The Travelers Companies, Inc. (TRV) 10-Q 20 Jul 21 2021 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2021	Jul. 15, 2021
Document and Entity Information
Document type	10-Q
Document quarterly report	true
Document period end date	Jun. 30, 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		249,492,900
Central index key	0000086312
Amendment flag	false
Current fiscal year end date	--12-31
Document fiscal year focus	2021
Document fiscal period focus	Q2

Consolidated Statement of Incom

Consolidated Statement of Income (Loss) (Unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Revenues
Premiums	$ 7,616	$ 6,955	$ 15,002	$ 14,184
Net investment income	818	268	1,519	879
Fee income	104	114	205	222
Net realized investment gains (losses)	61	13	105	(85)
Other revenues	88	51	169	109
Total revenues	8,687	7,401	17,000	15,309
Claims and expenses
Claims and claim adjustment expenses	5,045	5,107	10,015	9,896
Amortization of deferred acquisition costs	1,254	1,173	2,461	2,351
General and administrative expenses	1,174	1,121	2,337	2,258
Interest expense	83	85	165	169
Total claims and expenses	7,556	7,486	14,978	14,674
Income (loss) before income taxes	1,131	(85)	2,022	635
Income tax expense (benefit)	197	(45)	355	75
Net income (loss)	$ 934	$ (40)	$ 1,667	$ 560
Net income (loss) per share
Basic (in dollars per share)	$ 3.70	$ (0.16)	$ 6.58	$ 2.19
Diluted (in dollars per share)	$ 3.66	$ (0.16)	$ 6.53	$ 2.19
Weighted average number of common shares outstanding
Basic (in shares)	250.7	251.6	251.4	253.6
Diluted (in shares)	253.1	251.6	253.6	254.7
Cash dividends declared per common share (in dollars per share)	$ 0.88	$ 0.85	$ 1.73	$ 1.67

Consolidated Statement of Compr

Consolidated Statement of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 934	$ (40)	$ 1,667	$ 560
Other comprehensive income (loss)
Changes in net unrealized gains on investment securities having no credit losses recognized in the consolidated statement of income (loss)	533	2,359	(1,063)	1,784
Changes in net unrealized gains on investment securities having credit losses recognized in the consolidated statement of income (loss)	0	3	0	(3)
Net changes in benefit plan assets and obligations	26	21	51	44
Net changes in unrealized foreign currency translation	40	52	66	(216)
Other comprehensive income (loss) before income taxes	599	2,435	(946)	1,609
Income tax expense (benefit)	121	504	(213)	367
Other comprehensive income (loss), net of taxes	478	1,931	(733)	1,242
Comprehensive income	$ 1,412	$ 1,891	$ 934	$ 1,802

Consolidated Balance Sheet (Una

Consolidated Balance Sheet (Unaudited at June 30, 2021) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Assets
Fixed maturities, available for sale, at fair value (amortized cost $71,465 and $68,830; allowance for expected credit losses of $2 and $2)	$ 75,576	$ 74,003
Equity securities, at fair value (cost $394 and $387)	513	453
Real estate investments	1,015	1,026
Short-term securities	5,703	5,511
Other investments	3,738	3,430
Total investments	86,545	84,423
Cash	689	721
Investment income accrued	608	603
Premiums receivable (net of allowance for expected credit losses of $105 and $105)	8,555	7,829
Reinsurance recoverables (net of allowance for estimated uncollectible reinsurance of $135 and $146)	8,209	8,350
Ceded unearned premiums	1,080	772
Deferred acquisition costs	2,501	2,358
Contractholder receivables (net of allowance for expected credit losses of $19 and $19)	4,016	4,242
Goodwill	4,020	3,976
Other intangible assets	314	317
Other assets	3,222	3,173
Total assets	119,759	116,764
Liabilities
Claims and claim adjustment expense reserves	55,906	54,521
Unearned premium reserves	16,210	15,222
Contractholder payables	4,035	4,261
Payables for reinsurance premiums	638	356
Deferred taxes	415	558
Debt	7,290	6,550
Other liabilities	6,109	6,095
Total liabilities	90,603	87,563
Shareholders’ equity
Common stock (1,750.0 shares authorized; 249.5 and 252.4 shares issued and outstanding)	24,002	23,743
Retained earnings	39,998	38,771
Accumulated other comprehensive income	1,769	2,502
Treasury stock, at cost (532.6 and 527.3 shares)	(36,613)	(35,815)
Total shareholders’ equity	29,156	29,201
Total liabilities and shareholders’ equity	$ 119,759	$ 116,764

Consolidated Balance Sheet Pare

Consolidated Balance Sheet Parentheticals (Unaudited at June 30, 2021) - USD ($) shares in Millions, $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Fixed maturities, available for sale, amortized cost	$ 71,465	$ 68,830
Fixed maturities, available for sale, allowance for expected credit losses	2	2
Equity securities, cost	394	387
Premiums receivable, allowance for expected credit losses	105	105
Reinsurance recoverables, allowance for estimated uncollectible reinsurance	135	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)	249.5	252.4
Common stock, shares outstanding (in shares)	249.5	252.4
Treasury stock, at cost (in shares)	532.6	527.3

Consolidated Statement of Chang

Consolidated Statement of Changes in Shareholders' Equity (Unaudited) - USD ($) $ in Thousands, shares 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		$ 23,469,000	$ 36,977,000	$ (43,000)	$ 640,000	$ (35,143,000)
Balance, beginning of period at Dec. 31, 2019		23,469,000	36,977,000	$ (43,000)	640,000	(35,143,000)
Shareholders' Equity [Roll Forward]
Employee share-based compensation		56,000
Compensation amortization under share-based plans and other changes		81,000
Net income (loss)	$ 560,000		560,000
Dividends			(428,000)
Other			3,000
Other comprehensive income (loss)	1,242,000				1,242,000
Treasury stock acquired — share repurchase authorizations						(425,000)
Net shares acquired related to employee share-based compensation plans						(46,000)
Balance, end of period at Jun. 30, 2020	26,943,000	23,606,000	37,069,000		1,882,000	(35,614,000)
Balance, beginning of year (in shares) at Dec. 31, 2019							255.5
Common shares outstanding
Treasury stock acquired - share repurchase authorizations (in shares)							(3.5)
Net shares issued under employee share-based compensation plans (in shares)							1.2
Balance, end of period (in shares) at Jun. 30, 2020							253.2
Shareholders' Equity [Roll Forward]
Shareholders' equity		23,542,000	37,325,000		(49,000)	(35,614,000)
Balance, beginning of period at Mar. 31, 2020		23,542,000	37,325,000		(49,000)	(35,614,000)
Shareholders' Equity [Roll Forward]
Employee share-based compensation		29,000
Compensation amortization under share-based plans and other changes		35,000
Net income (loss)	(40,000)		(40,000)
Dividends			(218,000)
Other			2,000
Other comprehensive income (loss)	1,931,000				1,931,000
Treasury stock acquired — share repurchase authorizations						0
Net shares acquired related to employee share-based compensation plans						0
Balance, end of period at Jun. 30, 2020	26,943,000	23,606,000	37,069,000		1,882,000	(35,614,000)
Balance, beginning of year (in shares) at Mar. 31, 2020							252.8
Common shares outstanding
Treasury stock acquired - share repurchase authorizations (in shares)							0
Net shares issued under employee share-based compensation plans (in shares)							0.4
Balance, end of period (in shares) at Jun. 30, 2020							253.2
Shareholders' Equity [Roll Forward]
Shareholders' equity	26,943,000	23,606,000	37,069,000		1,882,000	(35,614,000)
Shareholders' equity	29,201,000	23,743,000	38,771,000		2,502,000	(35,815,000)
Balance, beginning of period at Dec. 31, 2020	29,201,000	23,743,000	38,771,000		2,502,000	(35,815,000)
Shareholders' Equity [Roll Forward]
Employee share-based compensation		169,000
Compensation amortization under share-based plans and other changes		90,000
Net income (loss)	1,667,000		1,667,000
Dividends			(440,000)
Other			0
Other comprehensive income (loss)	(733,000)				(733,000)
Treasury stock acquired — share repurchase authorizations	(756,000)					(756,000)
Net shares acquired related to employee share-based compensation plans	(42,000)					(42,000)
Balance, end of period at Jun. 30, 2021	$ 29,156,000	24,002,000	39,998,000		1,769,000	(36,613,000)
Balance, beginning of year (in shares) at Dec. 31, 2020	252.4						252.4
Common shares outstanding
Treasury stock acquired - share repurchase authorizations (in shares)	(5)						(5)
Net shares issued under employee share-based compensation plans (in shares)							2.1
Balance, end of period (in shares) at Jun. 30, 2021	249.5						249.5
Shareholders' Equity [Roll Forward]
Shareholders' equity		23,905,000	39,285,000		1,291,000	(36,212,000)
Balance, beginning of period at Mar. 31, 2021		23,905,000	39,285,000		1,291,000	(36,212,000)
Shareholders' Equity [Roll Forward]
Employee share-based compensation		61,000
Compensation amortization under share-based plans and other changes		36,000
Net income (loss)	$ 934,000		934,000
Dividends			(224,000)
Other			3,000
Other comprehensive income (loss)	478,000				478,000
Treasury stock acquired — share repurchase authorizations	(400,000)					(400,000)
Net shares acquired related to employee share-based compensation plans	(144)					(1,000)
Balance, end of period at Jun. 30, 2021	$ 29,156,000	24,002,000	39,998,000		1,769,000	(36,613,000)
Balance, beginning of year (in shares) at Mar. 31, 2021							251.5
Common shares outstanding
Treasury stock acquired - share repurchase authorizations (in shares)	(2.6)						(2.6)
Net shares issued under employee share-based compensation plans (in shares)							0.6
Balance, end of period (in shares) at Jun. 30, 2021	249.5						249.5
Shareholders' Equity [Roll Forward]
Shareholders' equity	$ 29,156,000	$ 24,002,000	$ 39,998,000		$ 1,769,000	$ (36,613,000)

Consolidated Statement of Cash

Consolidated Statement of Cash Flows (Unaudited) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Cash flows from operating activities
Net income	$ 1,667	$ 560
Adjustments to reconcile net income to net cash provided by operating activities:
Net realized investment (gains) losses	(105)	85
Depreciation and amortization	450	391
Deferred federal income tax expense (benefit)	57	(71)
Amortization of deferred acquisition costs	2,461	2,351
Equity in (income) loss from other investments	(513)	186
Premiums receivable	(718)	(571)
Reinsurance recoverables	154	60
Deferred acquisition costs	(2,601)	(2,453)
Claims and claim adjustment expense reserves	1,313	1,455
Unearned premium reserves	968	643
Other operating activities	(94)	(344)
Net cash provided by operating activities	3,039	2,292
Cash flows from investing activities
Proceeds from maturities of fixed maturities	4,347	3,071
Proceeds from sales of investments:
Fixed maturities	2,482	1,220
Equity securities	45	54
Other investments	195	139
Purchases of investments:
Fixed maturities	(9,462)	(4,790)
Equity securities	(41)	(59)
Real estate investments	(14)	(24)
Other investments	(221)	(228)
Net purchases of short-term securities	(194)	(1,147)
Securities transactions in course of settlement	229	94
Acquisition, net of cash acquired	(38)	0
Other investing activities	(113)	(144)
Net cash used in investing activities	(2,785)	(1,814)
Cash flows from financing activities
Treasury stock acquired — share repurchase authorizations	(756)	(425)
Treasury stock acquired — net employee share-based compensation	(42)	(46)
Dividends paid to shareholders	(436)	(426)
Issuance of debt	739	490
Issuance of common stock — employee share options	206	65
Net cash used in financing activities	(289)	(342)
Effect of exchange rate changes on cash	3	(7)
Net increase (decrease) in cash	(32)	129
Cash at beginning of year	721	494
Cash at end of period	689	623
Supplemental disclosure of cash flow information
Income taxes paid	342	17
Interest paid	$ 163	$ 166

Basis of Presentation and Accou

Basis of Presentation and Accounting Policies	6 Months Ended
	Jun. 30, 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	6 Months Ended
	Jun. 30, 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 (loss) and total assets by reportable business segments: (For the three months ended June 30, in millions) Business Bond & Specialty Personal Total 2021 Premiums $ 3,880 $ 776 $ 2,960 $ 7,616 Net investment income 615 64 139 818 Fee income 97 — 7 104 Other revenues 57 7 24 88 Total segment revenues (1) $ 4,649 $ 847 $ 3,130 $ 8,626 Segment income (1) $ 643 $ 187 $ 121 $ 951 2020 Premiums $ 3,735 $ 693 $ 2,527 $ 6,955 Net investment income 180 42 46 268 Fee income 108 — 6 114 Other revenues 36 5 10 51 Total segment revenues (1) $ 4,059 $ 740 $ 2,589 $ 7,388 Segment income (loss) (1) $ (58) $ 72 $ 10 $ 24 _________________________________________________________ (1) Segment revenues for reportable business segments exclude net realized investment gains (losses) and revenues included in "interest expense and other." Segment income (loss) for reportable business segments equals net income (loss) excluding the after-tax impact of net realized investment gains (losses) and income (loss) from "interest expense and other." (For the six months ended June 30, in millions) Business Bond & Specialty Personal Total 2021 Premiums $ 7,679 $ 1,519 $ 5,804 $ 15,002 Net investment income 1,138 123 258 1,519 Fee income 192 — 13 205 Other revenues 110 12 47 169 Total segment revenues (1) $ 9,119 $ 1,654 $ 6,122 $ 16,895 Segment income (1) $ 960 $ 324 $ 435 $ 1,719 2020 Premiums $ 7,599 $ 1,360 $ 5,225 $ 14,184 Net investment income 633 97 149 879 Fee income 210 — 12 222 Other revenues 67 10 32 109 Total segment revenues (1) $ 8,509 $ 1,467 $ 5,418 $ 15,394 Segment income (1) $ 231 $ 194 $ 346 $ 771 (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 Six Months Ended (in millions) 2021 2020 2021 2020 Revenue reconciliation Earned premiums Business Insurance: Domestic: Workers’ compensation $ 810 $ 818 $ 1,621 $ 1,717 Commercial automobile 709 676 1,404 1,360 Commercial property 556 514 1,087 1,022 General liability 618 580 1,225 1,181 Commercial multi-peril 899 883 1,769 1,769 Other 14 11 28 23 Total Domestic 3,606 3,482 7,134 7,072 International 274 253 545 527 Total Business Insurance 3,880 3,735 7,679 7,599 Bond & Specialty Insurance: Domestic: Fidelity and surety 276 271 542 528 General liability 347 296 678 583 Other 55 60 111 118 Total Domestic 678 627 1,331 1,229 International 98 66 188 131 Total Bond & Specialty Insurance 776 693 1,519 1,360 Personal Insurance: Domestic: Automobile 1,405 1,154 2,775 2,505 Homeowners and Other 1,377 1,221 2,685 2,397 Total Domestic 2,782 2,375 5,460 4,902 International 178 152 344 323 Total Personal Insurance 2,960 2,527 5,804 5,225 Total earned premiums 7,616 6,955 15,002 14,184 Net investment income 818 268 1,519 879 Fee income 104 114 205 222 Other revenues 88 51 169 109 Total segment revenues 8,626 7,388 16,895 15,394 Other revenues — — — — Net realized investment gains (losses) 61 13 105 (85) Total revenues $ 8,687 $ 7,401 $ 17,000 $ 15,309 Income reconciliation, net of tax Total segment income $ 951 $ 24 $ 1,719 $ 771 Interest Expense and Other (1) (72) (74) (141) (145) Core income (loss) 879 (50) 1,578 626 Net realized investment gains (losses) 47 10 81 (66) Impact of changes in tax laws and/or tax rates (2) 8 — 8 — Net income (loss) $ 934 $ (40) $ 1,667 $ 560 _________________________________________________________ (1) The primary component of Interest Expense and Other was after-tax interest expense of $65 million and $67 million for the three months ended June 30, 2021 and 2020, respectively, and $130 million and $133 million for the six months ended June 30, 2021 and 2020, respectively. (2) Impact is recognized in the accounting period in which the change is enacted. (in millions) June 30, December 31, Asset reconciliation Business Insurance $ 90,219 $ 88,422 Bond & Specialty Insurance 10,073 9,420 Personal Insurance 18,846 18,328 Total assets by reportable segment 119,138 116,170 Other assets (1) 621 594 Total consolidated assets $ 119,759 $ 116,764 _________________________________________________________ (1) The primary components of other assets at both June 30, 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

Investments	6 Months Ended
	Jun. 30, 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 June 30, 2021, in millions) Gains Losses U.S. Treasury securities and obligations of U.S. government and government agencies and authorities $ 3,560 $ — $ 38 $ 8 $ 3,590 Obligations of states, municipalities and political subdivisions: Local general obligation 17,590 — 1,188 24 18,754 Revenue 11,048 — 787 12 11,823 State general obligation 1,324 — 85 1 1,408 Pre-refunded 3,482 — 205 — 3,687 Total obligations of states, municipalities and political subdivisions 33,444 — 2,265 37 35,672 Debt securities issued by foreign governments 1,024 — 15 3 1,036 Mortgage-backed securities, collateralized mortgage obligations and pass-through securities 1,722 — 99 1 1,820 All other corporate bonds 31,703 2 1,813 70 33,444 Redeemable preferred stock 12 — 2 — 14 Total $ 71,465 $ 2 $ 4,232 $ 119 $ 75,576 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 $3.69 billion and $3.54 billion at June 30, 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 $2.48 billion and $1.22 billion during the six months ended June 30, 2021 and 2020, respectively. Gross gains of $43 million and $31 million and gross losses of $5 million and $1 million were realized on those sales during the six months ended June 30, 2021 and 2020, respectively. Equity Securities The cost and fair value of investments in equity securities were as follows: Fair (at June 30, 2021, in millions) Cost Gross Gains Gross Losses Value Public common stock $ 359 $ 111 $ 3 $ 467 Non-redeemable preferred stock 35 11 — 46 Total $ 394 $ 122 $ 3 $ 513 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 six months ended June 30, 2021 and 2020, the Company recognized $51 million and $(33) million of net gains (losses) on equity securities still held as of June 30, 2021 and 2020, respectively. Net realized losses on equity securities still held for the first six months 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 June 30, 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 June 30, 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 $ 451 $ 8 $ — $ — $ 451 $ 8 Obligations of states, municipalities and political subdivisions 2,719 37 — — 2,719 37 Debt securities issued by foreign governments 273 3 — — 273 3 Mortgage-backed securities, collateralized mortgage obligations and pass-through securities 45 1 1 — 46 1 All other corporate bonds 3,007 68 64 2 3,071 70 Total $ 6,495 $ 117 $ 65 $ 2 $ 6,560 $ 119 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 June 30, 2021, the Company had no fixed maturity investments reported at fair value for which fair value was less than 80% of amortized cost. Credit Impairment Charges The following tables present changes in the allowance for expected credit losses on fixed maturities classified as available for sale for the category of All Other Corporate Bonds (no other categories of fixed maturities currently have an allowance for expected credit losses): Fixed Maturities At and For the Three Months Ended June 30, 2021 At and For the Three Months Ended June 30, 2020 (in millions) All Other Corporate Bonds All Other Corporate Bonds Balance, beginning of period $ 2 $ 4 Additions for expected credit losses on securities where no credit losses were previously recognized 1 4 Additions (reductions) for expected credit losses on securities where credit losses were previously recognized (1) — 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, end of period $ 2 $ 8 (1) Credit impairment charges recognized in net realized investment gains (losses) for the three months ended June 30, 2021 and 2020 included $0 million and $2 million, respectively, 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. Fixed Maturities At and For the Six Months Ended June 30, 2021 At and For the Six Months Ended June 30, 2020 (in millions) All Other Corporate Bonds All Other Corporate Bonds Balance, beginning of period $ 2 $ — Additions for expected credit losses on securities where no credit losses were previously recognized 1 8 Additions (reductions) for expected credit losses on securities where credit losses were previously recognized (1) — 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, end of period $ 2 $ 8 (1) Credit impairment charges recognized in net realized investment gains (losses) for the six months ended June 30, 2021 and 2020 included $0 million and $14 million, respectively, 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 included in net realized investment gains (losses) in the consolidated statement of income (loss) were $0 million and $46 million for the three months ended June 30, 2021 and 2020, respectively and $0 million and $62 million for the six months ended June 30, 2021 and 2020, respectively. Credit losses related to the fixed maturity portfolio for the three months and six months ended June 30, 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	6 Months Ended
	Jun. 30, 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 June 30, 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 June 30, 2021 and December 31, 2020 was $4 million and $5 million, respectively, and 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 June 30, 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 $ 3,590 $ 3,590 $ — $ — Obligations of states, municipalities and political subdivisions 35,672 — 35,668 4 Debt securities issued by foreign governments 1,036 — 1,036 — Mortgage-backed securities, collateralized mortgage obligations and pass-through securities 1,820 — 1,806 14 All other corporate bonds 33,444 — 33,299 145 Redeemable preferred stock 14 — 14 — Total fixed maturities 75,576 3,590 71,823 163 Equity securities Public common stock 467 467 — — Non-redeemable preferred stock 46 21 25 — Total equity securities 513 488 25 — Other investments 53 18 — 35 Total $ 76,142 $ 4,096 $ 71,848 $ 198 Other liabilities $ 4 $ — $ — $ 4 (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 six months ended June 30, 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 June 30, 2021, in millions) Carrying Fair Level 1 Level 2 Level 3 Financial assets Short-term securities $ 5,703 $ 5,703 $ 831 $ 4,814 $ 58 Financial liabilities Debt $ 7,190 $ 9,258 $ — $ 9,258 $ — 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 six months ended June 30, 2021 or the year ended December 31, 2020.

Allowance for Expected Credit L

Allowance for Expected Credit Losses	6 Months Ended
	Jun. 30, 2021
Credit Loss [Abstract]
Allowance for Expected Credit Losses	ALLOWANCE FOR EXPECTED CREDIT LOSSES Premiums Receivable The following tables present the balances of premiums receivable, net of the allowance for expected credit losses, at June 30, 2021 and 2020, and the changes in the allowance for expected credit losses for the three and six months ended June 30, 2021 and 2020. At and For the Three Months Ended June 30, 2021 At and For the Three Months Ended June 30, 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 $ 8,167 $ 110 $ 8,202 $ 78 Current period change for expected credit losses 14 24 Write-offs of uncollectible premiums receivable 19 8 Balance, end of period $ 8,555 $ 105 $ 8,459 $ 94 At and For the Six Months Ended June 30, 2021 At and For the Six Months Ended June 30, 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 30 67 Write-offs of uncollectible premiums receivable 30 22 Balance, end of period $ 8,555 $ 105 $ 8,459 $ 94 Reinsurance Recoverables The following tables present the balances of reinsurance recoverables, net of the allowance for estimated uncollectible reinsurance, at June 30, 2021 and 2020, and the changes in the allowance for estimated uncollectible reinsurance for the three and six months ended June 30, 2021 and 2020. At and For the Three Months Ended June 30, 2021 At and For the Three Months Ended June 30, 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 $ 8,345 $ 142 $ 8,152 $ 149 Current period change for estimated uncollectible reinsurance (7) 7 Write-offs of uncollectible reinsurance recoverables — — Balance, end of period $ 8,209 $ 135 $ 8,093 $ 156 At and For the Six Months Ended June 30, 2021 At and For the Six Months Ended June 30, 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 (11) 11 Write-offs of uncollectible reinsurance recoverables — — Balance, end of period $ 8,209 $ 135 $ 8,093 $ 156 Of the total reinsurance recoverables at June 30, 2021, after deducting mandatory pools and associations and before allowances for estimated uncollectible reinsurance, $5.72 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 tables present the balances of contractholder receivables, net of the allowance for expected credit losses, at June 30, 2021 and 2020, and the changes in the allowance for expected credit losses for the three and six months ended June 30, 2021 and 2020. At and For the Three Months Ended June 30, 2021 At and For the Three Months Ended June 30, 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 $ 4,271 $ 19 $ 4,634 $ 20 Current period change for expected credit losses — 2 Write-offs of uncollectible contractholder receivables — — Balance, end of period $ 4,016 $ 19 $ 4,314 $ 22 At and For the Six Months Ended June 30, 2021 At and For the Six Months Ended June 30, 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 — 2 Write-offs of uncollectible contractholder receivables — — Balance, end of period $ 4,016 $ 19 $ 4,314 $ 22

Goodwill and Other Intangible A

Goodwill and Other Intangible Assets	6 Months Ended
	Jun. 30, 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) June 30, December 31, Business Insurance $ 2,619 $ 2,613 Bond & Specialty Insurance 550 550 Personal Insurance (1) 825 787 Other 26 26 Total $ 4,020 $ 3,976 _________________________________________________________ (1) Goodwill at June 30, 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 June 30, 2021, in millions) Gross Accumulated Net Subject to amortization Customer-related $ 105 $ 37 $ 68 Contract-based (1) 205 186 19 Total subject to amortization 310 223 87 Not subject to amortization 227 — 227 Total $ 537 $ 223 $ 314 (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

Insurance Claim Reserves	6 Months Ended
	Jun. 30, 2021
Insurance Loss Reserves [Abstract]
Insurance Claim Reserves	Claims and claim adjustment expense reserves were as follows: (in millions) June 30, December 31, Property-casualty $ 55,895 $ 54,510 Accident and health 11 11 Total $ 55,906 $ 54,521 The following table presents a reconciliation of beginning and ending property casualty reserve balances for claims and claim adjustment expenses: Six Months Ended June 30, (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 10,430 9,826 Estimated increase (decrease) in claims and claim adjustment expenses for claims arising in prior years (459) 16 Total increases 9,971 9,842 Claims and claim adjustment expense payments for claims arising in: Current year 3,113 2,664 Prior years 5,274 5,674 Total payments 8,387 8,338 Unrealized foreign exchange (gain) loss 53 (137) Net reserves at end of period 47,994 45,221 Plus reinsurance recoverables on unpaid losses 7,901 7,876 Claims and claim adjustment expense reserves at end of period $ 55,895 $ 53,097 Gross claims and claim adjustment expense reserves at June 30, 2021 increased by $1.39 billion from December 31, 2020, primarily reflecting the impacts of (i) catastrophe losses in the first six 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 June 30, 2021 decreased by $252 million from December 31, 2020, primarily reflecting the impacts of cash collections in the first six 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 six months ended June 30, 2021 and 2020, estimated claims and claim adjustment expenses incurred included $459 million and $(16) million, respectively, of net favorable (unfavorable) development for claims arising in prior years, including $499 million and $29 million, respectively, of net favorable prior year reserve development, and $24 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 second quarter of 2021 totaled $73 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 in reserves related to run-off operations. There was no net prior year reserve development in the second quarter of 2020, which reflected better than expected loss experience in domestic operations in the workers' compensation and commercial property product lines for multiple accident years, offset by higher than expected loss experience in domestic operations for primary and excess coverages in the general liability (excluding asbestos and environmental) product line for multiple accident years and higher than expected loss experience in domestic operations in the commercial multi-peril product line for recent accident years. Net favorable prior year reserve development in the first six months of 2021 totaled $207 million, primarily driven by better than expected loss experience in domestic operations in the workers' compensation product line for multiple accident years and in the commercial property and commercial automobile product lines for recent accident years, partially offset by an increase in reserves related to run-off operations and an increase to environmental reserves. Net favorable prior year reserve development in the first six months 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 domestic operations in the commercial automobile and commercial multi-peril product lines for recent accident years and higher than expected loss experience in domestic operations for primary and excess coverages in the general liability (excluding asbestos and environmental) product line for multiple accident years. Bond & Specialty Insurance. Net favorable prior year reserve development in the second quarter and first six months of 2021 totaled $44 million and $59 million, respectively, primarily driven by better than expected loss experience in the segment's domestic operations in the fidelity and surety product lines for recent accident years. Net unfavorable prior year reserve development in both of the second quarter and first six months of 2020 was $33 million, primarily driven by higher than expected loss experience in domestic operations in the general liability product line for recent accident years.

Other Comprehensive Income and

Other Comprehensive Income and Accumulated Other Comprehensive Income	6 Months Ended
	Jun. 30, 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 and six months ended June 30, 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, March 31, 2021 $ 2,635 $ 182 $ (812) $ (714) $ 1,291 Other comprehensive income (OCI) before reclassifications, net of tax 441 — — 36 477 Amounts reclassified from AOCI, net of tax (19) — 20 — 1 Net OCI, current period 422 — 20 36 478 Balance, June 30, 2021 $ 3,057 $ 182 $ (792) $ (678) $ 1,769 Changes in Net Unrealized Gains on Investment Securities (in millions) Having No Credit Losses Recognized in the Consolidated Statement of Income (Loss) Having Credit Net Benefit Plan Assets and Obligations Recognized in Shareholders’ Equity Net Unrealized Foreign Currency Translation Total Accumulated Other Comprehensive Income Balance, December 31, 2020 $ 3,892 $ 182 $ (832) $ (740) $ 2,502 Other comprehensive income (loss) (OCI) before reclassifications, net of tax (805) — — 62 (743) Amounts reclassified from AOCI, net of tax (30) — 40 — 10 Net OCI, current period (835) — 40 62 (733) Balance, June 30, 2021 $ 3,057 $ 182 $ (792) $ (678) $ 1,769 The following table presents the pre-tax components of the Company’s other comprehensive income (loss) and the related income tax expense (benefit). Three Months Ended Six Months Ended (in millions) 2021 2020 2021 2020 Changes in net unrealized gains on investment securities: Having no credit losses recognized in the consolidated statement of income (loss) $ 533 $ 2,359 $ (1,063) $ 1,784 Income tax expense (benefit) 111 500 (228) 382 Net of taxes 422 1,859 (835) 1,402 Having credit losses recognized in the consolidated statement of income (loss) — 3 — (3) Income tax expense (benefit) — 1 — (1) Net of taxes — 2 — (2) Net changes in benefit plan assets and obligations 26 21 51 44 Income tax expense 6 4 11 9 Net of taxes 20 17 40 35 Net changes in unrealized foreign currency translation 40 52 66 (216) Income tax expense (benefit) 4 (1) 4 (23) Net of taxes 36 53 62 (193) Total other comprehensive income (loss) 599 2,435 (946) 1,609 Total income tax expense (benefit) 121 504 (213) 367 Total other comprehensive income (loss), net of taxes $ 478 $ 1,931 $ (733) $ 1,242 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 (loss). Three Months Ended Six Months Ended (in millions) 2021 2020 2021 2020 Reclassification adjustments related to unrealized gains on investment securities: Having no credit losses recognized in the consolidated statement of income (loss) (1) $ (24) $ (10) $ (38) $ (8) Income tax expense (2) (5) (2) (8) (2) Net of taxes (19) (8) (30) (6) Having credit losses recognized in the consolidated statement of income (loss) (1) — — — — Income tax benefit (2) — — — — Net of taxes — — — — Reclassification adjustment related to benefit plan assets and obligations: Claims and claim adjustment expenses (3) 11 9 21 18 General and administrative expenses (3) 15 13 30 25 Total 26 22 51 43 Income tax benefit (2) 6 5 11 9 Net of taxes 20 17 40 34 Reclassification adjustment related to foreign currency translation (1) — — — — Income tax benefit (2) — — — — Net of taxes — — — — Total reclassifications 2 12 13 35 Total income tax benefit 1 3 3 7 Total reclassifications, net of taxes $ 1 $ 9 $ 10 $ 28 _________________________________________________________ (1) (Increases) decreases net realized investment gains (losses) on the consolidated statement of income (loss). (2) (Increases) decreases income tax expense on the consolidated statement of income (loss). (3) Increases (decreases) expenses on the consolidated statement of income (loss).

Debt

Debt	6 Months Ended
	Jun. 30, 2021
Debt Disclosure [Abstract]
Debt	DEBT Debt Issuance . On June 8, 2021, the Company issued $750 million aggregate principal amount of 3.05% senior notes that will mature on June 8, 2051. The net proceeds of the issuance, after the deduction of the underwriting discount and expenses payable by the Company, totaled approximately $739 million. Interest on the senior notes is payable semi-annually in arrears on June 8 and December 8. Prior to December 8, 2050, the senior notes may be redeemed, in whole or in part, at the Company’s option, at any time or from time to time, at a redemption price equal to the greater of (a) 100% of the principal amount of any senior notes to be redeemed or (b) the sum of the present values of the remaining scheduled payments of principal and interest to but excluding December 8, 2050 on any senior notes to be redeemed (exclusive of interest accrued to the date of redemption) discounted to the date of redemption on a semi-annual basis (assuming a 360-day year consisting of twelve 30-day months) at the then current Treasury rate (as defined in the senior notes), plus 15 basis points. On or after

Common Share Repurchases

Common Share Repurchases	6 Months Ended
	Jun. 30, 2021
Treasury Stock Transactions, Excluding Value of Shares Reissued [Abstract]
Common Share Repurchases	COMMON SHARE REPURCHASES During the three and six months ended June 30, 2021, the Company repurchased 2.6 million and 5.0 million common shares, respectively, under its share repurchase authorizations for total cost of $400 million and $756 million, respectively. The average cost per share repurchased was $157.18 and $152.65, respectively. In addition, the Company acquired 917 shares and 0.3 million shares for a total cost of approximately $144,000 and $42 million during the three and six months ended June 30, 2021, respectively, that were not part of its publicly announced share repurchase authorizations. 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.

Earnings per Share

Earnings per Share	6 Months Ended
	Jun. 30, 2021
Earnings Per Share Reconciliation [Abstract]
Earnings per Share	EARNINGS (LOSS) PER SHARE The following is a reconciliation of the income (loss) and share data used in the basic and diluted earnings (loss) per share computations for the periods presented: Three Months Ended Six Months Ended (in millions, except per share amounts) 2021 2020 2021 2020 Basic and Diluted Net income (loss), as reported $ 934 $ (40) $ 1,667 $ 560 Participating share-based awards — allocated income (7) (1) (12) (3) Net income (loss) available to common shareholders — basic and diluted $ 927 $ (41) $ 1,655 $ 557 Common Shares Basic Weighted average shares outstanding 250.7 251.6 251.4 253.6 Diluted Weighted average shares outstanding 250.7 251.6 251.4 253.6 Weighted average effects of dilutive securities — stock options and performance shares 2.4 — 2.2 1.1 Total 253.1 251.6 253.6 254.7 Net Income (Loss) per Common Share Basic $ 3.70 $ (0.16) $ 6.58 $ 2.19 Diluted $ 3.66 $ (0.16) $ 6.53 $ 2.19 Net loss per basic and diluted common share for the three months ended June 30, 2020 excluded the allocation of $2 million of undistributed loss to participating share-based awards, since such allocation would result in anti-dilution of basic and diluted earnings per share for the three months ended June 30, 2020. In addition, the net loss per diluted common share for the three months ended June 30, 2020 excluded the weighted average effects of 0.7 million stock options and performance shares, since the impact of these potential shares of common stock and their effects on income was anti-dilutive for the three months ended June 30, 2020.

Share-Based Incentive Compensat

Share-Based Incentive Compensation	6 Months Ended
	Jun. 30, 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 June 30, 2021: Stock Options Number Weighted Weighted Aggregate Vested at end of period (1) 7,604,850 $ 123.90 6.4 years $ 196 Exercisable at end of period 4,401,105 $ 117.65 4.9 years $ 141 _________________________________________________________ (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 $36 million and $34 million for the three months ended June 30, 2021 and 2020, respectively, and $89 million and $80 million for the six months ended June 30, 2021 and 2020, respectively. The related tax benefits recognized in the consolidated statement of income (loss) were $6 million for each of the three months ended June 30, 2021 and 2020, and $15 million and $14 million for the six months ended June 30, 2021 and 2020, respectively. The total unrecognized compensation cost related to all nonvested share-based incentive compensation awards at June 30, 2021 was $212 million, which is expected to be recognized over a weighted-average period of 2.0 years.

Pension Plans, Retirement Benef

Pension Plans, Retirement Benefits and Savings Plans	6 Months Ended
	Jun. 30, 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 (loss) for the three months ended June 30, 2021 and 2020. Pension Plans Postretirement Benefit Plans (for the three months ended June 30, in millions) 2021 2020 2021 2020 Net Periodic Benefit Cost (Benefit): Service cost $ 36 $ 33 $ — $ — Non-service cost (benefit): Interest cost on benefit obligation $ 20 $ 28 $ — $ 1 Expected return on plan assets (68) (68) — — Amortization of unrecognized: Prior service benefit — — (1) — Net actuarial (gain) loss 27 23 — (1) Total non-service cost (benefit) (21) (17) (1) — Net periodic benefit cost (benefit) $ 15 $ 16 $ (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 (loss) for the three months ended June 30, 2021 and 2020. Pension Plans Postretirement Benefit Plans (for the three months ended June 30, in millions) 2021 2020 2021 2020 Service Cost: Claims and claim adjustment expenses $ 15 $ 14 $ — $ — General and administrative expenses 21 19 — — Total service cost 36 33 — — Non-Service Cost (Benefit): Claims and claim adjustment expenses (8) (7) (1) — General and administrative expenses (13) (10) — — Total non-service cost (benefit) (21) (17) (1) — Net periodic benefit cost (benefit) $ 15 $ 16 $ (1) $ — 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 (loss) for the six months ended June 30, 2021 and 2020. Pension Plans Postretirement Benefit Plans (for the six months ended June 30, in millions) 2021 2020 2021 2020 Net Periodic Benefit Cost (Benefit): Service cost $ 71 $ 66 $ — $ — Non-service cost (benefit): Interest cost on benefit obligation 41 57 1 2 Expected return on plan assets (137) (137) — — Amortization of unrecognized: Prior service benefit — — (2) (2) Net actuarial (gain) loss 54 46 (1) (1) Total non-service cost (benefit) (42) (34) (2) (1) Net periodic benefit cost (benefit) $ 29 $ 32 $ (2) $ (1) The following table indicates the line items in which the respective service cost and non-service benefit cost (benefit) are presented in the consolidated statement of income (loss) for the six months ended June 30, 2021 and 2020. Pension Plans Postretirement Benefit Plans (for the six months ended June 30, in millions) 2021 2020 2021 2020 Service Cost: Claims and claim adjustment expenses $ 29 $ 28 $ — $ — General and administrative expenses 42 38 — — Total service cost 71 66 — — Non-Service Cost (Benefit): Claims and claim adjustment expenses (17) (14) (1) — General and administrative expenses (25) (20) (1) (1) Total non-service cost (benefit) (42) (34) (2) (1) Net periodic benefit cost (benefit) $ 29 $ 32 $ (2) $ (1)

Leases

Leases	6 Months Ended
	Jun. 30, 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 (loss). Additional information regarding the Company’s real estate operating leases is as follows: Three Months Ended Six Months Ended (in millions) 2021 2020 2021 2020 Lease cost Operating leases $ 22 $ 24 $ 45 $ 48 Short-term leases (1) 1 1 1 1 Lease expense 23 25 46 49 Less: sublease income (2) — — — — Net lease cost $ 23 $ 25 $ 46 $ 49 Other information on operating leases Cash payments to settle a lease liability reported in cash flows $ 27 $ 28 $ 53 $ 55 Right-of-use assets obtained in exchange for new lease liabilities $ 7 $ 4 $ 19 $ 18 Weighted average discount rate 2.41 % 2.94 % 2.41 % 2.94 % Weighted average remaining lease term 4.8 years 4.9 years 4.8 years 4.9 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	6 Months Ended
	Jun. 30, 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 $1.65 billion and $1.76 billion at June 30, 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 June 30, 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 June 30, 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)	6 Months Ended
	Jun. 30, 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)	6 Months Ended
	Jun. 30, 2021
Segment Reporting [Abstract]
Company's revenues and income by segment [Table Text Block]	(For the three months ended June 30, in millions) Business Bond & Specialty Personal Total 2021 Premiums $ 3,880 $ 776 $ 2,960 $ 7,616 Net investment income 615 64 139 818 Fee income 97 — 7 104 Other revenues 57 7 24 88 Total segment revenues (1) $ 4,649 $ 847 $ 3,130 $ 8,626 Segment income (1) $ 643 $ 187 $ 121 $ 951 2020 Premiums $ 3,735 $ 693 $ 2,527 $ 6,955 Net investment income 180 42 46 268 Fee income 108 — 6 114 Other revenues 36 5 10 51 Total segment revenues (1) $ 4,059 $ 740 $ 2,589 $ 7,388 Segment income (loss) (1) $ (58) $ 72 $ 10 $ 24 _________________________________________________________ (1) Segment revenues for reportable business segments exclude net realized investment gains (losses) and revenues included in "interest expense and other." Segment income (loss) for reportable business segments equals net income (loss) excluding the after-tax impact of net realized investment gains (losses) and income (loss) from "interest expense and other." (For the six months ended June 30, in millions) Business Bond & Specialty Personal Total 2021 Premiums $ 7,679 $ 1,519 $ 5,804 $ 15,002 Net investment income 1,138 123 258 1,519 Fee income 192 — 13 205 Other revenues 110 12 47 169 Total segment revenues (1) $ 9,119 $ 1,654 $ 6,122 $ 16,895 Segment income (1) $ 960 $ 324 $ 435 $ 1,719 2020 Premiums $ 7,599 $ 1,360 $ 5,225 $ 14,184 Net investment income 633 97 149 879 Fee income 210 — 12 222 Other revenues 67 10 32 109 Total segment revenues (1) $ 8,509 $ 1,467 $ 5,418 $ 15,394 Segment income (1) $ 231 $ 194 $ 346 $ 771 (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 Six Months Ended (in millions) 2021 2020 2021 2020 Revenue reconciliation Earned premiums Business Insurance: Domestic: Workers’ compensation $ 810 $ 818 $ 1,621 $ 1,717 Commercial automobile 709 676 1,404 1,360 Commercial property 556 514 1,087 1,022 General liability 618 580 1,225 1,181 Commercial multi-peril 899 883 1,769 1,769 Other 14 11 28 23 Total Domestic 3,606 3,482 7,134 7,072 International 274 253 545 527 Total Business Insurance 3,880 3,735 7,679 7,599 Bond & Specialty Insurance: Domestic: Fidelity and surety 276 271 542 528 General liability 347 296 678 583 Other 55 60 111 118 Total Domestic 678 627 1,331 1,229 International 98 66 188 131 Total Bond & Specialty Insurance 776 693 1,519 1,360 Personal Insurance: Domestic: Automobile 1,405 1,154 2,775 2,505 Homeowners and Other 1,377 1,221 2,685 2,397 Total Domestic 2,782 2,375 5,460 4,902 International 178 152 344 323 Total Personal Insurance 2,960 2,527 5,804 5,225 Total earned premiums 7,616 6,955 15,002 14,184 Net investment income 818 268 1,519 879 Fee income 104 114 205 222 Other revenues 88 51 169 109 Total segment revenues 8,626 7,388 16,895 15,394 Other revenues — — — — Net realized investment gains (losses) 61 13 105 (85) Total revenues $ 8,687 $ 7,401 $ 17,000 $ 15,309 Income reconciliation, net of tax Total segment income $ 951 $ 24 $ 1,719 $ 771 Interest Expense and Other (1) (72) (74) (141) (145) Core income (loss) 879 (50) 1,578 626 Net realized investment gains (losses) 47 10 81 (66) Impact of changes in tax laws and/or tax rates (2) 8 — 8 — Net income (loss) $ 934 $ (40) $ 1,667 $ 560 _________________________________________________________ (1) The primary component of Interest Expense and Other was after-tax interest expense of $65 million and $67 million for the three months ended June 30, 2021 and 2020, respectively, and $130 million and $133 million for the six months ended June 30, 2021 and 2020, respectively. (2) Impact is recognized in the accounting period in which the change is enacted.
Asset reconciliation [Table Text Block]	(in millions) June 30, December 31, Asset reconciliation Business Insurance $ 90,219 $ 88,422 Bond & Specialty Insurance 10,073 9,420 Personal Insurance 18,846 18,328 Total assets by reportable segment 119,138 116,170 Other assets (1) 621 594 Total consolidated assets $ 119,759 $ 116,764 _________________________________________________________ (1) The primary components of other assets at both June 30, 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)	6 Months Ended
	Jun. 30, 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 June 30, 2021, in millions) Gains Losses U.S. Treasury securities and obligations of U.S. government and government agencies and authorities $ 3,560 $ — $ 38 $ 8 $ 3,590 Obligations of states, municipalities and political subdivisions: Local general obligation 17,590 — 1,188 24 18,754 Revenue 11,048 — 787 12 11,823 State general obligation 1,324 — 85 1 1,408 Pre-refunded 3,482 — 205 — 3,687 Total obligations of states, municipalities and political subdivisions 33,444 — 2,265 37 35,672 Debt securities issued by foreign governments 1,024 — 15 3 1,036 Mortgage-backed securities, collateralized mortgage obligations and pass-through securities 1,722 — 99 1 1,820 All other corporate bonds 31,703 2 1,813 70 33,444 Redeemable preferred stock 12 — 2 — 14 Total $ 71,465 $ 2 $ 4,232 $ 119 $ 75,576 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 June 30, 2021, in millions) Cost Gross Gains Gross Losses Value Public common stock $ 359 $ 111 $ 3 $ 467 Non-redeemable preferred stock 35 11 — 46 Total $ 394 $ 122 $ 3 $ 513 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 June 30, 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 June 30, 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 $ 451 $ 8 $ — $ — $ 451 $ 8 Obligations of states, municipalities and political subdivisions 2,719 37 — — 2,719 37 Debt securities issued by foreign governments 273 3 — — 273 3 Mortgage-backed securities, collateralized mortgage obligations and pass-through securities 45 1 1 — 46 1 All other corporate bonds 3,007 68 64 2 3,071 70 Total $ 6,495 $ 117 $ 65 $ 2 $ 6,560 $ 119 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 for the category of All Other Corporate Bonds (no other categories of fixed maturities currently have an allowance for expected credit losses): Fixed Maturities At and For the Three Months Ended June 30, 2021 At and For the Three Months Ended June 30, 2020 (in millions) All Other Corporate Bonds All Other Corporate Bonds Balance, beginning of period $ 2 $ 4 Additions for expected credit losses on securities where no credit losses were previously recognized 1 4 Additions (reductions) for expected credit losses on securities where credit losses were previously recognized (1) — 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, end of period $ 2 $ 8 (1) Credit impairment charges recognized in net realized investment gains (losses) for the three months ended June 30, 2021 and 2020 included $0 million and $2 million, respectively, 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. Fixed Maturities At and For the Six Months Ended June 30, 2021 At and For the Six Months Ended June 30, 2020 (in millions) All Other Corporate Bonds All Other Corporate Bonds Balance, beginning of period $ 2 $ — Additions for expected credit losses on securities where no credit losses were previously recognized 1 8 Additions (reductions) for expected credit losses on securities where credit losses were previously recognized (1) — 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, end of period $ 2 $ 8 (1) Credit impairment charges recognized in net realized investment gains (losses) for the six months ended June 30, 2021 and 2020 included $0 million and $14 million, respectively, 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)	6 Months Ended
	Jun. 30, 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 June 30, 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 $ 3,590 $ 3,590 $ — $ — Obligations of states, municipalities and political subdivisions 35,672 — 35,668 4 Debt securities issued by foreign governments 1,036 — 1,036 — Mortgage-backed securities, collateralized mortgage obligations and pass-through securities 1,820 — 1,806 14 All other corporate bonds 33,444 — 33,299 145 Redeemable preferred stock 14 — 14 — Total fixed maturities 75,576 3,590 71,823 163 Equity securities Public common stock 467 467 — — Non-redeemable preferred stock 46 21 25 — Total equity securities 513 488 25 — Other investments 53 18 — 35 Total $ 76,142 $ 4,096 $ 71,848 $ 198 Other liabilities $ 4 $ — $ — $ 4 (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 June 30, 2021, in millions) Carrying Fair Level 1 Level 2 Level 3 Financial assets Short-term securities $ 5,703 $ 5,703 $ 831 $ 4,814 $ 58 Financial liabilities Debt $ 7,190 $ 9,258 $ — $ 9,258 $ — 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)	6 Months Ended
	Jun. 30, 2021
Credit Loss [Abstract]
Changes in the allowance for expected credit losses on premiums receivable [Table Text Block]	The following tables present the balances of premiums receivable, net of the allowance for expected credit losses, at June 30, 2021 and 2020, and the changes in the allowance for expected credit losses for the three and six months ended June 30, 2021 and 2020. At and For the Three Months Ended June 30, 2021 At and For the Three Months Ended June 30, 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 $ 8,167 $ 110 $ 8,202 $ 78 Current period change for expected credit losses 14 24 Write-offs of uncollectible premiums receivable 19 8 Balance, end of period $ 8,555 $ 105 $ 8,459 $ 94 At and For the Six Months Ended June 30, 2021 At and For the Six Months Ended June 30, 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 30 67 Write-offs of uncollectible premiums receivable 30 22 Balance, end of period $ 8,555 $ 105 $ 8,459 $ 94
Changes in the allowance for estimated uncollectible reinsurance [Table Text Block]	The following tables present the balances of reinsurance recoverables, net of the allowance for estimated uncollectible reinsurance, at June 30, 2021 and 2020, and the changes in the allowance for estimated uncollectible reinsurance for the three and six months ended June 30, 2021 and 2020. At and For the Three Months Ended June 30, 2021 At and For the Three Months Ended June 30, 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 $ 8,345 $ 142 $ 8,152 $ 149 Current period change for estimated uncollectible reinsurance (7) 7 Write-offs of uncollectible reinsurance recoverables — — Balance, end of period $ 8,209 $ 135 $ 8,093 $ 156 At and For the Six Months Ended June 30, 2021 At and For the Six Months Ended June 30, 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 (11) 11 Write-offs of uncollectible reinsurance recoverables — — Balance, end of period $ 8,209 $ 135 $ 8,093 $ 156
Changes in the allowance for expected credit losses on contractholder receivables [Table Text Block]	The following tables present the balances of contractholder receivables, net of the allowance for expected credit losses, at June 30, 2021 and 2020, and the changes in the allowance for expected credit losses for the three and six months ended June 30, 2021 and 2020. At and For the Three Months Ended June 30, 2021 At and For the Three Months Ended June 30, 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 $ 4,271 $ 19 $ 4,634 $ 20 Current period change for expected credit losses — 2 Write-offs of uncollectible contractholder receivables — — Balance, end of period $ 4,016 $ 19 $ 4,314 $ 22 At and For the Six Months Ended June 30, 2021 At and For the Six Months Ended June 30, 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 — 2 Write-offs of uncollectible contractholder receivables — — Balance, end of period $ 4,016 $ 19 $ 4,314 $ 22

Goodwill and Other Intangible_2

Goodwill and Other Intangible Assets (Tables)	6 Months Ended
	Jun. 30, 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) June 30, December 31, Business Insurance $ 2,619 $ 2,613 Bond & Specialty Insurance 550 550 Personal Insurance (1) 825 787 Other 26 26 Total $ 4,020 $ 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 June 30, 2021, in millions) Gross Accumulated Net Subject to amortization Customer-related $ 105 $ 37 $ 68 Contract-based (1) 205 186 19 Total subject to amortization 310 223 87 Not subject to amortization 227 — 227 Total $ 537 $ 223 $ 314 (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 June 30, 2021, in millions) Gross Accumulated Net Subject to amortization Customer-related $ 105 $ 37 $ 68 Contract-based (1) 205 186 19 Total subject to amortization 310 223 87 Not subject to amortization 227 — 227 Total $ 537 $ 223 $ 314 (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)	6 Months Ended
	Jun. 30, 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) June 30, December 31, Property-casualty $ 55,895 $ 54,510 Accident and health 11 11 Total $ 55,906 $ 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: Six Months Ended June 30, (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 10,430 9,826 Estimated increase (decrease) in claims and claim adjustment expenses for claims arising in prior years (459) 16 Total increases 9,971 9,842 Claims and claim adjustment expense payments for claims arising in: Current year 3,113 2,664 Prior years 5,274 5,674 Total payments 8,387 8,338 Unrealized foreign exchange (gain) loss 53 (137) Net reserves at end of period 47,994 45,221 Plus reinsurance recoverables on unpaid losses 7,901 7,876 Claims and claim adjustment expense reserves at end of period $ 55,895 $ 53,097

Other Comprehensive Income an_2

Other Comprehensive Income and Accumulated Other Comprehensive Income (Tables)	6 Months Ended
	Jun. 30, 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 and six months ended June 30, 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, March 31, 2021 $ 2,635 $ 182 $ (812) $ (714) $ 1,291 Other comprehensive income (OCI) before reclassifications, net of tax 441 — — 36 477 Amounts reclassified from AOCI, net of tax (19) — 20 — 1 Net OCI, current period 422 — 20 36 478 Balance, June 30, 2021 $ 3,057 $ 182 $ (792) $ (678) $ 1,769 Changes in Net Unrealized Gains on Investment Securities (in millions) Having No Credit Losses Recognized in the Consolidated Statement of Income (Loss) Having Credit Net Benefit Plan Assets and Obligations Recognized in Shareholders’ Equity Net Unrealized Foreign Currency Translation Total Accumulated Other Comprehensive Income Balance, December 31, 2020 $ 3,892 $ 182 $ (832) $ (740) $ 2,502 Other comprehensive income (loss) (OCI) before reclassifications, net of tax (805) — — 62 (743) Amounts reclassified from AOCI, net of tax (30) — 40 — 10 Net OCI, current period (835) — 40 62 (733) Balance, June 30, 2021 $ 3,057 $ 182 $ (792) $ (678) $ 1,769
Pre-tax components of other comprehensive income (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 income (loss) and the related income tax expense (benefit). Three Months Ended Six Months Ended (in millions) 2021 2020 2021 2020 Changes in net unrealized gains on investment securities: Having no credit losses recognized in the consolidated statement of income (loss) $ 533 $ 2,359 $ (1,063) $ 1,784 Income tax expense (benefit) 111 500 (228) 382 Net of taxes 422 1,859 (835) 1,402 Having credit losses recognized in the consolidated statement of income (loss) — 3 — (3) Income tax expense (benefit) — 1 — (1) Net of taxes — 2 — (2) Net changes in benefit plan assets and obligations 26 21 51 44 Income tax expense 6 4 11 9 Net of taxes 20 17 40 35 Net changes in unrealized foreign currency translation 40 52 66 (216) Income tax expense (benefit) 4 (1) 4 (23) Net of taxes 36 53 62 (193) Total other comprehensive income (loss) 599 2,435 (946) 1,609 Total income tax expense (benefit) 121 504 (213) 367 Total other comprehensive income (loss), net of taxes $ 478 $ 1,931 $ (733) $ 1,242
Pre-tax and related income tax (expense) benefit components of the amounts reclassified from accumulated other comprehensive income to the consolidated statement of income (loss) [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 (loss). Three Months Ended Six Months Ended (in millions) 2021 2020 2021 2020 Reclassification adjustments related to unrealized gains on investment securities: Having no credit losses recognized in the consolidated statement of income (loss) (1) $ (24) $ (10) $ (38) $ (8) Income tax expense (2) (5) (2) (8) (2) Net of taxes (19) (8) (30) (6) Having credit losses recognized in the consolidated statement of income (loss) (1) — — — — Income tax benefit (2) — — — — Net of taxes — — — — Reclassification adjustment related to benefit plan assets and obligations: Claims and claim adjustment expenses (3) 11 9 21 18 General and administrative expenses (3) 15 13 30 25 Total 26 22 51 43 Income tax benefit (2) 6 5 11 9 Net of taxes 20 17 40 34 Reclassification adjustment related to foreign currency translation (1) — — — — Income tax benefit (2) — — — — Net of taxes — — — — Total reclassifications 2 12 13 35 Total income tax benefit 1 3 3 7 Total reclassifications, net of taxes $ 1 $ 9 $ 10 $ 28 _________________________________________________________ (1) (Increases) decreases net realized investment gains (losses) on the consolidated statement of income (loss). (2) (Increases) decreases income tax expense on the consolidated statement of income (loss). (3) Increases (decreases) expenses on the consolidated statement of income (loss).

Earnings per Share (Table)

Earnings per Share (Table)	6 Months Ended
	Jun. 30, 2021
Earnings Per Share Reconciliation [Abstract]
Earnings per share reconciliation [Table Text Block]	The following is a reconciliation of the income (loss) and share data used in the basic and diluted earnings (loss) per share computations for the periods presented: Three Months Ended Six Months Ended (in millions, except per share amounts) 2021 2020 2021 2020 Basic and Diluted Net income (loss), as reported $ 934 $ (40) $ 1,667 $ 560 Participating share-based awards — allocated income (7) (1) (12) (3) Net income (loss) available to common shareholders — basic and diluted $ 927 $ (41) $ 1,655 $ 557 Common Shares Basic Weighted average shares outstanding 250.7 251.6 251.4 253.6 Diluted Weighted average shares outstanding 250.7 251.6 251.4 253.6 Weighted average effects of dilutive securities — stock options and performance shares 2.4 — 2.2 1.1 Total 253.1 251.6 253.6 254.7 Net Income (Loss) per Common Share Basic $ 3.70 $ (0.16) $ 6.58 $ 2.19 Diluted $ 3.66 $ (0.16) $ 6.53 $ 2.19

Share-Based Incentive Compens_2

Share-Based Incentive Compensation (Table)	6 Months Ended
	Jun. 30, 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 June 30, 2021: Stock Options Number Weighted Weighted Aggregate Vested at end of period (1) 7,604,850 $ 123.90 6.4 years $ 196 Exercisable at end of period 4,401,105 $ 117.65 4.9 years $ 141 _________________________________________________________ (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)	6 Months Ended
	Jun. 30, 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 (loss) [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 (loss) for the three months ended June 30, 2021 and 2020. Pension Plans Postretirement Benefit Plans (for the three months ended June 30, in millions) 2021 2020 2021 2020 Net Periodic Benefit Cost (Benefit): Service cost $ 36 $ 33 $ — $ — Non-service cost (benefit): Interest cost on benefit obligation $ 20 $ 28 $ — $ 1 Expected return on plan assets (68) (68) — — Amortization of unrecognized: Prior service benefit — — (1) — Net actuarial (gain) loss 27 23 — (1) Total non-service cost (benefit) (21) (17) (1) — Net periodic benefit cost (benefit) $ 15 $ 16 $ (1) $ — 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 (loss) for the six months ended June 30, 2021 and 2020. Pension Plans Postretirement Benefit Plans (for the six months ended June 30, in millions) 2021 2020 2021 2020 Net Periodic Benefit Cost (Benefit): Service cost $ 71 $ 66 $ — $ — Non-service cost (benefit): Interest cost on benefit obligation 41 57 1 2 Expected return on plan assets (137) (137) — — Amortization of unrecognized: Prior service benefit — — (2) (2) Net actuarial (gain) loss 54 46 (1) (1) Total non-service cost (benefit) (42) (34) (2) (1) Net periodic benefit cost (benefit) $ 29 $ 32 $ (2) $ (1)
Consolidated statement of income (loss) 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 (loss) for the three months ended June 30, 2021 and 2020. Pension Plans Postretirement Benefit Plans (for the three months ended June 30, in millions) 2021 2020 2021 2020 Service Cost: Claims and claim adjustment expenses $ 15 $ 14 $ — $ — General and administrative expenses 21 19 — — Total service cost 36 33 — — Non-Service Cost (Benefit): Claims and claim adjustment expenses (8) (7) (1) — General and administrative expenses (13) (10) — — Total non-service cost (benefit) (21) (17) (1) — Net periodic benefit cost (benefit) $ 15 $ 16 $ (1) $ — The following table indicates the line items in which the respective service cost and non-service benefit cost (benefit) are presented in the consolidated statement of income (loss) for the six months ended June 30, 2021 and 2020. Pension Plans Postretirement Benefit Plans (for the six months ended June 30, in millions) 2021 2020 2021 2020 Service Cost: Claims and claim adjustment expenses $ 29 $ 28 $ — $ — General and administrative expenses 42 38 — — Total service cost 71 66 — — Non-Service Cost (Benefit): Claims and claim adjustment expenses (17) (14) (1) — General and administrative expenses (25) (20) (1) (1) Total non-service cost (benefit) (42) (34) (2) (1) Net periodic benefit cost (benefit) $ 29 $ 32 $ (2) $ (1)

Leases (Table)

Leases (Table)	6 Months Ended
	Jun. 30, 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 (loss). Additional information regarding the Company’s real estate operating leases is as follows: Three Months Ended Six Months Ended (in millions) 2021 2020 2021 2020 Lease cost Operating leases $ 22 $ 24 $ 45 $ 48 Short-term leases (1) 1 1 1 1 Lease expense 23 25 46 49 Less: sublease income (2) — — — — Net lease cost $ 23 $ 25 $ 46 $ 49 Other information on operating leases Cash payments to settle a lease liability reported in cash flows $ 27 $ 28 $ 53 $ 55 Right-of-use assets obtained in exchange for new lease liabilities $ 7 $ 4 $ 19 $ 18 Weighted average discount rate 2.41 % 2.94 % 2.41 % 2.94 % Weighted average remaining lease term 4.8 years 4.9 years 4.8 years 4.9 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		6 Months Ended
	Jun. 30, 2021USD ($)	Jun. 30, 2020USD ($)	Jun. 30, 2021USD ($)segment	Jun. 30, 2020USD ($)
Segment reporting information
Number of reportable business segments | segment			3
Premiums	$ 7,616	$ 6,955	$ 15,002	$ 14,184
Net investment income	818	268	1,519	879
Fee income	104	114	205	222
Other revenues	88	51	169	109
Net realized investment gains (losses)	61	13	105	(85)
Total revenues	8,687	7,401	17,000	15,309
Core income (loss)	879	(50)	1,578	626
Net realized investment gains (losses), net of tax	47	10	81	(66)
Impact of changes in tax laws and/or tax rates	8	0	8	0
Net income (loss)	934	(40)	1,667	560
Reportable Segments [Member]
Segment reporting information
Premiums	7,616	6,955	15,002	14,184
Net investment income	818	268	1,519	879
Fee income	104	114	205	222
Other revenues	88	51	169	109
Total segment revenues	8,626	7,388	16,895	15,394
Core income (loss)	951	24	1,719	771
Reportable Segments [Member] | Business Insurance [Member]
Segment reporting information
Premiums	3,880	3,735	7,679	7,599
Net investment income	615	180	1,138	633
Fee income	97	108	192	210
Other revenues	57	36	110	67
Total segment revenues	4,649	4,059	9,119	8,509
Core income (loss)	643	(58)	960	231
Reportable Segments [Member] | Business Insurance [Member] | Domestic [Member]
Segment reporting information
Premiums	3,606	3,482	7,134	7,072
Reportable Segments [Member] | Business Insurance [Member] | Domestic [Member] | Workers' compensation [Member]
Segment reporting information
Premiums	810	818	1,621	1,717
Reportable Segments [Member] | Business Insurance [Member] | Domestic [Member] | Automobile [Member]
Segment reporting information
Premiums	709	676	1,404	1,360
Reportable Segments [Member] | Business Insurance [Member] | Domestic [Member] | Commercial property [Member]
Segment reporting information
Premiums	556	514	1,087	1,022
Reportable Segments [Member] | Business Insurance [Member] | Domestic [Member] | General liability [Member]
Segment reporting information
Premiums	618	580	1,225	1,181
Reportable Segments [Member] | Business Insurance [Member] | Domestic [Member] | Commercial multi-peril [Member]
Segment reporting information
Premiums	899	883	1,769	1,769
Reportable Segments [Member] | Business Insurance [Member] | Domestic [Member] | Other [Member]
Segment reporting information
Premiums	14	11	28	23
Reportable Segments [Member] | Business Insurance [Member] | International [Member]
Segment reporting information
Premiums	274	253	545	527
Reportable Segments [Member] | Bond & Specialty Insurance [Member]
Segment reporting information
Premiums	776	693	1,519	1,360
Net investment income	64	42	123	97
Fee income	0	0	0	0
Other revenues	7	5	12	10
Total segment revenues	847	740	1,654	1,467
Core income (loss)	187	72	324	194
Reportable Segments [Member] | Bond & Specialty Insurance [Member] | Domestic [Member]
Segment reporting information
Premiums	678	627	1,331	1,229
Reportable Segments [Member] | Bond & Specialty Insurance [Member] | Domestic [Member] | General liability [Member]
Segment reporting information
Premiums	347	296	678	583
Reportable Segments [Member] | Bond & Specialty Insurance [Member] | Domestic [Member] | Fidelity and surety [Member]
Segment reporting information
Premiums	276	271	542	528
Reportable Segments [Member] | Bond & Specialty Insurance [Member] | Domestic [Member] | Other [Member]
Segment reporting information
Premiums	55	60	111	118
Reportable Segments [Member] | Bond & Specialty Insurance [Member] | International [Member]
Segment reporting information
Premiums	98	66	188	131
Reportable Segments [Member] | Personal Insurance [Member]
Segment reporting information
Premiums	2,960	2,527	5,804	5,225
Net investment income	139	46	258	149
Fee income	7	6	13	12
Other revenues	24	10	47	32
Total segment revenues	3,130	2,589	6,122	5,418
Core income (loss)	121	10	435	346
Reportable Segments [Member] | Personal Insurance [Member] | Domestic [Member]
Segment reporting information
Premiums	2,782	2,375	5,460	4,902
Reportable Segments [Member] | Personal Insurance [Member] | Domestic [Member] | Automobile [Member]
Segment reporting information
Premiums	1,405	1,154	2,775	2,505
Reportable Segments [Member] | Personal Insurance [Member] | Domestic [Member] | Homeowners and Other [Member]
Segment reporting information
Premiums	1,377	1,221	2,685	2,397
Reportable Segments [Member] | Personal Insurance [Member] | International [Member]
Segment reporting information
Premiums	178	152	344	323
Other [Member]
Segment reporting information
Other revenues	0	0	0	0
Core income (loss)	(72)	(74)	(141)	(145)
After-tax interest expense	$ 65	$ 67	$ 130	$ 133

Segment Information (Details) -

Segment Information (Details) - Assets by Segment - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Assets by segment
Total assets	$ 119,759	$ 116,764
Reportable Segments [Member]
Assets by segment
Total assets	119,138	116,170
Reportable Segments [Member] | Business Insurance [Member]
Assets by segment
Total assets	90,219	88,422
Reportable Segments [Member] | Bond & Specialty Insurance [Member]
Assets by segment
Total assets	10,073	9,420
Reportable Segments [Member] | Personal Insurance [Member]
Assets by segment
Total assets	18,846	18,328
Other assets [Member]
Assets by segment
Total assets	$ 621	$ 594

Investments (Details) - Investm

Investments (Details) - Investment Information, Debt Securities - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
Investment disclosure details
Fixed maturities, amortized cost	$ 71,465			$ 68,830
Allowance for expected credit losses	2			2
Gross unrealized gains	4,232			5,186
Gross unrealized losses	119			11
Fixed maturities, at fair value	75,576			74,003
Proceeds from sales of fixed maturities classified as available for sale	2,482	$ 1,220
Gross realized gains	43	31
Gross realized losses	5	1
U.S. Treasury securities and obligations of U.S. government and government agencies and authorities [Member]
Investment disclosure details
Fixed maturities, amortized cost	3,560			2,111
Allowance for expected credit losses	0			0
Gross unrealized gains	38			38
Gross unrealized losses	8			0
Fixed maturities, at fair value	3,590			2,149
Obligations of states, municipalities and political subdivisions [Member]
Investment disclosure details
Fixed maturities, amortized cost	33,444			33,763
Allowance for expected credit losses	0			0
Gross unrealized gains	2,265			2,599
Gross unrealized losses	37			2
Fixed maturities, at fair value	35,672			36,360
Obligations of states, municipalities and political subdivisions, local general obligation [Member]
Investment disclosure details
Fixed maturities, amortized cost	17,590			17,289
Allowance for expected credit losses	0			0
Gross unrealized gains	1,188			1,370
Gross unrealized losses	24			2
Fixed maturities, at fair value	18,754			18,657
Obligations of states, municipalities and political subdivisions, revenue [Member]
Investment disclosure details
Fixed maturities, amortized cost	11,048			11,806
Allowance for expected credit losses	0			0
Gross unrealized gains	787			909
Gross unrealized losses	12			0
Fixed maturities, at fair value	11,823			12,715
Obligations of states, municipalities and political subdivisions, state general obligation [Member]
Investment disclosure details
Fixed maturities, amortized cost	1,324			1,343
Allowance for expected credit losses	0			0
Gross unrealized gains	85			101
Gross unrealized losses	1			0
Fixed maturities, at fair value	1,408			1,444
Obligations of states, municipalities and political subdivisions, pre-refunded [Member]
Investment disclosure details
Fixed maturities, amortized cost	3,482			3,325
Allowance for expected credit losses	0			0
Gross unrealized gains	205			219
Gross unrealized losses	0			0
Fixed maturities, at fair value	3,687			3,544
Debt securities issued by foreign governments [Member]
Investment disclosure details
Fixed maturities, amortized cost	1,024			1,028
Allowance for expected credit losses	0			0
Gross unrealized gains	15			26
Gross unrealized losses	3			0
Fixed maturities, at fair value	1,036			1,054
Mortgage-backed securities, collateralized mortgage obligations and pass-through securities [Member]
Investment disclosure details
Fixed maturities, amortized cost	1,722			2,222
Allowance for expected credit losses	0			0
Gross unrealized gains	99			139
Gross unrealized losses	1			0
Fixed maturities, at fair value	1,820			2,361
All other corporate bonds [Member]
Investment disclosure details
Fixed maturities, amortized cost	31,703			29,683
Allowance for expected credit losses	2	$ 8	$ 2	2	$ 4	$ 0
Gross unrealized gains	1,813			2,382
Gross unrealized losses	70			9
Fixed maturities, at fair value	33,444			32,054
Redeemable preferred stock [Member]
Investment disclosure details
Fixed maturities, amortized cost	12			23
Allowance for expected credit losses	0			0
Gross unrealized gains	2			2
Gross unrealized losses	0			0
Fixed maturities, at fair value	$ 14			$ 25

Investments (Details) - Inves_2

Investments (Details) - Investment Information, Equity Securities - USD ($) $ in Millions	6 Months Ended		12 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Investment disclosure details
Equity securities, cost	$ 394		$ 387
Gross gains	122		78
Gross losses	3		12
Equity securities, at fair value	513		453
Net recognized gains (losses) on equity securities still held	51	$ (33)
Public common stock [Member]
Investment disclosure details
Equity securities, cost	359		352
Gross gains	111		70
Gross losses	3		12
Equity securities, at fair value	467		410
Non-redeemable preferred stock [Member]
Investment disclosure details
Equity securities, cost	35		35
Gross gains	11		8
Gross losses	0		0
Equity securities, at fair value	$ 46		$ 43

Investments (Details) - Inves_3

Investments (Details) - Investment Information, Losses - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Investment disclosure details
Continuous unrealized loss position, less than 12 months, fair value	$ 6,495	$ 1,045
Continuous unrealized loss position, less than 12 months, gross unrealized losses	117	8
Continuous unrealized loss position, 12 months or longer, fair value	65	98
Continuous unrealized loss position, 12 months or longer, gross unrealized losses	2	3
Continuous unrealized loss position, total, fair value	6,560	1,143
Continuous unrealized loss position, total, gross unrealized losses	119	11
Unrealized investment losses on fixed maturity investments for which fair value is less than 80% of amortized cost, total	0
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	451	92
Continuous unrealized loss position, less than 12 months, gross unrealized losses	8	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	451	92
Continuous unrealized loss position, total, gross unrealized losses	8	0
Obligations of states, municipalities and political subdivisions [Member]
Investment disclosure details
Continuous unrealized loss position, less than 12 months, fair value	2,719	245
Continuous unrealized loss position, less than 12 months, gross unrealized losses	37	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	2,719	245
Continuous unrealized loss position, total, gross unrealized losses	37	2
Debt securities issued by foreign governments [Member]
Investment disclosure details
Continuous unrealized loss position, less than 12 months, fair value	273	7
Continuous unrealized loss position, less than 12 months, gross unrealized losses	3	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	273	7
Continuous unrealized loss position, total, gross unrealized losses	3	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	45	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	46	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	3,007	681
Continuous unrealized loss position, less than 12 months, gross unrealized losses	68	6
Continuous unrealized loss position, 12 months or longer, fair value	64	97
Continuous unrealized loss position, 12 months or longer, gross unrealized losses	2	3
Continuous unrealized loss position, total, fair value	3,071	778
Continuous unrealized loss position, total, gross unrealized losses	$ 70	$ 9

Investments (Details) - Allowan

Investments (Details) - Allowance for Expected Credit Losses - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 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
Allowance for expected credit losses on fixed maturities classified as available-for-sale, balance, end of period	$ 2		2
Total net credit impairment charges included in net realized investment gains (losses) in the consolidated statement of income	$ 0	$ 46	$ 0	$ 62
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%	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%	1.00%	1.00%
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	$ 4	$ 2	$ 0
Additions for expected credit losses on securities where no credit losses were previously recognized	1	4	1	8
Additions (reductions) for expected credit losses on securities where credit losses were previously recognized	(1)	0	(1)	0
Reductions due to sales/defaults of credit-impaired securities	0	0	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	0	0
Allowance for expected credit losses on fixed maturities classified as available-for-sale, balance, end of period	2	8	2	8
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	$ 2	$ 0	$ 14

Investments (Details) - Other I

Investments (Details) - Other Investments	6 Months Ended
	Jun. 30, 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	Jun. 30, 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	$ 4	$ 5

Fair Value Measurements (Deta_2

Fair Value Measurements (Details) - Fair Value Hierarchy - Recurring basis [Member] - USD ($) $ in Millions	Jun. 30, 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	$ 76,142	$ 74,508
Other liabilities measured on a recurring basis	4	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	75,576	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	3,590	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	35,672	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	1,036	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	1,820	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	33,444	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	14	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	513	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	467	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	46	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	53	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	4,096	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	3,590	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	3,590	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	0	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	0	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	488	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	467	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	21	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	18	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	71,848	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	71,823	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	35,668	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	1,036	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	1,806	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	33,299	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	14	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	25	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	25	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	198	201
Other liabilities measured on a recurring basis	4	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	163	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	4	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	14	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	145	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	Jun. 30, 2021	Dec. 31, 2020
Financial Instruments
Short-term securities	$ 5,703	$ 5,511
Carrying Value [Member]
Financial Instruments
Short-term securities	5,703	5,511
Debt	7,190	6,450
Commercial paper	100	100
Fair Value [Member]
Financial Instruments
Short-term securities	5,703	5,511
Debt	9,258	8,976
Commercial paper	100	100
Fair Value [Member] | Level 1 [Member]
Financial Instruments
Short-term securities	831	630
Debt	0	0
Commercial paper	0	0
Fair Value [Member] | Level 2 [Member]
Financial Instruments
Short-term securities	4,814	4,829
Debt	9,258	8,976
Commercial paper	100	100
Fair Value [Member] | Level 3 [Member]
Financial Instruments
Short-term securities	58	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		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Credit Loss [Abstract]
Premiums receivable (net of allowance for expected credit losses), balance, beginning of period	$ 8,167	$ 8,202	$ 7,829	$ 7,909
Premiums receivable (net of allowance for expected credit losses), balance, end of period	8,555	8,459	8,555	8,459
Premiums receivable, allowance for expected credit losses [Roll Forward]
Premiums receivable, allowance for expected credit losses, beginning balance	110	78	105	49
Current period change for expected credit losses	14	24	30	67
Write-offs of uncollectible premiums receivable	19	8	30	22
Premiums receivable, allowance for expected credit losses, ending balance	$ 105	$ 94	$ 105	$ 94

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	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Reinsurance recoverables, allowance for uncollectible reinsurance
Reinsurance recoverables (net of allowance for estimated uncollectible reinsurance), balance, beginning of period		$ 8,345	$ 8,152	$ 8,350	$ 8,235
Reinsurance recoverables (net of allowance for estimated uncollectible reinsurance), balance, end of period	$ 8,235	8,209	8,093	8,209	8,093
Reinsurance recoverables, allowance for uncollectible reinsurance [Roll Forward]
Reinsurance recoverables, allowance for uncollectible reinsurance, beginning balance		142	149	146	92
Reinsurance recoverables, allowance for estimated uncollectible reinsurance	$ 92	135	156	135	156
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member
Current period change for estimated uncollectible reinsurance		(7)	7	(11)	11
Write-offs of uncollectible reinsurance recoverables		0	0	0	0
Reinsurance recoverables, allowance for uncollectible reinsurance, ending balance	$ 92	$ 135	$ 156	$ 135	156
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
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	6 Months Ended
	Jun. 30, 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	$ 5,720
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		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Credit Loss [Abstract]
Contractholder receivables (net of the allowance for expected credit losses), balance, beginning of period	$ 4,271	$ 4,634	$ 4,242	$ 4,599
Contractholder receivables (net of the allowance for expected credit losses), balance, end of period	4,016	4,314	4,016	4,314
Contractholder receivables, allowance for expected credit losses [Roll Forward]
Contractholder receivables, allowance for expected credit losses, beginning balance	19	20	19	20
Current period change for expected credit losses	0	2	0	2
Write-offs of uncollectible contractholder receivables	0	0	0	0
Contractholder receivables, allowance for expected credit losses, ending balance	$ 19	$ 22	$ 19	$ 22

Goodwill and Other Intangible_3

Goodwill and Other Intangible Assets (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Goodwill by segment
Goodwill	$ 4,020	$ 3,976
Reportable Segments [Member] | Business Insurance [Member]
Goodwill by segment
Goodwill	2,619	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	825	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		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Other intangible assets by major asset class
Intangible assets subject to amortization, gross carrying amount	$ 310		$ 310		$ 306
Intangible assets subject to amortization, accumulated amortization	223		223		215
Intangible assets subject to amortization, net	87		87		91
Intangible assets not subject to amortization	227		227		226
Total other intangible assets, gross carrying amount	537		537		532
Total other intangible assets, net	314		314		317
Amortization expense of intangible assets	3	$ 3	7	$ 7
Estimated intangible asset amortization expense, remainder of 2021	7		7
Estimated intangible asset amortization expense, 2022	14		14
Estimated intangible asset amortization expense, 2023	13		13
Estimated intangible asset amortization expense, 2024	13		13
Estimated intangible asset amortization expense, 2025	12		12
Customer-related [Member]
Other intangible assets by major asset class
Intangible assets subject to amortization, gross carrying amount	105		105		101
Intangible assets subject to amortization, accumulated amortization	37		37		31
Intangible assets subject to amortization, net	68		68		70
Contract-based [Member]
Other intangible assets by major asset class
Intangible assets subject to amortization, gross carrying amount	205		205		205
Intangible assets subject to amortization, accumulated amortization	186		186		184
Intangible assets subject to amortization, net	19		19		$ 21
Insurance Contracts Acquired in Business Combination [Member]
Other intangible assets by major asset class
Estimated intangible asset amortization expense, remainder of 2021	2		2
Estimated intangible asset amortization expense, 2022	3		3
Estimated intangible asset amortization expense, 2023	3		3
Estimated intangible asset amortization expense, 2024	2		2
Estimated intangible asset amortization expense, 2025	$ 2		$ 2

Insurance Claim Reserves (Detai

Insurance Claim Reserves (Details) - Reserve Detail for Claims and Claim Adjustment Expenses - USD ($) $ in Millions	Dec. 31, 2019	Jun. 30, 2021	Jun. 30, 2020	Mar. 31, 2021	Dec. 31, 2020	Mar. 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	135	$ 156	$ 142	$ 146	$ 149
Claims and claim adjustment expense reserves at end of period		55,906
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		10,430	9,826
Estimated increase (decrease) in claims and claim adjustment expenses for claims arising in prior years		(459)	16
Total increases		9,971	9,842
Claims and claim adjustment expense payments for claims arising in current year		3,113	2,664
Claims and claim adjustment expense payments for claims arising in prior years		5,274	5,674
Total payments		8,387	8,338
Unrealized foreign exchange (gain) loss		53	(137)
Net reserves at end of period	43,854	47,994	45,221
Reinsurance recoverables on unpaid losses	8,035	7,901	7,876
Claims and claim adjustment expense reserves at end of period	51,836	55,895	$ 53,097
Amount of increase in gross claims and claim adjustment expense reserves		1,390
Amount of decrease in reinsurance recoverables on unpaid losses		252
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		$ 11

Insurance Claim Reserves (Det_2

Insurance Claim Reserves (Details) - Prior Year Reserve Development - Property-casualty [Member] - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Liability for claims and claim adjustment expense
Net favorable (unfavorable) prior year reserve development included in estimated claims and claim adjustment expenses incurred for claims arising in prior years			$ 459	$ (16)
Net favorable (unfavorable) prior year reserve development impacting the Company's results of operations			499	29
Accretion expense			24	24
Business Insurance [Member]
Liability for claims and claim adjustment expense
Net favorable (unfavorable) prior year reserve development impacting the Company's results of operations	$ 73	$ 0	207	5
Bond & Specialty Insurance [Member]
Liability for claims and claim adjustment expense
Net favorable (unfavorable) prior year reserve development impacting the Company's results of operations	44	(33)	59	(33)
Personal Insurance [Member]
Liability for claims and claim adjustment expense
Net favorable (unfavorable) prior year reserve development impacting the Company's results of operations	$ 65	$ 35	$ 233	$ 57

Other Comprehensive Income an_3

Other Comprehensive Income and Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Accumulated other comprehensive income [Roll Forward]
Balance, beginning of period			$ 29,201
Other comprehensive income (loss), net of taxes	$ 478	$ 1,931	(733)	$ 1,242
Balance, end of period	29,156	26,943	29,156	26,943
Pre-tax components of other comprehensive loss and the related income tax expense (benefit)
Other comprehensive income (loss), before taxes	599	2,435	(946)	1,609
Income tax expense (benefit)	121	504	(213)	367
Other comprehensive income (loss), net of taxes	478	1,931	(733)	1,242
Accumulated Other Comprehensive Income [Member]
Accumulated other comprehensive income [Roll Forward]
Balance, beginning of period	1,291	(49)	2,502	640
Other comprehensive income (loss) before reclassifications	477		(743)
Amounts reclassified from accumulated other comprehensive income, net of tax	1		10
Other comprehensive income (loss), net of taxes	478	1,931	(733)	1,242
Balance, end of period	1,769	1,882	1,769	1,882
Pre-tax components of other comprehensive loss and the related income tax expense (benefit)
Other comprehensive income (loss), before taxes	599	2,435	(946)	1,609
Income tax expense (benefit)	121	504	(213)	367
Other comprehensive income (loss), net of taxes	478	1,931	(733)	1,242
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	2,635		3,892
Other comprehensive income (loss) before reclassifications	441		(805)
Amounts reclassified from accumulated other comprehensive income, net of tax	(19)		(30)
Other comprehensive income (loss), net of taxes	422	1,859	(835)	1,402
Balance, end of period	3,057		3,057
Pre-tax components of other comprehensive loss and the related income tax expense (benefit)
Other comprehensive income (loss), before taxes	533	2,359	(1,063)	1,784
Income tax expense (benefit)	111	500	(228)	382
Other comprehensive income (loss), net of taxes	422	1,859	(835)	1,402
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		182
Other comprehensive income (loss) before reclassifications	0		0
Amounts reclassified from accumulated other comprehensive income, net of tax	0		0
Other comprehensive income (loss), net of taxes	0	2	0	(2)
Balance, end of period	182		182
Pre-tax components of other comprehensive loss and the related income tax expense (benefit)
Other comprehensive income (loss), before taxes	0	3	0	(3)
Income tax expense (benefit)	0	1	0	(1)
Other comprehensive income (loss), net of taxes	0	2	0	(2)
Net Benefit Plan Assets and Obligations Recognized in Shareholders' Equity [Member]
Accumulated other comprehensive income [Roll Forward]
Balance, beginning of period	(812)		(832)
Other comprehensive income (loss) before reclassifications	0		0
Amounts reclassified from accumulated other comprehensive income, net of tax	20		40
Other comprehensive income (loss), net of taxes	20	17	40	35
Balance, end of period	(792)		(792)
Pre-tax components of other comprehensive loss and the related income tax expense (benefit)
Other comprehensive income (loss), before taxes	26	21	51	44
Income tax expense (benefit)	6	4	11	9
Other comprehensive income (loss), net of taxes	20	17	40	35
Net Unrealized Foreign Currency Translation [Member]
Accumulated other comprehensive income [Roll Forward]
Balance, beginning of period	(714)		(740)
Other comprehensive income (loss) before reclassifications	36		62
Amounts reclassified from accumulated other comprehensive income, net of tax	0		0
Other comprehensive income (loss), net of taxes	36	53	62	(193)
Balance, end of period	(678)		(678)
Pre-tax components of other comprehensive loss and the related income tax expense (benefit)
Other comprehensive income (loss), before taxes	40	52	66	(216)
Income tax expense (benefit)	4	(1)	4	(23)
Other comprehensive income (loss), net of taxes	$ 36	$ 53	$ 62	$ (193)

Other Comprehensive Income an_4

Other Comprehensive Income and Accumulated Other Comprehensive Income (Details) - Reclassifications - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Reclassification adjustment impacting net realized investment gains (losses) on the income statement (loss)	$ (61)	$ (13)	$ (105)	$ 85
Reclassification adjustment impacting claims and claim adjustment expenses on the income statement (loss)	5,045	5,107	10,015	9,896
Reclassification adjustment impacting general and administrative expense on the income statement (loss)	1,174	1,121	2,337	2,258
Total reclassifications	(1,131)	85	(2,022)	(635)
Income tax (expense) benefit	(197)	45	(355)	(75)
Amounts reclassified from accumulated other comprehensive income, net of taxes	(934)	40	(1,667)	(560)
Accumulated Other Comprehensive Income [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Total reclassifications	2	12	13	35
Income tax (expense) benefit	1	3	3	7
Amounts reclassified from accumulated other comprehensive income, net of taxes	1	9	10	28
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 (loss)	(24)	(10)	(38)	(8)
Income tax (expense) benefit	(5)	(2)	(8)	(2)
Amounts reclassified from accumulated other comprehensive income, net of taxes	(19)	(8)	(30)	(6)
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 (loss)	0	0	0	0
Income tax (expense) benefit	0	0	0	0
Amounts reclassified from accumulated other comprehensive income, net of taxes	0	0	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 (loss)	11	9	21	18
Reclassification adjustment impacting general and administrative expense on the income statement (loss)	15	13	30	25
Total reclassifications	26	22	51	43
Income tax (expense) benefit	6	5	11	9
Amounts reclassified from accumulated other comprehensive income, net of taxes	20	17	40	34
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 (loss)	0	0	0	0
Income tax (expense) benefit	0	0	0	0
Amounts reclassified from accumulated other comprehensive income, net of taxes	$ 0	$ 0	$ 0	$ 0

Debt (Details)

Debt (Details) - USD ($) $ in Millions	Jun. 08, 2021	Jun. 30, 2021	Jun. 30, 2020
Debt Instrument
Net proceeds of issuance, after the deduction of the underwriting discount and expenses		$ 739	$ 490
Senior Notes [Member] | 3.050% Senior Notes due June 8, 2051 [Member]
Debt Instrument
Debt, principal amount	$ 750
Interest rate (percent)	3.05%
Net proceeds of issuance, after the deduction of the underwriting discount and expenses	$ 739
Percentage of principal amount at which redemption price may be set	100.00%
Basis points added to current Treasury rate used in calculation of alternative redemption price	0.15%

Common Share Repurchases (Detai

Common Share Repurchases (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2021	Apr. 20, 2021
Treasury Stock Transactions, Excluding Value of Shares Reissued [Abstract]
Number of shares repurchased (in shares)	2,600,000	5,000,000
Cost of shares repurchased	$ 400,000	$ 756,000
Average cost per share repurchased (in dollars per share)	$ 157.18	$ 152.65
Number of shares acquired to cover tax withholding costs and exercise costs (in shares)	917	300,000
Cost of shares acquired to cover tax withholding costs and exercise costs	$ 144	$ 42,000
Additional share repurchase authorization			$ 5,000,000
Remaining capacity under share repurchase authorization	$ 5,410,000	$ 5,410,000

Earnings per Share (Details)

Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Earnings Per Share Reconciliation [Abstract]
Net income (loss)	$ 934	$ (40)	$ 1,667	$ 560
Participating share-based awards — allocated income	(7)	(1)	(12)	(3)
Net income (loss) available to common shareholders -- basic	927	(41)	1,655	557
Net income (loss) available to common shareholders -- diluted	$ 927	$ (41)	$ 1,655	$ 557
Weighted average shares outstanding, basic (in shares)	250.7	251.6	251.4	253.6
Weighted average effects of dilutive securities - stock options and performance shares (in shares)	2.4	0	2.2	1.1
Weighted average shares outstanding, diluted (in shares)	253.1	251.6	253.6	254.7
Net income (loss) per common share, basic (in dollars per share)	$ 3.70	$ (0.16)	$ 6.58	$ 2.19
Net income (loss) per common share, diluted (in dollars per share)	$ 3.66	$ (0.16)	$ 6.53	$ 2.19
Excluded allocation of undistributed loss to participating share-based awards because such allocation would result in anti-dilution of basic and diluted earnings per share		$ 2
Amount of shares excluded from computation of net loss per diluted common share since their effects on income was anti-dilutive		0.7

Share-Based Incentive Compens_3

Share-Based Incentive Compensation (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Share-based Payment Arrangement [Abstract]
Stock options vested at end of period, number (in shares)	7,604,850		7,604,850
Stock options vested at end of period, weighted average exercise price (in dollars per share)	$ 123.90		$ 123.90
Stock options vested at end of period, weighted average contractual life remaining (in years)			6 years 4 months 24 days
Stock options vested at end of period, aggregate intrinsic value	$ 196		$ 196
Stock options exercisable at end of period, number (in shares)	4,401,105		4,401,105
Stock options exercisable at end of period, weighted average exercise price (in dollars per share)	$ 117.65		$ 117.65
Stock options exercisable at end of period, weighted average contractual life remaining (in years)			4 years 10 months 24 days
Stock options exercisable at end of period, aggregate intrinsic value	$ 141		$ 141
Total compensation cost recognized in earnings for all share-based incentive compensation awards	36	$ 34	89	$ 80
Tax benefit recognized in earnings related to compensation costs	6	$ 6	15	$ 14
Total unrecognized compensation cost related to all nonvested share-based incentive compensation awards	$ 212		$ 212
Weighted-average period of recognition for unrecognized compensation cost (in years)			2 years

Pension Plans, Retirement Ben_3

Pension Plans, Retirement Benefits and Savings Plans (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Pension Plans [Member]
Defined benefit plan disclosure
Service cost	$ 36	$ 33	$ 71	$ 66
Interest cost on benefit obligation	20	28	41	57
Expected return on plan assets	(68)	(68)	(137)	(137)
Net periodic benefit cost (benefit), amortization of unrecognized prior service benefit	0	0	0	0
Net periodic benefit cost (benefit), amortization of unrecognized net actuarial (gain) loss	27	23	54	46
Total non-service cost (benefit)	(21)	(17)	(42)	(34)
Net periodic benefit cost (benefit)	15	16	29	32
Pension Plans [Member] | Claims and claim adjustment expenses [Member]
Defined benefit plan disclosure
Service cost	15	14	29	28
Total non-service cost (benefit)	(8)	(7)	(17)	(14)
Pension Plans [Member] | General and administrative expenses [Member]
Defined benefit plan disclosure
Service cost	21	19	42	38
Total non-service cost (benefit)	(13)	(10)	(25)	(20)
Postretirement Benefit Plans [Member]
Defined benefit plan disclosure
Service cost	0	0	0	0
Interest cost on benefit obligation	0	1	1	2
Expected return on plan assets	0	0	0	0
Net periodic benefit cost (benefit), amortization of unrecognized prior service benefit	(1)	0	(2)	(2)
Net periodic benefit cost (benefit), amortization of unrecognized net actuarial (gain) loss	0	(1)	(1)	(1)
Total non-service cost (benefit)	(1)	0	(2)	(1)
Net periodic benefit cost (benefit)	(1)	0	(2)	(1)
Postretirement Benefit Plans [Member] | Claims and claim adjustment expenses [Member]
Defined benefit plan disclosure
Service cost	0	0	0	0
Total non-service cost (benefit)	(1)	0	(1)	0
Postretirement Benefit Plans [Member] | General and administrative expenses [Member]
Defined benefit plan disclosure
Service cost	0	0	0	0
Total non-service cost (benefit)	$ 0	$ 0	$ (1)	$ (1)

Leases (Details)

Leases (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Leases [Abstract]
Operating leases	$ 22	$ 24	$ 45	$ 48
Short-term leases	1	1	1	1
Lease expense	23	25	46	49
Less: sublease income	0	0	0	0
Net lease cost	23	25	46	49
Cash payments to settle a lease liability reported in cash flows	27	28	53	55
Right-of-use assets obtained in exchange for new lease liabilities	$ 7	$ 4	$ 19	$ 18
Weighted average discount rate (percent)	2.41%	2.94%	2.41%	2.94%
Weighted average remaining lease term (in years)	4 years 9 months 18 days	4 years 10 months 24 days	4 years 9 months 18 days	4 years 10 months 24 days

Contingencies, Commitments an_2

Contingencies, Commitments and Guarantees (Details) - Commitments - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Contingencies, Commitments and Guarantees [Abstract]
Unfunded commitments to private equity limited partnerships, real estate partnerships and others	$ 1,650	$ 1,760

Contingencies, Commitments an_3

Contingencies, Commitments and Guarantees (Details) - Guarantees $ in Millions	Jun. 30, 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