credit quality indicator
Concentration risk percentage	1.00%
Reinsurance Recoverables [Member] | Other Companies [Member]
Reinsurance recoverables, credit quality indicator
Concentration risk percentage	6.00%
Reinsurance Recoverables Rated by A.M. Best [Member] | Reinsurer Group Rated by A.M. Best [Member] | A.M. Best, A- Rating Or Better [Member]
Reinsurance recoverables, credit quality indicator
Concentration risk percentage	94.00%

Allowance for Expected Credit_6

Allowance for Expected Credit Losses (Details) - Changes in the Allowance for Expected Credit Losses on Contractholder Receivables (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Credit Loss [Abstract]
Contractholder receivables (net of the allowance for expected credit losses), balance, beginning of period	$ 4,242	$ 4,599
Contractholder receivables (net of the allowance for expected credit losses), balance, end of period	4,271	4,242
Contractholder receivables, allowance for expected credit losses [Roll Forward]
Contractholder receivables, allowance for expected credit losses, beginning balance	19	20
Current period change for expected credit losses	0	1
Write-offs of uncollectible contractholder receivables	0	2
Contractholder receivables, allowance for expected credit losses, ending balance	$ 19	$ 19

Goodwill and Other Intangible_3

Goodwill and Other Intangible Assets (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Goodwill by segment
Goodwill	$ 4,017	$ 3,976
Reportable Segments [Member] | Business Insurance [Member]
Goodwill by segment
Goodwill	2,618	2,613
Reportable Segments [Member] | Bond & Specialty Insurance [Member]
Goodwill by segment
Goodwill	550	550
Reportable Segments [Member] | Personal Insurance [Member]
Goodwill by segment
Goodwill	823	787
Reportable Segments [Member] | Personal Insurance [Member] | Business Acquisition [Member]
Goodwill by segment
Goodwill	33
Other [Member]
Goodwill by segment
Goodwill	$ 26	$ 26

Goodwill and Other Intangible_4

Goodwill and Other Intangible Assets (Details) - Other Intangible Assets - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Other intangible assets by major asset class
Intangible assets subject to amortization, gross carrying amount	$ 310		$ 306
Intangible assets subject to amortization, accumulated amortization	219		215
Intangible assets subject to amortization, net	91		91
Intangible assets not subject to amortization	227		226
Total other intangible assets, gross carrying amount	537		532
Total other intangible assets, net	318		317
Amortization expense of intangible assets	4	$ 4
Estimated intangible asset amortization expense, remainder of 2021	11
Estimated intangible asset amortization expense, 2022	14
Estimated intangible asset amortization expense, 2023	13
Estimated intangible asset amortization expense, 2024	13
Estimated intangible asset amortization expense, 2025	12
Customer-related [Member]
Other intangible assets by major asset class
Intangible assets subject to amortization, gross carrying amount	105		101
Intangible assets subject to amortization, accumulated amortization	34		31
Intangible assets subject to amortization, net	71		70
Contract-based [Member]
Other intangible assets by major asset class
Intangible assets subject to amortization, gross carrying amount	205		205
Intangible assets subject to amortization, accumulated amortization	185		184
Intangible assets subject to amortization, net	20		$ 21
Insurance Contracts Acquired in Business Combination [Member]
Other intangible assets by major asset class
Estimated intangible asset amortization expense, remainder of 2021	3
Estimated intangible asset amortization expense, 2022	3
Estimated intangible asset amortization expense, 2023	3
Estimated intangible asset amortization expense, 2024	2
Estimated intangible asset amortization expense, 2025	$ 2

Insurance Claim Reserves (Detai

Insurance Claim Reserves (Details) - Reserve Detail for Claims and Claim Adjustment Expenses - USD ($) $ in Millions	Dec. 31, 2019	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Reconciliation of beginning and ending reserve balances for claims and claim adjustment expenses [Roll Forward]
Claims and claim adjustment expense reserves at beginning of year		$ 54,521
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member
Reinsurance recoverables, allowance for estimated uncollectible reinsurance	$ 92	142		$ 146
Claims and claim adjustment expense reserves at end of period		55,340
Cumulative Effect, Period of Adoption, Adjustment [Member]
Reconciliation of beginning and ending reserve balances for claims and claim adjustment expenses [Roll Forward]
Reinsurance recoverables, allowance for estimated uncollectible reinsurance	53
Property-casualty [Member]
Reconciliation of beginning and ending reserve balances for claims and claim adjustment expenses [Roll Forward]
Claims and claim adjustment expense reserves at beginning of year		54,510	$ 51,836
Reinsurance recoverables on unpaid losses		8,153	8,035
Net reserves at beginning of year		46,357	43,854
Estimated claims and claim adjustment expenses for claims arising in the current year		5,242	4,763
Estimated decrease in claims and claim adjustment expenses for claims arising in prior years		(294)	(3)
Total increases		4,948	4,760
Claims and claim adjustment expense payments for claims arising in current year		1,059	947
Claims and claim adjustment expense payments for claims arising in prior years		3,012	3,439
Total payments		4,071	4,386
Unrealized foreign exchange (gain) loss		28	(210)
Net reserves at end of period	43,854	47,262	44,018
Reinsurance recoverables on unpaid losses	8,035	8,068	7,926
Claims and claim adjustment expense reserves at end of period	51,836	55,330	$ 51,944
Amount of increase in gross claims and claim adjustment expense reserves		820
Amount of decrease in reinsurance recoverables on unpaid losses		85
Property-casualty [Member] | Cumulative Effect, Period of Adoption, Adjustment [Member]
Reconciliation of beginning and ending reserve balances for claims and claim adjustment expenses [Roll Forward]
Reinsurance recoverables, allowance for estimated uncollectible reinsurance	$ 53
Accident and health [Member]
Reconciliation of beginning and ending reserve balances for claims and claim adjustment expenses [Roll Forward]
Claims and claim adjustment expense reserves at beginning of year		11
Claims and claim adjustment expense reserves at end of period		$ 10

Insurance Claim Reserves (Det_2

Insurance Claim Reserves (Details) - Prior Year Reserve Development - Property-casualty [Member] - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Liability for claims and claim adjustment expense
Net favorable prior year reserve development included in estimated claims and claim adjustment expenses incurred for claims arising in prior years	$ 294	$ 3
Net favorable prior year reserve development impacting the Company's results of operations	317	27
Accretion expense	12	12
Business Insurance [Member]
Liability for claims and claim adjustment expense
Net favorable prior year reserve development impacting the Company's results of operations	134	5
Subrogation benefit	10
Bond & Specialty Insurance [Member]
Liability for claims and claim adjustment expense
Net favorable prior year reserve development impacting the Company's results of operations	15	0
Personal Insurance [Member]
Liability for claims and claim adjustment expense
Net favorable prior year reserve development impacting the Company's results of operations	168	$ 22
Subrogation benefit	$ 62

Other Comprehensive Income an_3

Other Comprehensive Income and Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Accumulated other comprehensive income [Roll Forward]
Balance, beginning of period	$ 29,201
Other comprehensive loss, net of taxes	(1,211)	$ (689)
Balance, end of period	28,269	25,204
Pre-tax components of other comprehensive loss and the related income tax expense (benefit)
Other comprehensive income (loss), before taxes	(1,545)	(826)
Income tax expense (benefit)	(334)	(137)
Other comprehensive loss, net of taxes	(1,211)	(689)
Accumulated Other Comprehensive Income [Member]
Accumulated other comprehensive income [Roll Forward]
Balance, beginning of period	2,502	640
Other comprehensive income (loss) before reclassifications	(1,220)
Amounts reclassified from accumulated other comprehensive income, net of tax	9
Other comprehensive loss, net of taxes	(1,211)	(689)
Balance, end of period	1,291	(49)
Pre-tax components of other comprehensive loss and the related income tax expense (benefit)
Other comprehensive income (loss), before taxes	(1,545)	(826)
Income tax expense (benefit)	(334)	(137)
Other comprehensive loss, net of taxes	(1,211)	(689)
Changes in Net Unrealized Gains on Investment Securities Having No Credit Losses Recognized in the Consolidated Statement of Income [Member]
Accumulated other comprehensive income [Roll Forward]
Balance, beginning of period	3,892
Other comprehensive income (loss) before reclassifications	(1,246)
Amounts reclassified from accumulated other comprehensive income, net of tax	(11)
Other comprehensive loss, net of taxes	(1,257)	(457)
Balance, end of period	2,635
Pre-tax components of other comprehensive loss and the related income tax expense (benefit)
Other comprehensive income (loss), before taxes	(1,596)	(575)
Income tax expense (benefit)	(339)	(118)
Other comprehensive loss, net of taxes	(1,257)	(457)
Changes in Net Unrealized Gains on Investment Securities Having Credit Losses Recognized in the Consolidated Statement of Income [Member]
Accumulated other comprehensive income [Roll Forward]
Balance, beginning of period	182
Other comprehensive income (loss) before reclassifications	0
Amounts reclassified from accumulated other comprehensive income, net of tax	0
Other comprehensive loss, net of taxes	0	(4)
Balance, end of period	182
Pre-tax components of other comprehensive loss and the related income tax expense (benefit)
Other comprehensive income (loss), before taxes	0	(6)
Income tax expense (benefit)	0	(2)
Other comprehensive loss, net of taxes	0	(4)
Net Benefit Plan Assets and Obligations Recognized in Shareholders' Equity [Member]
Accumulated other comprehensive income [Roll Forward]
Balance, beginning of period	(832)
Other comprehensive income (loss) before reclassifications	0
Amounts reclassified from accumulated other comprehensive income, net of tax	20
Other comprehensive loss, net of taxes	20	18
Balance, end of period	(812)
Pre-tax components of other comprehensive loss and the related income tax expense (benefit)
Other comprehensive income (loss), before taxes	25	23
Income tax expense (benefit)	5	5
Other comprehensive loss, net of taxes	20	18
Net Unrealized Foreign Currency Translation [Member]
Accumulated other comprehensive income [Roll Forward]
Balance, beginning of period	(740)
Other comprehensive income (loss) before reclassifications	26
Amounts reclassified from accumulated other comprehensive income, net of tax	0
Other comprehensive loss, net of taxes	26	(246)
Balance, end of period	(714)
Pre-tax components of other comprehensive loss and the related income tax expense (benefit)
Other comprehensive income (loss), before taxes	26	(268)
Income tax expense (benefit)	0	(22)
Other comprehensive loss, net of taxes	$ 26	$ (246)

Other Comprehensive Income an_4

Other Comprehensive Income and Accumulated Other Comprehensive Income (Details) - Reclassifications - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Reclassification adjustment impacting net realized investment gains (losses) on the income statement	$ (44)	$ 98
Reclassification adjustment impacting claims and claim adjustment expenses on the income statement	4,970	4,789
Reclassification adjustment impacting general and administrative expense on the income statement	1,163	1,137
Total reclassifications	(891)	(720)
Income tax (expense) benefit	(158)	(120)
Amounts reclassified from accumulated other comprehensive income, net of taxes	(733)	(600)
Accumulated Other Comprehensive Income [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Total reclassifications	11	23
Income tax (expense) benefit	2	4
Amounts reclassified from accumulated other comprehensive income, net of taxes	9	19
Changes in Net Unrealized Gains on Investment Securities Having No Credit Losses Recognized in the Consolidated Statement of Income [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Reclassification adjustment impacting net realized investment gains (losses) on the income statement	(14)	2
Income tax (expense) benefit	(3)	0
Amounts reclassified from accumulated other comprehensive income, net of taxes	(11)	2
Changes in Net Unrealized Gains on Investment Securities Having Credit Losses Recognized in the Consolidated Statement of Income [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Reclassification adjustment impacting net realized investment gains (losses) on the income statement	0	0
Income tax (expense) benefit	0	0
Amounts reclassified from accumulated other comprehensive income, net of taxes	0	0
Net Benefit Plan Assets and Obligations Recognized in Shareholders' Equity [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Reclassification adjustment impacting claims and claim adjustment expenses on the income statement	10	9
Reclassification adjustment impacting general and administrative expense on the income statement	15	12
Total reclassifications	25	21
Income tax (expense) benefit	5	4
Amounts reclassified from accumulated other comprehensive income, net of taxes	20	17
Net Unrealized Foreign Currency Translation [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Reclassification adjustment impacting net realized investment gains (losses) on the income statement	0	0
Income tax (expense) benefit	0	0
Amounts reclassified from accumulated other comprehensive income, net of taxes	$ 0	$ 0

Common Share Repurchases (Detai

Common Share Repurchases (Details) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2021USD ($)$ / sharesshares
Treasury Stock Transactions, Excluding Value of Shares Reissued [Abstract]
Number of shares repurchased (in shares) | shares	2.4
Cost of shares repurchased	$ 356
Average cost per share repurchased (in dollars per share) | $ / shares	$ 147.87
Number of shares acquired to cover tax withholding costs and exercise costs (in shares) | shares	0.3
Cost of shares acquired to cover tax withholding costs and exercise costs	$ 41
Remaining capacity under share repurchase authorization	$ 805

Common Share Repurchases (Det_2

Common Share Repurchases (Details) - Additional Shares $ in Billions	Apr. 20, 2021USD ($)
Subsequent Event [Member]
Class of Treasury Stock
Additional share repurchase authorization	$ 5

Earnings per Share (Details)

Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Earnings Per Share Reconciliation [Abstract]
Net income	$ 733	$ 600
Participating share-based awards — allocated income	(5)	(5)
Net income available to common shareholders -- basic	728	595
Net income available to common shareholders -- diluted	$ 728	$ 595
Weighted average shares outstanding, basic (in shares)	252.1	254.4
Weighted average effects of dilutive securities - stock options and performance shares (in shares)	2	1.5
Weighted average shares outstanding, diluted (in shares)	254.1	255.9
Net income per common share, basic (in dollars per share)	$ 2.89	$ 2.34
Net income per common share, diluted (in dollars per share)	$ 2.87	$ 2.33

Share-Based Incentive Compens_3

Share-Based Incentive Compensation (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Share-based Payment Arrangement [Abstract]
Stock options vested at end of period, number (in shares)	8,045,981
Stock options vested at end of period, weighted average exercise price (in dollars per share)	$ 122.61
Stock options vested at end of period, weighted average contractual life remaining (in years)	6 years 6 months
Stock options vested at end of period, aggregate intrinsic value	$ 224
Stock options exercisable at end of period, number (in shares)	4,930,089
Stock options exercisable at end of period, weighted average exercise price (in dollars per share)	$ 116.37
Stock options exercisable at end of period, weighted average contractual life remaining (in years)	5 years
Stock options exercisable at end of period, aggregate intrinsic value	$ 168
Total compensation cost recognized in earnings for all share-based incentive compensation awards	53	$ 46
Tax benefit recognized in earnings related to compensation costs	9	$ 8
Total unrecognized compensation cost related to all nonvested share-based incentive compensation awards	$ 240
Weighted-average period of recognition for unrecognized compensation cost (in years)	2 years 2 months 12 days

Pension Plans, Retirement Ben_3

Pension Plans, Retirement Benefits and Savings Plans (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Pension Plans [Member]
Defined benefit plan disclosure
Service cost	$ 35	$ 33
Interest cost on benefit obligation	21	29
Expected return on plan assets	(69)	(69)
Net periodic benefit cost (benefit), amortization of unrecognized prior service benefit	0	0
Net periodic benefit cost (benefit), amortization of unrecognized net actuarial (gain) loss	27	23
Total non-service cost (benefit)	(21)	(17)
Net periodic benefit cost (benefit)	14	16
Pension Plans [Member] | Claims and claim adjustment expenses [Member]
Defined benefit plan disclosure
Service cost	14	14
Total non-service cost (benefit)	(9)	(7)
Pension Plans [Member] | General and administrative expenses [Member]
Defined benefit plan disclosure
Service cost	21	19
Total non-service cost (benefit)	(12)	(10)
Postretirement Benefit Plans [Member]
Defined benefit plan disclosure
Service cost	0	0
Interest cost on benefit obligation	1	1
Expected return on plan assets	0	0
Net periodic benefit cost (benefit), amortization of unrecognized prior service benefit	(1)	(2)
Net periodic benefit cost (benefit), amortization of unrecognized net actuarial (gain) loss	(1)	0
Total non-service cost (benefit)	(1)	(1)
Net periodic benefit cost (benefit)	(1)	(1)
Postretirement Benefit Plans [Member] | Claims and claim adjustment expenses [Member]
Defined benefit plan disclosure
Service cost	0	0
Total non-service cost (benefit)	0	0
Postretirement Benefit Plans [Member] | General and administrative expenses [Member]
Defined benefit plan disclosure
Service cost	0	0
Total non-service cost (benefit)	$ (1)	$ (1)

Leases (Details)

Leases (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Leases [Abstract]
Operating leases	$ 23	$ 24
Short-term leases	0	0
Lease expense	23	24
Less: sublease income	0	0
Net lease cost	23	24
Cash payments to settle a lease liability reported in cash flows	26	27
Right-of-use assets obtained in exchange for new lease liabilities	$ 12	$ 14
Weighted average discount rate (percent)	2.46%	2.97%
Weighted average remaining lease term (in years)	4 years 10 months 24 days	5 years

Contingencies, Commitments an_2

Contingencies, Commitments and Guarantees (Details) - Commitments - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Contingencies, Commitments and Guarantees [Abstract]
Unfunded commitments to private equity limited partnerships, real estate partnerships and others	$ 1,660	$ 1,760

Contingencies, Commitments an_3

Contingencies, Commitments and Guarantees (Details) - Guarantees $ in Millions	Mar. 31, 2021USD ($)
Indemnifications related to the sale of businesses [Member]
Guarantor obligations
Maximum amount of contingent obligation	$ 351
Guarantees of certain insurance policy obligations [Member]
Guarantor obligations
Maximum amount of contingent obligation	480
Amount indemnified by a third party	$ 480