The Travelers Companies, Inc. (TRV) 10-K 14 Feb 19 2018 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2018	Feb. 08, 2019	Jun. 30, 2018
Document and Entity Information
Registrant name	TRAVELERS COMPANIES, INC.
Central index key	86,312
Document type	10-K
Document period end date	Dec. 31, 2018
Amendment flag	false
Current fiscal year end date	--12-31
Current reporting status	Yes
Well-known seasoned issuer	Yes
Voluntary filers	No
Filer category	Large Accelerated Filer
Entity emerging growth company	false
Entity small business	false
Entity shell company	false
Common stock shares outstanding		263,391,034
Document fiscal year focus	2,018
Document fiscal period focus	FY
Entity public float			$ 32,661,754,275

Consolidated Statement of Incom

Consolidated Statement of Income - USD ($) shares in Millions, $ in Millions		3 Months Ended								12 Months Ended
		Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues
Premiums										$ 27,059	$ 25,683	$ 24,534
Net investment income										2,474	2,397	2,302
Fee income										432	447	458
Net realized investment gains	[1]									114	216	68
Other revenues										203	159	263
Total revenues		$ 7,796	$ 7,723	$ 7,477	$ 7,286	$ 7,451	$ 7,325	$ 7,184	$ 6,942	30,282	28,902	27,625
Claims and expenses
Claims and claim adjustment expenses										18,291	17,467	15,070
Amortization of deferred acquisition costs										4,381	4,166	3,985
General and administrative expenses										4,297	4,170	4,154
Interest expense										352	369	363
Total claims and expenses		7,050	6,917	6,846	6,508	6,591	7,005	6,394	6,182	27,321	26,172	23,572
Income before income taxes		746	806	631	778	860	320	790	760	2,961	2,730	4,053
Income tax expense		125	97	107	109	309	27	195	143	438	674	1,039
Net income		$ 621	$ 709	$ 524	$ 669	$ 551	$ 293	$ 595	$ 617	$ 2,523	$ 2,056	$ 3,014
Net income per share
Basic (in dollars per share)		$ 2.33	$ 2.65	$ 1.93	$ 2.45	$ 2	$ 1.06	$ 2.13	$ 2.19	$ 9.37	$ 7.39	$ 10.39
Diluted (in dollars per share)		$ 2.32	$ 2.62	$ 1.92	$ 2.42	$ 1.98	$ 1.05	$ 2.11	$ 2.17	$ 9.28	$ 7.33	$ 10.28
Weighted average number of common shares outstanding
Basic (in shares)										267.4	276	288.1
Diluted (in shares)										269.8	278.6	291
[1]	Total other-than-temporary impairment (OTTI) losses were $(1) million, $(13) million and $(40) million for the years ended December 31, 2018, 2017 and 2016, respectively. Of total OTTI, credit losses of $(1) million, $(14) million and $(29) million for the years ended December 31, 2018, 2017 and 2016, respectively, were recognized in net realized investment gains. In addition, unrealized gains (losses) from other changes in total OTTI of $0 million, $1 million and $(11) million for the years ended December 31, 2018, 2017 and 2016, respectively, were recognized in other comprehensive income (loss) as part of changes in net unrealized gains (losses) on investment securities having credit losses recognized in the consolidated statement of income.

Consolidated Statement of Inc_2

Consolidated Statement of Income Parentheticals - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Statement [Abstract]
Total other-than-temporary impairment losses	$ (1)	$ (13)	$ (40)
Other-than-temporary impairment, credit losses recognized in net realized investment gains	(1)
Other-than-temporary impairment, credit losses recognized in net realized investment gains		(14)	(29)
Unrealized gains from other changes in total other-than-temporary impairments recognized in other comprehensive income (loss) as part of changes in net unrealized gains (losses) on investment securities having credit losses recognized in the consolidated statement of income		$ 1
Unrealized losses from other changes in total other-than-temporary impairments recognized in other comprehensive income (loss) as part of changes in net unrealized gains (losses) on investment securities having credit losses recognized in the consolidated statement of income	$ 0		$ (11)

Consolidated Statement of Compr

Consolidated Statement of Comprehensive Income - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 621	$ 709	$ 524	$ 669	$ 551	$ 293	$ 595	$ 617	$ 2,523	$ 2,056	$ 3,014
Other comprehensive income (loss):
Changes in net unrealized gains (losses) on investment securities having no credit losses recognized in the consolidated statement of income									(1,489)	294	(883)
Changes in net unrealized gains (losses) on investment securities having credit losses recognized in the consolidated statement of income									(27)	8	21
Net changes in benefit plan assets and obligations									(56)	29	16
Net changes in unrealized foreign currency translation									(247)	191	(41)
Other comprehensive income (loss) before income taxes									(1,819)	522	(887)
Income tax expense (benefit)									(349)	110	(289)
Other comprehensive income (loss), net of taxes									(1,470)	412	(598)
Comprehensive income									$ 1,053	$ 2,468	$ 2,416

Consolidated Balance Sheet

Consolidated Balance Sheet - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Assets
Fixed maturities, available for sale, at fair value (amortized cost $63,601 and $61,316)	$ 63,464	$ 62,694
Equity securities, at fair value (cost $382)	368
Equity securities, available for sale, at fair value (cost $440)		453
Real estate investments	904	932
Short-term securities	3,985	4,895
Other investments	3,557	3,528
Total investments	72,278	72,502
Cash	373	344	$ 307	$ 380
Investment income accrued	624	606
Premiums receivable	7,506	7,144
Reinsurance recoverables	8,370	8,309
Ceded unearned premiums	578	551
Deferred acquisition costs	2,120	2,025
Deferred taxes	445	70
Contractholder receivables	4,785	4,775
Goodwill	3,937	3,951
Other intangible assets	345	342
Other assets	2,872	2,864
Total assets	104,233	103,483
Liabilities
Claims and claim adjustment expense reserves	50,668	49,650
Unearned premium reserves	13,555	12,915
Contractholder payables	4,785	4,775
Payables for reinsurance premiums	289	274
Debt	6,564	6,571
Other liabilities	5,478	5,567
Total liabilities	81,339	79,752
Shareholders’ equity
Common stock (1,750.0 shares authorized; 263.7 and 271.5 shares issued, 263.6 and 271.4 shares outstanding)	23,144	22,886
Retained earnings	35,204	33,462
Accumulated other comprehensive loss	(1,859)	(343)
Treasury stock, at cost (510.9 and 500.9 shares)	(33,595)	(32,274)
Total shareholders’ equity	22,894	23,731	$ 23,221
Total liabilities and shareholders’ equity	$ 104,233	$ 103,483

Consolidated Balance Sheet Pare

Consolidated Balance Sheet Parentheticals - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Fixed maturities, available for sale, amortized cost	$ 63,601	$ 61,316
Equity securities, cost	$ 382
Equity securities, available for sale, cost		$ 440
Common stock, shares authorized (in shares)	1,750,000,000	1,750,000,000
Common stock, shares issued (in shares)	263,700,000	271,500,000
Common stock, shares outstanding (in shares)	263,600,000	271,400,000
Treasury stock, at cost, shares (in shares)	510,900,000	500,900,000

Consolidated Statement of Chang

Consolidated Statement of Changes in Shareholders' Equity - USD ($) shares in Millions, $ in Millions	Total	Common stock [Member]	Retained earnings [Member]	Accumulated other comprehensive income (loss), net of tax [Member]	Treasury stock, at cost [Member]	Common shares outstanding [Member]
Balance, beginning of year at Dec. 31, 2015		$ 22,172	$ 29,945	$ (157)	$ (28,362)
Shareholders' Equity [Roll Forward]
Employee share-based compensation		287
Compensation amortization under share-based plans and other changes		155
Net income	$ 3,014		3,014
Dividends			(762)
Other			(1)
Other comprehensive income (loss)	(598)			(598)
Treasury stock acquired — share repurchase authorization					(2,400)
Net shares acquired related to employee share-based compensation plans					(72)
Balance, end of year at Dec. 31, 2016	23,221	22,614	32,196	(755)	(30,834)
Balance, beginning of year (in shares) at Dec. 31, 2015						295.9
Common shares outstanding
Treasury stock acquired — share repurchase authorization (in shares)						(21.3)
Net shares issued under employee share-based compensation plans (in shares)						5
Balance, end of year (in shares) at Dec. 31, 2016						279.6
Shareholders' Equity [Roll Forward]
Employee share-based compensation		136
Compensation amortization under share-based plans and other changes		136
Net income	2,056		2,056
Dividends			(789)
Other			(1)
Other comprehensive income (loss)	412			412
Treasury stock acquired — share repurchase authorization					(1,378)
Net shares acquired related to employee share-based compensation plans	(62)				(62)
Balance, end of year at Dec. 31, 2017	$ 23,731	22,886	33,462	(343)	(32,274)
Common shares outstanding
Treasury stock acquired — share repurchase authorization (in shares)						(10.9)
Net shares issued under employee share-based compensation plans (in shares)						2.7
Balance, end of year (in shares) at Dec. 31, 2017	271.4					271.4
Shareholders' Equity [Roll Forward]
Reclassification of certain tax effects from adoption of updated accounting guidance				(24)
Cumulative effect of adoption of updated accounting guidance for equity financial instruments			22	(22)
Balance, beginning of year at Dec. 31, 2017	$ 23,731	22,886	33,462	(343)	(32,274)
Shareholders' Equity [Roll Forward]
Employee share-based compensation		108
Compensation amortization under share-based plans and other changes		150
Reclassification of certain tax effects from adoption of updated accounting guidance			24	(24)
Net income	2,523		2,523
Dividends			(818)
Other			(9)
Other comprehensive income (loss)	(1,470)			(1,470)
Treasury stock acquired — share repurchase authorization	(1,270)				(1,270)
Net shares acquired related to employee share-based compensation plans	(51)				(51)
Balance, end of year at Dec. 31, 2018	$ 22,894	$ 23,144	$ 35,204	(1,859)	$ (33,595)
Balance, beginning of year (in shares) at Dec. 31, 2017	271.4					271.4
Common shares outstanding
Treasury stock acquired — share repurchase authorization (in shares)	(9.6)					(9.6)
Net shares issued under employee share-based compensation plans (in shares)						1.8
Balance, end of year (in shares) at Dec. 31, 2018	263.6					263.6
Shareholders' Equity [Roll Forward]
Cumulative effect of adoption of updated accounting guidance for equity financial instruments				$ (22)

Consolidated Statement of Cash

Consolidated Statement of Cash Flows - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities
Net income		$ 2,523	$ 2,056	$ 3,014
Adjustments to reconcile net income to net cash provided by operating activities:
Net realized investment gains	[1]	(114)	(216)	(68)
Depreciation and amortization		803	813	826
Deferred federal income tax expense (benefit)		(13)	337	110
Amortization of deferred acquisition costs		4,381	4,166	3,985
Equity in income from other investments		(365)	(397)	(232)
Premiums receivable		(393)	(394)	(286)
Reinsurance recoverables		(100)	16	610
Deferred acquisition costs		(4,488)	(4,257)	(4,061)
Claims and claim adjustment expense reserves		1,246	1,460	(257)
Unearned premium reserves		710	521	372
Other operating activities		190	43	456
Net cash provided by operating activities		4,380	4,148	4,469
Cash flows from investing activities
Proceeds from maturities of fixed maturities		7,086	8,750	8,975
Proceeds from sales of investments:
Fixed maturities		3,546	1,854	1,417
Equity securities		178
Equity securities			765	92
Real estate investments		74	23	69
Other investments		511	468	566
Purchases of investments:
Fixed maturities		(13,526)	(12,250)	(11,609)
Equity securities		(117)
Equity securities			(459)	(51)
Real estate investments		(74)	(59)	(48)
Other investments		(537)	(541)	(580)
Net sales (purchases) of short-term securities		908	(26)	(199)
Securities transactions in the course of settlement		(56)	(47)	(21)
Acquisitions, net of cash acquired		(4)	(439)
Other investing activities		(318)	(241)	(338)
Net cash used in investing activities		(2,329)	(2,202)	(1,727)
Cash flows from financing activities
Treasury stock acquired — share repurchase authorization		(1,270)	(1,378)	(2,400)
Treasury stock acquired — net employee share-based compensation		(51)	(62)	(72)
Dividends paid to shareholders		(814)	(785)	(757)
Payment of debt		(600)	(657)	(400)
Issuance of debt		591	789	491
Issuance of common stock -- employee share options		132	173	332
Net cash used in financing activities		(2,012)	(1,920)	(2,806)
Effect of exchange rate changes on cash		(10)	11	(9)
Net increase (decrease) in cash		29	37	(73)
Cash at beginning of year		344	307	380
Cash at end of year		373	344	307
Supplemental disclosure of cash flow information
Income taxes paid		408	514	892
Interest paid		$ 347	$ 367	$ 358
[1]	Total other-than-temporary impairment (OTTI) losses were $(1) million, $(13) million and $(40) million for the years ended December 31, 2018, 2017 and 2016, respectively. Of total OTTI, credit losses of $(1) million, $(14) million and $(29) million for the years ended December 31, 2018, 2017 and 2016, respectively, were recognized in net realized investment gains. In addition, unrealized gains (losses) from other changes in total OTTI of $0 million, $1 million and $(11) million for the years ended December 31, 2018, 2017 and 2016, respectively, were recognized in other comprehensive income (loss) as part of changes in net unrealized gains (losses) on investment securities having credit losses recognized in the consolidated statement of income.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Basis of Presentation The consolidated financial statements include the accounts of The Travelers Companies, Inc. (together with its subsidiaries, the Company). The preparation of the consolidated financial statements in conformity with U.S. generally accepted accounting principles (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 consolidated financial statements and the reported amounts of revenues and claims and expenses during the reporting period. Actual results could differ from those estimates. Certain reclassifications have been made to the 2017 and 2016 financial statements to conform to the 2018 presentation. All material intercompany transactions and balances have been eliminated. On August 4, 2017, the Company completed its acquisition of all issued and outstanding shares of Simply Business Holdings Ltd (Simply Business), a leading provider of small business insurance policies primarily in the United Kingdom, for a purchase price of approximately $464 million , which included the repayment of debt and other obligations of Simply Business. In addition, the Company issued 95,953 shares of restricted common stock valued at approximately $12 million to certain employees of Simply Business who were equity holders of Simply Business. Subject to the satisfaction of certain conditions, 50% of the restricted stock will vest two years from the issuance date and the remainder will vest three years from the issuance date. The Company used a portion of the net proceeds from the issuance of senior notes in May 2017 (described in more detail in note 8) and internal resources to fund this transaction. Adoption of Accounting Standards Financial Instruments: Recognition and Measurement of Financial Assets and Financial Liabilities In January 2016, the Financial Accounting Standards Board (FASB) issued updated guidance to address the recognition, measurement, presentation and disclosure of certain financial instruments. The updated guidance requires equity investments, except those accounted for under the equity method of accounting, that have readily determinable fair value to be measured at fair value with any changes in fair value recognized in net income. Equity securities that do not have readily determinable fair values may be measured at estimated fair value or cost less impairment, if any, adjusted for subsequent observable price changes, with changes in the carrying value recognized in net income. A qualitative assessment for impairment is required for equity investments without readily determinable fair values. The updated guidance also eliminates the requirement to disclose the method and significant assumptions used to estimate the fair value of financial instruments measured at amortized cost on the balance sheet. The updated guidance was effective for the quarter ended March 31, 2018. The adoption of this guidance resulted in the recognition of $22 million of net after-tax unrealized gains on equity investments as a cumulative effect adjustment that increased retained earnings as of January 1, 2018 and decreased accumulated other comprehensive income (AOCI) by the same amount. The Company elected to report changes in the fair value of equity investments in net realized investment gains (losses). At December 31, 2017, equity investments were classified as available-for-sale on the Company's balance sheet. However, upon adoption, the updated guidance eliminated the available-for-sale balance sheet classification for equity investments. Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income On February 14, 2018, the FASB issued updated guidance that allows a reclassification from AOCI to retained earnings of the stranded tax effects that occurred due to the enactment of the Tax Cuts and Jobs Act of 2017 (TCJA). The updated guidance is effective for reporting periods beginning after December 15, 2018 and is to be applied retrospectively to each period in which there are items impacted by the TCJA remaining in AOCI or at the beginning of the period of adoption. Early adoption is permitted. The Company adopted the updated guidance effective January 1, 2018 and elected to reclassify the income tax effects of the TCJA from AOCI to retained earnings as of January 1, 2018. This reclassification resulted in an increase in retained earnings of $24 million as of January 1, 2018 and a decrease in AOCI by the same amount. Revenue from Contracts with Customers In May 2014, the FASB issued updated guidance to clarify the principles for recognizing revenue. The updated guidance was effective for reporting periods beginning after December 15, 2017, and requires an entity to recognize revenue as performance obligations are met, in order to reflect the transfer of goods or services to customers in an amount that reflects the consideration the entity is entitled to receive for those goods or services. For the year ended December 31, 2018 , approximately $171 million , or less than 1% of the Company's total revenues, were within the scope of this updated guidance and were generated from the services described below. While insurance contracts are not within the scope of this updated guidance, the Company’s revenue related to certain services with no underlying insurance risk is subject to the updated guidance. These services include the following: (i) insurance-related services, such as risk management services, claims administration, loss control and risk management information services on behalf of non-insureds; (ii) servicing carrier fees for various residual market pools and associations; and (iii) administrative fees related to servicing third-party insurers’ obligations to participate in the Workers' Compensation Residual Market Plans in certain states. The revenues earned from these service contracts were not impacted by the adoption of the updated guidance. These revenues are earned as the Company completes its performance obligations, which primarily occurs on a pro rata basis over the contract service period and reported in fee income in the Company’s consolidated statement of income. Commissions earned from on-line insurance brokerage services are also subject to this updated guidance and were also not impacted by the adoption of the updated guidance. Commissions are earned upon collection of the gross premium in accordance with the contracts and an accrual is made to recognize policy cancellations, either at the policyholder’s direction or for non-payment. Commissions are reported in other revenues in the Company's consolidated statement of income. The Company does not capitalize the costs to obtain or fulfill the contracts for which revenues are reported in fee income and other revenues, and has not recognized any material impairment losses on the receivables related to these contracts during the twelve months ended December 31, 2018. The Company adopted the updated guidance effective January 1, 2018. The adoption did not have an effect on the Company’s results of operations, financial position or liquidity. Statement of Cash Flows: Classification of Certain Cash Receipts and Cash Payments In August 2016, the FASB issued updated guidance on the classification of cash flows related to certain activities in the statement of cash flows to reduce diversity in practice. The updated guidance was effective for reporting periods beginning after December 15, 2017 and was applied retrospectively to all periods presented. Under the new guidance, distributions received on equity method investments that are considered to be a return on investment are reported as cash flows from operating activities. These distributions were previously reported as cash flows from investing activities. The adoption of this guidance did not have an effect on the Company’s results of operations, financial position or liquidity. Other Accounting Standards Not Yet Adopted Leases In February 2016, the FASB issued updated guidance to require lessees to recognize a right-of-use asset and a lease liability for leases with terms of more than 12 months. The updated guidance retains the two classifications of a lease as either an operating or finance lease (previously referred to as a capital lease). Both lease classifications require the lessee to record the right-of-use asset and the lease liability based upon the present value of cash flows. Finance leases will reflect the financial arrangement by recognizing interest expense on the lease liability separately from the amortization expense of the right-of-use asset. Operating leases will recognize lease expense (with no separate recognition of interest expense) on a straight-line basis over the term of the lease. The accounting by lessors is not significantly changed by the updated guidance. The updated guidance requires expanded qualitative and quantitative disclosures, including additional information about the amounts recorded in the financial statements. In July 2018, the FASB amended the updated guidance on leases that was issued in February 2016 and provided an additional transition method with which to adopt the updated guidance. Under the additional transition method, entities may elect to recognize a cumulative-effect adjustment to the opening balance of retained earnings in the year of adoption. Consequently, if this transition method is elected, an entity’s reporting for the comparative periods prior to adoption presented in the financial statements would continue to be in accordance with current lease guidance. The amendments also provide lessors with a practical expedient to combine nonlease components (e.g., a fee for common area maintenance when leasing office space) with the associated lease component rather than accounting for those components separately if certain criteria are met. The updated guidance requires entities to recognize a right-of-use asset and lease liability equal to the present value of lease payments for all leases other than those that are less than one year. The updated guidance, as amended, is effective for reporting periods beginning after December 15, 2018. The Company plans to adopt the updated guidance effective January 1, 2019 using the additional transition method described above. The adoption of the updated guidance will result in the recognition of a right-of-use asset and a lease liability of the same amount, which will be less than 1% of total assets and total liabilities, and is not expected to have a material effect on the Company’s results of operations, financial position or liquidity. Financial Instruments - Credit Losses: Measurement of Credit Losses on Financial Instruments In June 2016, the FASB issued updated guidance for the accounting for credit losses for financial instruments. The updated guidance applies a new credit loss model (current expected credit losses or CECL) for determining credit-related impairments for financial instruments measured at amortized cost (e.g. reinsurance recoverables, including structured settlements that are recorded as part of reinsurance recoverables) and requires an entity to estimate the credit losses expected over the life of an exposure or pool of exposures. The estimate of expected credit losses should consider historical information, current information, as well as reasonable and supportable forecasts, including estimates of prepayments. The expected credit losses, and subsequent adjustments to such losses, will be recorded through an allowance account that is deducted from the amortized cost basis of the financial asset, with the net carrying value of the financial asset presented on the consolidated balance sheet at the amount expected to be collected. The updated guidance also amends the current other-than-temporary impairment model for available-for-sale debt securities by requiring the recognition of impairments relating to credit losses through an allowance account and limits the amount of credit loss to the difference between a security’s amortized cost basis and its fair value. In addition, the length of time a security has been in an unrealized loss position will no longer impact the determination of whether a credit loss exists. The updated guidance is effective for reporting periods beginning after December 15, 2019. Early adoption is permitted for reporting periods beginning after December 15, 2018. Based on the financial instruments currently held by the Company, there would not be a material effect on the Company’s results of operations, financial position or liquidity if the new guidance were able to be adopted in the current accounting period. The impact on the Company’s results of operations, financial position or liquidity at the date of adoption of the updated guidance will be determined by the financial instruments held by the Company and the economic conditions at that time. Intangibles - Goodwill and Other In January 2017, the FASB issued updated guidance that eliminates the requirement to calculate the implied fair value of goodwill (i.e., Step 2 of the current goodwill impairment test) to measure a goodwill impairment charge. Instead, entities will record an impairment charge by comparing a reporting unit’s fair value with its carrying amount and recognizing an impairment charge for the excess of the carrying amount over estimated fair value (i.e., Step 1 of current guidance). The implied fair value of goodwill is currently determined in Step 2 by deducting the fair value of all assets and liabilities of the reporting unit (determined in the same manner as a business combination) from the reporting unit’s fair value as determined in Step 1 (including any corporate-level assets or liabilities that were included in the determination of the carrying amount and fair value of the reporting unit in Step 1). The updated guidance requires an entity to perform its annual, or interim, impairment test by either: (1) an initial qualitative assessment of factors (such as changes in management, key personnel, strategy, key technology or customers) that may impact a reporting unit’s fair value and lead to the determination that it is more likely than not that the reporting unit’s fair value is less than its carrying value, including goodwill (consistent with current guidance), or (2) applying Step 1. The updated guidance is effective for reporting periods beginning after December 15, 2019 and is to be applied prospectively. Early adoption is permitted for interim or annual goodwill impairment tests performed on testing dates after January 1, 2017. The adoption of this guidance is not expected to have a material effect on the Company’s results of operations, financial position or liquidity. Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract In August 2018, the FASB issued updated guidance to align the accounting for implementation costs incurred in a software hosting arrangement (i.e., a cloud computing arrangement) that is a service contract with the guidance for capitalizing implementation costs incurred to develop or obtain internal-use software. Accordingly, the updated guidance requires an entity to determine the stage of a project that the implementation activity relates to and the nature of the associated costs in order to determine whether those costs should be expensed as incurred or capitalized. The updated guidance also requires the entity to amortize the capitalized implementation costs as an expense over the term of the hosting arrangement. The updated guidance is effective for reporting periods beginning after December 15, 2019. Early adoption is permitted. The Company plans to early adopt the updated guidance effective January 1, 2019 using the prospective method of adoption. The adoption of the updated guidance is not expected to have a material effect on the Company’s results of operations, financial position or liquidity. Accounting Policies Investments Fixed Maturities Fixed maturities include bonds, notes and redeemable preferred stocks. Fixed maturities, including instruments subject to securities lending agreements, are classified as available for sale and reported at fair value, with unrealized investment gains and losses, net of income taxes, charged or credited directly to other comprehensive income. Equity Securities Equity securities, which include public common and non-redeemable preferred stocks, are reported at fair value with changes in fair value recognized in net income. Prior to January 1, 2018, equity securities were classified as available for sale and changes in their fair value were charged or credited directly to other comprehensive income. Real Estate Investments The Company’s real estate investments include warehouses, office buildings and other commercial land and properties that are directly owned. Real estate is recorded on the purchase date at the purchase price, which generally represents fair value, and is supported by internal analysis or external appraisals that use discounted cash flow analyses and other acceptable valuation techniques. Real estate held for investment purposes is subsequently carried at cost less accumulated depreciation. Buildings are depreciated on a straight-line basis over the shorter of the expected useful life of the building or 39 years . Real estate held for sale is carried at lower of cost or fair value, less estimated costs to sell. Short-term Securities Short-term securities have an original maturity of less than one year and are carried at amortized cost, which approximates fair value. Other Investments Investments in Private Equity Limited Partnerships, Hedge Funds and Real Estate Partnerships The Company uses the equity method of accounting for investments in private equity limited partnerships, hedge funds and real estate partnerships. The partnerships and the hedge funds generally report investments on their balance sheet at fair value. The financial statements prepared by the investee are received by the Company on a lag basis, with the lag period generally dependent upon the type of underlying investments. The private equity and real estate partnerships provide financial information quarterly which is generally available to investors, including the Company, within three months following the date of the reporting period. The hedge funds provide financial information monthly, which is generally available to investors within one month following the date of the reporting period. The Company regularly requests financial information from the partnerships prior to the receipt of the partnerships’ financial statements and records any material information obtained from these requests in its consolidated financial statements. Other Also included in other investments are non-public common equities, preferred equities and derivatives. Non-public common equities and preferred equities are reported at fair value with changes in fair value recognized in net income. Prior to January 1, 2018, non-public common equities and preferred equities were reported at fair value with changes in fair value, net of taxes, charged or credited directly to other comprehensive income. The Company’s derivative financial instruments are carried at fair value, with the changes in fair value reflected in the consolidated statement of income in net realized investment gains (losses). For a further discussion of the derivatives used by the Company, see note 3. Net Investment Income Investment income from fixed maturities is recognized based on the constant effective yield method which includes an adjustment for estimated principal pre-payments, if any. The effective yield used to determine amortization for fixed maturities subject to prepayment risk (e.g., asset-backed, loan-backed and structured securities) is recalculated and adjusted periodically based upon actual historical and/or projected future cash flows, which are obtained from a widely-accepted securities data provider. The adjustments to the yield for highly rated prepayable fixed maturities are accounted for using the retrospective method. The adjustments to the yield for non-highly rated prepayable fixed maturities are accounted for using the prospective method. Dividends on equity securities (including those with transfer restrictions) are recognized in income when declared. Rental income on real estate is recognized on a straight-line basis over the lease term. See the section titled: Real Estate in note 3 for further discussion. Investments in private equity limited partnerships, hedge funds, real estate partnerships and joint ventures are accounted for using the equity method of accounting, whereby the Company’s share of the investee’s earnings or losses in the fund is reported in net investment income. Accrual of income is suspended on non-securitized fixed maturities that are in default, or on which it is likely that future payments will not be made as scheduled. Interest income on investments in default is recognized only when payments are received. Investments included in the consolidated balance sheet that were not income-producing for the preceding 12 months were not material. For fixed maturities where the Company records an other-than-temporary impairment, a determination is made as to the cause of the impairment and whether the Company expects a recovery in the value. For fixed maturities where the Company expects a recovery in value, not necessarily to par, the constant effective yield method is utilized, and the investment is amortized to the expected recovery amount. Investment Gains and Losses Net realized investment gains and losses are included as a component of pre-tax revenues based upon specific identification of the investments sold on the trade date. Included in net realized investment gains (losses) are other-than-temporary impairment losses on invested assets other than those investments accounted for using the equity method of accounting as described in the “Investment Impairments” section that follows. Investment Impairments The Company conducts a periodic review to identify and evaluate invested assets having other-than-temporary impairments. Other-Than-Temporary Impairments of Fixed Maturities Some of the factors considered in identifying other-than-temporary impairments of fixed maturities include: (1) the extent to which the fair value has been less than amortized cost; (2) the financial condition, near-term and long-term prospects for the issuer, including the relevant industry conditions and trends, and implications of rating agency actions and offering prices; (3) the likelihood of the recoverability of principal and interest; (4) whether it is more likely than not that the Company will be required to sell the investment prior to an anticipated recovery in value; and (5) the length of time and extent to which the fair value has been less than amortized cost. For fixed maturity investments that the Company does not intend to sell or for which it is more likely than not that the Company would not be required to sell before an anticipated recovery in value, the Company separates the credit loss component of the impairment from the amount related to all other factors and reports the credit loss component in net realized investment gains (losses). The impairment related to all other factors is reported in other comprehensive income. For fixed maturity investments the Company intends to sell or for which it is more likely than not that the Company will be required to sell before an anticipated recovery in value, the full amount of the impairment is included in net realized investment gains (losses). Upon recognizing an other-than-temporary impairment, the new cost basis of the investment is the previous amortized cost basis less the other-than-temporary impairment recognized in net realized investment gains (losses). The new cost basis is not adjusted for any subsequent recoveries in fair value; however, for fixed maturity investments the difference between the new cost basis and the expected cash flows is accreted on a quarterly basis to net investment income over the remaining expected life of the investment. Determination of Credit Loss — Fixed Maturities The Company determines the credit loss component of fixed maturity investments by utilizing discounted cash flow modeling to determine the present value of the security and comparing the present value with the amortized cost of the security. If the amortized cost is greater than the present value of the expected cash flows, the difference is considered a credit loss and recognized in net realized investment gains (losses). For non-structured fixed maturities (U.S. Treasury securities, obligations of U.S. government and government agencies and authorities, obligations of states, municipalities and political subdivisions, debt securities issued by foreign governments and certain corporate debt), the estimate of expected cash flows is determined by projecting a recovery value and a recovery time frame and assessing whether further principal and interest will be received. The determination of recovery value incorporates an issuer valuation assumption utilizing one or a combination of valuation methods as deemed appropriate by the Company. The Company determines the undiscounted recovery value by allocating the estimated value of the issuer to the Company’s assessment of the priority of claims. The present value of the cash flows is determined by applying the effective yield of the security at the date of acquisition (or the most recent implied rate used to accrete the security if the implied rate has changed as a result of a previous impairment) and an estimated recovery time frame. Generally, that time frame for securities for which the issuer is in bankruptcy is 12 months . For securities for which the issuer is financially troubled but not in bankruptcy, that time frame is generally 24 months . Included in the present value calculation are expected principal and interest payments; however, for securities for which the issuer is classified as bankrupt or in default, the present value calculation assumes no interest payments and a single recovery amount. In estimating the recovery value, significant judgment is involved in the development of assumptions relating to a myriad of factors related to the issuer including, but not limited to, revenue, margin and earnings projections, the likely market or liquidation values of assets, potential additional debt to be incurred pre- or post-bankruptcy/restructuring, the ability to shift existing or new debt to different priority layers, the amount of restructuring/bankruptcy expenses, the size and priority of unfunded pension obligations, litigation or other contingent claims, the treatment of intercompany claims and the likely outcome with respect to inter-creditor conflicts. For structured fixed maturity securities (primarily residential and commercial mortgage-backed securities and asset-backed securities), the Company estimates the present value of the security by projecting future cash flows of the assets underlying the securitization, allocating the flows to the various tranches based on the structure of the securitization and determining the present value of the cash flows using the effective yield of the security at the date of acquisition (or the most recent implied rate used to accrete the security if the implied rate has changed as a result of a previous impairment or changes in expected cash flows). The Company incorporates levels of delinquencies, defaults and severities as well as credit attributes of the remaining assets in the securitization, along with other economic data, to arrive at its estimate of the parameters applied to the assets underlying the securitization. Real Estate Investments On at least an annual basis, the Company obtains independent appraisals for substantially all of its real estate investments. In addition, the carrying value of all real estate investments is reviewed for impairment on a quarterly basis or when events or changes in circumstances indicate that the carrying amount may not be recoverable. The review for impairment considers the valuation from the independent appraisal, when applicable, and incorporates an estimate of the undiscounted cash flows expected to result from the use and eventual disposition of the real estate property. An impairment loss is recognized if the expected future undiscounted cash flows are less than the carrying value of the real estate property. The impairment loss is the amount by which the carrying amount exceeds fair value. Other Investments The Company reviews its investments in private equity limited partnerships, hedge funds and real estate partnerships for impairment no less frequently than quarterly and monitors the performance throughout the year through discussions with the managers/general partners. If the Company becomes aware of an impairment of a partnership’s investments at the balance sheet date prior to receiving the partnership’s financial statements, it will recognize an impairment by recording a reduction in the carrying value of the partnership with a corresponding charge to net investment income. Changes in Intent to Sell Temporarily Impaired Assets The Company may, from time to time, sell invested assets subsequent to the balance sheet date that it did not intend to sell at the balance sheet date. Conversely, the Company may not sell invested assets that it asserted that it intended to sell at the balance sheet date. Such changes in intent are due to events occurring subsequent to the balance sheet date. The types of events that may result in a change in intent include, but are not limited to, significant changes in the economic facts and circumstances related to the invested asset (e.g., a downgrade or upgrade from a rating agency), significant unforeseen changes in liquidity needs, or changes in tax laws or the regulatory environment. Securities Lending The Company has, from time to time, engaged in securities lending activities from which it generates net investment income by lending certain of its investments to other institutions for short periods of time. Borrowers of these securities provide collateral equal to at least 102% of the market value of the loaned securities plus accrued interest. This collateral is held by a third-party custodian, and the Company has the right to access the collateral only in the event that the institution borrowing the Company’s securities is in default under the lending agreement (i.e., the Company is not permitted to re-pledge or sell any such collateral). Therefore, the Company does not recognize the receipt of the collateral held by the third-party custodian or the obligation to return the collateral. The loaned securities remain a recorded asset of the Company. The Company accepts only cash as collateral for securities on loan and restricts the manner in which that cash is invested. Reinsurance Recoverables Amounts recoverable from reinsurers are estimated in a manner consistent with the associated claim liability. The Company reports its reinsurance recoverables net of an allowance for estimated uncollectible reinsurance recoverables. The allowance is based upon the Company’s ongoing review of amounts outstanding, length of collection periods, changes in reinsurer credit standing, disputes, applicable coverage defenses and other relevant factors. Amounts deemed to be uncollectible, including amounts due from known insolvent reinsurers, are written off against the allowance for estimated uncollectible reinsurance recoverables. Any subsequent collections of amounts previously written off are reported as part of claims and claim adjustment expenses. The Company evaluates and monitors the financial condition of its reinsurers under voluntary reinsurance arrangements to minimize its exposure to significant losses from reinsurer insolvencies. Deferred Acquisition Costs Incremental direct costs of acquired, new and renewal insurance contracts, consisting of commissions (other than contingent commissions) and premium-related taxes, are capitalized and charged to expense pro rata over the contract periods in which the related premiums are earned. Deferred acquisition costs are reviewed to determine if they are recoverable from future income and, if not, are charged to expense. Future investment income attributable to related premiums is taken into account in measuring the recoverability of t

Segment Information

Segment Information	12 Months Ended
	Dec. 31, 2018
Segment Reporting [Abstract]
Segment Information	SEGMENT INFORMATION The accounting policies used to prepare the segment reporting data for the Company’s three reportable business segments are the same as those described in the Summary of Significant Accounting Policies in note 1. Except as described below for certain legal entities, the Company allocates its invested assets and the related net investment income to its reportable business segments. Pre-tax net investment income is allocated based upon an investable funds concept, which takes into account liabilities (net of non-invested assets) and appropriate capital considerations for each segment. For investable funds, a benchmark investment yield is developed that reflects the estimated duration of the loss reserves’ future cash flows, the interest rate environment at the time the losses were incurred and A+ rated corporate debt instrument yields. For capital, a benchmark investment yield is developed that reflects the average yield on the total investment portfolio. The benchmark investment yields are applied to each segment’s investable funds and capital, respectively, to produce a total notional investment income by segment. The Company’s actual net investment income is allocated to each segment in proportion to the respective segment’s notional investment income to total notional investment income. There are certain legal entities within the Company that are dedicated to specific reportable business segments. The invested assets and related net investment income from these legal entities are reported in the applicable business segment and are not allocated among the other business segments. The cost of the Company’s catastrophe treaty program is included in the Company’s ceded premiums and is allocated among reportable business segments based on an estimate of actual market reinsurance pricing using expected losses calculated by the Company’s catastrophe model, adjusted for any experience adjustments. The following tables summarize the components of the Company’s revenues, income, net written premiums and total assets by reportable business segments. (for the year ended December 31, in millions) Business Insurance Bond & Specialty Insurance Personal Insurance Total Reportable Segments 2018 Premiums $ 14,722 $ 2,420 $ 9,917 $ 27,059 Net investment income 1,833 233 408 2,474 Fee income 412 — 20 432 Other revenues 112 23 66 201 Total segment revenues (1) $ 17,079 $ 2,676 $ 10,411 $ 30,166 Amortization and depreciation $ 2,943 $ 515 $ 1,719 $ 5,177 Income tax expense 259 198 42 499 Segment income (1) 1,638 793 297 2,728 2017 Premiums $ 14,146 $ 2,307 $ 9,230 $ 25,683 Net investment income 1,786 228 383 2,397 Fee income 430 — 17 447 Other revenues 69 24 60 153 Total segment revenues (1) $ 16,431 $ 2,559 $ 9,690 $ 28,680 Amortization and depreciation $ 2,852 $ 493 $ 1,627 $ 4,972 Income tax expense (benefit) 448 208 (44 ) 612 Segment income (1) 1,613 556 128 2,297 2016 Premiums $ 13,855 $ 2,260 $ 8,419 $ 24,534 Net investment income 1,701 239 362 2,302 Fee income 442 — 16 458 Other revenues 168 21 63 252 Total segment revenues (1) $ 16,166 $ 2,520 $ 8,860 $ 27,546 Amortization and depreciation $ 2,783 $ 491 $ 1,530 $ 4,804 Income tax expense 656 309 192 1,157 Segment income (1) 1,982 712 517 3,211 _________________________________________ (1) Segment revenues for reportable business segments exclude net realized investment gains. Segment income for reportable business segments equals net income excluding the after-tax impact of net realized investment gains and, in 2017, the impact of the Tax Cuts and Jobs Act of 2017 at enactment. Net written premiums by market were as follows: (for the year ended December 31, in millions) 2018 2017 2016 Business Insurance: Domestic: Select Accounts $ 2,828 $ 2,800 $ 2,729 Middle Market 8,214 7,756 7,379 National Accounts 1,025 1,010 1,058 National Property and Other 1,805 1,691 1,779 Total Domestic 13,872 13,257 12,945 International 1,084 1,013 955 Total Business Insurance 14,956 14,270 13,900 Bond & Specialty Insurance: Domestic: Management Liability 1,455 1,367 1,342 Surety 835 793 757 Total Domestic 2,290 2,160 2,099 International 238 199 172 Total Bond & Specialty Insurance 2,528 2,359 2,271 Personal Insurance: Domestic: Agency: Automobile 4,972 4,646 4,103 Homeowners and Other 4,148 3,933 3,772 Total Agency 9,120 8,579 7,875 Direct-to-Consumer 396 361 309 Total Domestic 9,516 8,940 8,184 International 708 650 603 Total Personal Insurance 10,224 9,590 8,787 Total consolidated net written premiums $ 27,708 $ 26,219 $ 24,958 Business Segment Reconciliations (for the year ended December 31, in millions) 2018 2017 2016 Revenue reconciliation Earned premiums Business Insurance: Domestic: Workers’ compensation $ 3,899 $ 3,962 $ 3,969 Commercial automobile 2,388 2,132 2,010 Commercial property 1,828 1,775 1,769 General liability 2,181 2,047 1,977 Commercial multi-peril 3,333 3,198 3,148 Other 28 29 31 Total Domestic 13,657 13,143 12,904 International 1,065 1,003 951 Total Business Insurance 14,722 14,146 13,855 Bond & Specialty Insurance: Domestic: Fidelity and surety 1,017 977 962 General liability 1,004 962 946 Other 195 187 180 Total Domestic 2,216 2,126 2,088 International 204 181 172 Total Bond & Specialty Insurance 2,420 2,307 2,260 Personal Insurance: Domestic Automobile 5,097 4,655 4,013 Homeowners and Other 4,135 3,943 3,813 Total Domestic 9,232 8,598 7,826 International 685 632 593 Total Personal Insurance 9,917 9,230 8,419 Total earned premiums 27,059 25,683 24,534 Net investment income 2,474 2,397 2,302 Fee income 432 447 458 Other revenues 201 153 252 Total segment revenues 30,166 28,680 27,546 Other revenues 2 6 11 Net realized investment gains 114 216 68 Total revenues $ 30,282 $ 28,902 $ 27,625 Income reconciliation, net of tax Total segment income $ 2,728 $ 2,297 $ 3,211 Interest Expense and Other (1) (298 ) (254 ) (244 ) Core income 2,430 2,043 2,967 Net realized investment gains 93 142 47 Impact of Tax Cuts and Jobs Act of 2017 at enactment — (129 ) — Net income $ 2,523 $ 2,056 $ 3,014 ________________________________________ (1) The primary component of Interest Expense and Other was after-tax interest expense of $278 million , $240 million and $236 million in 2018 , 2017 and 2016 , respectively. (at December 31, in millions) 2018 2017 Asset reconciliation: Business Insurance $ 78,965 $ 78,082 Bond & Specialty Insurance 8,693 8,776 Personal Insurance 15,943 15,949 Total assets for reportable segments 103,601 102,807 Other assets (1) 632 676 Total consolidated assets $ 104,233 $ 103,483 ___________________________________________ (1) The primary components of other assets at December 31, 2018 were accrued over-funded benefit plan assets related to the Company's qualified domestic pension plan and other intangible assets. The primary components of other assets at December 31, 2017 were accrued over-funded benefit plan assets related to the Company's qualified domestic pension plan, other intangible assets and deferred taxes. Enterprise-Wide Disclosures The Company does not have revenue from transactions with a single customer amounting to 10 percent or more of its revenues. The following table presents revenues of the Company’s operations based on location: (for the year ended December 31, in millions) 2018 2017 2016 U.S. $ 28,418 $ 27,253 $ 25,904 Non-U.S.: Canada 1,293 1,232 1,154 Other Non-U.S. 571 417 567 Total Non-U.S. 1,864 1,649 1,721 Total revenues $ 30,282 $ 28,902 $ 27,625

Investments

Investments	12 Months Ended
	Dec. 31, 2018
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 Gross Unrealized Fair (at December 31, 2018, in millions) Cost Gains Losses Value U.S. Treasury securities and obligations of U.S. government and government agencies and authorities $ 2,076 $ 4 $ 16 $ 2,064 Obligations of states, municipalities and political subdivisions: Local general obligation 14,473 219 120 14,572 Revenue 9,755 172 74 9,853 State general obligation 1,329 18 13 1,334 Pre-refunded 2,772 80 — 2,852 Total obligations of states, municipalities and political subdivisions 28,329 489 207 28,611 Debt securities issued by foreign governments 1,255 7 5 1,257 Mortgage-backed securities, collateralized mortgage obligations and pass-through securities 2,557 54 38 2,573 All other corporate bonds 29,307 156 583 28,880 Redeemable preferred stock 77 2 — 79 Total $ 63,601 $ 712 $ 849 $ 63,464 Amortized Gross Unrealized Fair (at December 31, 2017, in millions) Cost Gains Losses Value U.S. Treasury securities and obligations of U.S. government and government agencies and authorities $ 2,080 $ 4 $ 8 $ 2,076 Obligations of states, municipalities and political subdivisions: Local general obligation 13,488 444 26 13,906 Revenue 11,307 338 19 11,626 State general obligation 1,443 44 3 1,484 Pre-refunded 3,758 142 1 3,899 Total obligations of states, municipalities and political subdivisions 29,996 968 49 30,915 Debt securities issued by foreign governments 1,505 14 10 1,509 Mortgage-backed securities, collateralized mortgage obligations and pass-through securities 2,334 87 11 2,410 All other corporate bonds 25,311 478 100 25,689 Redeemable preferred stock 90 5 — 95 Total $ 61,316 $ 1,556 $ 178 $ 62,694 The amortized cost and fair value of fixed maturities by contractual maturity follow. Actual maturities will differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties. (at December 31, 2018, in millions) Amortized Cost Fair Value Due in one year or less $ 4,489 $ 4,505 Due after 1 year through 5 years 17,020 17,021 Due after 5 years through 10 years 17,030 16,785 Due after 10 years 22,505 22,580 61,044 60,891 Mortgage-backed securities, collateralized mortgage obligations and pass-through securities 2,557 2,573 Total $ 63,601 $ 63,464 Pre-refunded bonds of $2.85 billion and $3.90 billion at December 31, 2018 and 2017 , 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. The Company’s fixed maturity investment portfolio at December 31, 2018 and 2017 included $2.57 billion and $2.41 billion , respectively, of residential mortgage-backed securities, which include pass-through securities and collateralized mortgage obligations (CMOs). Included in the totals at December 31, 2018 and 2017 were $859 million and $804 million , respectively, of GNMA, FNMA, FHLMC (excluding FHA project loans) and Canadian government guaranteed residential mortgage-backed pass-through securities classified as available for sale. Also included in those totals were residential CMOs classified as available for sale with a fair value of $1.71 billion and $1.61 billion at December 31, 2018 and 2017 , respectively. Approximately 52% and 55% of the Company’s CMO holdings at December 31, 2018 and 2017 , respectively, were guaranteed by or fully collateralized by securities issued by GNMA, FNMA or FHLMC. The weighted average credit rating of the $828 million and $717 million of non-guaranteed CMO holdings at December 31, 2018 and 2017 , respectively, was “Aa1” and “A1,” respectively. The weighted average credit rating of all of the above securities was “Aaa/Aa1” and “Aa1” at December 31, 2018 and 2017 , respectively. At December 31, 2018 and 2017 , the Company held commercial mortgage-backed securities (CMBS, including FHA project loans) of $1.22 billion and $1.17 billion , respectively, which are included in “All other corporate bonds” in the tables above. At December 31, 2018 and 2017 , approximately $458 million and $475 million of these securities, respectively, or the loans backing such securities, contained guarantees by the U.S. government or a government-sponsored enterprise. The weighted average credit rating of the $759 million and $693 million of non-guaranteed securities at December 31, 2018 and 2017 , respectively, was “Aaa” at both dates. The CMBS portfolio is supported by loans that are diversified across economic sectors and geographical areas. The weighted average credit rating of the CMBS portfolio was “Aaa” at both December 31, 2018 and 2017 . At December 31, 2018 and 2017 , the Company had $367 million and $304 million , respectively, of securities on loan as part of a tri-party lending agreement. Proceeds from sales of fixed maturities classified as available for sale were $3.55 billion , $1.85 billion and $1.42 billion in 2018 , 2017 and 2016 , respectively. Gross gains of $51 million , $42 million and $79 million and gross losses of $18 million , $38 million and $20 million were realized on those sales in 2018 , 2017 and 2016 , respectively. At December 31, 2018 and 2017 , the Company’s insurance subsidiaries had $4.23 billion and $4.41 billion , respectively, of securities on deposit at financial institutions in certain states pursuant to the respective states’ insurance regulatory requirements. Funds deposited with third parties to be used as collateral to secure various liabilities on behalf of insureds, cedants and other creditors had a fair value of $37 million and $35 million at December 31, 2018 and 2017 , respectively. Other investments pledged as collateral securing outstanding letters of credit had a fair value of $1 million at both December 31, 2018 and 2017 . In addition, the Company utilizes Lloyd’s trust deposits, whereby owned securities with a fair value of approximately $115 million and $37 million held by a wholly-owned subsidiary at December 31, 2018 and 2017 , respectively, and $33 million held by TRV at both December 31, 2018 and 2017 were pledged into Lloyd’s trust accounts to provide a portion of the capital needed to support the Company’s obligations at Lloyd’s. Equity Securities The cost and fair value of investments in equity securities were as follows: (at December 31, 2018, in millions) Cost Gross Gains Gross Losses Fair Value Public common stock $ 338 $ 2 $ 24 $ 316 Non-redeemable preferred stock 44 8 — 52 Total $ 382 $ 10 $ 24 $ 368 (at December 31, 2017, in millions) Cost Gross Gains Gross Losses Fair Value Public common stock $ 332 $ 8 $ 1 $ 339 Non-redeemable preferred stock 108 12 6 114 Total $ 440 $ 20 $ 7 $ 453 For the year ended December 31, 2018, the Company recognized $29 million of net losses on equity securities still held as of December 31, 2018. Proceeds from sales of equity securities previously classified as available for sale were $765 million and $92 million in 2017 and 2016 , respectively. Gross gains of $239 million and $17 million and gross losses of $3 million and $3 million were realized on those sales in 2017 and 2016 , respectively. Real Estate The Company’s real estate investments include warehouses, office buildings and other commercial land and properties that are directly owned. The Company negotiates commercial leases with individual tenants through unrelated, licensed real estate brokers. Negotiated terms and conditions include, among others, rental rates, length of lease period and improvements to the premises to be provided by the landlord. Proceeds from the sale of real estate investments were $74 million , $23 million and $69 million in 2018 , 2017 and 2016 , respectively. Gross gains of $23 million , $10 million and $7 million were realized on those sales in 2018 , 2017 and 2016 , respectively, and there were no gross losses. Accumulated depreciation on real estate held for investment purposes was $383 million and $364 million at December 31, 2018 and 2017 , respectively. Future minimum rental income on operating leases relating to the Company’s real estate properties is expected to be $101 million , $90 million , $77 million , $62 million and $39 million for 2019 , 2020 , 2021 , 2022 and 2023 , respectively, and $75 million for 2024 and thereafter. Short-term Securities The Company’s short-term securities consist of Aaa-rated registered money market funds, U.S. Treasury securities, high-quality commercial paper (primarily A1/P1) and high-quality corporate securities purchased within a year to their maturity with a combined average of 54 days to maturity at December 31, 2018 . The amortized cost of these securities, which totaled $3.99 billion and $4.90 billion at December 31, 2018 and 2017 , respectively, approximated their fair value. Variable Interest Entities Entities which do not have sufficient equity at risk to allow the entity to finance its activities without additional financial support or in which the equity investors, as a group, do not have the characteristic of a controlling financial interest are referred to as variable interest entities (VIE). A VIE is consolidated by the variable interest holder that is determined to have the controlling financial interest (primary beneficiary) as a result of having both the power to direct the activities of a VIE that most significantly impact the VIE’s economic performance and the obligation to absorb losses or right to receive benefits from the VIE that could potentially be significant to the VIE. The Company determines whether it is the primary beneficiary of an entity subject to consolidation based on a qualitative assessment of the VIE’s capital structure, contractual terms, nature of the VIE’s operations and purpose and the Company’s relative exposure to the related risks of the VIE on the date it becomes initially involved in the VIE. The Company reassesses its VIE determination with respect to an entity on an ongoing basis. The Company is a passive investor in limited partner equity interests issued by third party VIEs. These include certain of the Company’s investments in private equity limited partnerships, hedge funds and real estate partnerships where the Company is not related to the general partner. These investments are generally accounted for under the equity method and reported in the Company’s consolidated balance sheet as other investments unless the Company is deemed the primary beneficiary. These equity interests generally cannot be redeemed. Distributions from these investments are received by the Company as a result of liquidation of the underlying investments of the funds and/or as income distribution. The Company’s maximum exposure to loss with respect to these investments is limited to the investment carrying amounts reported in the Company’s consolidated balance sheet and any unfunded commitment. The Company considers an investment in a VIE in which it has a 20% or greater equity interest as a significant VIE. Neither the Company’s carrying amounts nor the unfunded commitments related to these significant VIE’s are material individually or in the aggregate. Unrealized Investment Losses The following tables summarize, for all investments in an unrealized loss position at December 31, 2018 and 2017 , 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. The Company also relies upon estimates of several factors in its review and evaluation of individual investments, using the process described in note 1, in determining whether such investments are other-than-temporarily impaired. Less than 12 months 12 months or longer Total (at December 31, 2018, in millions) Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Fixed maturities U.S. Treasury securities and obligations of U.S. government and government agencies and authorities $ 484 $ 5 $ 1,011 $ 11 $ 1,495 $ 16 Obligations of states, municipalities and political subdivisions 5,241 82 3,298 125 8,539 207 Debt securities issued by foreign governments 96 — 328 5 424 5 Mortgage-backed securities, collateralized mortgage obligations and pass-through securities 593 9 1,070 29 1,663 38 All other corporate bonds 12,622 303 6,872 280 19,494 583 Total fixed maturities $ 19,036 $ 399 $ 12,579 $ 450 $ 31,615 $ 849 Less than 12 months 12 months or longer Total (at December 31, 2017, in millions) Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Fixed maturities U.S. Treasury securities and obligations of U.S. government and government agencies and authorities $ 1,150 $ 5 $ 470 $ 3 $ 1,620 $ 8 Obligations of states, municipalities and political subdivisions 505 2 2,959 47 3,464 49 Debt securities issued by foreign governments 394 6 111 4 505 10 Mortgage-backed securities, collateralized mortgage obligations and pass-through securities 1,021 7 250 4 1,271 11 All other corporate bonds 6,062 48 1,990 52 8,052 100 Total fixed maturities 9,132 68 5,780 110 14,912 178 Equity securities Public common stock 18 — 34 1 52 1 Non-redeemable preferred stock 3 — 56 6 59 6 Total equity securities 21 — 90 7 111 7 Total $ 9,153 $ 68 $ 5,870 $ 117 $ 15,023 $ 185 At December 31, 2018 , the amount of gross unrealized losses for all fixed maturity investments reported at fair value for which fair value was less than 80% of amortized cost was not significant. Impairment Charges Impairment charges included in net realized investment gains in the consolidated statement of income were as follows: (for the year ended December 31, in millions) 2018 2017 2016 Fixed maturities U.S. Treasury securities and obligations of U.S. government and government agencies and authorities $ — $ — $ — Obligations of states, municipalities and political subdivisions — — — Debt securities issued by foreign governments — — — Mortgage-backed securities, collateralized mortgage obligations and pass-through securities — — — All other corporate bonds 1 4 15 Redeemable preferred stock — — — Total fixed maturities 1 4 15 Equity securities Public common stock — 9 9 Non-redeemable preferred stock — — 3 Total equity securities — 9 12 Other investments — 1 2 Total $ 1 $ 14 $ 29 The following tables present the cumulative amount of and the changes during the year in credit losses on fixed maturities held at December 31, 2018 and 2017 , that were recognized in the consolidated statement of income from other-than-temporary impairments (OTTI) and for which a portion of the OTTI was recognized in other comprehensive income (loss) in the consolidated balance sheet. Year ended December 31, 2018 (in millions) Cumulative OTTI Credit Losses Recognized for Securities Held, Beginning of Period Additions for OTTI Securities Where No Credit Losses Were Previously Recognized Additions for OTTI Securities Where Credit Losses Have Been Previously Recognized Reductions Due to Sales/Defaults of Credit- Impaired Securities Adjustments to Book Value of Credit- Impaired Securities due to Changes in Cash Flows Cumulative OTTI Credit Losses Recognized for Securities Still Held, End of Period Fixed maturities Mortgage-backed securities, collateralized mortgage obligations and pass-through securities $ 29 $ — $ — $ (18 ) $ 4 $ 15 All other corporate bonds 46 — — (12 ) 8 42 Total fixed maturities $ 75 $ — $ — $ (30 ) $ 12 $ 57 Year ended December 31, 2017 (in millions) Cumulative OTTI Credit Losses Recognized for Securities Held, Beginning of Period Additions for OTTI Securities Where No Credit Losses Were Previously Recognized Additions for OTTI Securities Where Credit Losses Have Been Previously Recognized Reductions Due to Sales/Defaults of Credit- Impaired Securities Adjustments to Book Value of Credit- Impaired Securities due to Changes in Cash Flows Cumulative OTTI Credit Losses Recognized for Securities Still Held, End of Period Fixed maturities Mortgage-backed securities, collateralized mortgage obligations and pass-through securities $ 31 $ — $ — $ — $ (2 ) $ 29 All other corporate bonds 54 — 1 (7 ) (2 ) 46 Total fixed maturities $ 85 $ — $ 1 $ (7 ) $ (4 ) $ 75 Concentrations and Credit Quality Concentrations of credit risk arise from exposure to counterparties that are engaged in similar activities and have similar economic characteristics that could cause their ability to meet contractual obligations to be similarly affected by changes in economic or other conditions. The Company seeks to mitigate credit risk by actively monitoring the creditworthiness of counterparties, obtaining collateral as deemed appropriate and applying controls that include credit approvals, limits of credit exposure and other monitoring procedures. At December 31, 2018 and 2017 , other than U.S. Treasury securities and obligations of U.S. government and government agencies and authorities, the Company was not exposed to any concentration of credit risk of a single issuer greater than 5% of the Company’s shareholders’ equity. Included in fixed maturities are below investment grade securities totaling $1.48 billion and $1.67 billion at December 31, 2018 and 2017 , respectively. The Company defines its below investment grade securities as those securities rated below investment grade by external rating agencies, or the equivalent by the Company when a public rating does not exist. Such securities include below investment grade bonds that are publicly traded and certain other privately issued bonds that are classified as below investment grade loans. Net Investment Income (for the year ended December 31, in millions) 2018 2017 2016 Gross investment income Fixed maturities $ 1,980 $ 1,895 $ 1,981 Equity securities 16 28 37 Short-term securities 92 62 29 Real estate investments 48 44 51 Other investments 377 406 242 Gross investment income 2,513 2,435 2,340 Investment expenses 39 38 38 Net investment income $ 2,474 $ 2,397 $ 2,302 Changes in net unrealized gains on investment securities that are included as a separate component of other comprehensive income (loss) were as follows: (at and for the year ended December 31, in millions) 2018 2017 2016 Changes in net unrealized investment gains Fixed maturities $ (1,515 ) $ 513 $ (915 ) Equity securities — (215 ) 51 Other investments (1 ) 4 2 Change in net pre-tax unrealized gains on investment securities (1,516 ) 302 (862 ) Related tax expense (benefit) (319 ) 78 (303 ) Change in net unrealized gains on investment securities (1,197 ) 224 (559 ) Cumulative effect of adoption of updated accounting guidance for equity financial instruments at January 1, 2018 (22 ) — — Reclassification of certain tax effects from accumulated other comprehensive income at January 1, 2018 152 — — Balance, beginning of year 954 730 1,289 Balance, end of year $ (113 ) $ 954 $ 730 The total impact of net unrealized gains on investment securities was $1.11 billion after-tax at December 31, 2017, which included the $954 million reported in accumulated other comprehensive income shown above, as well as $158 million included in retained earnings that was part of the impact of enactment of the Tax Cuts and Jobs Act of 2017 recorded in earnings. Derivative Financial Instruments From time to time, the Company enters into U.S. Treasury note futures contracts to modify the effective duration of specific assets within the investment portfolio. U.S. Treasury futures contracts require a daily mark-to-market and settlement with the broker. At December 31, 2018 and 2017 , the Company had $0 and $400 million notional value of open U.S. Treasury futures contracts, respectively. Net realized investment gains and losses related to U.S. Treasury futures contracts in 2018 , 2017 and 2016 were not significant. The Company also sells a small amount of U.S. equity index put option contracts that are settled for cash upon their expiration or when they are rolled over. Net realized investment losses related to these derivatives in 2018 , 2017 and 2016 were not significant.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2018
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 fair value of a financial instrument is the estimated amount at which the instrument could be exchanged in an orderly transaction between knowledgeable, unrelated, willing parties, i.e., not in a forced transaction. The estimated fair value of a financial instrument may differ from the amount that could be realized if the security was sold in an immediate sale, e.g., a forced transaction. Additionally, the valuation of investments is more subjective when markets are less liquid due to the lack of market based inputs, which may increase the potential that the estimated fair value of an investment is not reflective of the price at which an actual transaction would occur. For investments that have quoted market prices in active markets, the Company uses the unadjusted quoted market prices as fair value and includes these prices in the amounts disclosed in Level 1 of the hierarchy. The Company receives the quoted market prices from third party, nationally recognized pricing services. When quoted market prices are unavailable, the Company utilizes these pricing services to determine an estimate of fair value. The fair value estimates provided from these pricing services are included in the amount disclosed in Level 2 of the hierarchy. If quoted market prices and an estimate from a pricing service are unavailable, the Company produces an estimate of fair value based on internally developed valuation techniques, which, depending on the level of observable market inputs, will render the fair value estimate as Level 2 or Level 3. The Company bases all of its estimates of fair value for assets on the bid price as it represents what a third-party market participant would be willing to pay in an arm’s length transaction. Fixed Maturities The Company utilized a pricing service to estimate fair value measurements for approximately 99% and 98% of its fixed maturities at December 31, 2018 and 2017 , respectively. The pricing service utilizes market quotations for fixed maturity securities that have quoted prices in active markets. Since fixed maturities other than U.S. Treasury securities generally do not trade on a daily basis, the pricing service prepares estimates of fair value measurements for these securities using its proprietary pricing applications, which include available relevant market information, benchmark curves, benchmarking of like securities, sector groupings and matrix pricing. Additionally, the pricing service uses an Option Adjusted Spread model to develop prepayment and interest rate scenarios. The pricing service evaluates each asset class based on relevant market information, relevant credit information, perceived market movements and sector news. The market inputs utilized in the pricing evaluation, listed in the approximate order of priority, include: benchmark yields, reported trades, broker/dealer quotes, issuer spreads, two-sided markets, benchmark securities, bids, offers, reference data, and industry and economic events. The extent of the use of each market input depends on the asset class and the market conditions. Depending on the security, the priority of the use of inputs may change or some market inputs may not be relevant. For some securities, additional inputs may be necessary. The pricing service utilized by the Company has indicated that it will only produce an estimate of fair value if there is objectively verifiable information to produce a valuation. If the pricing service discontinues pricing an investment, the Company would be required to produce an estimate of fair value using some of the same methodologies as the pricing service but would have to make assumptions for any market-based inputs that were unavailable due to market conditions. The Company reviews the estimates of fair value provided by the pricing service and compares the estimates to the Company’s knowledge of the market to determine if the estimates obtained are representative of the prices in the market. In addition, the Company has periodic discussions with the pricing service to discuss and understand any changes in process and their responsiveness to changes occurring in the markets. The Company also monitors all monthly price changes and further evaluates any securities whose value changed more than 10% from the prior month. The Company has implemented various other processes including randomly selecting purchased or sold securities and comparing execution prices to the estimates from the pricing service as well as reviewing securities whose valuation did not change from their previous valuation (stale price review). The Company also uses a second independent pricing service to further test the primary pricing service’s valuation of the Company’s fixed maturity portfolio. These processes have not highlighted any significant issues with the fair value estimates received from the primary pricing service. The fair value estimates of most fixed maturity investments are based on observable market information rather than market quotes. Accordingly, the estimates of fair value for such fixed maturities, other than U.S. Treasury securities, provided by the pricing service are included in the amount disclosed in Level 2 of the hierarchy. The estimated fair value of U.S. Treasury securities is included in the amount disclosed in Level 1 as the estimates are based on unadjusted market prices. The Company also holds certain fixed maturity investments which are not priced by the pricing service and, accordingly, estimates the fair value of such fixed maturities using an internal matrix that is based on market information regarding interest rates, credit spreads and liquidity. The underlying source data for calculating the matrix of credit spreads relative to the U.S. Treasury curve are observable market-based indices that relate to corporate and high-yield fixed maturity investments. The Company includes the fair value estimates of these corporate bonds in Level 2, since all significant inputs are market observable. 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 also estimates the fair value of these bonds using another internal pricing matrix that includes some unobservable inputs that are significant to the valuation. Due to the limited amount of observable market information, the Company includes the fair value estimates for these particular bonds in Level 3. The fair value of the fixed maturities for which the Company used this internal pricing matrix was $82 million and $127 million at December 31, 2018 and 2017 , respectively. Additionally, the Company holds a small amount of other fixed maturity investments that have characteristics that make them unsuitable for matrix pricing. For these fixed maturities, the Company obtains a quote from a broker (primarily the market maker). The fair value of the fixed maturities for which the Company received a broker quote was $104 million and $77 million at December 31, 2018 and 2017 , respectively. Due to the disclaimers on the quotes that indicate that the price is indicative only, the Company includes these fair value estimates in Level 3. Equity Securities — Public Common Stock and Non-Redeemable Preferred Stock For public common stock and non-redeemable preferred stocks, the Company receives prices from pricing services that are based on observable market transactions and includes these estimates in the amount disclosed in Level 1. When current market quotes in active markets are unavailable for certain non-redeemable preferred stocks held by the Company, the Company receives an estimate of fair value from the pricing services. The services utilize similar methodologies to price the non-redeemable preferred stocks as they do for the fixed maturities. The Company includes the fair value estimate for these non-redeemable preferred stocks in the amount disclosed in Level 2. Other Investments The Company holds investments in various publicly-traded securities which are reported in other investments. These investments include mutual funds and other small holdings. The $16 million and $19 million fair value of these investments at December 31, 2018 and 2017 , respectively, was disclosed in Level 1. At December 31, 2018 and 2017 , the Company held investments in non-public common and preferred equity securities, with fair value estimates of $36 million and $38 million , respectively, reported in other investments, where the fair value estimate is determined either internally or by an external fund manager based on recent filings, operating results, balance sheet stability, growth and other business and market sector fundamentals. Due to the significant unobservable inputs in these valuations, the Company includes the total fair value estimate for all of these investments at December 31, 2018 and 2017 in the amount disclosed in Level 3. 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 at December 31, 2018 was $10 million 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 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. An investment transferred between levels during a period is transferred at its fair value as of the beginning of that period. (at December 31, 2018, 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 $ 2,064 $ 2,064 $ — $ — Obligations of states, municipalities and political subdivisions 28,611 — 28,599 12 Debt securities issued by foreign governments 1,257 — 1,257 — Mortgage-backed securities, collateralized mortgage obligations and pass-through securities 2,573 — 2,554 19 All other corporate bonds 28,880 — 28,725 155 Redeemable preferred stock 79 3 76 — Total fixed maturities 63,464 2,067 61,211 186 Equity securities Public common stock 316 316 — — Non-redeemable preferred stock 52 30 22 — Total equity securities 368 346 22 — Other investments 52 16 — 36 Total $ 63,884 $ 2,429 $ 61,233 $ 222 Other liabilities $ 10 $ — $ — $ 10 (at December 31, 2017, 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 $ 2,076 $ 2,076 $ — $ — Obligations of states, municipalities and political subdivisions 30,915 — 30,910 5 Debt securities issued by foreign governments 1,509 — 1,509 — Mortgage-backed securities, collateralized mortgage obligations and pass-through securities 2,410 — 2,371 39 All other corporate bonds 25,689 11 25,518 160 Redeemable preferred stock 95 3 92 — Total fixed maturities 62,694 2,090 60,400 204 Equity securities Public common stock 339 339 — — Non-redeemable preferred stock 114 45 69 — Total equity securities 453 384 69 — Other investments 57 19 — 38 Total $ 63,204 $ 2,493 $ 60,469 $ 242 During the years ended December 31, 2018 and 2017 , the Company’s transfers between Level 1 and Level 2 were not significant. The following tables present the changes in the Level 3 fair value category for the years ended December 31, 2018 and 2017 . (in millions) Fixed Maturities Other Investments Total Balance at December 31, 2017 $ 204 $ 38 $ 242 Total realized and unrealized investment gains (losses): Reported in net realized investment gains (1) 2 7 9 Reported in increases in other comprehensive income (loss) (4 ) — (4 ) Purchases, sales and settlements/maturities: Purchases 146 3 149 Sales (11 ) (12 ) (23 ) Settlements/maturities (71 ) — (71 ) Gross transfers into Level 3 11 — 11 Gross transfers out of Level 3 (91 ) — (91 ) Balance at December 31, 2018 $ 186 $ 36 $ 222 Amount of total realized investment gains (losses) for the period included in the consolidated statement of income attributable to changes in the fair value of assets still held at the reporting date $ — $ — $ — ___________________________________________ (1) Includes impairments on investments held at the end of the period as well as amortization on fixed maturities. The Company also includes in Level 3 the put/call option entered into in connection with a business combination that is reported in other liabilities and had a fair value of $10 million at December 31, 2018 . (in millions) Fixed Maturities Other Investments Total Balance at December 31, 2016 $ 184 $ 36 $ 220 Total realized and unrealized investment gains (losses): Reported in net realized investment gains (1) — (1 ) (1 ) Reported in increases in other comprehensive income (loss) 1 3 4 Purchases, sales and settlements/maturities: Purchases 312 — 312 Sales (2 ) — (2 ) Settlements/maturities (47 ) — (47 ) Gross transfers into Level 3 21 — 21 Gross transfers out of Level 3 (265 ) — (265 ) Balance at December 31, 2017 $ 204 $ 38 $ 242 Amount of total realized investment gains (losses) for the period included in the consolidated statement of income attributable to changes in the fair value of assets still held at the reporting date $ — $ (1 ) $ (1 ) ___________________________________________ (1) Includes impairments on investments held at the end of the period as well as amortization on fixed maturities. 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 December 31, 2018, in millions) Carrying Value Fair Value Level 1 Level 2 Level 3 Financial assets: Short-term securities $ 3,985 $ 3,985 $ 632 $ 3,316 $ 37 Financial liabilities: Debt $ 6,464 $ 7,128 $ — $ 7,128 $ — Commercial paper 100 100 — 100 — (at December 31, 2017, in millions) Carrying Value Fair Value Level 1 Level 2 Level 3 Financial assets: Short-term securities $ 4,895 $ 4,895 $ 1,238 $ 3,622 $ 35 Financial liabilities: Debt $ 6,471 $ 7,702 $ — $ 7,702 $ — 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 years ended December 31, 2018 and 2017 .

Reinsurance

Reinsurance	12 Months Ended
	Dec. 31, 2018
Reinsurance Disclosures [Abstract]
Reinsurance	REINSURANCE The Company’s consolidated financial statements reflect the effects of assumed and ceded reinsurance transactions. Assumed reinsurance refers to the acceptance of certain insurance risks that other insurance companies have underwritten. Ceded reinsurance involves transferring certain insurance risks (along with the related written and earned premiums) the Company has underwritten to other insurance companies who agree to share these risks. The primary purpose of ceded reinsurance is to protect the Company, at a cost, from losses in excess of the amount it is prepared to accept and to protect the Company’s capital. Reinsurance is placed on both a quota-share and excess-of-loss basis. Ceded reinsurance arrangements do not discharge the Company as the primary insurer, except for instances where the primary policy or policies have been novated, such as in certain structured settlement agreements. The Company utilizes a corporate catastrophe excess-of-loss reinsurance treaty with unaffiliated reinsurers to manage its exposure to losses resulting from catastrophes and to protect its capital. In addition to the coverage provided under this treaty, the Company also utilizes catastrophe bonds to protect against certain weather-related and earthquake losses in the Northeastern United States, and a Northeast catastrophe reinsurance treaty to protect against losses resulting from weather-related and earthquake catastrophes in the Northeastern United States. The Company also utilizes excess-of-loss treaties to protect against earthquake losses up to a certain threshold in Business Insurance (for certain markets) and for Personal Insurance, and several reinsurance treaties specific to its international operations. The Company monitors the financial condition of its reinsurers under voluntary reinsurance arrangements to evaluate the collectability of amounts due from reinsurers and as a basis for determining the reinsurers with which the Company conducts ongoing business. In addition, in the ordinary course of business, the Company may become involved in coverage disputes with its reinsurers. Some of these disputes could result in lawsuits and arbitrations brought by or against the reinsurers to determine the Company’s rights and obligations under the various reinsurance agreements. The Company employs dedicated specialists and strategies to manage reinsurance collections and disputes. Included in reinsurance recoverables are amounts related to involuntary reinsurance arrangements. The Company is required to participate in various involuntary reinsurance arrangements through assumed reinsurance, principally with regard to residual market mechanisms in workers’ compensation and automobile insurance, as well as homeowners’ insurance in certain coastal areas. In addition, the Company provides services for several of these involuntary arrangements (mandatory pools and associations) under which it writes such residual market business directly, then cedes 100% of this business to the mandatory pool. Such participations and servicing arrangements are arranged to mitigate credit risk to the Company, as any ceded balances are jointly backed by all the pool members. Also included in reinsurance recoverables are amounts related to certain structured settlements. Structured settlements are annuities purchased from various life insurance companies to settle certain personal physical injury claims, of which workers’ compensation claims comprise a significant portion. In cases where the Company did not receive a release from the claimant, the structured settlement is included in reinsurance recoverables and the related claim cost is included in the liability for claims and claim adjustment expense reserves, as the Company retains the contingent liability to the claimant. If it is expected that the life insurance company is not able to pay, the Company would recognize an impairment of the related reinsurance recoverable if, and to the extent, the purchased annuities are not covered by state guaranty associations. In the event that the life insurance company fails to make the required annuity payments, the Company would be required to make such payments. The following is a summary of reinsurance financial data reflected in the consolidated statement of income: (for the year ended December 31, in millions) 2018 2017 2016 Written premiums Direct $ 28,210 $ 26,648 $ 25,567 Assumed 1,042 1,000 928 Ceded (1,544 ) (1,429 ) (1,537 ) Total net written premiums $ 27,708 $ 26,219 $ 24,958 Earned premiums Direct $ 27,536 $ 26,189 $ 25,262 Assumed 1,024 965 875 Ceded (1,501 ) (1,471 ) (1,603 ) Total net earned premiums $ 27,059 $ 25,683 $ 24,534 Percentage of assumed earned premiums to net earned premiums 3.8 % 3.8 % 3.6 % Ceded claims and claim adjustment expenses incurred $ 1,293 $ 1,225 $ 762 Ceded premiums include the premiums paid for coverage provided by the Company’s catastrophe bonds. Reinsurance recoverables include amounts recoverable on both paid and unpaid claims and claim adjustment expenses and were as follows: (at December 31, in millions) 2018 2017 Gross reinsurance recoverables on paid and unpaid claims and claim adjustment expenses $ 3,485 $ 3,303 Allowance for uncollectible reinsurance (110 ) (111 ) Net reinsurance recoverables 3,375 3,192 Mandatory pools and associations 2,005 2,011 Structured settlements 2,990 3,106 Total reinsurance recoverables $ 8,370 $ 8,309 Terrorism Risk Insurance Program The Terrorism Risk Insurance Program is a Federal program administered by the Department of the Treasury authorized through December 31, 2020 that provides for a system of shared public and private compensation for certain insured losses resulting from certified acts of terrorism. In order for a loss to be covered under the program (subject losses), the loss must meet certain aggregate industry loss minimums and must be the result of an event that is certified as an act of terrorism by the U.S. Secretary of the Treasury, in consultation with the Secretary of Homeland Security and the Attorney General of the United States. The annual aggregate industry loss minimum under the program is $180 million for 2019 and will increase to $200 million for 2020. The program excludes from participation the following types of insurance: Federal crop insurance, private mortgage insurance, financial guaranty insurance, medical malpractice insurance, health or life insurance, flood insurance, reinsurance, commercial automobile, professional liability (other than directors' and officers’), surety, burglary and theft, and farm-owners multi-peril. In the case of a war declared by Congress, only workers’ compensation losses are covered by the program. All commercial property and casualty insurers licensed in the United States are generally required to participate in the program. Under the program, a participating insurer, in exchange for making terrorism insurance available, is entitled to be reimbursed by the Federal Government for 81% of subject losses in 2019 , after an insurer deductible, subject to an annual cap. This reimbursement percentage will decrease to 80% of subject losses in 2020. The deductible for any calendar year is equal to 20% of the insurer’s direct earned premiums for covered lines for the preceding calendar year. The Company’s estimated deductible under the program is $2.52 billion for 2019 . The annual cap limits the amount of aggregate subject losses for all participating insurers to $100 billion . Once subject losses have reached the $100 billion aggregate during a program year, participating insurers will not be liable under the program for additional covered terrorism losses for that program year. There have been no terrorism-related losses that have triggered program coverage since the program was established. Since the law is untested, there is substantial uncertainty as to how it will be applied if an act of terrorism is certified under the program. It is also possible that future legislative action could change or eliminate the program. Further, given the unpredictable frequency and severity of terrorism losses, as well as the limited terrorism coverage in the Company’s own reinsurance program, future losses from acts of terrorism, particularly involving nuclear, biological, chemical or radiological events, could be material to the Company’s operating results, financial position and/or liquidity in future periods. In addition, the Company may not have sufficient resources to respond to claims arising from a high frequency of high severity natural catastrophes and/or of man-made catastrophic events involving conventional means. While the Company seeks to manage its exposure to man-made catastrophic events involving conventional means, the Company may not have sufficient resources to respond to claims arising out of one or more man-made catastrophic events involving nuclear, biological, chemical or radiological means.

Goodwill and Other Intangible A

Goodwill and Other Intangible Assets	12 Months Ended
	Dec. 31, 2018
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. (at December 31, in millions) 2018 2017 Business Insurance (1) $ 2,585 $ 2,585 Bond & Specialty Insurance 550 550 Personal Insurance 776 790 Other 26 26 Total $ 3,937 $ 3,951 ___________________________________________ (1) Goodwill at December 31, 2018 included $26 million associated with a business acquisition in 2018, none of which will be 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 December 31, 2018, in millions) Gross Carrying Amount Accumulated Amortization Net Subject to amortization Customer-related $ 98 $ 12 $ 86 Contract-based (1) 208 175 33 Total subject to amortization 306 187 119 Not subject to amortization 226 — 226 Total $ 532 $ 187 $ 345 (at December 31, 2017, in millions) Gross Carrying Amount Accumulated Amortization Net Subject to amortization Customer-related $ 77 $ 4 $ 73 Contract-based (1) 209 167 42 Total subject to amortization 286 171 115 Not subject to amortization 227 — 227 Total $ 513 $ 171 $ 342 ___________________________________________ (1) Contract-based intangible assets subject to amortization are comprised of fair value adjustments on claims and claim adjustment expense reserves, reinsurance recoverables and other contract-related intangible assets. Fair value adjustments recorded in connection with insurance acquisitions were based on management’s estimate of nominal claims and claim adjustment expense reserves and reinsurance recoverables. The method used calculated a risk adjustment to a risk-free discounted reserve that would, if reserves ran off as expected, produce results that yielded the assumed cost-of-capital on the capital supporting the loss reserves. The fair value adjustments are reported as other intangible assets on the consolidated balance sheet, and the amounts measured in accordance with the acquirer’s accounting policies for insurance contracts have been reported as part of the claims and claim adjustment expense reserves and reinsurance recoverables. The intangible assets are being recognized into income over the expected payment pattern. Because the time value of money and the risk adjustment (cost of capital) components of the intangible assets run off at different rates, the amount recognized in income may be a net benefit in some periods and a net expense in other periods. Amortization expense of intangible assets was $17 million , $13 million and $11 million for the years ended December 31, 2018 , 2017 and 2016 , respectively. Amortization expense for all intangible assets subject to amortization is estimated to be $16 million in 2019 , $15 million in 2020 , $14 million in 2021 , $13 million in 2022 and $12 million in 2023 .

Insurance Claim Reserves

Insurance Claim Reserves	12 Months Ended
	Dec. 31, 2018
Insurance Loss Reserves [Abstract]
Insurance Claim Reserves	INSURANCE CLAIM RESERVES Claims and claim adjustment expense reserves were as follows: (at December 31, in millions) 2018 2017 Property-casualty $ 50,653 $ 49,633 Accident and health 15 17 Total $ 50,668 $ 49,650 The following table presents a reconciliation of beginning and ending property casualty reserve balances for claims and claim adjustment expenses: (at and for the year ended December 31, in millions) 2018 2017 2016 Claims and claim adjustment expense reserves at beginning of year $ 49,633 $ 47,929 $ 48,272 Less reinsurance recoverables on unpaid losses 8,123 7,981 8,449 Net reserves at beginning of year 41,510 39,948 39,823 Estimated claims and claim adjustment expenses for claims arising in the current year 18,614 17,846 15,675 Estimated decrease in claims and claim adjustment expenses for claims arising in prior years (406 ) (458 ) (680 ) Total increases 18,208 17,388 14,995 Claims and claim adjustment expense payments for claims arising in: Current year 7,697 7,335 6,220 Prior years 9,363 8,708 8,576 Total payments 17,060 16,043 14,796 Unrealized foreign exchange loss (gain) (187 ) 217 (74 ) Net reserves at end of year 42,471 41,510 39,948 Plus reinsurance recoverables on unpaid losses 8,182 8,123 7,981 Claims and claim adjustment expense reserves at end of year $ 50,653 $ 49,633 $ 47,929 Gross claims and claim adjustment expense reserves at December 31, 2018 increased by $1.02 billion over December 31, 2017 , primarily reflecting the impacts of (i) higher volumes of insured exposures and loss cost trends for the current accident year and (ii) catastrophe losses in 2018, partially offset by the impacts of (iii) payments related to catastrophe losses incurred in 2017 and (iv) net favorable prior year reserve development. Gross claims and claim adjustment expense reserves at December 31, 2017 increased by $1.70 billion over December 31, 2016 , primarily reflecting the impacts of (i) catastrophe losses in the second half of 2017 and (ii) higher volumes of insured exposures and loss cost trends for the current accident year, partially offset by the impacts of (iii) payments related to operations in runoff and (iv) net favorable prior year reserve development. Reinsurance recoverables on unpaid losses at December 31, 2018 increased by $59 million over December 31, 2017 , primarily reflecting the 2018 impacts of catastrophe losses and the asbestos reserve increase, partially offset by cash collections. Reinsurance recoverables on unpaid losses at December 31, 2017 increased by $142 million from December 31, 2016 , primarily reflecting the impacts of catastrophe losses and the asbestos reserve increase in the second half of 2017, partially offset by cash collections in 2017, including the settlement of certain disputes as discussed in more detail in note 16. Included in the claims and claim adjustment expense reserves are reserves for long-term disability and annuity claim payments, primarily arising from workers’ compensation insurance and workers’ compensation excess insurance policies, that are discounted to the present value of the estimated future payments. The discount rate used was 5% at both December 31, 2018 and 2017 . Total reserves net of the discount were $2.45 billion and $2.32 billion , and the related amount of discount was $1.16 billion and $1.10 billion , at December 31, 2018 and 2017 , respectively. Accretion of the discount is reported as part of “claims and claim adjustment expenses” in the consolidated statement of income and was $49 million , $50 million and $50 million in 2018 , 2017 and 2016 , respectively. Prior Year Reserve Development The following disclosures regarding reserve development are on a “net of reinsurance” basis. 2018 In 2018 , estimated claims and claim adjustment expenses incurred included $406 million of net favorable development for claims arising in prior years, including $517 million of net favorable prior year reserve development and $49 million of accretion of discount that impacted the Company's results of operations. Business Insurance . Net favorable prior year reserve development in 2018 totaled $142 million , primarily driven by better than expected loss experience in the segment’s domestic operations in (i) the workers’ compensation product line for multiple accident years and (ii) the commercial property product line for recent accident years, partially offset by higher than expected loss experience in the segment's domestic operations in (iii) the general liability product line for both primary and excess coverages for multiple accident years, including a $225 million increase to asbestos reserves and a $55 million increase to environmental reserves and (iv) the commercial automobile product line for recent accident years. Bond & Specialty Insurance . Net favorable prior year reserve development in 2018 totaled $266 million , primarily driven by better than expected loss experience in the segment’s domestic operations in the general liability product line for management liability coverages for multiple accident years. Personal Insurance . Net favorable prior year reserve development in 2018 totaled $109 million , primarily driven by better than expected loss experience in the segment's domestic operations in the automobile product line for recent accident years. 2017 In 2017 , estimated claims and claim adjustment expenses incurred included $458 million of net favorable development for claims arising in prior years, including $592 million of net favorable prior year reserve development and $50 million of accretion of discount that impacted the Company's results of operations. Business Insurance . Net favorable prior year reserve development in 2017 totaled $439 million , primarily driven by better than expected loss experience in the segment's domestic operations in (i) the workers’ compensation product line for multiple accident years, (ii) the general liability product line (excluding an increase to asbestos and environmental reserves) for both primary and excess coverages for multiple accident years and (iii) the commercial multi-peril product line for liability coverages for multiple accident years, partially offset by (iv) a $225 million increase to asbestos reserves, (v) the impact of higher than expected loss experience in the commercial automobile product line for recent accident years and (vi) a $65 million increase to environmental reserves. The net favorable prior year reserve development in the segment’s domestic operations was partially offset by net unfavorable prior year reserve development in the segment’s international operations in Europe primarily due to the U.K. Ministry of Justice’s “Ogden” discount rate adjustment applied to lump sum bodily injury payouts. Bond & Specialty Insurance . Net favorable prior year reserve development in 2017 totaled $140 million , primarily driven by better than expected loss experience in the segment’s domestic operations in the general liability product line for management liability coverages for multiple accident years. Personal Insurance . Net favorable prior year reserve development in 2017 was not significant and totaled $13 million . 2016 In 2016 , estimated claims and claim adjustment expenses incurred included $680 million of net favorable development for claims arising in prior years, including $771 million of net favorable prior year reserve development and $50 million of accretion of discount that impacted the Company's results of operations. Business Insurance . Net favorable prior year reserve development in 2016 totaled $424 million , primarily driven by better than expected loss experience in the Company’s domestic operations in (i) the workers’ compensation product line for multiple accident years and (ii) the general liability product line (excluding an increase to asbestos and environmental reserves), related to both primary and excess coverages for multiple accident years, partially offset by (iii) a $225 million increase to asbestos reserves and (iv) a $82 million increase to environmental reserves, as well as net favorable prior year reserve development in the segment's international operations in Europe. Bond & Specialty Insurance . Net favorable prior year reserve development in 2016 totaled $350 million , primarily driven by better than expected loss experience in the Company’s domestic operations in (i) the fidelity and surety product line for multiple accident years and (ii) the general liability product line for management liability coverages for multiple accident years. Personal Insurance . Net unfavorable prior year reserve development in 2016 was not significant and totaled $3 million . Claims Development The following is a summary of claims and claim adjustment expense reserves, including certain components, for the Company’s major product lines by reporting segment at December 31, 2018 . (at December 31, 2018, in mllions) Net Undiscounted Claims and Claim Adjustment Expense Reserves Discount (Net of Reinsurance) Subtotal: Net Claims and Claim Adjustment Expense Reserves Reinsurance Recoverables on Unpaid Losses (4) Claims and Claim Adjustment Expense Reserves Business Insurance General liability $ 7,159 $ (174 ) $ 6,985 $ 854 $ 7,839 Commercial property 973 — 973 429 1,402 Commercial multi-peril 3,535 — 3,535 181 3,716 Commercial automobile 2,861 — 2,861 226 3,087 Workers’ compensation (1) 16,039 (909 ) 15,130 698 15,828 Bond & Specialty Insurance General liability 1,833 — 1,833 152 1,985 Fidelity and surety 419 — 419 7 426 Personal Insurance Automobile 2,776 — 2,776 480 3,256 Homeowners (excluding Other) 1,376 — 1,376 3 1,379 International - Canada 710 — 710 26 736 Subtotal — claims and allocated claim adjustment expenses for the products presented in the development tables below 37,681 (1,083 ) 36,598 3,056 39,654 Other insurance contracts (2) 3,762 (5 ) 3,757 2,116 5,873 Unallocated loss adjustment expense reserves 2,053 — 2,053 37 2,090 Structured settlements (3) — — — 2,990 2,990 Other 63 — 63 (17 ) 46 Total property-casualty 43,559 (1,088 ) 42,471 8,182 50,653 Accident and health — — — 15 15 Total $ 43,559 $ (1,088 ) $ 42,471 $ 8,197 $ 50,668 ___________________________________________ (1) Net discount amount includes discount of $70 million on reinsurance recoverables for long-term disability and annuity claim payments. (2) Primarily includes residual market, international (other than operations in Canada within the Personal Insurance segment) and runoff assumed reinsurance business. (3) Includes structured settlements in cases where the Company did not receive a release from the claimant. (4) Total reinsurance recoverables (on paid and unpaid losses) at December 31, 2018 were $8.37 billion . The claim development tables that follow present, by accident year, incurred and cumulative paid claims and allocated claim adjustment expense on a historical basis. This claim development information is presented on an undiscounted, net of reinsurance basis for ten years, or the number of years for which claims incurred typically remain outstanding if less than ten years. The claim development tables also provide the historical average annual percentage payout of incurred claims by age, net of reinsurance, as supplementary information (identified as unaudited in the tables below). For Personal Insurance - International - Canada, the claim development information reflects the acquisition of The Dominion of Canada General Insurance Company (Dominion) in November 2013 on a retrospective basis (includes Dominion data for years prior to the Company’s acquisition of Dominion). Business Insurance General Liability ( dollars in millions ) For the Years Ended December 31, 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Unaudited Accident Year IBNR Reserves Dec 31, 2018 Cumulative Number of Reported Claims 2009 $ 1,060 $ 1,071 $ 1,028 $ 960 $ 869 $ 837 $ 809 $ 796 $ 783 $ 775 $ 56 25,702 2010 1,028 1,031 1,021 959 927 912 918 908 911 79 27,911 2011 1,004 1,074 1,065 998 972 935 913 908 80 27,444 2012 989 985 935 913 892 905 917 98 24,801 2013 965 975 958 940 927 933 101 22,446 2014 976 989 983 948 956 177 22,108 2015 998 956 923 967 222 21,033 2016 1,075 1,058 1,087 439 19,190 2017 1,133 1,143 717 16,464 2018 1,253 1,080 13,107 Total $ 9,850 Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Accident Year Unaudited 2009 $ 35 $ 167 $ 314 $ 446 $ 543 $ 613 $ 643 $ 667 $ 689 $ 701 2010 35 139 324 487 629 702 756 781 800 2011 47 187 355 539 660 725 762 799 2012 32 150 295 489 589 699 754 Liability for Claims 2013 35 175 363 498 639 745 And Allocated Claim 2014 37 163 321 515 640 Adjustment Expenses, 2015 36 137 336 558 Net of Reinsurance 2016 35 191 421 2017 40 180 2009 - Before 2018 42 2018 2009 Total $ 5,640 $ 4,210 $ 2,949 Total net liability $ 7,159 Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Unaudited Years 1 2 3 4 5 6 7 8 9 10 3.8 % 13.6 % 19.0 % 19.1 % 13.4 % 9.5 % 5.0 % 3.2 % 2.5 % 1.5 % Commercial Property ( dollars in millions ) For the Years Ended December 31, 2014 2015 2016 2017 2018 Incurred Claims and Allocated Claims Adjustment Expenses, Net of Reinsurance Unaudited Accident Year IBNR Reserves December 31, 2018 Cumulative Number of Reported Claims 2014 $ 936 $ 860 $ 836 $ 835 $ 834 $ 6 21,568 2015 786 750 741 731 6 20,143 2016 896 863 820 22 22,267 2017 1,209 1,177 30 24,855 2018 1,093 73 21,547 Total $ 4,655 Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Unaudited Liability for Claims Accident Year And Allocated Claim 2014 $ 464 $ 710 $ 775 $ 803 $ 817 Adjustment Expenses, 2015 376 615 681 699 Net of Reinsurance 2016 441 685 745 2017 618 1,003 2014 - Before 2018 561 2018 2014 Total $ 3,825 $ 830 $ 143 Total net liability $ 973 Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Unaudited Years 1 2 3 4 5 52.9 % 31.2 % 8.0 % 2.9 % 1.7 % Commercial Multi-Peril ( dollars in millions ) For the Years Ended December 31, 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Unaudited Accident Year IBNR Reserves December 31, 2018 Cumulative Number of Reported Claims 2009 $ 1,484 $ 1,506 $ 1,501 $ 1,498 $ 1,511 $ 1,514 $ 1,514 $ 1,509 $ 1,500 $ 1,493 $ 21 103,448 2010 1,711 1,826 1,832 1,861 1,895 1,892 1,898 1,885 1,881 32 111,931 2011 2,235 2,244 2,269 2,286 2,296 2,287 2,283 2,279 38 125,743 2012 1,885 1,883 1,903 1,888 1,888 1,867 1,859 42 104,800 2013 1,615 1,623 1,620 1,609 1,591 1,600 51 83,667 2014 1,663 1,627 1,625 1,617 1,626 72 78,097 2015 1,568 1,625 1,593 1,597 110 71,242 2016 1,662 1,623 1,598 204 68,024 2017 1,872 1,928 357 69,218 2018 1,976 605 58,784 Total $ 17,837 Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Accident Year Unaudited 2009 $ 603 $ 958 $ 1,121 $ 1,264 $ 1,360 $ 1,408 $ 1,436 $ 1,449 $ 1,457 $ 1,466 2010 709 1,180 1,395 1,579 1,698 1,763 1,798 1,819 1,834 2011 1,060 1,573 1,803 1,979 2,088 2,156 2,193 2,222 2012 795 1,246 1,424 1,590 1,699 1,752 1,780 Liability for Claims 2013 644 987 1,167 1,304 1,410 1,475 And Allocated Claim 2014 628 956 1,154 1,328 1,448 Adjustment Expenses, 2015 595 970 1,144 1,310 Net of Reinsurance 2016 585 950 1,133 2017 716 1,199 2009 - Before 2018 792 2018 2009 Total $ 14,659 $ 3,178 $ 357 Total net liability $ 3,535 Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Unaudited Years 1 2 3 4 5 6 7 8 9 10 39.7 % 23.2 % 11.0 % 9.4 % 6.2 % 3.3 % 1.7 % 1.1 % 0.7 % 0.6 % Commercial Automobile ( dollars in millions ) For the Years Ended December 31, 2014 2015 2016 2017 2018 Incurred Claims and Allocated Claims Adjustment Expenses, Net of Reinsurance Unaudited Accident Year IBNR Reserves December 31, 2018 Cumulative Number of Reported Claims 2014 $ 1,156 $ 1,153 $ 1,155 $ 1,171 $ 1,193 $ 36 177,493 2015 1,188 1,202 1,234 1,283 83 173,333 2016 1,278 1,303 1,371 191 182,647 2017 1,386 1,501 401 190,126 2018 1,645 736 185,419 Total $ 6,993 Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Unaudited Liability for Claims Accident Year And Allocated Claim 2014 $ 394 $ 611 $ 812 $ 977 $ 1,089 Adjustment Expenses, 2015 405 650 885 1,058 Net of Reinsurance 2016 412 688 931 2017 456 746 2014 - Before 2018 515 2018 2014 Total $ 4,339 $ 2,654 $ 207 Total net liability $ 2,861 Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Unaudited Years 1 2 3 4 5 31.3 % 19.2 % 17.6 % 13.7 % 9.3 % Workers’ Compensation ( dollars in millions ) For the Years Ended December 31, 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Unaudited Accident Year IBNR Reserves December 31, 2018 Cumulative Number of Reported Claims 2009 $ 1,799 $ 1,778 $ 1,746 $ 1,753 $ 1,753 $ 1,766 $ 1,775 $ 1,750 $ 1,736 $ 1,728 $ 221 104,789 2010 1,886 2,042 2,035 2,056 2,049 2,052 2,055 2,021 2,003 271 117,368 2011 2,284 2,303 2,347 2,350 2,379 2,385 2,363 2,348 356 136,728 2012 2,447 2,456 2,457 2,456 2,445 2,453 2,416 404 137,922 2013 2,553 2,545 2,540 2,506 2,463 2,423 473 132,424 2014 2,554 2,553 2,547 2,476 2,430 563 124,507 2015 2,644 2,585 2,505 2,441 751 122,388 2016 2,768 2,690 2,569 863 122,493 2017 2,779 2,681 1,179 119,890 2018 2,744 1,738 109,002 Total $ 23,783 Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Accident Year Unaudited 2009 $ 288 $ 623 $ 828 $ 961 $ 1,065 $ 1,137 $ 1,193 $ 1,235 $ 1,274 $ 1,303 2010 341 750 978 1,133 1,246 1,321 1,385 1,430 1,465 2011 420 911 1,185 1,365 1,487 1,583 1,652 1,696 2012 443 940 1,217 1,394 1,536 1,629 1,689 Liability for Claims 2013 458 954 1,237 1,413 1,525 1,604 And Allocated Claim 2014 455 944 1,224 1,399 1,505 Adjustment Expenses, 2015 430 893 1,154 1,310 Net of Reinsurance 2016 421 873 1,118 2017 433 890 2009 - Before 2018 440 2018 2009 Total $ 13,020 $ 10,763 $ 5,276 Total net liability $ 16,039 Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Unaudited Years 1 2 3 4 5 6 7 8 9 10 17.4 % 19.5 % 11.2 % 7.3 % 5.3 % 3.8 % 3.0 % 2.2 % 2.0 % 1.7 % Bond & Specialty Insurance General Liability ( dollars in millions ) For the Years Ended December 31, 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Unaudited Accident Year IBNR Reserves December 31, 2018 Cumulative Number of Reported Claims 2009 $ 592 $ 624 $ 665 $ 686 $ 680 $ 660 $ 655 $ 641 $ 631 $ 626 $ 11 6,297 2010 571 612 679 679 661 668 653 653 657 18 5,673 2011 565 596 639 632 601 545 520 508 (12 ) 5,212 2012 538 591 614 605 601 599 605 97 4,853 2013 510 565 606 630 654 607 103 4,442 2014 549 571 563 518 473 67 4,335 2015 528 524 486 437 92 4,155 2016 512 511 504 153 4,235 2017 534 517 266 4,128 2018 530 406 2,894 Total $ 5,464 Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Accident Year Unaudited 2009 $ 36 $ 167 $ 310 $ 390 $ 460 $ 497 $ 563 $ 592 $ 595 $ 597 2010 33 152 291 396 482 565 597 623 631 2011 33 143 249 324 414 447 476 490 2012 38 160 255 342 383 419 436 Liability for Claims 2013 34 154 252 352 400 434 And Allocated Claim 2014 38 150 239 312 367 Adjustment Expenses, 2015 38 141 234 310 Net of Reinsurance 2016 30 141 233 2017 38 155 2009 - Before 2018 49 2018 2009 Total $ 3,702 $ 1,762 $ 71 Total net liability $ 1,833 Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Unaudited Years 1 2 3 4 5 6 7 8 9 10 6.8 % 21.4 % 19.4 % 15.3 % 11.4 % 7.3 % 6.0 % 3.7 % 0.9 % 0.2 % Fidelity and Surety ( dollars in millions ) For the Years Ended December 31, 2014 2015 2016 2017 2018 IBNR Reserves December 31, 2018 Cumulative Incurred Claims and Allocated Claims Adjustment Number of Expenses, Net of Reinsurance Reported Accident Year Unaudited Claims 2014 $ 223 $ 212 $ 165 $ 136 $ 130 $ (4 ) 1,069 2015 217 191 179 145 38 827 2016 226 239 205 12 866 2017 244 271 64 863 2018 220 121 595 Total $ 971 Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Accident Year Unaudited Liability for Claims And Allocated Claim 2014 $ 58 $ 96 $ 111 $ 127 $ 124 Adjustment Expenses, 2015 32 75 87 86 Net of Reinsurance 2016 54 121 142 2017 70 166 2014 - Before 2018 64 2018 2014 Total $ 582 $ 389 $ 30 Total net liability $ 419 Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Unaudited Years 1 2 3 4 5 29.5 % 31.8 % 9.9 % 6.1 % (2.7 )% Personal Insurance Automobile ( dollars in millions ) For the Years Ended December 31, 2014 2015 2016 2017 2018 IBNR Reserves December 31, 2018 Cumulative Incurred Claims and Allocated Claims Adjustment Number of Expenses, Net of Reinsurance Reported Accident Year Unaudited Claims 2014 $ 2,014 $ 1,994 $ 1,981 $ 1,985 $ 1,980 $ 14 670,431 2015 2,186 2,244 2,236 2,222 35 757,837 2016 2,779 2,791 2,772 126 921,479 2017 3,323 3,256 341 1,059,610 2018 3,281 825 960,293 Total $ 13,511 Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Accident Year Unaudited Liability for Claims And Allocated Claim 2014 $ 1,193 $ 1,564 $ 1,763 $ 1,879 $ 1,936 Adjustment Expenses, 2015 1,319 1,768 1,985 2,109 Net of Reinsurance 2016 1,610 2,203 2,466 2017 1,912 2,575 2014 - Before 2018 1,889 2018 2014 Total $ 10,975 $ 2,536 $ 240 Total net liability $ 2,776 Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Unaudited Years 1 2 3 4 5 58.8 % 20.2 % 9.8 % 5.7 % 2.9 % Homeowners (excluding Other) ( dollars in millions ) For the Years Ended December 31, 2014 2015 2016 2017 2018 IBNR Reserves December 31, 2018 Cumulative Incurred Claims and Allocated Claims Adjustment Number of Expenses, Net of Reinsurance Reported Accident Year Unaudited Claims 2014 $ 1,515 $ 1,450 $ 1,453 $ 1,457 $ 1,451 $ 7 151,705 2015 1,438 1,454 1,461 1,452 10 145,088 2016 1,556 1,547 1,525 27 143,797 2017 2,312 2,340 101 168,357 2018 2,610 568 165,780 Total $ 9,378 Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Accident Year Unaudited Liability for Claims And Allocated Claim 2014 $ 1,053 $ 1,338 $ 1,402 $ 1,425 $ 1,433 Adjustment Expenses, 2015 994 1,333 1,395 1,421 Net of Reinsurance 2016 1,049 1,392 1,455 2017 1,471 2,059 2014 - Before 2018 1,657 2018 2014 Total $ 8,025 $ 1,353 $ 23 Total net liability $ 1,376 Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Unaudited Years 1 2 3 4 5 67.2 % 22.7 % 4.3 % 1.7 % 0.5 % International - Canada ( dollars in millions ) For the Years Ended December 31, IBNR Reserves December 31, 2018 Cumulative 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 Number of Accident Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Reported Year Unaudited Claims 2009 $ 454 $ 442 $ 450 $ 456 $ 464 $ 456 $ 449 $ 449 $ 442 $ 440 $ — 55,162 2010 463 464 475 488 477 469 465 459 457 5 54,919 2011 436 416 424 420 412 406 401 396 4 55,783 2012 413 393 394 378 377 361 355 12 51,226 2013 461 455 446 435 422 421 14 54,231 2014 408 422 423 412 405 (3 ) 52,291 2015 343 342 342 339 16 45,201 2016 343 389 389 32 45,728 2017 329 362 26 46,545 2018 418 89 46,883 Total $ 3,982 Accident Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Year Unaudited 2009 $ 189 $ 283 $ 323 $ 350 $ 379 $ 403 $ 419 $ 430 $ 433 $ 434 2010 182 278 313 351 380 409 425 437 442 2011 167 237 266 299 332 353 370 378 2012 157 219 249 274 300 317 325 Liability for Claims 2013 184 258 289 320 351 368 And Allocated Claim 2014 180 252 287 314 344 Adjustment Expenses, 2015 154 215 241 269 Net of Reinsurance 2016 201 269 294 2017 173 244 2009 - Before 2018 208 2018 2009 Total $ 3,306 $ 676 $ 34 Total net liability $ 710 Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Unaudited Years 1 2 3 4 5 6 7 8 9 10 45.2 % 18.7 % 7.8 % 7.4 % 7.3 % 5.2 % 3.5 % 2.2 % 1.0 % 0.2 % The incurred and paid amounts have been translated from the local currency to U.S. dollars using the December 31, 2018 spot rate for all years presented in the table above in order to isolate changes in foreign exchange rates from loss development. Methodology for Estimating Incurred But Not Reported (IBNR) Reserves Claims and claim adjustment expense reserves represent management’s estimate of the ultimate liability for unpaid losses and loss adjustment expenses for claims that have been reported and claims that have been incurred but not yet reported as of the balance sheet date. Claims and claim adjustment expense reserves do not represent an exact calculation of the liability, but instead represent management estimates, primarily utilizing actuarial expertise and projection methods that develop estimates for the ultimate cost of claims and claim adjustment expenses. Because the establishment of claims and claims adjustment expense reserves is an inherently uncertain process involving estimates and judgment, currently estimated claims and claim adjustment expense reserves may change. The Company reflects changes to the reserves in the results of operations in the period the estimates are changed. Cumulative amounts paid and case reserves held as of the balance sheet date are subtracted from the estimate of the ultimate cost of claims and claim adjustment expenses to derive incurred but not reported (IBNR) reserves. Accordingly, IBNR reserves include the cost of unreported claims, development on known claims and re-opened claims. This approach to estimating IBNR reserves has been in place for many years, with no material changes in methodology in the past year. Detailed claim data is typically insufficient to produce a reliable indication of the initial estimate for ultimate claims and claim adjustment expenses for an accident year. As a result, the initial estimate for an accident year is generally based on an exposure-based method using either the loss ratio projection or the expected loss method. The loss ratio projection method, which is typically used for guaranteed-cost business, develops an initial estimate of ultimate claims and claim adjustment expenses for an accident year by multiplying earned premium for the accident year by a projected loss ratio. The projected loss ratio is determined by analyzing prior period experience, and adjusting for loss cost trends, rate level differences, mix of business changes and other known or observed factors influencing the accident year relative to prior accident years. The expected loss method, which is typically used for loss sensitive business, develops an initial estimate of ultimate claims and claim adjustment expenses for an accident year by analyzing exposures by account. For prior accident years, the following estimation and analysis methods are principally used by the Company’s actuaries to estimate the ultimate cost of claims and claim adjustment expenses. These estimation and analysis methods are typically referred to as conventional actuarial methods. • The paid loss development method assumes that the future change (positive or negative) in cumulative paid losses for a given cohort of claims will occur in a stable, predictable pattern from year-to-year, consistent with the pattern observed in past cohorts. • The case incurred development method is the same as the paid loss development method but is based on cumulative case-incurred losses rather than paid losses. • The Bornhuetter-Ferguson method uses an initial estimate of ultimate losses for a given product line reserve component, typically expressed as a ratio to earned premium. The method assumes that the ratio of additional claim activity to earned premium for that component is relatively stable and predictable over time and that actual claim activity to date is not a credible predictor of further activity for that component. The method is used most often for more recent accident years where claim data is sparse and/or volatile, with a transition to other methods as the underlying claim data becomes more voluminous and therefore more credible. • The average value analysis combined with the reported claim development method assumes that average claim values are stable and predictable over time for a particular cohort of claims. It is typically limited to analysis at more granular levels, such as coverage or hazard/peril, where a more homogeneous subset of claims produce a more stable and fairly predictable average value. The reported claim development method is the same as the paid loss development method but uses changes in cumulative claim counts to produce estimates of ultimate claim counts rather than ultimate dollars. The resulting estimate of ultimate claim counts by cohort is multiplied by an average value per claim from an average value analysis to obtain estimated ultimate claims and claim adjustment expenses. While these are the principal methods utilized, the Company’s actuaries have available to them the full range of actuarial methods developed by the casualty actuarial profession. The Company’s actuaries are also continually monitoring developments within the profession for advances in existing techniques or the creation of new techniques that might improve current and future estimates. Most actuarial methods assume that past patterns demonstrated in the data will repeat themselves in the future. For certain reserve components where this assumption may not hold, such as asbestos and environmental reserves, conventional actuarial methods are not utilized by the Company. Methodology for Determining Cumulative Number of Reported Claims A claim file is created when the Company is notified of an actual demand for payment, notified of an event that may lead to a demand for payment or when it is determined that a demand for payment could possibly lead to a future demand for payment on another coverage on the same policy or on another policy. Claim files are generally created for a policy at the claimant by coverage level, depending on the particular facts and circumstances of the underlying event. For Business Insurance and for Personal Insurance, claim file information is summarized such that the Company generally recognizes one count for each policy claim event by internal regulatory line of business, regardless of the number of claimants or coverages involved. The claims counts are then accumulated and reported by product line. While the methodology is generally consistent within each segment for the product lines displayed, there are some minor differences between and within segments. For Bond & Specialty Insurance, the Company generally recognizes one count per coverage per policy claim event and one count per bond per surety claim event. For purposes of the claims development tables above, claims reported for direct business are counted even if they eventually close with no loss payment, except in the case of (i) deductible business, where the claim is not counted until the case incurred claim estimate is above the deductible, and (ii) International-Canada reported claim counts where claims closed with no loss payment are not counted. Note that claims with zero claim dollars may still generate some level of claim adjustment expenses. Claim counts for assumed business are included only to the extent such counts are available. The Company generally does not receive claim count information for which the underlying claim activity is handled by others, including pools and associations. The Company does not generate claim counts for ceded business. The methods used to summarize claim counts have not changed significantly over the time periods reported in the tables above. The Company cautions against using the summarized claim count information provided in this disclosure in attempting to project ultimate loss payouts by product line. The Company generally finds claim count data to be useful only on a more granular basis than the aggregated basis disclosed in the claim development tables above, as the risks, average values and other dynamics of the claim process can vary materially by the cause of loss and coverage within product line. For example, in Personal Automobile, the introduction of a new roadside assistance coverage feature several years ago resulted in a significant increase in claim counts with a low average claim cost. For this reason the Company varies its approach to, and in many cases the level of aggregation for, counting claims for internal analysis purposes depending on the particular granular analysis performed. Asbestos and Env

Debt

Debt	12 Months Ended
	Dec. 31, 2018
Debt Disclosure [Abstract]
Debt	DEBT Debt outstanding was as follows: (at December 31, in millions) 2018 2017 Short-term: Commercial paper $ 100 $ 100 5.90% Senior notes due June 2, 2019 500 — 5.80% Senior notes due May 15, 2018 — 500 Total short-term debt 600 600 Long-term: 5.90% Senior notes due June 2, 2019 — 500 3.90% Senior notes due November 1, 2020 500 500 7.75% Senior notes due April 15, 2026 200 200 7.625% Junior subordinated debentures due December 15, 2027 125 125 6.375% Senior notes due March 15, 2033 500 500 6.75% Senior notes due June 20, 2036 400 400 6.25% Senior notes due June 15, 2037 800 800 5.35% Senior notes due November 1, 2040 750 750 4.60% Senior notes due August 1, 2043 500 500 4.30% Senior notes due August 25, 2045 400 400 8.50% Junior subordinated debentures due December 15, 2045 56 56 3.75% Senior notes due May 15, 2046 500 500 8.312% Junior subordinated debentures due July 1, 2046 73 73 4.00% Senior notes due May 30, 2047 700 700 4.05% Senior notes due March 7, 2048 500 — Total long-term debt 6,004 6,004 Total debt principal 6,604 6,604 Unamortized fair value adjustment 44 46 Unamortized debt issuance costs (84 ) (79 ) Total debt $ 6,564 $ 6,571 2018 Debt Issuance. On March 7, 2018, the Company issued $500 million aggregate principal amount of 4.05% senior notes that will mature on March 7, 2048. The net proceeds of the issuance, after the deduction of the underwriting discount and expenses payable by the Company, totaled approximately $491 million . Interest on the senior notes is payable semi-annually in arrears on March 7 and September 7. Prior to September 7, 2047, 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 September 7, 2047 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 September 7, 2047, 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 100% of the principal amount of any senior notes to be redeemed, plus accrued and unpaid interest to, but excluding, the redemption date. 2018 Debt Repayment . On May 15, 2018, the Company's $500 million , 5.80% senior notes matured and were fully paid. 2017 Debt Issuance . On May 22, 2017, the Company issued $700 million aggregate principal amount of 4.00% senior notes that will mature on May 30, 2047. The net proceeds of the issuance, after the deduction of the underwriting discount and expenses payable by the Company, totaled approximately $689 million . Interest on the senior notes is payable semi-annually in arrears on May 30 and November 30. Prior to November 30, 2046, 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 November 30, 2046 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 November 30, 2046, 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 100% of the principal amount of any senior notes to be redeemed, plus accrued and unpaid interest to, but excluding, the redemption date. 2017 Debt Redemption and Repayment. On June 2, 2017, the Company redeemed the remaining $107 million aggregate principal amount of its 6.25% Fixed-to-Floating Rate Junior Subordinated Debentures due 2067 at a price per debenture of 100% of the principal amount thereof, plus accrued and unpaid interest to the redemption date. On December 15, 2017, the Company’s $450 million , 5.75% senior notes matured and were fully paid. 2016 Debt Issuance . On May 11, 2016, the Company issued $500 million aggregate principal amount of 3.75% senior notes that will mature on May 15, 2046. The net proceeds of the issuance, after the deduction of underwriting and other expenses, totaled approximately $491 million . Interest on the senior notes is payable semi-annually in arrears on May 15 and November 15. Prior to November 15, 2045, 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 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 20 basis points. On or after November 15, 2045, 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 100% of the principal amount of any senior notes to be redeemed, plus accrued and unpaid interest to, but excluding, the redemption date. 2016 Debt Repayment. On June 20, 2016, the Company’s $400 million , 6.25% senior notes matured and were fully paid. Description of Debt Commercial Paper —The Company maintains an $800 million commercial paper program. (See “Credit Agreement” discussion that follows.) Interest rates on commercial paper issued in 2018 ranged from 1.47% to 2.37% , and in 2017 ranged from 0.65% to 1.17% . Senior Notes —The Company’s various senior debt issues are unsecured obligations that rank equally with one another. Interest payments are made semi-annually. The Company generally may redeem some or all of the notes prior to maturity in accordance with terms unique to each debt instrument. Junior Subordinated Debentures —The Company’s three junior subordinated debenture instruments are all similar in nature to each other. Three separate business trusts issued preferred securities to investors and used the proceeds to purchase the Company’s junior subordinated debentures. Interest on each of the instruments is paid semi-annually. The Company’s consolidated balance sheet includes the debt instruments acquired in a business acquisition, which were recorded at fair value as of the acquisition date. The resulting fair value adjustment is being amortized over the remaining life of the respective debt instruments using the effective-interest method. The amortization of the fair value adjustment reduced interest expense by $2 million and $1 million for the years ended December 31, 2018 and 2017 , respectively. The following table presents merger-related unamortized fair value adjustments and the related effective interest rate: Unamortized Fair Value Purchase Adjustment at December 31, Effective Interest Rate to Maturity (in millions) Issue Rate Maturity Date 2018 2017 Junior subordinated debentures 7.625 % Dec. 2027 $ 12 $ 13 6.147 % 8.500 % Dec. 2045 14 15 6.362 % 8.312 % Jul. 2046 18 18 6.362 % Total $ 44 $ 46 The Travelers Companies, Inc. fully and unconditionally guarantees the payment of all principal, premiums, if any, and interest on certain debt obligations of its subsidiaries Travelers Property Casualty Corp. and Travelers Insurance Group Holdings, Inc. The guarantees pertain to the $200 million 7.75% notes due 2026 and the $500 million 6.375% notes due 2033. Maturities —The amount of debt obligations, other than commercial paper, that become due in each of the next five years is as follows: 2019 , $500 million ; 2020 , $500 million ; 2021 , $0 ; 2022 , $0 ; and 2023 , $0 . Credit Agreement On June 4, 2018, the Company entered into a five-year, $1.0 billion revolving credit agreement with a syndicate of financial institutions, replacing its five-year, $1.0 billion credit agreement that was due to expire on June 7, 2018. Pursuant to the credit agreement covenants, the Company must maintain a minimum consolidated net worth, defined as shareholders’ equity determined in accordance with GAAP (excluding accumulated other comprehensive income (loss)) plus (a) trust preferred securities (not to exceed 15% of total capital) and (b) mandatorily convertible securities (combined with trust preferred securities, not to exceed 25% of total capital) less goodwill and other intangible assets. The threshold is adjusted downward by an amount equal to 70% of the aggregate amount of common stock repurchased by the Company after March 31, 2018, up to a maximum deduction of $1.75 billion . The threshold was $13.60 billion at December 31, 2018 and could decline to a minimum of $12.494 billion during the term of the credit agreement, subject to the Company repurchasing an additional $1.58 billion of its common stock. In addition, the credit agreement contains other customary restrictive covenants as well as certain customary events of default, including with respect to a change in control, which is defined to include the acquisition of 35% or more of the Company’s voting stock and certain changes in the composition of the Company’s board of directors. At December 31, 2018 , the Company was in compliance with these covenants. Generally, the cost of borrowing under this agreement will range from LIBOR plus 75 basis points to LIBOR plus 137.5 basis points, depending on the Company’s credit ratings. At December 31, 2018 , that cost would have been LIBOR plus 100 basis points, had there been any amounts outstanding under the credit agreement. In the event that LIBOR is no longer available, the credit agreement provides that the Company and the syndicate of financial institutions use commercially reasonable efforts to jointly agree upon an alternate rate of interest. Shelf Registration The Company has a shelf registration statement filed with the Securities and Exchange Commission that expires on June 17, 2019 which permits it to issue securities from time to time at prices and on other terms to be determined at the time of offering.

Shareholders' Equity and Divide

Shareholders' Equity and Dividend Availability	12 Months Ended
	Dec. 31, 2018
Stockholders' Equity Note [Abstract]
Shareholders' Equity and Dividend Availability	SHAREHOLDERS’ EQUITY AND DIVIDEND AVAILABILITY Authorized Shares The number of authorized shares of the Company is 1.755 billion , consisting of five million shares of preferred stock, 1.745 billion shares of voting common stock and five million undesignated shares. The Company’s Articles of Incorporation authorize the Board of Directors to establish, from the undesignated shares, one or more classes and series of shares, and to further designate the type of shares and terms thereof. Preferred Stock The Company’s Articles of Incorporation provide authority to issue up to five million shares of preferred stock. Common Stock The Company is governed by the Minnesota Business Corporation Act. All authorized shares of voting common stock have no par value. Shares of common stock reacquired are considered authorized and unissued shares. Restricted Stock In August 2017, the Company issued 95,953 shares of restricted stock valued at approximately $12 million in connection with a business acquisition to certain employees of the acquired business, of which 92,995 shares remained outstanding and unvested at December 31, 2018. The restricted stock is subject to service conditions and as such is recognized as share-based compensation; 50% of the restricted stock will vest two years from the issuance date and the remainder will vest three years from the issuance date. The value is being recognized over the respective vesting periods and included with the share-based compensation cost of awards that are issued under the Company’s share-based incentive compensation plan (see note 13). The recipients generally have all the rights of a shareholder of the Company including the right to vote the applicable shares of common stock and to receive dividends on such shares, if and as declared by the Board of Directors. The restricted stock is held under the Company’s control with the Company’s transfer agent and will be released upon vesting. Treasury Stock The Company’s Board of Directors has approved common share repurchase authorizations under which repurchases may be made from time to time in the open market, pursuant to pre-set trading plans meeting the requirements of Rule 10b5-1 under the Securities Exchange Act of 1934, in private transactions or otherwise. The authorizations do not have a stated expiration date. The timing and actual number of shares to be repurchased in the future will depend on a variety of factors, including the Company’s financial position, earnings, share price, catastrophe losses, maintaining capital levels commensurate with the Company’s desired ratings from independent rating agencies, funding of the Company’s qualified pension plan, capital requirements of the Company’s operating subsidiaries, legal requirements, regulatory constraints, other investment opportunities (including mergers and acquisitions and related financings), market conditions and other factors. In April 2017, the Board of Directors approved a share repurchase authorization that added an additional $5.0 billion of repurchase capacity. The following table summarizes repurchase activity in 2018 and remaining repurchase capacity at December 31, 2018 . (in millions, except per share amounts) Quarterly Period Ending Number of shares repurchased Cost of shares repurchased Average price paid per share Remaining capacity under share repurchase authorization March 31, 2018 2.5 $ 350 $ 141.84 $ 4,206 June 30, 2018 2.7 350 129.66 3,856 September 30, 2018 3.0 400 130.22 3,456 December 31, 2018 1.4 170 125.09 3,286 Total 9.6 $ 1,270 132.33 3,286 The Company’s Amended and Restated 2004 Stock Incentive Plan and the Amended and Restated 2014 Stock Incentive Plan provide settlement alternatives to employees in which the Company retains shares to cover payroll withholding taxes in connection with the vesting of restricted stock unit awards and performance share awards, and to cover the price of certain stock options that were exercised. During the years ended December 31, 2018 and 2017 , the Company acquired $51 million and $62 million , respectively, of its common stock under these plans. Common shares acquired are reported as treasury stock in the consolidated balance sheet. Dividend Availability The Company’s U.S. insurance subsidiaries, domiciled principally in the State of Connecticut, are subject to various regulatory restrictions that limit the maximum amount of dividends available to be paid by each insurance subsidiary to its respective parent company without prior approval of insurance regulatory authorities. A maximum of $2.52 billion is available by the end of 2019 for such dividends to the holding company, TRV, without prior approval of the Connecticut Insurance Department. The Company may choose to accelerate the timing within 2019 and/or increase the amount of dividends from its insurance subsidiaries in 2019 , which could result in certain dividends being subject to approval by the Connecticut Insurance Department. In addition to the regulatory restrictions on the availability of dividends that can be paid by the Company’s U.S. insurance subsidiaries, the maximum amount of dividends that may be paid to the Company’s shareholders is limited, to a lesser degree, by certain covenants contained in its line of credit agreement with a syndicate of financial institutions that require the Company to maintain a minimum consolidated net worth as described in note 8. TRV is not dependent on dividends or other forms of repatriation from its foreign operations to support its liquidity needs. The undistributed earnings of the Company’s foreign operations are intended to be permanently reinvested in those operations, and such earnings were not material to the Company's financial position or liquidity at December 31, 2018 . TRV and its two non-insurance holding company subsidiaries received dividends of $2.30 billion , $2.33 billion and $3.05 billion from their U.S. insurance subsidiaries in 2018 , 2017 and 2016 , respectively. For the years ended December 31, 2018 , 2017 and 2016 , TRV declared cash dividends per common share of $3.03 , $2.83 and $2.62 , respectively, and paid cash dividends of $814 million , $785 million and $757 million , respectively. Statutory Net Income and Statutory Capital and Surplus Statutory net income of the Company’s domestic and international insurance subsidiaries was $2.61 billion , $2.30 billion and $3.20 billion for the years ended December 31, 2018 , 2017 and 2016 , respectively. Statutory capital and surplus of the Company’s domestic and international insurance subsidiaries was $20.77 billion and $20.45 billion at December 31, 2018 and 2017 , respectively.

Other Comprehensive Income and

Other Comprehensive Income and Accumulated Other Comprehensive Income	12 Months Ended
	Dec. 31, 2018
Other Comprehensive Income and Accumulated Other Comprehensive Income disclosure
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 years ended December 31, 2018 , 2017 and 2016 . Changes in Net Unrealized Gains on Investment Securities (in millions) Having No Credit Losses Recognized in the Consolidated Statement of Income Having Credit Losses Recognized in the Consolidated Statement of Income Net Benefit Plan Assets and Obligations Recognized in Shareholders’ Equity Net Unrealized Foreign Currency Translation Total Accumulated Other Comprehensive Income (Loss) Balance, December 31, 2015 $ 1,100 $ 189 $ (713 ) $ (733 ) $ (157 ) Other comprehensive income (loss) (OCI) before reclassifications (530 ) 4 (30 ) (49 ) (605 ) Amounts reclassified from AOCI, net of tax (42 ) 9 40 — 7 Net OCI, current period (572 ) 13 10 (49 ) (598 ) Balance, December 31, 2016 528 202 (703 ) (782 ) (755 ) OCI before reclassifications 367 4 (24 ) 171 518 Amounts reclassified from AOCI, net of tax (148 ) 1 41 — (106 ) Net OCI, current period 219 5 17 171 412 Balance, December 31, 2017 747 207 (686 ) (611 ) (343 ) Cumulative effect of adoption of updated accounting guidance for equity financial instruments at January 1, 2018 (34 ) — — — (34 ) Income tax benefit (12 ) — — — (12 ) Net of taxes (22 ) — — — (22 ) Reclassification of certain tax effects from accumulated other comprehensive income at January 1, 2018 145 7 (141 ) (35 ) (24 ) Total effect of adoption of new guidance at January 1, 2018, net of tax 123 7 (141 ) (35 ) (46 ) OCI before reclassifications, net of tax (1,151 ) (21 ) (114 ) (227 ) (1,513 ) Amounts reclassified from AOCI, net of tax (25 ) — 68 — 43 Net OCI, current period (1,176 ) (21 ) (46 ) (227 ) (1,470 ) Balance, December 31, 2018 $ (306 ) $ 193 $ (873 ) $ (873 ) $ (1,859 ) The following table presents the pre-tax components of the Company’s other comprehensive income (loss) and the related income tax expense (benefit). (for the year ended December 31, in millions) 2018 2017 2016 Changes in net unrealized gains on investment securities: Having no credit losses recognized in the consolidated statement of income $ (1,489 ) $ 294 $ (883 ) Income tax expense (benefit) (313 ) 75 (311 ) Net of taxes (1,176 ) 219 (572 ) Having credit losses recognized in the consolidated statement of income (27 ) 8 21 Income tax expense (benefit) (6 ) 3 8 Net of taxes (21 ) 5 13 Net changes in benefit plan assets and obligations (56 ) 29 16 Income tax expense (benefit) (10 ) 12 6 Net of taxes (46 ) 17 10 Net changes in unrealized foreign currency translation (247 ) 191 (41 ) Income tax expense (benefit) (20 ) 20 8 Net of taxes (227 ) 171 (49 ) Total other comprehensive income (loss) (1,819 ) 522 (887 ) Total income tax expense (benefit) (349 ) 110 (289 ) Total other comprehensive income (loss), net of taxes $ (1,470 ) $ 412 $ (598 ) 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. (for the year ended December 31, in millions) 2018 2017 2016 Reclassification adjustments related to unrealized gains on investment securities: Having no credit losses recognized in the consolidated statement of income (1) $ (32 ) $ (228 ) $ (64 ) Income tax expense (2) (7 ) (80 ) (22 ) Net of taxes (25 ) (148 ) (42 ) Having credit losses recognized in the consolidated statement of income (1) — 1 13 Income tax benefit (2) — — 4 Net of taxes — 1 9 Reclassification adjustment related to benefit plan assets and obligations: Claims and claim adjustment expenses (3) 35 32 25 General and administrative expenses (3) 51 48 37 Total 86 80 62 Income tax benefit (2) 18 39 22 Net of taxes 68 41 40 Reclassification adjustment related to foreign currency translation (1) — — — Income tax benefit (2) — — — Net of taxes — — — Total reclassifications 54 (147 ) 11 Total income tax (expense) benefit 11 (41 ) 4 Total reclassifications, net of taxes $ 43 $ (106 ) $ 7 ___________________________________________ (1) (Increases) decreases net realized investment gains on the consolidated statement of income. (2) (Increases) decreases income tax expense on the consolidated statement of income. (3) Increases (decreases) expenses on the consolidated statement of income.

Earnings per Share

Earnings per Share	12 Months Ended
	Dec. 31, 2018
Earnings Per Share Reconciliation [Abstract]
Earnings Per Share	EARNINGS PER SHARE Basic earnings per share was computed by dividing net income available to common shareholders by the weighted average number of common shares outstanding during the period. The computation of diluted earnings per share reflected the effect of potentially dilutive securities. The following is a reconciliation of the income and share data used in the basic and diluted earnings per share computations: (for the year ended December 31, in millions, except per share amounts) 2018 2017 2016 Basic and Diluted Net income, as reported $ 2,523 $ 2,056 $ 3,014 Participating share-based awards — allocated income (19 ) (15 ) (22 ) Net income available to common shareholders — basic and diluted $ 2,504 $ 2,041 $ 2,992 Common Shares Basic Weighted average shares outstanding 267.4 276.0 288.1 Diluted Weighted average shares outstanding 267.4 276.0 288.1 Weighted average effects of dilutive securities: Stock options and performance shares 2.4 2.6 2.9 Total 269.8 278.6 291.0 Net income Per Common Share Basic $ 9.37 $ 7.39 $ 10.39 Diluted $ 9.28 $ 7.33 $ 10.28

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Income Taxes	INCOME TAXES Tax Cuts and Jobs Act of 2017 On December 22, 2017, the U.S. enacted the Tax Cuts and Jobs Act of 2017 (TCJA) which, among other changes, reduced the U.S. federal tax rate from 35% to 21% beginning on January 1, 2018 and imposed a tax on undistributed and previously untaxed post-1986 foreign earnings and profits (accumulated foreign earnings). Total income tax expense for 2017 included a net charge of $129 million to reflect the estimated impacts of the changes in tax laws and tax rates included in TCJA at the date of enactment, primarily reflecting the revaluation of the Company's deferred tax assets and liabilities at the new statutory federal tax rate of 21%, and the recognition of tax imposed on accumulated foreign earnings. The estimated effects of enactment of TCJA were reflected in the Company's net deferred tax asset and current income tax receivable reported on the Company’s consolidated balance sheet at December 31, 2017. Components of Income Tax Expense The following table presents the components of income tax expense included in the amounts reported in the Company’s consolidated financial statements: (for the year ended December 31, in millions) 2018 2017 2016 Composition of income tax expense included in the consolidated statement of income Current expense: Federal $ 424 $ 314 $ 899 Impact of TCJA at enactment — 21 — Foreign 41 56 21 State 8 4 8 Total current tax expense 473 395 928 Deferred expense (benefit): Federal (13 ) 229 110 Impact of TCJA at enactment — 108 — Foreign (22 ) (58 ) 1 Total deferred tax expense (benefit) (35 ) 279 111 Total income tax expense included in the consolidated statement of income 438 674 1,039 Composition of income tax expense (benefit) included in shareholders’ equity Expense (benefit) relating to changes in the unrealized gain (loss) on investments, unrealized loss on foreign exchange and other items in other comprehensive income (loss) (349 ) 110 (289 ) Total income tax expense included in the consolidated financial statements $ 89 $ 784 $ 750 The following is a reconciliation of income tax expense at the U.S. federal statutory income tax rate to the income tax expense reported in the Company’s consolidated statement of income: (for the year ended December 31, in millions) 2018 2017 2016 Income (loss) before income taxes U.S. $ 3,039 $ 2,798 $ 3,946 Foreign (78 ) (68 ) 107 Total income before income taxes 2,961 2,730 4,053 Effective tax rate Statutory tax rate 21 % 35 % 35 % Expected federal income tax expense 622 956 1,419 Tax effect of: Nontaxable investment income (150 ) (297 ) (323 ) TCJA at enactment — 129 — Other, net (34 ) (114 ) (57 ) Total income tax expense $ 438 $ 674 $ 1,039 Effective tax rate 15 % 25 % 26 % The Company paid income taxes of $408 million , $514 million and $892 million during the years ended December 31, 2018 , 2017 and 2016 , respectively. The current income tax receivable of $12 million and $65 million at December 31, 2018 and 2017 , respectively, was included in other assets in the consolidated balance sheet. In computing taxable income, property and casualty insurers reduce underwriting income by claims and claim adjustment expenses incurred. The deduction for claims incurred is discounted at the interest rates and for the claim payment patterns prescribed by the U.S. Treasury. TCJA changed the prescribed interest rates to rates based on corporate bond yield curves and extended the applicable time periods for the claim payment pattern. These changes were effective for tax years beginning after 2017 and are subject to a transition rule that spreads the additional tax payment from the amount determined by applying these changes over the subsequent eight years beginning in 2018. This item is a taxable temporary difference and had no direct impact on total tax expense for 2017 and will not directly impact total tax expense in future years. The required additional tax payments are currently estimated to approximate $23 million per year over the eight-year period through 2025 and will result in a modest reduction in net investment income over that period. The net deferred tax asset comprises the tax effects of temporary differences related to the following assets and liabilities: (at December 31, in millions) 2018 2017 Deferred tax assets Claims and claim adjustment expense reserves $ 571 $ 930 Unearned premium reserves 503 478 Compensation-related liabilities 92 61 Other 200 191 Total gross deferred tax assets 1,366 1,660 Less: valuation allowance 8 6 Adjusted gross deferred tax assets 1,358 1,654 Deferred tax liabilities Claims and claim adjustment expense reserve discounting (transition rule) 159 560 Deferred acquisition costs 397 376 Investments 152 454 Internally developed software 92 97 Depreciation 67 57 Other 46 40 Total gross deferred tax liabilities 913 1,584 Net deferred tax asset $ 445 $ 70 If the Company determines that any of its deferred tax assets will not result in future tax benefits, a valuation allowance must be established for the portion of these assets that are not expected to be realized. The net change in the valuation allowance for deferred tax assets was an increase of $2 million in 2018 relating to the Company’s consolidated Brazilian subsidiary. Based upon a review of the Company’s anticipated future taxable income, and also including all other available evidence, both positive and negative, the Company’s management concluded that it is more likely than not that the net deferred tax assets will be realized. For tax return purposes, as of December 31, 2018 , the Company had net operating loss (NOL) carryforwards in the United States, Brazil, Canada and the United Kingdom. The amount and timing of realizing the benefits of NOL carryforwards depend on future taxable income and limitations imposed by tax laws. Only the benefits of the United Kingdom NOL carryforwards have been recognized in the consolidated financial statements and are included in net deferred tax assets. The NOL amounts by jurisdiction and year of expiration are as follows: (in millions) Amount Year of expiration United States $ 2 2035 - 2036 Brazil $ 19 None Canada $ 1 2037 - 2038 United Kingdom $ 146 None The Company recognized $41 million of tax expense resulting from deemed repatriation of foreign earnings as part of the net charge of $129 million to record the effect of TCJA at enactment during December 2017. These undistributed foreign earnings are intended to be permanently reinvested in those operations. Provisional Tax Amounts During the fourth quarter of 2017, the Company recorded provisional amounts for the tax imposed on accumulated foreign earnings and partnership investments, as well as the amount due under the transition rule relating to the change in discounting of claims incurred, based on information available at December 31, 2017. In 2018, the Company made minor adjustments to the provisional amounts for taxes related to accumulated foreign earnings based upon final earnings from its foreign operations and the proposed regulations issued by the U.S. Treasury. These minor adjustments were consistent with final regulations issued by the U.S. Treasury in January 2019. The Company also made minor adjustments to the provisional amount for taxes related to partnership investments based upon the latest available information associated with those investments (Form K-1s) that were received in 2018. In November 2018, the U.S. Treasury issued proposed regulations which would establish the interest rate and discounting methodology to be used in determining the tax discount on claims and claim adjustment expense reserves under TCJA. The proposed regulations significantly reduce the deferred tax assets and liabilities related to the transition rule for discounting of reserves and reduced the estimated additional tax payments associated with the transition rule from $70 million to $23 million per year over the eight years beginning in 2018 as discussed above. The Company estimated the amounts payable related to the transition rules for discounting of loss reserves using the regulations proposed by the U.S. Treasury during 2018. These amounts are subject to change once the final regulations are issued, which is expected to occur in 2019. Unrecognized Tax Benefits The following is a reconciliation of the beginning and ending amount of unrecognized tax benefits for the years ended December 31, 2018 and 2017 : (in millions) 2018 2017 Balance at January 1 $ 6 $ 13 Additions for tax positions of prior years 25 — Reductions for tax positions of prior years — (1 ) Reductions based on tax positions related to current year — (6 ) Balance at December 31 $ 31 $ 6 Included in the balances at December 31, 2018 and 2017 were $29 million and $3 million , respectively, of unrecognized tax benefits that, if recognized, would affect the annual effective tax rate. Also included in the balances at those dates were $2 million and $3 million , respectively, of tax positions for which the ultimate deductibility is certain, but for which there is uncertainty about the timing of deductibility. The timing of such deductibility could affect the annual effective tax rate depending on the year of deduction and tax rate at the time. The Company recognizes accrued interest and penalties, if any, related to unrecognized tax benefits in income taxes. During the years ended December 31, 2018 , 2017 and 2016 , the Company recognized approximately $(10) million , $(33) million and $31 million in interest, respectively. The Company had approximately $14 million and $25 million accrued for the payment of interest at December 31, 2018 and 2017 , respectively. The IRS has completed examinations of the Company’s U.S. income tax returns for all years through 2014. The Company does not expect any significant changes to its liability for unrecognized tax benefits during the next twelve months.

Share-Based Incentive Compensat

Share-Based Incentive Compensation	12 Months Ended
	Dec. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-based Incentive Compensation	SHARE-BASED INCENTIVE COMPENSATION The Company has a share-based incentive compensation plan, The Travelers Companies, Inc. Amended and Restated 2014 Stock Incentive Plan (the 2014 Incentive Plan), the purposes of which are to align the interests of the Company’s non-employee directors, executive officers and other employees with those of the Company’s shareholders and to attract and retain personnel by providing incentives in the form of share-based awards. The 2014 Incentive Plan permits grants of nonqualified stock options, incentive stock options, stock appreciation rights, restricted stock, restricted stock units, deferred stock, deferred stock units, performance awards and other share-based or share-denominated awards with respect to the Company’s common stock. The Company has a policy of issuing new shares to settle the exercise of stock option awards and the vesting of other equity awards. In connection with the adoption of the 2014 Incentive Plan, The Travelers Companies, Inc. Amended and Restated 2004 Stock Incentive Plan, as amended (the 2004 Incentive Plan) was terminated, joining several other legacy share-based incentive compensation plans that had been terminated in prior years (together, the legacy plans). Outstanding grants were not affected by the termination of the legacy plans. The 2014 Incentive Plan is currently the only plan pursuant to which future stock-based awards may be granted. The number of shares of the Company’s common stock initially authorized for grant under the 2014 Incentive Plan was 10 million shares. In May 2017 and 2016, the Company’s shareholders authorized an additional 2.5 million and 4.4 million shares of the Company’s common stock, respectively, for grant under the 2014 Incentive Plan. The following are not counted towards the combined 16.9 million shares available and will be available for future grants under the 2014 Incentive Plan: (i) shares of common stock subject to awards that expire unexercised, that are forfeited, terminated or canceled, that are settled in cash or other forms of property, or otherwise do not result in the issuance of shares of common stock, in whole or in part; (ii) shares that are used to pay the exercise price of stock options and shares used to pay withholding taxes on awards generally; and (iii) shares purchased by the Company on the open market using cash option exercise proceeds; provided, however, that the increase in the number of shares of common stock available for grant pursuant to such market purchases shall not be greater than the number that could be repurchased at fair market value on the date of exercise of the stock option giving rise to such option proceeds. In addition, the 16.9 million shares authorized by shareholders for issuance under the 2014 Incentive Plan will be increased by any shares subject to awards under the 2004 Incentive Plan that were outstanding as of May 27, 2014 and subsequently expire, are forfeited, canceled, settled in cash or otherwise terminate without the issuance of shares. The Company also has a compensation program for non-employee directors (the Director Compensation Program). Under the Director Compensation Program, non-employee directors’ compensation consists of an annual retainer, a deferred stock award, committee chair fees and a lead director fee. Each non-employee director may choose to receive all or a portion of his or her annual retainer, committee chair fee and lead director fee in the form of cash or deferred stock units which vest upon grant. The annual deferred stock awards vest in full one day prior to the date of the Company’s annual meeting of shareholders occurring in the year following the year of the grant date, subject to continued service. The deferred stock awards, including dividend equivalents, accumulate until distribution either in a lump sum six months after termination of service as a director or, if the director so elects, in annual installments beginning at least six months following termination of service as a director. The deferred stock units issued under the Director Compensation Program are awarded under the 2014 Incentive Plan. Stock Option Awards Stock option awards granted to eligible officers and key employees have a ten -year term. All stock options are granted with an exercise price equal to the closing price of the Company’s common stock on the date of grant. The stock options granted generally vest upon meeting certain years of service criteria. Except as the Compensation Committee of the Board of Directors may allow in the future, stock options cannot be sold or transferred by the participant. Stock options outstanding under the 2014 Incentive Plan and the 2004 Incentive Plan generally vest three years after grant date (cliff vest). The fair value of each option award is estimated on the date of grant by application of a variation of the Black-Scholes option pricing model using the assumptions noted in the following table. The expected term of newly granted stock options is the time to vest plus half the remaining time to expiration. This considers the vesting restriction and represents an even pattern of exercise behavior over the remaining term. The expected volatility assumption is based on the historical volatility of the Company’s common stock for the same period as the estimated option term generally using the volatility of the week prior to the stock option grant. The expected dividend is based upon the Company’s current quarter dividend annualized and assumed to be constant over the expected option term. The risk-free interest rate for each option is the interpolated market yield of a U.S. Treasury bill with a term comparable to the expected option term for the same week used for measuring volatility. The following table provides information about options granted: (for the year ended December 31,) 2018 2017 2016 Assumptions used in estimating fair value of options on grant date Expected term of stock options 6 years 6 years 5 – 6 years Expected volatility of Company’s stock 14.94 % 16.50 % 15.14% – 16.80% Weighted average volatility 14.94 % 16.50 % 16.79 % Expected annual dividend per share $2.88 $2.68 $2.44 – $2.68 Risk-free rate 2.68 % 2.08 % 1.36% – 2.23% Additional information Weighted average grant-date fair value of options granted (per share) $ 20.13 $ 16.15 $ 13.29 Total intrinsic value of options exercised during the year (in millions) $ 67 $ 90 $ 167 A summary of stock option activity under the 2014 Incentive Plan and the legacy plans as of and for the year ended December 31, 2018 is as follows: Stock Options Number Weighted Average Exercise Price Weighted Average Contractual Life Remaining Aggregate Intrinsic Value ($ in millions) Outstanding, beginning of year 8,712,467 $ 97.45 Original grants 1,632,361 140.85 Exercised (1,229,850 ) 83.74 Forfeited or expired (120,622 ) 117.39 Outstanding, end of year 8,994,356 $ 106.93 6.2 years $ 149 Vested at end of year (1) 5,861,909 $ 99.28 5.3 years $ 134 Exercisable at end of year 3,889,013 $ 88.83 3.9 years $ 123 ___________________________________________ (1) Represents awards for which the requisite service has been rendered, including those that are retirement eligible. On February 5, 2019, the Company, under the 2014 Incentive Plan, granted 2,051,673 stock option awards with an exercise price of $126.18 per share. The fair value attributable to the stock option awards on the date of grant was $16.65 per share. Restricted Stock Units, Deferred Stock Units and Performance Share Award Programs The Company issues restricted stock unit awards to eligible officers and key employees under the Equity Awards program established pursuant to the 2014 Incentive Plan. A restricted stock unit represents the right to receive a share of common stock. These restricted stock unit awards are granted at market price, generally vest three years from the date of grant, do not have voting rights and the underlying shares of common stock are not issued until the vesting criteria is satisfied. In addition, members of the Company’s Board of Directors can be issued deferred stock units from (i) an annual award; (ii) deferred compensation (in lieu of cash retainer, committee chair fees and lead director fees); and (iii) dividend equivalents earned on outstanding deferred compensation. The Company also has a Performance Share Awards Program established pursuant to the 2004 Incentive Plan and which continues pursuant to the 2014 Incentive Plan. Under the program, the Company may issue performance share awards to certain employees of the Company who hold positions of Vice President (or its equivalent) or above. The performance share awards provide the recipient the right to earn shares of the Company’s common stock based upon the Company’s attainment of certain performance goals and the recipient meeting certain years of service criteria. The performance goals for performance share awards are based on the Company’s adjusted return on equity over a three -year performance period. Vesting of performance shares is contingent upon the Company attaining the relevant performance period minimum threshold return on equity and the recipient meeting certain years of service criteria, generally three years for full vesting, subject to proration for certain termination conditions. If the performance period return on equity is below the minimum threshold, none of the performance shares will vest. If performance meets or exceeds the minimum performance threshold, a range of performance shares will vest ( 50% to 150% for awards granted in 2017, 2018 and 2019), depending on the actual return on equity attained. The fair value of restricted stock units, deferred stock units and performance shares is measured at the market price of the Company stock at date of grant. Under terms of the 2014 Incentive Plan, holders of deferred stock units and performance shares may receive dividend equivalents. The total fair value of shares that vested during the years ended December 31, 2018 , 2017 and 2016 was $135 million , $166 million and $175 million , respectively. A summary of restricted stock units, deferred stock units and performance share activity under the 2014 Incentive Plan and the legacy plans as of and for the year ended December 31, 2018 is as follows: Restricted and Deferred Stock Units Performance Shares Other Equity Instruments Number Weighted Average Grant-Date Fair Value Number Weighted Average Grant-Date Fair Value Nonvested, beginning of year 1,286,970 $ 111.74 787,732 $ 112.40 Granted 559,807 139.20 319,408 140.85 Vested (554,640 ) (1) 114.77 (385,604 ) (2) 106.06 Forfeited (75,461 ) 122.29 (68,593 ) 123.01 Performance-based adjustment — — 31,946 (3) 126.29 Nonvested, end of year 1,216,676 (4) $ 122.34 684,889 $ 128.83 ___________________________________________ (1) Represents awards for which the requisite service has been rendered. (2) Reflects the number of performance shares attributable to the performance goals attained over the completed performance period ( three years ) and for which service conditions have been met. (3) Represents the current year change in estimated performance shares to reflect the attainment of performance goals for the awards that were granted in each of the years 2016 through 2018 . (4) 95,953 shares of restricted common stock were also issued outside of the 2014 Incentive Plan in 2017 in connection with the acquisition of Simply Business, of which 92,995 shares remain unvested and are not included in this table. See note 9. In addition to the nonvested shares presented in the above table, there are related nonvested dividend equivalent shares. The number of nonvested dividend equivalent shares related to deferred stock units was 379 at the beginning of the year and 329 at the end of the year and the number of nonvested dividend equivalent shares related to performance shares was 26,584 at the beginning of the year and 24,876 at the end of the year. The dividend equivalent shares are subject to the same vesting terms as the deferred stock units and performance shares. On February 5, 2019, the Company, under the 2014 Incentive Plan, granted 929,391 common stock awards in the form of restricted stock units, deferred stock units and performance share awards to participating officers, non-employee directors and other key employees. The restricted stock units and deferred stock units totaled 557,637 shares while the performance share awards totaled 371,754 shares. The fair value per share attributable to the common stock awards on the date of grant was $126.18 . Share-Based Compensation Cost Recognition The amount of compensation cost for awards subject to a service condition is based on the number of shares expected to be issued and is recognized over the time period for which service is to be provided (requisite service period). Awards granted to retiree-eligible employees or to employees who become retiree-eligible before an award’s vesting date are considered to have met the requisite service condition. The compensation cost for awards subject to a performance condition is based upon the probable outcome of the performance condition, which on the grant date reflects an estimate of attaining 100% of the performance shares granted. The compensation cost reflects an estimated annual forfeiture rate from 3.5% to 4.5% over the requisite service period of the awards. That estimate is revised if subsequent information indicates that the actual number of instruments expected to vest is likely to differ from previous estimates. Compensation costs for awards are recognized on a straight-line basis over the requisite service period. For awards that have graded vesting terms, the compensation cost is recognized on a straight-line basis over the requisite service period for each separate vesting portion of the award as if the award was, in substance, multiple awards. The total compensation cost for all share-based incentive compensation awards recognized in earnings for the years ended December 31, 2018 , 2017 and 2016 was $140 million , $136 million and $155 million , respectively. Included in these amounts are compensation cost adjustments of $3 million , $3 million and $11 million , for the years ended December 31, 2018 , 2017 and 2016 , respectively, that reflected the cost associated with the updated estimate of performance shares due to attaining certain performance levels from the date of the initial grant of the performance awards. The related tax benefits recognized in earnings were $26 million , $45 million and $52 million for the years ended December 31, 2018 , 2017 and 2016 , respectively. At December 31, 2018 , there was $141 million of total unrecognized compensation cost related to all nonvested share-based incentive compensation awards. This includes stock options, restricted and deferred stock units and performance shares granted under the 2014 Incentive Plan and restricted common stock issued in connection with a 2017 business acquisition. The unrecognized compensation cost is expected to be recognized over a weighted-average period of 1.8 years . Cash received from the exercise of employee stock options under share-based compensation plans totaled $132 million and $173 million in 2018 and 2017 , respectively. The tax benefit for tax deductions from employee stock options exercised during 2018 and 2017 totaled $14 million and $31 million , respectively.

Pension Plans, Retirement Benef

Pension Plans, Retirement Benefits and Savings Plans	12 Months Ended
	Dec. 31, 2018
Retirement Benefits [Abstract]
Pension Plans, Retirement Benefits and Savings Plans	PENSION PLANS, RETIREMENT BENEFITS AND SAVINGS PLANS The Company sponsors a qualified non-contributory defined benefit pension plan (the qualified domestic pension plan), which covers substantially all U.S. domestic employees and provides benefits under a cash balance formula, except that certain limited groups of legacy participants are covered by a prior traditional final average pay formula. In addition, the Company sponsors a nonqualified defined benefit pension plan which covers certain highly-compensated employees, pension plans for employees of its foreign subsidiaries, and a postretirement health and life insurance benefit plan for employees satisfying certain age and service requirements and for certain retirees. Obligations and Funded Status The following tables summarize the funded status, obligations and amounts recognized in the consolidated balance sheet for the Company’s benefit plans. The Company uses a December 31 measurement date for its pension and postretirement benefit plans. (at and for the year ended December 31, in millions) Qualified Domestic Pension Plan Nonqualified and Foreign Pension Plans Total 2018 2017 2018 2017 2018 2017 Change in projected benefit obligation: Benefit obligation at beginning of year $ 3,679 $ 3,367 $ 230 $ 225 $ 3,909 $ 3,592 Benefits earned 126 112 7 7 133 119 Interest cost on benefit obligation 119 120 7 7 126 127 Actuarial (gain) loss (273 ) 258 (11 ) 1 (284 ) 259 Benefits paid (207 ) (178 ) (12 ) (9 ) (219 ) (187 ) Settlement — — — (11 ) — (11 ) Foreign currency exchange rate change — — (6 ) 10 (6 ) 10 Benefit obligation at end of year $ 3,444 $ 3,679 $ 215 $ 230 $ 3,659 $ 3,909 Change in plan assets: Fair value of plan assets at beginning of year $ 3,957 $ 3,387 $ 113 $ 106 $ 4,070 $ 3,493 Actual return on plan assets (179 ) 448 (1 ) 11 (180 ) 459 Company contributions 200 300 10 7 210 307 Benefits paid (207 ) (178 ) (12 ) (9 ) (219 ) (187 ) Settlement — — — (12 ) — (12 ) Foreign currency exchange rate change — — (7 ) 10 (7 ) 10 Fair value of plan assets at end of year 3,771 3,957 103 113 3,874 4,070 Funded status of plan at end of year $ 327 $ 278 $ (112 ) $ (117 ) $ 215 $ 161 Amounts recognized in the consolidated balance sheet consist of: Accrued over-funded benefit plan assets $ 327 $ 278 $ 4 $ 6 $ 331 $ 284 Accrued under-funded benefit plan liabilities — — (116 ) (123 ) (116 ) (123 ) Total $ 327 $ 278 $ (112 ) $ (117 ) $ 215 $ 161 Amounts recognized in accumulated other comprehensive income consist of: Net actuarial loss $ 1,113 $ 1,035 $ 36 $ 47 $ 1,149 $ 1,082 Prior service benefit (5 ) (6 ) 1 — (4 ) (6 ) Total $ 1,108 $ 1,029 $ 37 $ 47 $ 1,145 $ 1,076 Postretirement Benefit Plans (at and for the year ended December 31, in millions) 2018 2017 Change in projected benefit obligation: Benefit obligation at beginning of year $ 225 $ 214 Benefits earned — — Interest cost on benefit obligation 7 7 Actuarial (gain) loss (18 ) 13 Benefits paid (10 ) (10 ) Foreign currency exchange rate change (1 ) 1 Benefit obligation at end of year $ 203 $ 225 Change in plan assets: Fair value of plan assets at beginning of year $ 13 $ 14 Actual return on plan assets — — Company contributions 9 9 Benefits paid (10 ) (10 ) Fair value of plan assets at end of year 12 13 Funded status of plan at end of year $ (191 ) $ (212 ) Amounts recognized in the consolidated balance sheet consist of: Accrued under-funded benefit plan liability $ (191 ) $ (212 ) Amounts recognized in accumulated other comprehensive income consist of: Net actuarial gain $ (17 ) $ — Prior service benefit (25 ) (28 ) Total $ (42 ) $ (28 ) The total accumulated benefit obligation for the Company’s defined benefit pension plans was $3.53 billion and $3.77 billion at December 31, 2018 and 2017 , respectively. The qualified domestic pension plan accounted for $3.32 billion and $3.55 billion of the total accumulated benefit obligation at December 31, 2018 and 2017 , respectively, whereas the nonqualified and foreign plans accounted for $0.21 billion and $0.22 billion of the total accumulated benefit obligation at December 31, 2018 and 2017 , respectively. For pension plans with a projected benefit obligation in excess of plan assets, the aggregate projected benefit obligation was $203 million and $183 million at December 31, 2018 and 2017 , respectively, and the aggregate plan assets were $87 million and $60 million at December 31, 2018 and 2017 , respectively. For pension plans with an accumulated benefit obligation in excess of plan assets, the aggregate accumulated benefit obligation was $195 million and $174 million at December 31, 2018 and 2017 , respectively, and the aggregate plan assets were $87 million and $60 million at December 31, 2018 and 2017 , respectively. For postretirement benefit plans with an accumulated benefit obligation in excess of plan assets, the aggregate accumulated benefit obligation was $203 million and $225 million at December 31, 2018 and 2017 , respectively, and the aggregate plan assets were $12 million and $13 million at December 31, 2018 and 2017 , respectively. The $273 million actuarial gain experienced in 2018 for the qualified domestic pension plan was largely driven by the increase in the assumed discount rate from the prior year that was used to determine the projected benefit obligation at December 31, 2018. The $258 million actuarial loss experienced in 2017 for the qualified domestic pension plan was largely driven by the decrease in the assumed discount rate from the prior year that was used to determine the projected benefit obligation at December 31, 2017. The Company has discretion regarding whether to provide additional funding and when to provide such funding to its qualified domestic pension plan. In 2018 , 2017 and 2016 , there were no required contributions to the qualified domestic pension plan. In 2018 , 2017 and 2016 , the Company voluntarily made contributions totaling $200 million , $300 million and $200 million , respectively, to the qualified domestic pension plan. There is no required contribution to the qualified domestic pension plan during 2019 , and the Company has not determined whether or not additional funding will be made during 2019 . With respect to the Company’s foreign pension plans, there are no significant required contributions in 2019 . The following table summarizes the components of net periodic benefit cost and other amounts recognized in other comprehensive income related to the benefit plans. Pension Plans Postretirement Benefit Plans (for the year ended December 31, in millions) 2018 2017 2016 2018 2017 2016 Net Periodic Benefit Cost: Service cost $ 133 $ 119 $ 118 $ — $ — $ — Non-service cost: Interest cost on benefit obligation 126 127 122 7 7 8 Expected return on plan assets (264 ) (240 ) (230 ) — — — Settlement — 3 1 — — — Amortization of unrecognized: Prior service benefit (1 ) (1 ) (1 ) (4 ) (4 ) (3 ) Net actuarial loss 91 85 66 — — — Total non-service cost (benefit) (48 ) (26 ) (42 ) 3 3 5 Net periodic benefit cost 85 93 76 3 3 5 Other Changes in Benefit Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income: Prior service benefit — — — — — — Net actuarial loss (gain) 160 40 66 (18 ) 13 (17 ) Foreign currency exchange rate change (1 ) 2 (2 ) — (1 ) 1 Settlement — (2 ) (1 ) — — — Amortization of prior service benefit 1 1 1 4 4 3 Amortization of net actuarial loss (91 ) (85 ) (66 ) — — — Total other changes recognized in other comprehensive income 69 (44 ) (2 ) (14 ) 16 (13 ) Total other changes recognized in net periodic benefit cost and other comprehensive income $ 154 $ 49 $ 74 $ (11 ) $ 19 $ (8 ) The following table indicates the line items in which the respective service costs and non-service costs are presented in the consolidated statement of income for the years ended December 31, 2018 , 2017 and 2016 . Pension Plans Postretirement Benefit Plans (for the year ended December 31, in millions) 2018 2017 2016 2018 2017 2016 Service Cost: Net investment income $ 1 $ — $ — $ — $ — $ — Claims and claim adjustment expenses 54 48 48 — $ — — General and administrative expenses 78 71 70 — — — Total service cost 133 119 118 — — — Non-Service Cost: Claims and claim adjustment expenses (19 ) (11 ) (18 ) 1 1 2 General and administrative expenses (29 ) (15 ) (24 ) 2 2 3 Total non-service cost (benefit) (48 ) (26 ) (42 ) 3 3 5 Net periodic benefit cost $ 85 $ 93 $ 76 $ 3 $ 3 $ 5 Assumptions The following table summarizes assumptions used with regard to the Company’s qualified and nonqualified domestic pension plans and the domestic postretirement benefit plans. (at and for the year ended December 31,) 2018 2017 Assumptions used to determine benefit obligations Discount rate: Qualified domestic pension plan 4.39 % 3.71 % Nonqualified domestic pension plan 4.33 % 3.66 % Domestic postretirement benefit plan 4.26 % 3.60 % Cash balance interest crediting rate 4.01 % 4.01 % Future compensation increase rate 4.00 % 4.00 % Assumptions used to determine net periodic benefit cost Discount rate: Qualified domestic pension plan: Service cost 3.87 % 4.52 % Interest cost 3.34 % 3.55 % Nonqualified domestic pension plan: Service cost 3.73 % 4.24 % Interest cost 3.26 % 3.43 % Domestic postretirement benefit plan: Interest cost 3.21 % 3.42 % Expected long-term rate of return on assets: Pension plan 7.00 % 7.00 % Postretirement benefit plan 4.00 % 4.00 % Assumed health care cost trend rates Following year: Medical (before age 65) 7.50 % 7.50 % Medical (age 65 and older) 8.75 % 8.75 % Rate to which the cost trend rate is assumed to decline (ultimate trend rate) 4.50 % 4.50 % Year that the rate reaches the ultimate trend rate: Medical (before age 65) 2026 2026 Medical (age 65 and older) 2026 2026 The discount rate assumption used to determine the benefit obligation is based on a yield-curve approach. Under this approach, individual spot rates from the yield curve of a hypothetical portfolio of high quality fixed maturity corporate bonds (rated Aa) available at the year-end valuation date, for which the timing and amount of cash outflows correspond with the timing and amount of the estimated benefit payouts of the Company’s benefit plan, are applied to expected future benefits payments in measuring the projected benefit obligation . The discount rate assumption used to determine benefit obligations disclosed above represents the weighted average of the individual spot rates. The discount rate assumption used to determine the net periodic benefit cost is the single weighted average discount rate derived from the yield curve used to measure the benefit obligation at the beginning of the year. In choosing the expected long-term rate of return on plan assets, the Company selected the rate that was set as the return objective by the Company’s Benefit Plans Investment Committee, which had considered the historical returns of equity and fixed maturity markets in conjunction with prevailing economic and financial market conditions. The assumptions made for the Company’s foreign pension and foreign postretirement benefit plans are not materially different from those of the Company’s qualified domestic pension plan and the domestic postretirement benefit plan. Plan Assets The qualified domestic pension plan assets are invested for the exclusive benefit of the plan participants and beneficiaries and are intended, over time, to satisfy the benefit obligations under the plan. Risk tolerance is established through consideration of plan liabilities, plan funded status and corporate financial position. The asset mix guidelines have been established and are reviewed quarterly. These guidelines are intended to serve as tools to facilitate the investment of plan assets to maximize long-term total return and the ongoing oversight of the plan’s investment performance. Investment risk is measured and monitored on an ongoing basis through daily and monthly investment portfolio reviews, annual liability measurements and periodic asset/liability studies. The Company’s overall investment strategy for the qualified domestic pension plan is to achieve a mix of approximately 85% to 90% of investments for long-term growth and 10% to 15% for near-term benefit payments with a diversification of asset types, fund strategies and fund managers. The current target allocations for plan assets are 55% to 65% equity securities and 20% to 40% fixed income securities, with the remainder allocated to short-term securities. Equity securities primarily include investments in large, medium and small-cap companies primarily located in the United States. Fixed income securities include corporate bonds of companies from diversified industries, mortgage-backed securities, U.S. Treasury securities and debt securities issued by foreign governments. Assets of the Company’s foreign pension plans are not significant. Fair Value Measurement — Pension Plans and Other Postretirement Benefit Assets For a discussion of the methods employed by the Company to measure the fair value of invested assets, see note 4. The following discussion of fair value measurements applies exclusively to the Company’s pension plans and other postretirement benefit assets. Fair value estimates for equity and bond mutual funds held by the pension plans reflect prices received from an external pricing service that are based on observable market transactions. These estimates are primarily included in Level 1. Short-term securities are carried at fair value which approximates cost plus accrued interest or amortized discount. The fair value or market value of these is periodically compared to this amortized cost and is based on significant observable inputs as determined by an external pricing service. Accordingly, the estimates of fair value for such short-term securities, other than U.S. Treasury securities and money market mutual funds, provided by an external pricing service are included in the amount disclosed in Level 2 of the hierarchy. The estimated fair value of U.S. Treasury securities and money market mutual funds is included in the amount disclosed in Level 1 as the estimates are based on unadjusted market prices. Fair Value Hierarchy — Pension Plans The following tables present the level within the fair value hierarchy at which the financial assets of the Company’s pension plans are measured on a recurring basis. (at December 31, 2018, in millions) Total Level 1 Level 2 Level 3 Invested assets: Fixed maturities Obligations of states, municipalities and political subdivisions $ 3 $ — $ 3 $ — Debt securities issued by foreign governments 27 — 27 — Mortgage-backed securities, collateralized mortgage obligations and pass-through securities 30 — 30 — All other corporate bonds 712 — 712 — Total fixed maturities 772 — 772 — Mutual funds Equity mutual funds 1,288 1,282 6 — Bond mutual funds 760 757 3 — Total mutual funds 2,048 2,039 9 — Equity securities 783 783 — — Other investments 1 — — 1 Cash and short-term securities U.S. Treasury securities 30 30 — — Other 240 19 221 — Total cash and short-term securities 270 49 221 — Total $ 3,874 $ 2,871 $ 1,002 $ 1 (at December 31, 2017, in millions) Total Level 1 Level 2 Level 3 Invested assets: Fixed maturities Obligations of states, municipalities and political subdivisions $ 3 $ — $ 3 $ — Debt securities issued by foreign governments 16 — 16 — Mortgage-backed securities, collateralized mortgage obligations and pass-through securities 10 — 10 — All other corporate bonds 514 — 514 — Total fixed maturities 543 — 543 — Mutual funds Equity mutual funds 1,335 1,328 7 — Bond mutual funds 822 819 3 — Total mutual funds 2,157 2,147 10 — Equity securities 883 882 1 — Other investments 1 — — 1 Cash and short-term securities U.S. Treasury securities 241 241 — — Money market mutual funds 27 27 — — Other 218 27 191 — Total cash and short-term securities 486 295 191 — Total $ 4,070 $ 3,324 $ 745 $ 1 Other Postretirement Benefit Plans The Company’s overall investment strategy is to achieve a mix of approximately 35% to 65% of investments for long-term growth and 35% to 60% for near-term insurance payments with a wide diversification of asset types, fund strategies and fund managers. The current target allocations for plan assets are 25% to 75% fixed income securities, with the remainder allocated to short-term securities. Fixed income securities include corporate bonds of companies from diversified industries, mortgage-backed securities and U.S. Treasuries. Fair Value — Other Postretirement Benefit Plans The Company’s other postretirement benefit plans had financial assets of $12 million and $13 million at December 31, 2018 and 2017 , respectively, which are measured at fair value on a recurring basis. The assets are primarily corporate bonds and short-term securities and categorized as level 2 in the fair value hierarchy. Estimated Future Benefit Payments The following table presents the estimated benefits expected to be paid by the Company’s pension and postretirement benefit plans for the next ten years (reflecting estimated future employee service). Benefits Expected to be Paid (in millions) Pension Plans Postretirement Benefit Plans 2019 $ 239 $ 13 2020 246 14 2021 255 15 2022 260 15 2023 268 15 2024 through 2028 1,361 72 Savings Plan The Company has a savings plan, The Travelers 401(k) Savings Plan (the Savings Plan), in which substantially all U.S. domestic Company employees are eligible to participate. Under the Savings Plan, the Company matches employee contributions up to 5% of eligible pay, with a maximum annual match of $6,500 which becomes 100% vested after three years of service. The Company’s matching contribution is made in cash and invested according to the employee’s current investment elections and can be reinvested into other investment options in accordance with the terms of the Savings Plan. The Company’s non-U.S. employees participate in separate savings plans. The total expense related to all of the savings plans was $118 million , $119 million and $114 million for the years ended December 31, 2018 , 2017 and 2016 , respectively. All common shares held by the Savings Plan are considered outstanding for basic and diluted EPS computations and dividends paid on all shares are charged to retained earnings.

Leases

Leases	12 Months Ended
	Dec. 31, 2018
Leases [Abstract]
Leases	LEASES Rent expense was $185 million , $188 million and $197 million in 2018 , 2017 and 2016 , respectively. Future minimum annual rental payments under noncancellable operating leases for 2019 , 2020 , 2021 , 2022 and 2023 are $127 million , $105 million , $89 million , $61 million and $41 million , respectively, and $77 million for 2024 and thereafter. Future sublease rental income aggregating approximately $1 million will partially offset these commitments.

Contingencies, Commitments and

Contingencies, Commitments and Guarantees	12 Months Ended
	Dec. 31, 2018
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. Gain Contingency On August 17, 2010, in a reinsurance dispute in New York state court captioned United States Fidelity & Guaranty Company v. American Re-Insurance Company, et al. , the trial court granted summary judgment for United States Fidelity and Guaranty Company (USF&G), a subsidiary of the Company, and denied summary judgment for the reinsurers. The Court of Appeals largely affirmed the entry of summary judgment, but remanded two discrete issues for trial. On November 7, 2016, the Company agreed to a settlement with one of the three defendants then remaining in this dispute. The Company received payment under the settlement in the fourth quarter of 2016 and, as a result, recognized a $126 million pre-tax ( $82 million after-tax) gain in the fourth quarter, which was included in “other revenues” in the consolidated statement of income for the year ended December 31, 2016. In connection with that settlement, the reinsurance recoverable balance related to this case was reduced from approximately $238 million to approximately $31 million in the Company’s consolidated balance sheet. At March 31, 2017, the claim related to the remaining defendants totaled $71 million , comprising the $31 million of reinsurance recoverable plus interest amounting to $40 million as of that date. The interest was treated for accounting purposes as a gain contingency in accordance with FASB Topic 450, Contingencies , and accordingly was not recognized in the Company’s consolidated financial statements. On May 1, 2017, the Company agreed to a settlement of this dispute with the two remaining defendants, along with the settlement of several other disputes with these same parties. As a result of the settlement of all of these matters, the Company recorded an immaterial gain in “other revenues” in its consolidated statement of income for the three months ended June 30, 2017, and the reinsurance recoverable of $31 million in the Company’s balance sheet was fully satisfied. Other Commitments and Guarantees Commitments Investment Commitments — The Company has unfunded commitments to private equity limited partnerships and real estate partnerships in which it invests. These commitments totaled $1.60 billion and $1.56 billion at December 31, 2018 and 2017 , respectively. Guarantees In the ordinary course of selling businesses to third parties, the Company has agreed to indemnify purchasers for losses arising out of breaches of representations and warranties with respect to the businesses being sold, covenants and obligations of the Company and/or its subsidiaries and, in certain cases, obligations arising from certain liabilities. Such indemnification provisions generally are applicable from the closing date to the expiration of the relevant statutes of limitations, although, in some cases, there may be agreed upon term limitations or no term limitations. Certain of these contingent obligations are subject to deductibles which have to be incurred by the obligee before the Company is obligated to make payments. The maximum amount of the Company’s contingent obligation for indemnifications related to the sale of businesses that are quantifiable was $358 million at December 31, 2018 , of which $2 million was recognized on the balance sheet at that date. The Company also has contingent obligations for guarantees related to certain investments, third-party loans related to certain investments, certain insurance policy obligations of former insurance subsidiaries and various other indemnifications. The Company also provides standard indemnifications to service providers in the normal course of business. The indemnification clauses are often standard contractual terms. The maximum amount of the Company’s obligation for guarantees of certain investments and third-party loans related to certain investments that are quantifiable was $45 million at December 31, 2018 , approximately $23 million of which is indemnified by a third party. 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 December 31, 2018 , all of which is indemnified by a third party. Certain of the guarantees and indemnifications described above have no stated or notional amounts or limitation to the maximum potential future payments, and, accordingly, the Company is unable to provide an estimate of the maximum potential payments for such arrangements.

Noncash Investing and Financing

Noncash Investing and Financing Activities	12 Months Ended
	Dec. 31, 2018
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Noncash Investing and Financing Activities	NONCASH INVESTING AND FINANCING ACTIVITIES There were no material noncash financing or investing activities during the years ended December 31, 2018 , 2017 and 2016 .

Consolidating Financial Stateme

Consolidating Financial Statements	12 Months Ended
	Dec. 31, 2018
Consolidating Financial Statements of The Travelers Companies, Inc. and Subsidiaries (Unaudited) disclosure
Consolidating Financial Statements of The Travelers Companies, Inc. and Subsidiaries (Unaudited)	CONSOLIDATING FINANCIAL STATEMENTS OF THE TRAVELERS COMPANIES, INC. AND SUBSIDIARIES The following consolidating financial statements of the Company have been prepared pursuant to Rule 3-10 of Regulation S-X. These consolidating financial statements have been prepared from the Company’s financial information on the same basis of accounting as the consolidated financial statements. The Travelers Companies, Inc. (excluding its subsidiaries, TRV) has fully and unconditionally guaranteed certain debt obligations of Travelers Property Casualty Corp. (TPC) and Travelers Insurance Group Holdings, Inc. (TIGHI), which totaled $700 million at December 31, 2018 . Prior to the merger of TPC and The St. Paul Companies, Inc. in 2004, TPC fully and unconditionally guaranteed the payment of all principal, premiums, if any, and interest on certain debt obligations of its wholly-owned subsidiary, TIGHI. Concurrent with the merger, TRV fully and unconditionally assumed such guarantee obligations of TPC. TPC is deemed to have no assets or operations independent of TIGHI. Consolidating financial information for TIGHI has not been presented herein because such financial information would be substantially the same as the financial information provided for TPC. CONSOLIDATING STATEMENT OF INCOME (Unaudited) For the year ended December 31, 2018 (in millions) TPC Other Subsidiaries TRV Eliminations Consolidated Revenues Premiums $ 18,508 $ 8,551 $ — $ — $ 27,059 Net investment income 1,704 738 32 — 2,474 Fee income 432 — — — 432 Net realized investment gains (losses) (1) 118 9 (13 ) — 114 Other revenues 96 112 — (5 ) 203 Total revenues 20,858 9,410 19 (5 ) 30,282 Claims and expenses Claims and claim adjustment expenses 12,344 5,947 — — 18,291 Amortization of deferred acquisition costs 2,972 1,409 — — 4,381 General and administrative expenses 2,947 1,335 20 (5 ) 4,297 Interest expense 48 — 304 — 352 Total claims and expenses 18,311 8,691 324 (5 ) 27,321 Income (loss) before income taxes 2,547 719 (305 ) — 2,961 Income tax expense (benefit) 437 115 (114 ) — 438 Net income of subsidiaries — — 2,714 (2,714 ) — Net income $ 2,110 $ 604 $ 2,523 $ (2,714 ) $ 2,523 ___________________________________________ (1) Total other-than-temporary impairments (OTTI) for the year ended December 31, 2018 , and the amounts comprising total OTTI that were recognized in net realized investment gains (losses) and in other comprehensive income (OCI), were as follows: (in millions) TPC Other Subsidiaries TRV Eliminations Consolidated Total OTTI losses $ (1 ) $ — $ — $ — $ (1 ) OTTI losses recognized in net realized investment gains (losses) $ (1 ) $ — $ — $ — $ (1 ) OTTI losses recognized in OCI $ — $ — $ — $ — $ — CONSOLIDATING STATEMENT OF INCOME (Unaudited) For the year ended December 31, 2017 (in millions) TPC Other Subsidiaries TRV Eliminations Consolidated Revenues Premiums $ 17,562 $ 8,121 $ — $ — $ 25,683 Net investment income 1,627 759 24 (13 ) 2,397 Fee income 447 — — — 447 Net realized investment gains (1) 19 131 66 — 216 Other revenues 101 68 — (10 ) 159 Total revenues 19,756 9,079 90 (23 ) 28,902 Claims and expenses Claims and claim adjustment expenses 11,735 5,732 — — 17,467 Amortization of deferred acquisition costs 2,820 1,346 — — 4,166 General and administrative expenses 2,906 1,249 25 (10 ) 4,170 Interest expense 48 — 321 — 369 Total claims and expenses 17,509 8,327 346 (10 ) 26,172 Income (loss) before income taxes 2,247 752 (256 ) (13 ) 2,730 Income tax expense (benefit) 519 290 (130 ) (5 ) 674 Net income of subsidiaries — — 2,190 (2,190 ) — Net income $ 1,728 $ 462 $ 2,064 $ (2,198 ) $ 2,056 ___________________________________________ (1) Total other-than-temporary impairments (OTTI) for the year ended December 31, 2017 , and the amounts comprising total OTTI that were recognized in net realized investment gains and in other comprehensive income (OCI), were as follows: (in millions) TPC Other Subsidiaries TRV Eliminations Consolidated Total OTTI losses $ (4 ) $ (9 ) $ — $ — $ (13 ) OTTI losses recognized in net realized investment gains $ (5 ) $ (9 ) $ — $ — $ (14 ) OTTI gains recognized in OCI $ 1 $ — $ — $ — $ 1 CONSOLIDATING STATEMENT OF INCOME (Unaudited) For the year ended December 31, 2016 (in millions) TPC Other Subsidiaries TRV Eliminations Consolidated Revenues Premiums $ 16,788 $ 7,746 $ — $ — $ 24,534 Net investment income 1,569 720 13 — 2,302 Fee income 458 — — — 458 Net realized investment gains (losses) (1) 30 39 (1 ) — 68 Other revenues 248 36 — (21 ) 263 Total revenues 19,093 8,541 12 (21 ) 27,625 Claims and expenses Claims and claim adjustment expenses 10,232 4,838 — — 15,070 Amortization of deferred acquisition costs 2,702 1,283 — — 3,985 General and administrative expenses 2,928 1,242 5 (21 ) 4,154 Interest expense 48 — 315 — 363 Total claims and expenses 15,910 7,363 320 (21 ) 23,572 Income (loss) before income taxes 3,183 1,178 (308 ) — 4,053 Income tax expense (benefit) 999 208 (168 ) — 1,039 Net income of subsidiaries — — 3,154 (3,154 ) — Net income $ 2,184 $ 970 $ 3,014 $ (3,154 ) $ 3,014 ___________________________________________ (1) Total other-than-temporary impairments (OTTI) for the year ended December 31, 2016 , and the amounts comprising total OTTI that were recognized in net realized investment gains (losses) and in other comprehensive income (OCI), were as follows: (in millions) TPC Other Subsidiaries TRV Eliminations Consolidated Total OTTI losses $ (19 ) $ (20 ) $ (1 ) $ — $ (40 ) OTTI losses recognized in net realized investment gains (losses) $ (13 ) $ (15 ) $ (1 ) $ — $ (29 ) OTTI losses recognized in OCI $ (6 ) $ (5 ) $ — $ — $ (11 ) CONSOLIDATING STATEMENT OF COMPREHENSIVE INCOME (Unaudited) For the year ended December 31, 2018 (in millions) TPC Other Subsidiaries TRV Eliminations Consolidated Net income $ 2,110 $ 604 $ 2,523 $ (2,714 ) $ 2,523 Other comprehensive loss: Changes in net unrealized gains on investment securities: Having no credit losses recognized in the consolidated statement of income (1,028 ) (461 ) — — (1,489 ) Having credit losses recognized in the consolidated statement of income (20 ) (7 ) — — (27 ) Net changes in benefit plan assets and obligations 1 (4 ) (53 ) — (56 ) Net changes in unrealized foreign currency translation (144 ) (103 ) — — (247 ) Other comprehensive loss before income taxes and other comprehensive loss of subsidiaries (1,191 ) (575 ) (53 ) — (1,819 ) Income tax benefit (231 ) (101 ) (17 ) — (349 ) Other comprehensive loss, net of taxes, before other comprehensive loss of subsidiaries (960 ) (474 ) (36 ) — (1,470 ) Other comprehensive loss of subsidiaries — — (1,434 ) 1,434 — Other comprehensive loss (960 ) (474 ) (1,470 ) 1,434 (1,470 ) Comprehensive income $ 1,150 $ 130 $ 1,053 $ (1,280 ) $ 1,053 CONSOLIDATING STATEMENT OF COMPREHENSIVE INCOME (Unaudited) For the year ended December 31, 2017 (in millions) TPC Other Subsidiaries TRV Eliminations Consolidated Net income $ 1,728 $ 462 $ 2,064 $ (2,198 ) $ 2,056 Other comprehensive income (loss): Changes in net unrealized gains on investment securities: Having no credit losses recognized in the consolidated statement of income 313 25 (44 ) — 294 Having credit losses recognized in the consolidated statement of income 6 2 — — 8 Net changes in benefit plan assets and obligations (1 ) 8 22 — 29 Net changes in unrealized foreign currency translation 83 108 — — 191 Other comprehensive income (loss) before income taxes and other comprehensive income of subsidiaries 401 143 (22 ) — 522 Income tax expense 98 10 2 — 110 Other comprehensive income (loss), net of taxes, before other comprehensive income of subsidiaries 303 133 (24 ) — 412 Other comprehensive income of subsidiaries — — 436 (436 ) — Other comprehensive income 303 133 412 (436 ) 412 Comprehensive income $ 2,031 $ 595 $ 2,476 $ (2,634 ) $ 2,468 CONSOLIDATING STATEMENT OF COMPREHENSIVE INCOME (Unaudited) For the year ended December 31, 2016 (in millions) TPC Other Subsidiaries TRV Eliminations Consolidated Net income $ 2,184 $ 970 $ 3,014 $ (3,154 ) $ 3,014 Other comprehensive loss: Changes in net unrealized gains on investment securities: Having no credit losses recognized in the consolidated statement of income (696 ) (198 ) 11 — (883 ) Having credit losses recognized in the consolidated statement of income 11 10 — — 21 Net changes in benefit plan assets and obligations 25 11 (20 ) — 16 Net changes in unrealized foreign currency translation 73 (114 ) — — (41 ) Other comprehensive loss before income taxes and other comprehensive loss of subsidiaries (587 ) (291 ) (9 ) — (887 ) Income tax benefit (222 ) (66 ) (1 ) — (289 ) Other comprehensive loss, net of taxes, before other comprehensive loss of subsidiaries (365 ) (225 ) (8 ) — (598 ) Other comprehensive loss of subsidiaries — — (590 ) 590 — Other comprehensive loss (365 ) (225 ) (598 ) 590 (598 ) Comprehensive income $ 1,819 $ 745 $ 2,416 $ (2,564 ) $ 2,416 CONSOLIDATING BALANCE SHEET (Unaudited) At December 31, 2018 (in millions) TPC Other Subsidiaries TRV Eliminations Consolidated Assets Fixed maturities, available for sale, at fair value (amortized cost $63,601) $ 43,683 $ 19,697 $ 84 $ — $ 63,464 Equity securities, at fair value (cost $382) 105 92 171 — 368 Real estate investments 2 902 — — 904 Short-term securities 1,855 759 1,371 — 3,985 Other investments 2,746 810 1 — 3,557 Total investments 48,391 22,260 1,627 — 72,278 Cash 181 192 — — 373 Investment income accrued 434 187 3 — 624 Premiums receivable 5,089 2,417 — — 7,506 Reinsurance recoverables 5,904 2,466 — — 8,370 Ceded unearned premiums 522 56 — — 578 Deferred acquisition costs 1,930 190 — — 2,120 Deferred taxes 167 302 (24 ) — 445 Contractholder receivables 3,867 918 — — 4,785 Goodwill 2,578 1,368 — (9 ) 3,937 Other intangible assets 224 121 — — 345 Investment in subsidiaries — — 26,993 (26,993 ) — Other assets 2,220 15 669 (32 ) 2,872 Total assets $ 71,507 $ 30,492 $ 29,268 $ (27,034 ) $ 104,233 Liabilities Claims and claim adjustment expense reserves $ 34,093 $ 16,575 $ — $ — $ 50,668 Unearned premium reserves 9,414 4,141 — — 13,555 Contractholder payables 3,867 918 — — 4,785 Payables for reinsurance premiums 169 120 — — 289 Debt 693 32 5,871 (32 ) 6,564 Other liabilities 4,133 849 496 — 5,478 Total liabilities 52,369 22,635 6,367 (32 ) 81,339 Shareholders’ equity Common stock (1,750.0 shares authorized; 263.7 shares issued and 263.6 shares outstanding) — 401 23,144 (401 ) 23,144 Additional paid-in capital 11,634 7,023 — (18,657 ) — Retained earnings 8,065 879 35,211 (8,951 ) 35,204 Accumulated other comprehensive loss (561 ) (446 ) (1,859 ) 1,007 (1,859 ) Treasury stock, at cost (510.9 shares) — — (33,595 ) — (33,595 ) Total shareholders’ equity 19,138 7,857 22,901 (27,002 ) 22,894 Total liabilities and shareholders’ equity $ 71,507 $ 30,492 $ 29,268 $ (27,034 ) $ 104,233 CONSOLIDATING BALANCE SHEET (Unaudited) At December 31, 2017 (in millions) TPC Other Subsidiaries TRV Eliminations Consolidated Assets Fixed maturities, available for sale, at fair value (amortized cost $61,316) $ 43,240 $ 19,372 $ 82 $ — $ 62,694 Equity securities, available for sale, at fair value (cost $440) 161 111 181 — 453 Real estate investments 54 878 — — 932 Short-term securities 2,751 914 1,230 — 4,895 Other investments 2,673 854 1 — 3,528 Total investments 48,879 22,129 1,494 — 72,502 Cash 157 187 — — 344 Investment income accrued 418 183 5 — 606 Premiums receivable 4,852 2,292 — — 7,144 Reinsurance recoverables 5,842 2,467 — — 8,309 Ceded unearned premiums 493 58 — — 551 Deferred acquisition costs 1,835 190 — — 2,025 Deferred taxes (89 ) 173 (14 ) — 70 Contractholder receivables 3,854 921 — — 4,775 Goodwill 2,592 1,368 — (9 ) 3,951 Other intangible assets 202 140 — — 342 Investment in subsidiaries — — 27,946 (27,946 ) — Other assets 2,181 (3 ) 700 (14 ) 2,864 Total assets $ 71,216 $ 30,105 $ 30,131 $ (27,969 ) $ 103,483 Liabilities Claims and claim adjustment expense reserves $ 33,386 $ 16,264 $ — $ — $ 49,650 Unearned premium reserves 8,957 3,958 — — 12,915 Contractholder payables 3,854 921 — — 4,775 Payables for reinsurance premiums 165 109 — — 274 Debt 693 14 5,878 (14 ) 6,571 Other liabilities 4,161 882 524 — 5,567 Total liabilities 51,216 22,148 6,402 (14 ) 79,752 Shareholders’ equity Common stock (1,750.0 shares authorized; 271.5 shares issued and 271.4 shares outstanding) — 390 22,886 (390 ) 22,886 Additional paid-in capital 11,634 6,972 — (18,606 ) — Retained earnings 8,036 594 33,460 (8,628 ) 33,462 Accumulated other comprehensive income (loss) 330 1 (343 ) (331 ) (343 ) Treasury stock, at cost (500.9 shares) — — (32,274 ) — (32,274 ) Total shareholders’ equity 20,000 7,957 23,729 (27,955 ) 23,731 Total liabilities and shareholders’ equity $ 71,216 $ 30,105 $ 30,131 $ (27,969 ) $ 103,483 CONSOLIDATING STATEMENT OF CASH FLOWS (Unaudited) For the year ended December 31, 2018 (in millions) TPC Other Subsidiaries TRV Eliminations Consolidated Cash flows from operating activities Net income $ 2,110 $ 604 $ 2,523 $ (2,714 ) $ 2,523 Net adjustments to reconcile net income to net cash provided by operating activities 1,141 605 (363 ) 474 1,857 Net cash provided by operating activities 3,251 1,209 2,160 (2,240 ) 4,380 Cash flows from investing activities Proceeds from maturities of fixed maturities 5,158 1,906 22 — 7,086 Proceeds from sales of investments: Fixed maturities 2,449 1,096 1 — 3,546 Equity securities 65 107 6 — 178 Real estate investments 66 8 — — 74 Other investments 403 108 — — 511 Purchases of investments: Fixed maturities (9,404 ) (4,096 ) (26 ) — (13,526 ) Equity securities (8 ) (99 ) (10 ) — (117 ) Real estate investments (1 ) (73 ) — — (74 ) Other investments (454 ) (83 ) — — (537 ) Net sales (purchases) of short-term securities 895 154 (141 ) — 908 Securities transactions in course of settlement (80 ) 24 — — (56 ) Acquisition, net of cash acquired — (4 ) — — (4 ) Other (310 ) (8 ) — — (318 ) Net cash used in investing activities (1,221 ) (960 ) (148 ) — (2,329 ) Cash flows from financing activities Treasury stock acquired — share repurchase authorization — — (1,270 ) — (1,270 ) Treasury stock acquired — net employee share-based compensation — — (51 ) — (51 ) Dividends paid to shareholders — — (814 ) — (814 ) Payment of debt — — (600 ) — (600 ) Issuance of debt — 18 591 (18 ) 591 Issuance of common stock — employee share options — — 132 — 132 Dividends paid to parent company (2,003 ) (255 ) — 2,258 — Net cash used in financing activities (2,003 ) (237 ) (2,012 ) 2,240 (2,012 ) Effect of exchange rate changes on cash (3 ) (7 ) — — (10 ) Net increase in cash 24 5 — — 29 Cash at beginning of year 157 187 — — 344 Cash at end of year $ 181 $ 192 $ — $ — $ 373 Supplemental disclosure of cash flow information Income taxes paid (received) $ 437 $ 254 $ (283 ) $ — $ 408 Interest paid $ 47 $ — $ 300 $ — $ 347 CONSOLIDATING STATEMENT OF CASH FLOWS (Unaudited) For the year ended December 31, 2017 (in millions) TPC Other Subsidiaries TRV Eliminations Consolidated Cash flows from operating activities Net income $ 1,728 $ 462 $ 2,064 $ (2,198 ) $ 2,056 Net adjustments to reconcile net income to net cash provided by operating activities 1,500 701 (32 ) (77 ) 2,092 Net cash provided by operating activities 3,228 1,163 2,032 (2,275 ) 4,148 Cash flows from investing activities Proceeds from maturities of fixed maturities 6,576 2,168 6 — 8,750 Proceeds from sales of investments: Fixed maturities 1,007 846 1 — 1,854 Equity securities 97 414 254 — 765 Real estate investments — 23 — — 23 Other investments 357 124 — (13 ) 468 Purchases of investments: Fixed maturities (8,513 ) (3,697 ) (40 ) — (12,250 ) Equity securities (68 ) (133 ) (258 ) — (459 ) Real estate investments (1 ) (58 ) — — (59 ) Other investments (444 ) (97 ) — — (541 ) Net sales (purchases) of short-term securities (303 ) (120 ) 397 — (26 ) Securities transactions in course of settlement (55 ) 5 3 — (47 ) Acquisition, net of cash acquired — 25 (477 ) 13 (439 ) Other (244 ) 3 — — (241 ) Net cash used in investing activities (1,591 ) (497 ) (114 ) — (2,202 ) Cash flows from financing activities Treasury stock acquired — share repurchase authorization — — (1,378 ) — (1,378 ) Treasury stock acquired — net employee share-based compensation — — (62 ) — (62 ) Dividends paid to shareholders — — (785 ) — (785 ) Payment of debt — — (657 ) — (657 ) Issuance of debt — 14 789 (14 ) 789 Issuance of common stock — employee share options — — 173 — 173 Dividends paid to parent company (1,624 ) (665 ) — 2,289 — Net cash used in financing activities (1,624 ) (651 ) (1,920 ) 2,275 (1,920 ) Effect of exchange rate changes on cash 3 8 — — 11 Net increase (decrease) in cash 16 23 (2 ) — 37 Cash at beginning of year 141 164 2 — 307 Cash at end of year $ 157 $ 187 $ — $ — $ 344 Supplemental disclosure of cash flow information Income taxes paid (received) $ 481 $ 206 $ (173 ) $ — $ 514 Interest paid $ 47 $ — $ 320 $ — $ 367 CONSOLIDATING STATEMENT OF CASH FLOWS (Unaudited) For the year ended December 31, 2016 (in millions) TPC Other Subsidiaries TRV Eliminations Consolidated Cash flows from operating activities Net income $ 2,184 $ 970 $ 3,014 $ (3,154 ) $ 3,014 Net adjustments to reconcile net income to net cash provided by operating activities 1,282 139 (122 ) 156 1,455 Net cash provided by operating activities 3,466 1,109 2,892 (2,998 ) 4,469 Cash flows from investing activities Proceeds from maturities of fixed maturities 6,589 2,380 6 — 8,975 Proceeds from sales of investments: Fixed maturities 768 647 2 — 1,417 Equity securities 47 45 — — 92 Real estate investments — 69 — — 69 Other investments 386 180 — — 566 Purchases of investments: Fixed maturities (7,921 ) (3,676 ) (12 ) — (11,609 ) Equity securities (6 ) (42 ) (3 ) — (51 ) Real estate investments (1 ) (47 ) — — (48 ) Other investments (453 ) (127 ) — — (580 ) Net sales (purchases) of short-term securities (501 ) 383 (81 ) — (199 ) Securities transactions in course of settlement 12 (32 ) (1 ) — (21 ) Other (331 ) (10 ) 3 — (338 ) Net cash used in investing activities (1,411 ) (230 ) (86 ) — (1,727 ) Cash flows from financing activities Treasury stock acquired — share repurchase authorization — — (2,400 ) — (2,400 ) Treasury stock acquired — net employee share-based compensation — — (72 ) — (72 ) Dividends paid to shareholders — — (757 ) — (757 ) Payment of debt — — (400 ) — (400 ) Issuance of debt — — 491 — 491 Issuance of common stock — employee share options — — 332 — 332 Dividends paid to parent company (2,140 ) (858 ) — 2,998 — Net cash used in financing activities (2,140 ) (858 ) (2,806 ) 2,998 (2,806 ) Effect of exchange rate changes on cash 1 (10 ) — — (9 ) Net increase (decrease) in cash (84 ) 11 — — (73 ) Cash at beginning of year 225 153 2 — 380 Cash at end of year $ 141 $ 164 $ 2 $ — $ 307 Supplemental disclosure of cash flow information Income taxes paid (received) $ 737 $ 287 $ (132 ) $ — $ 892 Interest paid $ 47 $ — $ 311 $ — $ 358

Selected Quarterly Financial Da

Selected Quarterly Financial Data (Unaudited)	12 Months Ended
	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Selected Quarterly Financial Data (Unaudited)	SELECTED QUARTERLY FINANCIAL DATA (Unaudited) 2018 (in millions, except per share amounts) First Quarter Second Quarter Third Quarter Fourth Quarter Total Total revenues $ 7,286 $ 7,477 $ 7,723 $ 7,796 $ 30,282 Total expenses 6,508 6,846 6,917 7,050 27,321 Income before income taxes 778 631 806 746 2,961 Income tax expense 109 107 97 125 438 Net income $ 669 $ 524 $ 709 $ 621 $ 2,523 Net income per share (1) : Basic $ 2.45 $ 1.93 $ 2.65 $ 2.33 $ 9.37 Diluted 2.42 1.92 2.62 2.32 9.28 2017 (in millions, except per share amounts) First Second Third Fourth Total Total revenues $ 6,942 $ 7,184 $ 7,325 $ 7,451 $ 28,902 Total expenses 6,182 6,394 7,005 6,591 26,172 Income before income taxes 760 790 320 860 2,730 Income tax expense (2) 143 195 27 309 674 Net income $ 617 $ 595 $ 293 $ 551 $ 2,056 Net income per share (1) : Basic $ 2.19 $ 2.13 $ 1.06 $ 2.00 $ 7.39 Diluted 2.17 2.11 1.05 1.98 7.33 ___________________________________________ (1) Due to the use of an average number of shares for each quarter, the sum of the quarterly earnings per share may not equal the total earnings per share for the full year. (2) Income tax expense for the fourth quarter and full year of 2017 included a net charge of $129 million to reflect the change in tax laws and tax rates enacted in the U.S. on December 22, 2017 as part of the Tax Cuts and Jobs Act of 2017, resulting primarily from revaluing the Company’s deferred tax assets and liabilities and the tax imposed on accumulated foreign earnings.

Schedule II

Schedule II	12 Months Ended
	Dec. 31, 2018
Condensed Financial Information Disclosure [Abstract]
Schedule II	THE TRAVELERS COMPANIES, INC. (Parent Company Only) CONDENSED FINANCIAL INFORMATION OF REGISTRANT (in millions) CONDENSED STATEMENT OF INCOME For the year ended December 31, 2018 2017 2016 Revenues Net investment income $ 32 $ 24 $ 13 Net realized investment gains (losses) (1) (13 ) 66 (1 ) Total revenues 19 90 12 Expenses Interest 304 321 315 Other 20 25 5 Total expenses 324 346 320 Loss before income taxes and net income of subsidiaries (305 ) (256 ) (308 ) Income tax benefit (114 ) (130 ) (168 ) Loss before net income of subsidiaries (191 ) (126 ) (140 ) Net income of subsidiaries 2,714 2,190 3,154 Net income $ 2,523 $ 2,064 $ 3,014 ___________________________________________ (1) The parent company had $0 , $0 and $(1) million of other-than-temporary impairment losses recognized in net realized investment gains (losses) during the years ended December 31, 2018 , 2017 and 2016 , respectively. The parent company had no other-than-temporary impairment gains or losses recognized in other comprehensive income (loss) during the years ended December 31, 2018 , 2017 and 2016 . The condensed financial statements should be read in conjunction with the notes to the condensed financial information of the registrant, as well as the consolidated financial statements and notes thereto. See the Report of Independent Registered Public Accounting Firm. SCHEDULE II THE TRAVELERS COMPANIES, INC. (Parent Company Only) CONDENSED FINANCIAL INFORMATION OF REGISTRANT (in millions) CONDENSED STATEMENT OF COMPREHENSIVE INCOME For the year ended December 31, 2018 2017 2016 Net income $ 2,523 $ 2,064 $ 3,014 Other comprehensive income (loss) — parent company: Changes in net unrealized gains on investment securities having no credit losses recognized in the consolidated statement of income — (44 ) 11 Net changes in benefit plan assets and obligations (53 ) 22 (20 ) Other comprehensive loss before income taxes and other comprehensive income (loss) of subsidiaries (53 ) (22 ) (9 ) Income tax expense (benefit) (17 ) 2 (1 ) Other comprehensive loss, net of taxes, before other comprehensive income (loss) of subsidiaries (36 ) (24 ) (8 ) Other comprehensive income (loss) of subsidiaries (1,434 ) 436 (590 ) Other comprehensive income (loss) (1,470 ) 412 (598 ) Comprehensive income $ 1,053 $ 2,476 $ 2,416 The condensed financial statements should be read in conjunction with the notes to the condensed financial information of the registrant, as well as the consolidated financial statements and notes thereto. See the Report of Independent Registered Public Accounting Firm. SCHEDULE II THE TRAVELERS COMPANIES, INC. (Parent Company Only) CONDENSED FINANCIAL INFORMATION OF REGISTRANT (in millions) CONDENSED BALANCE SHEET At December 31, 2018 2017 Assets Fixed maturities $ 84 $ 82 Equity securities 171 181 Short-term securities 1,371 1,230 Investment in subsidiaries 26,993 27,946 Other assets 649 692 Total assets $ 29,268 $ 30,131 Liabilities Debt $ 5,871 $ 5,878 Other liabilities 496 524 Total liabilities 6,367 6,402 Shareholders’ equity Common stock (1,750.0 shares authorized; 263.7 and 271.5 shares issued, 263.6 and 271.4 shares outstanding) 23,144 22,886 Retained earnings 35,211 33,460 Accumulated other comprehensive loss (1,859 ) (343 ) Treasury stock, at cost (510.9 and 500.9 shares) (33,595 ) (32,274 ) Total shareholders’ equity 22,901 23,729 Total liabilities and shareholders’ equity $ 29,268 $ 30,131 The condensed financial statements should be read in conjunction with the notes to the condensed financial information of the registrant, as well as the consolidated financial statements and notes thereto. See the Report of Independent Registered Public Accounting Firm. SCHEDULE II THE TRAVELERS COMPANIES, INC. (Parent Company Only) CONDENSED FINANCIAL INFORMATION OF REGISTRANT (in millions) CONDENSED STATEMENT OF CASH FLOWS For the year ended December 31, 2018 2017 2016 Cash flows from operating activities Net income $ 2,523 $ 2,064 $ 3,014 Adjustments to reconcile net income to net cash provided by operating activities: Equity in net income of subsidiaries (2,714 ) (2,190 ) (3,154 ) Dividends received from consolidated subsidiaries 2,258 2,289 2,998 Deferred federal income tax expense 28 40 12 Change in income taxes payable 100 3 (48 ) Other (35 ) (174 ) 70 Net cash provided by operating activities 2,160 2,032 2,892 Cash flows from investing activities Net sales (purchases) of short-term securities (141 ) 397 (81 ) Other investments, net (7 ) (34 ) (5 ) Acquisition, net of cash acquired — (477 ) — Net cash used in investing activities (148 ) (114 ) (86 ) Cash flows from financing activities Treasury stock acquired—share repurchase authorization (1,270 ) (1,378 ) (2,400 ) Treasury stock acquired—net employee share-based compensation (51 ) (62 ) (72 ) Dividends paid to shareholders (814 ) (785 ) (757 ) Payment of debt (600 ) (657 ) (400 ) Issuance of debt 591 789 491 Issuance of common stock—employee share options 132 173 332 Net cash used in financing activities (2,012 ) (1,920 ) (2,806 ) Net decrease in cash — (2 ) — Cash at beginning of year — 2 2 Cash at end of year $ — $ — $ 2 Supplemental disclosure of cash flow information Cash received during the year for taxes $ 283 $ 173 $ 132 Cash paid during the year for interest $ 300 $ 320 $ 311 The condensed financial statements should be read in conjunction with the notes to the condensed financial information of the registrant, as well as the consolidated financial statements and notes thereto. See the Report of Independent Registered Public Accounting Firm. SCHEDULE II THE TRAVELERS COMPANIES, INC. (Parent Company Only) NOTES TO THE CONDENSED FINANCIAL INFORMATION OF REGISTRANT 1. GUARANTEES The Travelers Companies, Inc. (TRV) fully and unconditionally guarantees the payment of all principal, premiums, if any, and interest on certain debt obligations of its subsidiaries TPC and TIGHI. The guarantees pertain to the $200 million 7.75% notes due 2026 and the $500 million 6.375% notes due 2033. TRV also has contingent obligations for guarantees in connection with the selling of businesses to third parties, certain insurance obligations of a subsidiary and various indemnifications including indemnifications to service providers in the normal course of business. The guarantees and indemnification clauses are often standard contractual terms and include indemnifications for breaches of representations and warranties and in some cases obligations arising from certain liabilities. The terms of these provisions vary in duration and nature. Certain of the guarantees and indemnifications described above have no stated or notional amounts or limitation to the maximum potential future payments. Accordingly, TRV is unable to provide an estimate of the maximum potential payments for such arrangements, and the likelihood for any payment under these guarantees is remote.

Schedule III

Schedule III	12 Months Ended
	Dec. 31, 2018
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Abstract]
Schedule III	THE TRAVELERS COMPANIES, INC. AND SUBSIDIARIES Supplementary Insurance Information 2016-2018 (in millions) Segment Deferred Acquisition Costs Claims and Claim Adjustment Expense Reserves Unearned Premiums Earned Premiums Net Investment Income (1) Claims and Claim Adjustment Expenses Amortization of Deferred Acquisition Costs Other Operating Expenses (2) Net Written Premiums 2018 Business Insurance $ 1,102 $ 41,132 $ 7,112 $ 14,722 $ 1,833 $ 10,171 $ 2,388 $ 2,623 $ 14,956 Bond & Specialty Insurance 277 3,255 1,619 2,420 233 772 454 459 2,528 Personal Insurance 741 6,266 4,824 9,917 408 7,348 1,539 1,185 10,224 Total—Reportable Segments 2,120 50,653 13,555 27,059 2,474 18,291 4,381 4,267 27,708 Other — 15 — — — — — 382 — Consolidated $ 2,120 $ 50,668 $ 13,555 $ 27,059 $ 2,474 $ 18,291 $ 4,381 $ 4,649 $ 27,708 2017 Business Insurance $ 1,060 $ 40,352 $ 6,857 $ 14,146 $ 1,786 $ 9,521 $ 2,286 $ 2,563 $ 14,270 Bond & Specialty Insurance 258 3,421 1,515 2,307 228 899 432 464 2,359 Personal Insurance 707 5,860 4,543 9,230 383 7,047 1,448 1,111 9,590 Total—Reportable Segments 2,025 49,633 12,915 25,683 2,397 17,467 4,166 4,138 26,219 Other — 17 — — — — — 401 — Consolidated $ 2,025 $ 49,650 $ 12,915 $ 25,683 $ 2,397 $ 17,467 $ 4,166 $ 4,539 $ 26,219 2016 Business Insurance $ 1,026 $ 39,555 $ 6,725 $ 13,855 $ 1,701 $ 8,753 $ 2,221 $ 2,554 $ 13,900 Bond & Specialty Insurance 246 3,323 1,444 2,260 239 633 421 445 2,271 Personal Insurance 651 5,051 4,160 8,419 362 5,684 1,343 1,124 8,787 Total—Reportable Segments 1,923 47,929 12,329 24,534 2,302 15,070 3,985 4,123 24,958 Other — 20 — — — — — 394 — Consolidated $ 1,923 $ 47,949 $ 12,329 $ 24,534 $ 2,302 $ 15,070 $ 3,985 $ 4,517 $ 24,958 ___________________________________________ (1) See note 2 of notes to the consolidated financial statements for discussion of the method used to allocate net investment income and invested assets to the identified segments. (2) Expense allocations are determined in accordance with prescribed statutory accounting practices. These practices make a reasonable allocation of all expenses to those product lines with which they are associated. See the Report of Independent Registered Public Accounting Firm.

Schedule V

Schedule V	12 Months Ended
	Dec. 31, 2018
SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract]
Schedule V	THE TRAVELERS COMPANIES, INC. AND SUBSIDIARIES Valuation and Qualifying Accounts (in millions) Balance at beginning of period Charged to costs and expenses Charged to other accounts Deductions (1) Balance at end of period 2018 Reinsurance recoverables $ 111 $ — $ — $ 1 $ 110 Allowance for uncollectible: Premiums receivable from underwriting activities $ 58 $ 50 $ — $ 54 $ 54 Deductibles $ 26 $ (1 ) $ — $ 1 $ 24 2017 Reinsurance recoverables $ 116 $ — $ — $ 5 $ 111 Allowance for uncollectible: Premiums receivable from underwriting activities $ 61 $ 38 $ — $ 41 $ 58 Deductibles $ 34 $ (2 ) $ — $ 6 $ 26 2016 Reinsurance recoverables $ 157 $ — $ — $ 41 $ 116 Allowance for uncollectible: Premiums receivable from underwriting activities $ 65 $ 35 $ — $ 39 $ 61 Deductibles $ 35 $ 5 $ — $ 6 $ 34 ___________________________________________ (1) Credited to the related asset account. See the Report of Independent Registered Public Accounting Firm.

Schedule VI

Schedule VI	12 Months Ended
	Dec. 31, 2018
SEC Schedule, 12-18, Supplemental Information, Property-Casualty Insurance Underwriters [Abstract]
Schedule VI	THE TRAVELERS COMPANIES, INC. AND SUBSIDIARIES Supplementary Information Concerning Property-Casualty Insurance Operations (1) 2016-2018 (in millions) Claims and Claim Adjustment Expenses Incurred Related to: Amortization of Deferred Acquisition Costs Paid Claims and Claim Adjustment Expenses Affiliation with Registrant(2) Deferred Acquisition Costs Claims and Claim Adjustment Expense Reserves Discount From Reserves for Unpaid Claims(3) Unearned Premiums Earned Premiums Net Investment Income Current Year Prior Year Net Written Premiums 2018 $ 2,120 $ 50,653 $ 1,158 $ 13,555 $ 27,059 $ 2,474 $ 18,614 $ (406 ) $ 4,381 $ 17,060 $ 27,708 2017 $ 2,025 $ 49,633 $ 1,102 $ 12,915 $ 25,683 $ 2,397 $ 17,846 $ (458 ) $ 4,166 $ 16,043 $ 26,219 2016 $ 1,923 $ 47,929 $ 1,083 $ 12,329 $ 24,534 $ 2,302 $ 15,675 $ (680 ) $ 3,985 $ 14,796 $ 24,958 ___________________________________________ (1) Excludes accident and health insurance business. (2) Consolidated property-casualty insurance operations. (3) For a discussion of types of reserves discounted and discount rates used, see note 7 of notes to the consolidated financial statements. See the Report of Independent Registered Public Accounting Firm.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Basis of Presentation [Policy Text Block]	Basis of Presentation The consolidated financial statements include the accounts of The Travelers Companies, Inc. (together with its subsidiaries, the Company). The preparation of the consolidated financial statements in conformity with U.S. generally accepted accounting principles (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 consolidated financial statements and the reported amounts of revenues and claims and expenses during the reporting period. Actual results could differ from those estimates. Certain reclassifications have been made to the 2017 and 2016 financial statements to conform to the 2018 presentation. All material intercompany transactions and balances have been eliminated.
Acquisition [Policy Text Block]	On August 4, 2017, the Company completed its acquisition of all issued and outstanding shares of Simply Business Holdings Ltd (Simply Business), a leading provider of small business insurance policies primarily in the United Kingdom, for a purchase price of approximately $464 million , which included the repayment of debt and other obligations of Simply Business. In addition, the Company issued 95,953 shares of restricted common stock valued at approximately $12 million to certain employees of Simply Business who were equity holders of Simply Business. Subject to the satisfaction of certain conditions, 50% of the restricted stock will vest two years from the issuance date and the remainder will vest three years from the issuance date. The Company used a portion of the net proceeds from the issuance of senior notes in May 2017 (described in more detail in note 8) and internal resources to fund this transaction.
Adoption of Accounting Standards [Policy Text Block]	Adoption of Accounting Standards Financial Instruments: Recognition and Measurement of Financial Assets and Financial Liabilities In January 2016, the Financial Accounting Standards Board (FASB) issued updated guidance to address the recognition, measurement, presentation and disclosure of certain financial instruments. The updated guidance requires equity investments, except those accounted for under the equity method of accounting, that have readily determinable fair value to be measured at fair value with any changes in fair value recognized in net income. Equity securities that do not have readily determinable fair values may be measured at estimated fair value or cost less impairment, if any, adjusted for subsequent observable price changes, with changes in the carrying value recognized in net income. A qualitative assessment for impairment is required for equity investments without readily determinable fair values. The updated guidance also eliminates the requirement to disclose the method and significant assumptions used to estimate the fair value of financial instruments measured at amortized cost on the balance sheet. The updated guidance was effective for the quarter ended March 31, 2018. The adoption of this guidance resulted in the recognition of $22 million of net after-tax unrealized gains on equity investments as a cumulative effect adjustment that increased retained earnings as of January 1, 2018 and decreased accumulated other comprehensive income (AOCI) by the same amount. The Company elected to report changes in the fair value of equity investments in net realized investment gains (losses). At December 31, 2017, equity investments were classified as available-for-sale on the Company's balance sheet. However, upon adoption, the updated guidance eliminated the available-for-sale balance sheet classification for equity investments. Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income On February 14, 2018, the FASB issued updated guidance that allows a reclassification from AOCI to retained earnings of the stranded tax effects that occurred due to the enactment of the Tax Cuts and Jobs Act of 2017 (TCJA). The updated guidance is effective for reporting periods beginning after December 15, 2018 and is to be applied retrospectively to each period in which there are items impacted by the TCJA remaining in AOCI or at the beginning of the period of adoption. Early adoption is permitted. The Company adopted the updated guidance effective January 1, 2018 and elected to reclassify the income tax effects of the TCJA from AOCI to retained earnings as of January 1, 2018. This reclassification resulted in an increase in retained earnings of $24 million as of January 1, 2018 and a decrease in AOCI by the same amount. Revenue from Contracts with Customers In May 2014, the FASB issued updated guidance to clarify the principles for recognizing revenue. The updated guidance was effective for reporting periods beginning after December 15, 2017, and requires an entity to recognize revenue as performance obligations are met, in order to reflect the transfer of goods or services to customers in an amount that reflects the consideration the entity is entitled to receive for those goods or services. For the year ended December 31, 2018 , approximately $171 million , or less than 1% of the Company's total revenues, were within the scope of this updated guidance and were generated from the services described below. While insurance contracts are not within the scope of this updated guidance, the Company’s revenue related to certain services with no underlying insurance risk is subject to the updated guidance. These services include the following: (i) insurance-related services, such as risk management services, claims administration, loss control and risk management information services on behalf of non-insureds; (ii) servicing carrier fees for various residual market pools and associations; and (iii) administrative fees related to servicing third-party insurers’ obligations to participate in the Workers' Compensation Residual Market Plans in certain states. The revenues earned from these service contracts were not impacted by the adoption of the updated guidance. These revenues are earned as the Company completes its performance obligations, which primarily occurs on a pro rata basis over the contract service period and reported in fee income in the Company’s consolidated statement of income. Commissions earned from on-line insurance brokerage services are also subject to this updated guidance and were also not impacted by the adoption of the updated guidance. Commissions are earned upon collection of the gross premium in accordance with the contracts and an accrual is made to recognize policy cancellations, either at the policyholder’s direction or for non-payment. Commissions are reported in other revenues in the Company's consolidated statement of income. The Company does not capitalize the costs to obtain or fulfill the contracts for which revenues are reported in fee income and other revenues, and has not recognized any material impairment losses on the receivables related to these contracts during the twelve months ended December 31, 2018. The Company adopted the updated guidance effective January 1, 2018. The adoption did not have an effect on the Company’s results of operations, financial position or liquidity. Statement of Cash Flows: Classification of Certain Cash Receipts and Cash Payments In August 2016, the FASB issued updated guidance on the classification of cash flows related to certain activities in the statement of cash flows to reduce diversity in practice. The updated guidance was effective for reporting periods beginning after December 15, 2017 and was applied retrospectively to all periods presented. Under the new guidance, distributions received on equity method investments that are considered to be a return on investment are reported as cash flows from operating activities. These distributions were previously reported as cash flows from investing activities. The adoption of this guidance did not have an effect on the Company’s results of operations, financial position or liquidity.
Investments [Policy Text Block]	Investments Fixed Maturities Fixed maturities include bonds, notes and redeemable preferred stocks. Fixed maturities, including instruments subject to securities lending agreements, are classified as available for sale and reported at fair value, with unrealized investment gains and losses, net of income taxes, charged or credited directly to other comprehensive income. Equity Securities Equity securities, which include public common and non-redeemable preferred stocks, are reported at fair value with changes in fair value recognized in net income. Prior to January 1, 2018, equity securities were classified as available for sale and changes in their fair value were charged or credited directly to other comprehensive income. Real Estate Investments The Company’s real estate investments include warehouses, office buildings and other commercial land and properties that are directly owned. Real estate is recorded on the purchase date at the purchase price, which generally represents fair value, and is supported by internal analysis or external appraisals that use discounted cash flow analyses and other acceptable valuation techniques. Real estate held for investment purposes is subsequently carried at cost less accumulated depreciation. Buildings are depreciated on a straight-line basis over the shorter of the expected useful life of the building or 39 years . Real estate held for sale is carried at lower of cost or fair value, less estimated costs to sell. Short-term Securities Short-term securities have an original maturity of less than one year and are carried at amortized cost, which approximates fair value. Other Investments Investments in Private Equity Limited Partnerships, Hedge Funds and Real Estate Partnerships The Company uses the equity method of accounting for investments in private equity limited partnerships, hedge funds and real estate partnerships. The partnerships and the hedge funds generally report investments on their balance sheet at fair value. The financial statements prepared by the investee are received by the Company on a lag basis, with the lag period generally dependent upon the type of underlying investments. The private equity and real estate partnerships provide financial information quarterly which is generally available to investors, including the Company, within three months following the date of the reporting period. The hedge funds provide financial information monthly, which is generally available to investors within one month following the date of the reporting period. The Company regularly requests financial information from the partnerships prior to the receipt of the partnerships’ financial statements and records any material information obtained from these requests in its consolidated financial statements. Other Also included in other investments are non-public common equities, preferred equities and derivatives. Non-public common equities and preferred equities are reported at fair value with changes in fair value recognized in net income. Prior to January 1, 2018, non-public common equities and preferred equities were reported at fair value with changes in fair value, net of taxes, charged or credited directly to other comprehensive income. The Company’s derivative financial instruments are carried at fair value, with the changes in fair value reflected in the consolidated statement of income in net realized investment gains (losses). For a further discussion of the derivatives used by the Company, see note 3.
Net Investment Income [Policy Text Block]	Net Investment Income Investment income from fixed maturities is recognized based on the constant effective yield method which includes an adjustment for estimated principal pre-payments, if any. The effective yield used to determine amortization for fixed maturities subject to prepayment risk (e.g., asset-backed, loan-backed and structured securities) is recalculated and adjusted periodically based upon actual historical and/or projected future cash flows, which are obtained from a widely-accepted securities data provider. The adjustments to the yield for highly rated prepayable fixed maturities are accounted for using the retrospective method. The adjustments to the yield for non-highly rated prepayable fixed maturities are accounted for using the prospective method. Dividends on equity securities (including those with transfer restrictions) are recognized in income when declared. Rental income on real estate is recognized on a straight-line basis over the lease term. See the section titled: Real Estate in note 3 for further discussion. Investments in private equity limited partnerships, hedge funds, real estate partnerships and joint ventures are accounted for using the equity method of accounting, whereby the Company’s share of the investee’s earnings or losses in the fund is reported in net investment income. Accrual of income is suspended on non-securitized fixed maturities that are in default, or on which it is likely that future payments will not be made as scheduled. Interest income on investments in default is recognized only when payments are received. Investments included in the consolidated balance sheet that were not income-producing for the preceding 12 months were not material. For fixed maturities where the Company records an other-than-temporary impairment, a determination is made as to the cause of the impairment and whether the Company expects a recovery in the value. For fixed maturities where the Company expects a recovery in value, not necessarily to par, the constant effective yield method is utilized, and the investment is amortized to the expected recovery amount.
Investment Gains and Losses [Policy Text Block]	Investment Gains and Losses Net realized investment gains and losses are included as a component of pre-tax revenues based upon specific identification of the investments sold on the trade date. Included in net realized investment gains (losses) are other-than-temporary impairment losses on invested assets other than those investments accounted for using the equity method of accounting as described in the “Investment Impairments” section that follows.
Investment Impairments [Policy Text Block]	Investment Impairments The Company conducts a periodic review to identify and evaluate invested assets having other-than-temporary impairments. Other-Than-Temporary Impairments of Fixed Maturities Some of the factors considered in identifying other-than-temporary impairments of fixed maturities include: (1) the extent to which the fair value has been less than amortized cost; (2) the financial condition, near-term and long-term prospects for the issuer, including the relevant industry conditions and trends, and implications of rating agency actions and offering prices; (3) the likelihood of the recoverability of principal and interest; (4) whether it is more likely than not that the Company will be required to sell the investment prior to an anticipated recovery in value; and (5) the length of time and extent to which the fair value has been less than amortized cost. For fixed maturity investments that the Company does not intend to sell or for which it is more likely than not that the Company would not be required to sell before an anticipated recovery in value, the Company separates the credit loss component of the impairment from the amount related to all other factors and reports the credit loss component in net realized investment gains (losses). The impairment related to all other factors is reported in other comprehensive income. For fixed maturity investments the Company intends to sell or for which it is more likely than not that the Company will be required to sell before an anticipated recovery in value, the full amount of the impairment is included in net realized investment gains (losses). Upon recognizing an other-than-temporary impairment, the new cost basis of the investment is the previous amortized cost basis less the other-than-temporary impairment recognized in net realized investment gains (losses). The new cost basis is not adjusted for any subsequent recoveries in fair value; however, for fixed maturity investments the difference between the new cost basis and the expected cash flows is accreted on a quarterly basis to net investment income over the remaining expected life of the investment. Determination of Credit Loss — Fixed Maturities The Company determines the credit loss component of fixed maturity investments by utilizing discounted cash flow modeling to determine the present value of the security and comparing the present value with the amortized cost of the security. If the amortized cost is greater than the present value of the expected cash flows, the difference is considered a credit loss and recognized in net realized investment gains (losses). For non-structured fixed maturities (U.S. Treasury securities, obligations of U.S. government and government agencies and authorities, obligations of states, municipalities and political subdivisions, debt securities issued by foreign governments and certain corporate debt), the estimate of expected cash flows is determined by projecting a recovery value and a recovery time frame and assessing whether further principal and interest will be received. The determination of recovery value incorporates an issuer valuation assumption utilizing one or a combination of valuation methods as deemed appropriate by the Company. The Company determines the undiscounted recovery value by allocating the estimated value of the issuer to the Company’s assessment of the priority of claims. The present value of the cash flows is determined by applying the effective yield of the security at the date of acquisition (or the most recent implied rate used to accrete the security if the implied rate has changed as a result of a previous impairment) and an estimated recovery time frame. Generally, that time frame for securities for which the issuer is in bankruptcy is 12 months . For securities for which the issuer is financially troubled but not in bankruptcy, that time frame is generally 24 months . Included in the present value calculation are expected principal and interest payments; however, for securities for which the issuer is classified as bankrupt or in default, the present value calculation assumes no interest payments and a single recovery amount. In estimating the recovery value, significant judgment is involved in the development of assumptions relating to a myriad of factors related to the issuer including, but not limited to, revenue, margin and earnings projections, the likely market or liquidation values of assets, potential additional debt to be incurred pre- or post-bankruptcy/restructuring, the ability to shift existing or new debt to different priority layers, the amount of restructuring/bankruptcy expenses, the size and priority of unfunded pension obligations, litigation or other contingent claims, the treatment of intercompany claims and the likely outcome with respect to inter-creditor conflicts. For structured fixed maturity securities (primarily residential and commercial mortgage-backed securities and asset-backed securities), the Company estimates the present value of the security by projecting future cash flows of the assets underlying the securitization, allocating the flows to the various tranches based on the structure of the securitization and determining the present value of the cash flows using the effective yield of the security at the date of acquisition (or the most recent implied rate used to accrete the security if the implied rate has changed as a result of a previous impairment or changes in expected cash flows). The Company incorporates levels of delinquencies, defaults and severities as well as credit attributes of the remaining assets in the securitization, along with other economic data, to arrive at its estimate of the parameters applied to the assets underlying the securitization. Real Estate Investments On at least an annual basis, the Company obtains independent appraisals for substantially all of its real estate investments. In addition, the carrying value of all real estate investments is reviewed for impairment on a quarterly basis or when events or changes in circumstances indicate that the carrying amount may not be recoverable. The review for impairment considers the valuation from the independent appraisal, when applicable, and incorporates an estimate of the undiscounted cash flows expected to result from the use and eventual disposition of the real estate property. An impairment loss is recognized if the expected future undiscounted cash flows are less than the carrying value of the real estate property. The impairment loss is the amount by which the carrying amount exceeds fair value. Other Investments The Company reviews its investments in private equity limited partnerships, hedge funds and real estate partnerships for impairment no less frequently than quarterly and monitors the performance throughout the year through discussions with the managers/general partners. If the Company becomes aware of an impairment of a partnership’s investments at the balance sheet date prior to receiving the partnership’s financial statements, it will recognize an impairment by recording a reduction in the carrying value of the partnership with a corresponding charge to net investment income. Changes in Intent to Sell Temporarily Impaired Assets The Company may, from time to time, sell invested assets subsequent to the balance sheet date that it did not intend to sell at the balance sheet date. Conversely, the Company may not sell invested assets that it asserted that it intended to sell at the balance sheet date. Such changes in intent are due to events occurring subsequent to the balance sheet date. The types of events that may result in a change in intent include, but are not limited to, significant changes in the economic facts and circumstances related to the invested asset (e.g., a downgrade or upgrade from a rating agency), significant unforeseen changes in liquidity needs, or changes in tax laws or the regulatory environment.
Securities Lending [Policy Text Block]	Securities Lending The Company has, from time to time, engaged in securities lending activities from which it generates net investment income by lending certain of its investments to other institutions for short periods of time. Borrowers of these securities provide collateral equal to at least 102% of the market value of the loaned securities plus accrued interest. This collateral is held by a third-party custodian, and the Company has the right to access the collateral only in the event that the institution borrowing the Company’s securities is in default under the lending agreement (i.e., the Company is not permitted to re-pledge or sell any such collateral). Therefore, the Company does not recognize the receipt of the collateral held by the third-party custodian or the obligation to return the collateral. The loaned securities remain a recorded asset of the Company. The Company accepts only cash as collateral for securities on loan and restricts the manner in which that cash is invested.
Reinsurance Recoverables [Policy Text Block]	Reinsurance Recoverables Amounts recoverable from reinsurers are estimated in a manner consistent with the associated claim liability. The Company reports its reinsurance recoverables net of an allowance for estimated uncollectible reinsurance recoverables. The allowance is based upon the Company’s ongoing review of amounts outstanding, length of collection periods, changes in reinsurer credit standing, disputes, applicable coverage defenses and other relevant factors. Amounts deemed to be uncollectible, including amounts due from known insolvent reinsurers, are written off against the allowance for estimated uncollectible reinsurance recoverables. Any subsequent collections of amounts previously written off are reported as part of claims and claim adjustment expenses. The Company evaluates and monitors the financial condition of its reinsurers under voluntary reinsurance arrangements to minimize its exposure to significant losses from reinsurer insolvencies.
Deferred Acquisition Costs [Policy Text Block]	Deferred Acquisition Costs Incremental direct costs of acquired, new and renewal insurance contracts, consisting of commissions (other than contingent commissions) and premium-related taxes, are capitalized and charged to expense pro rata over the contract periods in which the related premiums are earned. Deferred acquisition costs are reviewed to determine if they are recoverable from future income and, if not, are charged to expense. Future investment income attributable to related premiums is taken into account in measuring the recoverability of the carrying value of this asset. All other acquisition expenses are charged to operations as incurred.
Contractholder Receivables and Payables [Policy Text Block]	Contractholder Receivables and Payables Under certain workers’ compensation insurance contracts with deductible features, the Company is obligated to pay the claimant for the full amount of the claim. The Company is subsequently reimbursed by the policyholder for the deductible amount. These amounts are included on a gross basis in the consolidated balance sheet in contractholder payables and contractholder receivables, respectively.
Goodwill and Intangible Assets [Policy Text Block]	Goodwill and Other Intangible Assets The Company performs a review, on at least an annual basis, of goodwill held by the reporting units which are the Company’s three operating and reportable segments: Business Insurance; Bond & Specialty Insurance; and Personal Insurance. The Company estimates the fair value of its reporting units and compares it to their carrying value, including goodwill. If the carrying values of the reporting units were to exceed their fair value, the amount of the impairment would be calculated and goodwill adjusted accordingly. The Company uses a discounted cash flow model to estimate the fair value of its reporting units. The discounted cash flow model is an income approach to valuation that is based on a detailed cash flow analysis for deriving a current fair value of reporting units and is representative of the Company’s reporting units’ current and expected future financial performance. The discount rate assumptions reflect the Company’s assessment of the risks inherent in the projected future cash flows and the Company’s weighted-average cost of capital, and are compared against available market data for reasonableness. Other indefinite-lived intangible assets held by the Company are also reviewed for impairment on at least an annual basis. The classification of the asset as indefinite-lived is reassessed and an impairment is recognized if the carrying amount of the asset exceeds its fair value. Intangible assets that are deemed to have a finite useful life are amortized over their useful lives. The carrying amount of intangible assets with a finite useful life is regularly reviewed for indicators of impairment in value. Impairment is recognized only if the carrying amount of the intangible asset is not recoverable from its undiscounted cash flows and is measured as the difference between the carrying amount and the fair value of the asset. As a result of the reviews performed for the years ended December 31, 2018 , 2017 and 2016 , the Company determined that the estimated fair value substantially exceeded the respective carrying value of its reporting units for those years and that goodwill was not impaired. The Company also determined during its reviews for each year that its other indefinite-lived intangible assets and finite-lived intangible assets were not impaired.
Claims and Claims Adjustment Expense Reserves [Policy Text Block]	Claims and Claim Adjustment Expense Reserves Claims and claim adjustment expense reserves represent estimates for the ultimate cost of unpaid reported and unreported claims incurred and related expenses. The reserves are adjusted regularly based upon experience. Included in the claims and claim adjustment expense reserves in the consolidated balance sheet are reserves for long-term disability and annuity claim payments, primarily arising from workers’ compensation insurance and workers’ compensation excess insurance policies, that are discounted to the present value of estimated future payments. The Company performs a continuing review of its claims and claim adjustment expense reserves, including its reserving techniques and the impact of reinsurance. The reserves are also reviewed regularly by qualified actuaries employed by the Company. Since the reserves are based on estimates, the ultimate liability may be more or less than such reserves. The effects of changes in such estimated reserves are included in the results of operations in the period in which the estimates are changed. Such changes in estimates could occur in a future period and may be material to the Company’s results of operations and financial position in such period.
Other Liabilities [Policy Text Block]	Other Liabilities Included in other liabilities in the consolidated balance sheet is the Company’s estimate of its liability for guaranty fund and other insurance-related assessments. The liability for expected state guaranty fund and other premium-based assessments is recognized as the Company writes or becomes obligated to write or renew the premiums on which the assessments are expected to be based. The liability for loss-based assessments is recognized as the related losses are incurred. At December 31, 2018 and 2017 , the Company had a liability of $217 million and $231 million , respectively, for guaranty fund and other insurance-related assessments and related recoverables of $16 million at both dates. The liability for such assessments and the related recoverables are not discounted for the time value of money. The loss-based assessments are expected to be paid over a period ranging from one year to the life expectancy of certain workers’ compensation claimants and the recoveries are expected to occur over the same period of time. Also included in other liabilities is an accrual for policyholder dividends. Certain insurance contracts, primarily workers’ compensation, are participating whereby dividends are paid to policyholders in accordance with contract provisions. Net written premiums for participating dividend policies were approximately 1% of total net written premiums for each of the years ended December 31, 2018 , 2017 and 2016 . Policyholder dividends are accrued against earnings using best available estimates of amounts to be paid. The liability accrued for policyholder dividends totaled $72 million and $67 million at December 31, 2018 and 2017 , respectively.
Treasury Stock [Policy Text Block]	Treasury Stock The cost of common stock repurchased by the Company is reported as treasury stock and represents authorized and unissued shares of the Company under the Minnesota Business Corporation Act.
Statutory Accounting Practices [Policy Text Block]	Statutory Accounting Practices The Company’s U.S. insurance subsidiaries, domiciled principally in the State of Connecticut, are required to prepare statutory financial statements in accordance with the accounting practices prescribed or permitted by the insurance departments of the states of domicile. Prescribed statutory accounting practices are those practices that are incorporated directly or by reference in state laws, regulations, and general administrative rules applicable to all insurance enterprises domiciled in a particular state. The State of Connecticut requires insurers domiciled in Connecticut to prepare their statutory financial statements in accordance with National Association of Insurance Commissioners’ (NAIC) statutory accounting practices. Permitted statutory accounting practices are those practices that differ either from state-prescribed statutory accounting practices or NAIC statutory accounting practices. The Company does not apply any statutory accounting practices that would be considered a prescribed or permitted statutory accounting practice that differs from NAIC statutory accounting practices. The Company’s non-U.S. insurance subsidiaries file financial statements prepared in accordance with the regulatory reporting requirements of their respective local jurisdiction.
Premiums and Unearned Premium Reserves [Policy Text Block]	Premiums and Unearned Premium Reserves Premiums are recognized as revenues pro rata over the policy period. Unearned premium reserves represent the unexpired portion of policy premiums. Accrued retrospective premiums are included in premium balances receivable. Premium balances receivable are reported net of an allowance for estimated uncollectible premium amounts. Ceded premiums are charged to income over the applicable term of the various reinsurance contracts with third party reinsurers. Prepaid reinsurance premiums represent the unexpired portion of premiums ceded to reinsurers and are reported as part of other assets.
Fee Income [Policy Text Block]	Fee Income Fee income includes servicing carrier fees and revenues from large deductible policies and service contracts and is recognized as the Company completes its performance obligations, which is primarily on a pro rata basis over the contract service period or the underlying policy periods.
Other Revenues [Policy Text Block]	Other Revenues Other revenues include revenues from premium installment charges, which are recognized as collected, revenues of noninsurance subsidiaries other than fee income and gains and losses on dispositions of assets and redemption of debt, and other miscellaneous revenues, including gains recognized as a result of settlements of reinsurance disputes and claims-related legal matters.
Income Taxes [Policy Text Block]	Income Taxes The Company recognizes deferred income tax assets and liabilities for the expected future tax effects attributable to temporary differences between the financial statement and tax return bases of assets and liabilities, based on enacted tax rates and other provisions of the tax law. The effect of a change in tax laws or rates on deferred tax assets and liabilities is recognized in income in the period in which such change is enacted. Deferred tax assets are reduced by a valuation allowance if it is more likely than not that all or some portion of the deferred tax assets will not be realized.
Foreign Currency Translation [Policy Text Block]	Foreign Currency Translation The Company assigns functional currencies to its foreign operations, which are generally the currencies of the local operating environment. Foreign currency amounts are remeasured to the functional currency, and the resulting foreign exchange gains or losses are reflected in earnings. Functional currency amounts are then translated into U.S. dollars. The foreign currency remeasurement and translation are calculated using current exchange rates for items reported in the balance sheets and average exchange rates for items recorded in earnings. The change in unrealized foreign currency translation gain or loss during the year, net of tax, is a component of other comprehensive income.
Share-based Compensation [Policy Text Block]	Share-Based Compensation The Company has an employee stock incentive compensation plan that permits grants of nonqualified stock options, incentive stock options, stock appreciation rights, restricted stock, deferred stock, stock units, performance awards and other share-based or share-denominated awards with respect to the Company’s common stock. Compensation cost is measured based on the grant-date fair value of an award , utilizing the assumptions discussed in note 13. Compensation cost is recognized for financial reporting purposes over the period in which the employee is required to provide service in exchange for the award (generally the vesting period). In connection with certain share-based awards, participants are entitled to receive dividends during the vesting period, either in cash or dividend equivalent shares, commensurate with the dividends paid to common shareholders. Dividends and dividend equivalent shares on awards that are expected to vest are recorded in retained earnings. Dividends paid on awards that are not expected to vest as part of the Company’s forfeiture estimate are recorded as compensation expense.

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2018
Segment Reporting [Abstract]
Company's revenues and income by segment [Table Text Block]	(for the year ended December 31, in millions) Business Insurance Bond & Specialty Insurance Personal Insurance Total Reportable Segments 2018 Premiums $ 14,722 $ 2,420 $ 9,917 $ 27,059 Net investment income 1,833 233 408 2,474 Fee income 412 — 20 432 Other revenues 112 23 66 201 Total segment revenues (1) $ 17,079 $ 2,676 $ 10,411 $ 30,166 Amortization and depreciation $ 2,943 $ 515 $ 1,719 $ 5,177 Income tax expense 259 198 42 499 Segment income (1) 1,638 793 297 2,728 2017 Premiums $ 14,146 $ 2,307 $ 9,230 $ 25,683 Net investment income 1,786 228 383 2,397 Fee income 430 — 17 447 Other revenues 69 24 60 153 Total segment revenues (1) $ 16,431 $ 2,559 $ 9,690 $ 28,680 Amortization and depreciation $ 2,852 $ 493 $ 1,627 $ 4,972 Income tax expense (benefit) 448 208 (44 ) 612 Segment income (1) 1,613 556 128 2,297 2016 Premiums $ 13,855 $ 2,260 $ 8,419 $ 24,534 Net investment income 1,701 239 362 2,302 Fee income 442 — 16 458 Other revenues 168 21 63 252 Total segment revenues (1) $ 16,166 $ 2,520 $ 8,860 $ 27,546 Amortization and depreciation $ 2,783 $ 491 $ 1,530 $ 4,804 Income tax expense 656 309 192 1,157 Segment income (1) 1,982 712 517 3,211 _________________________________________ (1) Segment revenues for reportable business segments exclude net realized investment gains. Segment income for reportable business segments equals net income excluding the after-tax impact of net realized investment gains and, in 2017, the impact of the Tax Cuts and Jobs Act of 2017 at enactment.
Net written premiums by market [Table Text Block]	Net written premiums by market were as follows: (for the year ended December 31, in millions) 2018 2017 2016 Business Insurance: Domestic: Select Accounts $ 2,828 $ 2,800 $ 2,729 Middle Market 8,214 7,756 7,379 National Accounts 1,025 1,010 1,058 National Property and Other 1,805 1,691 1,779 Total Domestic 13,872 13,257 12,945 International 1,084 1,013 955 Total Business Insurance 14,956 14,270 13,900 Bond & Specialty Insurance: Domestic: Management Liability 1,455 1,367 1,342 Surety 835 793 757 Total Domestic 2,290 2,160 2,099 International 238 199 172 Total Bond & Specialty Insurance 2,528 2,359 2,271 Personal Insurance: Domestic: Agency: Automobile 4,972 4,646 4,103 Homeowners and Other 4,148 3,933 3,772 Total Agency 9,120 8,579 7,875 Direct-to-Consumer 396 361 309 Total Domestic 9,516 8,940 8,184 International 708 650 603 Total Personal Insurance 10,224 9,590 8,787 Total consolidated net written premiums $ 27,708 $ 26,219 $ 24,958
Business segment reconciliations of revenue and income, net of tax [Table Text Block]	(for the year ended December 31, in millions) 2018 2017 2016 Revenue reconciliation Earned premiums Business Insurance: Domestic: Workers’ compensation $ 3,899 $ 3,962 $ 3,969 Commercial automobile 2,388 2,132 2,010 Commercial property 1,828 1,775 1,769 General liability 2,181 2,047 1,977 Commercial multi-peril 3,333 3,198 3,148 Other 28 29 31 Total Domestic 13,657 13,143 12,904 International 1,065 1,003 951 Total Business Insurance 14,722 14,146 13,855 Bond & Specialty Insurance: Domestic: Fidelity and surety 1,017 977 962 General liability 1,004 962 946 Other 195 187 180 Total Domestic 2,216 2,126 2,088 International 204 181 172 Total Bond & Specialty Insurance 2,420 2,307 2,260 Personal Insurance: Domestic Automobile 5,097 4,655 4,013 Homeowners and Other 4,135 3,943 3,813 Total Domestic 9,232 8,598 7,826 International 685 632 593 Total Personal Insurance 9,917 9,230 8,419 Total earned premiums 27,059 25,683 24,534 Net investment income 2,474 2,397 2,302 Fee income 432 447 458 Other revenues 201 153 252 Total segment revenues 30,166 28,680 27,546 Other revenues 2 6 11 Net realized investment gains 114 216 68 Total revenues $ 30,282 $ 28,902 $ 27,625 Income reconciliation, net of tax Total segment income $ 2,728 $ 2,297 $ 3,211 Interest Expense and Other (1) (298 ) (254 ) (244 ) Core income 2,430 2,043 2,967 Net realized investment gains 93 142 47 Impact of Tax Cuts and Jobs Act of 2017 at enactment — (129 ) — Net income $ 2,523 $ 2,056 $ 3,014 ________________________________________ (1) The primary component of Interest Expense and Other was after-tax interest expense of $278 million , $240 million and $236 million in 2018 , 2017 and 2016 , respectively.
Assets reconciliation [Table Text Block]	(at December 31, in millions) 2018 2017 Asset reconciliation: Business Insurance $ 78,965 $ 78,082 Bond & Specialty Insurance 8,693 8,776 Personal Insurance 15,943 15,949 Total assets for reportable segments 103,601 102,807 Other assets (1) 632 676 Total consolidated assets $ 104,233 $ 103,483 ___________________________________________ (1) The primary components of other assets at December 31, 2018 were accrued over-funded benefit plan assets related to the Company's qualified domestic pension plan and other intangible assets. The primary components of other assets at December 31, 2017 were accrued over-funded benefit plan assets related to the Company's qualified domestic pension plan, other intangible assets and deferred taxes.
Revenues of the Company's operations based on location [Table Text Block]	The following table presents revenues of the Company’s operations based on location: (for the year ended December 31, in millions) 2018 2017 2016 U.S. $ 28,418 $ 27,253 $ 25,904 Non-U.S.: Canada 1,293 1,232 1,154 Other Non-U.S. 571 417 567 Total Non-U.S. 1,864 1,649 1,721 Total revenues $ 30,282 $ 28,902 $ 27,625

Investments (Tables)

Investments (Tables)	12 Months Ended
	Dec. 31, 2018
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 Gross Unrealized Fair (at December 31, 2018, in millions) Cost Gains Losses Value U.S. Treasury securities and obligations of U.S. government and government agencies and authorities $ 2,076 $ 4 $ 16 $ 2,064 Obligations of states, municipalities and political subdivisions: Local general obligation 14,473 219 120 14,572 Revenue 9,755 172 74 9,853 State general obligation 1,329 18 13 1,334 Pre-refunded 2,772 80 — 2,852 Total obligations of states, municipalities and political subdivisions 28,329 489 207 28,611 Debt securities issued by foreign governments 1,255 7 5 1,257 Mortgage-backed securities, collateralized mortgage obligations and pass-through securities 2,557 54 38 2,573 All other corporate bonds 29,307 156 583 28,880 Redeemable preferred stock 77 2 — 79 Total $ 63,601 $ 712 $ 849 $ 63,464 Amortized Gross Unrealized Fair (at December 31, 2017, in millions) Cost Gains Losses Value U.S. Treasury securities and obligations of U.S. government and government agencies and authorities $ 2,080 $ 4 $ 8 $ 2,076 Obligations of states, municipalities and political subdivisions: Local general obligation 13,488 444 26 13,906 Revenue 11,307 338 19 11,626 State general obligation 1,443 44 3 1,484 Pre-refunded 3,758 142 1 3,899 Total obligations of states, municipalities and political subdivisions 29,996 968 49 30,915 Debt securities issued by foreign governments 1,505 14 10 1,509 Mortgage-backed securities, collateralized mortgage obligations and pass-through securities 2,334 87 11 2,410 All other corporate bonds 25,311 478 100 25,689 Redeemable preferred stock 90 5 — 95 Total $ 61,316 $ 1,556 $ 178 $ 62,694
Amortized cost and fair value of fixed maturities by contractual maturity [Table Text Block]	The amortized cost and fair value of fixed maturities by contractual maturity follow. Actual maturities will differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties. (at December 31, 2018, in millions) Amortized Cost Fair Value Due in one year or less $ 4,489 $ 4,505 Due after 1 year through 5 years 17,020 17,021 Due after 5 years through 10 years 17,030 16,785 Due after 10 years 22,505 22,580 61,044 60,891 Mortgage-backed securities, collateralized mortgage obligations and pass-through securities 2,557 2,573 Total $ 63,601 $ 63,464
Cost and fair value of investments in equity securities [Table Text Block]	(at December 31, 2018, in millions) Cost Gross Gains Gross Losses Fair Value Public common stock $ 338 $ 2 $ 24 $ 316 Non-redeemable preferred stock 44 8 — 52 Total $ 382 $ 10 $ 24 $ 368
Cost and fair value of investments in equity securities classified as available for sale [Table Text Block]	(at December 31, 2017, in millions) Cost Gross Gains Gross Losses Fair Value Public common stock $ 332 $ 8 $ 1 $ 339 Non-redeemable preferred stock 108 12 6 114 Total $ 440 $ 20 $ 7 $ 453
Unrealized investment losses [Table Text Block]	The following tables summarize, for all investments in an unrealized loss position at December 31, 2018 and 2017 , 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. The Company also relies upon estimates of several factors in its review and evaluation of individual investments, using the process described in note 1, in determining whether such investments are other-than-temporarily impaired. Less than 12 months 12 months or longer Total (at December 31, 2018, in millions) Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Fixed maturities U.S. Treasury securities and obligations of U.S. government and government agencies and authorities $ 484 $ 5 $ 1,011 $ 11 $ 1,495 $ 16 Obligations of states, municipalities and political subdivisions 5,241 82 3,298 125 8,539 207 Debt securities issued by foreign governments 96 — 328 5 424 5 Mortgage-backed securities, collateralized mortgage obligations and pass-through securities 593 9 1,070 29 1,663 38 All other corporate bonds 12,622 303 6,872 280 19,494 583 Total fixed maturities $ 19,036 $ 399 $ 12,579 $ 450 $ 31,615 $ 849 Less than 12 months 12 months or longer Total (at December 31, 2017, in millions) Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Fixed maturities U.S. Treasury securities and obligations of U.S. government and government agencies and authorities $ 1,150 $ 5 $ 470 $ 3 $ 1,620 $ 8 Obligations of states, municipalities and political subdivisions 505 2 2,959 47 3,464 49 Debt securities issued by foreign governments 394 6 111 4 505 10 Mortgage-backed securities, collateralized mortgage obligations and pass-through securities 1,021 7 250 4 1,271 11 All other corporate bonds 6,062 48 1,990 52 8,052 100 Total fixed maturities 9,132 68 5,780 110 14,912 178 Equity securities Public common stock 18 — 34 1 52 1 Non-redeemable preferred stock 3 — 56 6 59 6 Total equity securities 21 — 90 7 111 7 Total $ 9,153 $ 68 $ 5,870 $ 117 $ 15,023 $ 185
Impairment charges included in net realized investment gains [Table Text Block]	Impairment charges included in net realized investment gains in the consolidated statement of income were as follows: (for the year ended December 31, in millions) 2018 2017 2016 Fixed maturities U.S. Treasury securities and obligations of U.S. government and government agencies and authorities $ — $ — $ — Obligations of states, municipalities and political subdivisions — — — Debt securities issued by foreign governments — — — Mortgage-backed securities, collateralized mortgage obligations and pass-through securities — — — All other corporate bonds 1 4 15 Redeemable preferred stock — — — Total fixed maturities 1 4 15 Equity securities Public common stock — 9 9 Non-redeemable preferred stock — — 3 Total equity securities — 9 12 Other investments — 1 2 Total $ 1 $ 14 $ 29
Cumulative amount of and the changes during the year in the credit losses of other-than-temporary impairments (OTTI) on fixed maturities recognized [Table Text Block]	The following tables present the cumulative amount of and the changes during the year in credit losses on fixed maturities held at December 31, 2018 and 2017 , that were recognized in the consolidated statement of income from other-than-temporary impairments (OTTI) and for which a portion of the OTTI was recognized in other comprehensive income (loss) in the consolidated balance sheet. Year ended December 31, 2018 (in millions) Cumulative OTTI Credit Losses Recognized for Securities Held, Beginning of Period Additions for OTTI Securities Where No Credit Losses Were Previously Recognized Additions for OTTI Securities Where Credit Losses Have Been Previously Recognized Reductions Due to Sales/Defaults of Credit- Impaired Securities Adjustments to Book Value of Credit- Impaired Securities due to Changes in Cash Flows Cumulative OTTI Credit Losses Recognized for Securities Still Held, End of Period Fixed maturities Mortgage-backed securities, collateralized mortgage obligations and pass-through securities $ 29 $ — $ — $ (18 ) $ 4 $ 15 All other corporate bonds 46 — — (12 ) 8 42 Total fixed maturities $ 75 $ — $ — $ (30 ) $ 12 $ 57 Year ended December 31, 2017 (in millions) Cumulative OTTI Credit Losses Recognized for Securities Held, Beginning of Period Additions for OTTI Securities Where No Credit Losses Were Previously Recognized Additions for OTTI Securities Where Credit Losses Have Been Previously Recognized Reductions Due to Sales/Defaults of Credit- Impaired Securities Adjustments to Book Value of Credit- Impaired Securities due to Changes in Cash Flows Cumulative OTTI Credit Losses Recognized for Securities Still Held, End of Period Fixed maturities Mortgage-backed securities, collateralized mortgage obligations and pass-through securities $ 31 $ — $ — $ — $ (2 ) $ 29 All other corporate bonds 54 — 1 (7 ) (2 ) 46 Total fixed maturities $ 85 $ — $ 1 $ (7 ) $ (4 ) $ 75
Net investment income [Table Text Block]	(for the year ended December 31, in millions) 2018 2017 2016 Gross investment income Fixed maturities $ 1,980 $ 1,895 $ 1,981 Equity securities 16 28 37 Short-term securities 92 62 29 Real estate investments 48 44 51 Other investments 377 406 242 Gross investment income 2,513 2,435 2,340 Investment expenses 39 38 38 Net investment income $ 2,474 $ 2,397 $ 2,302
Change in net unrealized investments gains [Table Text Block]	Changes in net unrealized gains on investment securities that are included as a separate component of other comprehensive income (loss) were as follows: (at and for the year ended December 31, in millions) 2018 2017 2016 Changes in net unrealized investment gains Fixed maturities $ (1,515 ) $ 513 $ (915 ) Equity securities — (215 ) 51 Other investments (1 ) 4 2 Change in net pre-tax unrealized gains on investment securities (1,516 ) 302 (862 ) Related tax expense (benefit) (319 ) 78 (303 ) Change in net unrealized gains on investment securities (1,197 ) 224 (559 ) Cumulative effect of adoption of updated accounting guidance for equity financial instruments at January 1, 2018 (22 ) — — Reclassification of certain tax effects from accumulated other comprehensive income at January 1, 2018 152 — — Balance, beginning of year 954 730 1,289 Balance, end of year $ (113 ) $ 954 $ 730

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities reported at fair value 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. An investment transferred between levels during a period is transferred at its fair value as of the beginning of that period. (at December 31, 2018, 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 $ 2,064 $ 2,064 $ — $ — Obligations of states, municipalities and political subdivisions 28,611 — 28,599 12 Debt securities issued by foreign governments 1,257 — 1,257 — Mortgage-backed securities, collateralized mortgage obligations and pass-through securities 2,573 — 2,554 19 All other corporate bonds 28,880 — 28,725 155 Redeemable preferred stock 79 3 76 — Total fixed maturities 63,464 2,067 61,211 186 Equity securities Public common stock 316 316 — — Non-redeemable preferred stock 52 30 22 — Total equity securities 368 346 22 — Other investments 52 16 — 36 Total $ 63,884 $ 2,429 $ 61,233 $ 222 Other liabilities $ 10 $ — $ — $ 10 (at December 31, 2017, 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 $ 2,076 $ 2,076 $ — $ — Obligations of states, municipalities and political subdivisions 30,915 — 30,910 5 Debt securities issued by foreign governments 1,509 — 1,509 — Mortgage-backed securities, collateralized mortgage obligations and pass-through securities 2,410 — 2,371 39 All other corporate bonds 25,689 11 25,518 160 Redeemable preferred stock 95 3 92 — Total fixed maturities 62,694 2,090 60,400 204 Equity securities Public common stock 339 339 — — Non-redeemable preferred stock 114 45 69 — Total equity securities 453 384 69 — Other investments 57 19 — 38 Total $ 63,204 $ 2,493 $ 60,469 $ 242
Changes in the Level 3 fair value category [Table Text Block]	The following tables present the changes in the Level 3 fair value category for the years ended December 31, 2018 and 2017 . (in millions) Fixed Maturities Other Investments Total Balance at December 31, 2017 $ 204 $ 38 $ 242 Total realized and unrealized investment gains (losses): Reported in net realized investment gains (1) 2 7 9 Reported in increases in other comprehensive income (loss) (4 ) — (4 ) Purchases, sales and settlements/maturities: Purchases 146 3 149 Sales (11 ) (12 ) (23 ) Settlements/maturities (71 ) — (71 ) Gross transfers into Level 3 11 — 11 Gross transfers out of Level 3 (91 ) — (91 ) Balance at December 31, 2018 $ 186 $ 36 $ 222 Amount of total realized investment gains (losses) for the period included in the consolidated statement of income attributable to changes in the fair value of assets still held at the reporting date $ — $ — $ — ___________________________________________ (1) Includes impairments on investments held at the end of the period as well as amortization on fixed maturities. (in millions) Fixed Maturities Other Investments Total Balance at December 31, 2016 $ 184 $ 36 $ 220 Total realized and unrealized investment gains (losses): Reported in net realized investment gains (1) — (1 ) (1 ) Reported in increases in other comprehensive income (loss) 1 3 4 Purchases, sales and settlements/maturities: Purchases 312 — 312 Sales (2 ) — (2 ) Settlements/maturities (47 ) — (47 ) Gross transfers into Level 3 21 — 21 Gross transfers out of Level 3 (265 ) — (265 ) Balance at December 31, 2017 $ 204 $ 38 $ 242 Amount of total realized investment gains (losses) for the period included in the consolidated statement of income attributable to changes in the fair value of assets still held at the reporting date $ — $ (1 ) $ (1 ) ___________________________________________ (1) Includes impairments on investments held at the end of the period as well as amortization on fixed maturities.
Carrying value and fair value of financial instruments disclosed, but not carried, at fair value and the level within the fair vlaue hierarchy at which such financial instruments 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 December 31, 2018, in millions) Carrying Value Fair Value Level 1 Level 2 Level 3 Financial assets: Short-term securities $ 3,985 $ 3,985 $ 632 $ 3,316 $ 37 Financial liabilities: Debt $ 6,464 $ 7,128 $ — $ 7,128 $ — Commercial paper 100 100 — 100 — (at December 31, 2017, in millions) Carrying Value Fair Value Level 1 Level 2 Level 3 Financial assets: Short-term securities $ 4,895 $ 4,895 $ 1,238 $ 3,622 $ 35 Financial liabilities: Debt $ 6,471 $ 7,702 $ — $ 7,702 $ — Commercial paper 100 100 — 100 —

Reinsurance (Tables)

Reinsurance (Tables)	12 Months Ended
	Dec. 31, 2018
Reinsurance Disclosures [Abstract]
Summary of reinsurance financial data [Table Text Block]	The following is a summary of reinsurance financial data reflected in the consolidated statement of income: (for the year ended December 31, in millions) 2018 2017 2016 Written premiums Direct $ 28,210 $ 26,648 $ 25,567 Assumed 1,042 1,000 928 Ceded (1,544 ) (1,429 ) (1,537 ) Total net written premiums $ 27,708 $ 26,219 $ 24,958 Earned premiums Direct $ 27,536 $ 26,189 $ 25,262 Assumed 1,024 965 875 Ceded (1,501 ) (1,471 ) (1,603 ) Total net earned premiums $ 27,059 $ 25,683 $ 24,534 Percentage of assumed earned premiums to net earned premiums 3.8 % 3.8 % 3.6 % Ceded claims and claim adjustment expenses incurred $ 1,293 $ 1,225 $ 762
Reinsurance recoverables [Table Text Block]	Reinsurance recoverables include amounts recoverable on both paid and unpaid claims and claim adjustment expenses and were as follows: (at December 31, in millions) 2018 2017 Gross reinsurance recoverables on paid and unpaid claims and claim adjustment expenses $ 3,485 $ 3,303 Allowance for uncollectible reinsurance (110 ) (111 ) Net reinsurance recoverables 3,375 3,192 Mandatory pools and associations 2,005 2,011 Structured settlements 2,990 3,106 Total reinsurance recoverables $ 8,370 $ 8,309

Goodwill and Other Intangible_2

Goodwill and Other Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2018
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. (at December 31, in millions) 2018 2017 Business Insurance (1) $ 2,585 $ 2,585 Bond & Specialty Insurance 550 550 Personal Insurance 776 790 Other 26 26 Total $ 3,937 $ 3,951 ___________________________________________ (1) Goodwill at December 31, 2018 included $26 million associated with a business acquisition in 2018, none of which will be deductible for tax purposes.
Other intangible asset subject to amortization [Table Text Block]	The following tables present a summary of the Company’s other intangible assets by major asset class: (at December 31, 2018, in millions) Gross Carrying Amount Accumulated Amortization Net Subject to amortization Customer-related $ 98 $ 12 $ 86 Contract-based (1) 208 175 33 Total subject to amortization 306 187 119 Not subject to amortization 226 — 226 Total $ 532 $ 187 $ 345 (at December 31, 2017, in millions) Gross Carrying Amount Accumulated Amortization Net Subject to amortization Customer-related $ 77 $ 4 $ 73 Contract-based (1) 209 167 42 Total subject to amortization 286 171 115 Not subject to amortization 227 — 227 Total $ 513 $ 171 $ 342 ___________________________________________ (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 asset 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 December 31, 2018, in millions) Gross Carrying Amount Accumulated Amortization Net Subject to amortization Customer-related $ 98 $ 12 $ 86 Contract-based (1) 208 175 33 Total subject to amortization 306 187 119 Not subject to amortization 226 — 226 Total $ 532 $ 187 $ 345 (at December 31, 2017, in millions) Gross Carrying Amount Accumulated Amortization Net Subject to amortization Customer-related $ 77 $ 4 $ 73 Contract-based (1) 209 167 42 Total subject to amortization 286 171 115 Not subject to amortization 227 — 227 Total $ 513 $ 171 $ 342 ___________________________________________ (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)	12 Months Ended
	Dec. 31, 2018
Insurance Loss Reserves [Abstract]
Claims and claim adjustment expense reserves [Table Text Block]	Claims and claim adjustment expense reserves were as follows: (at December 31, in millions) 2018 2017 Property-casualty $ 50,653 $ 49,633 Accident and health 15 17 Total $ 50,668 $ 49,650
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: (at and for the year ended December 31, in millions) 2018 2017 2016 Claims and claim adjustment expense reserves at beginning of year $ 49,633 $ 47,929 $ 48,272 Less reinsurance recoverables on unpaid losses 8,123 7,981 8,449 Net reserves at beginning of year 41,510 39,948 39,823 Estimated claims and claim adjustment expenses for claims arising in the current year 18,614 17,846 15,675 Estimated decrease in claims and claim adjustment expenses for claims arising in prior years (406 ) (458 ) (680 ) Total increases 18,208 17,388 14,995 Claims and claim adjustment expense payments for claims arising in: Current year 7,697 7,335 6,220 Prior years 9,363 8,708 8,576 Total payments 17,060 16,043 14,796 Unrealized foreign exchange loss (gain) (187 ) 217 (74 ) Net reserves at end of year 42,471 41,510 39,948 Plus reinsurance recoverables on unpaid losses 8,182 8,123 7,981 Claims and claim adjustment expense reserves at end of year $ 50,653 $ 49,633 $ 47,929
Summary of claims and claim adjustment expense reserves, including certain components, for the Company's major product lines by reporting segment [Table Text Block]	The following is a summary of claims and claim adjustment expense reserves, including certain components, for the Company’s major product lines by reporting segment at December 31, 2018 . (at December 31, 2018, in mllions) Net Undiscounted Claims and Claim Adjustment Expense Reserves Discount (Net of Reinsurance) Subtotal: Net Claims and Claim Adjustment Expense Reserves Reinsurance Recoverables on Unpaid Losses (4) Claims and Claim Adjustment Expense Reserves Business Insurance General liability $ 7,159 $ (174 ) $ 6,985 $ 854 $ 7,839 Commercial property 973 — 973 429 1,402 Commercial multi-peril 3,535 — 3,535 181 3,716 Commercial automobile 2,861 — 2,861 226 3,087 Workers’ compensation (1) 16,039 (909 ) 15,130 698 15,828 Bond & Specialty Insurance General liability 1,833 — 1,833 152 1,985 Fidelity and surety 419 — 419 7 426 Personal Insurance Automobile 2,776 — 2,776 480 3,256 Homeowners (excluding Other) 1,376 — 1,376 3 1,379 International - Canada 710 — 710 26 736 Subtotal — claims and allocated claim adjustment expenses for the products presented in the development tables below 37,681 (1,083 ) 36,598 3,056 39,654 Other insurance contracts (2) 3,762 (5 ) 3,757 2,116 5,873 Unallocated loss adjustment expense reserves 2,053 — 2,053 37 2,090 Structured settlements (3) — — — 2,990 2,990 Other 63 — 63 (17 ) 46 Total property-casualty 43,559 (1,088 ) 42,471 8,182 50,653 Accident and health — — — 15 15 Total $ 43,559 $ (1,088 ) $ 42,471 $ 8,197 $ 50,668 ___________________________________________ (1) Net discount amount includes discount of $70 million on reinsurance recoverables for long-term disability and annuity claim payments. (2) Primarily includes residual market, international (other than operations in Canada within the Personal Insurance segment) and runoff assumed reinsurance business. (3) Includes structured settlements in cases where the Company did not receive a release from the claimant. (4) Total reinsurance recoverables (on paid and unpaid losses) at December 31, 2018 were $8.37 billion .
Allocated claim adjustment expense, by accident year, on a historical basis for incurred and paid claims on an undiscounted, net of reinsurance basis [Table Text Block]	Business Insurance General Liability ( dollars in millions ) For the Years Ended December 31, 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Unaudited Accident Year IBNR Reserves Dec 31, 2018 Cumulative Number of Reported Claims 2009 $ 1,060 $ 1,071 $ 1,028 $ 960 $ 869 $ 837 $ 809 $ 796 $ 783 $ 775 $ 56 25,702 2010 1,028 1,031 1,021 959 927 912 918 908 911 79 27,911 2011 1,004 1,074 1,065 998 972 935 913 908 80 27,444 2012 989 985 935 913 892 905 917 98 24,801 2013 965 975 958 940 927 933 101 22,446 2014 976 989 983 948 956 177 22,108 2015 998 956 923 967 222 21,033 2016 1,075 1,058 1,087 439 19,190 2017 1,133 1,143 717 16,464 2018 1,253 1,080 13,107 Total $ 9,850 Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Accident Year Unaudited 2009 $ 35 $ 167 $ 314 $ 446 $ 543 $ 613 $ 643 $ 667 $ 689 $ 701 2010 35 139 324 487 629 702 756 781 800 2011 47 187 355 539 660 725 762 799 2012 32 150 295 489 589 699 754 Liability for Claims 2013 35 175 363 498 639 745 And Allocated Claim 2014 37 163 321 515 640 Adjustment Expenses, 2015 36 137 336 558 Net of Reinsurance 2016 35 191 421 2017 40 180 2009 - Before 2018 42 2018 2009 Total $ 5,640 $ 4,210 $ 2,949 Total net liability $ 7,159 Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Unaudited Years 1 2 3 4 5 6 7 8 9 10 3.8 % 13.6 % 19.0 % 19.1 % 13.4 % 9.5 % 5.0 % 3.2 % 2.5 % 1.5 % Commercial Property ( dollars in millions ) For the Years Ended December 31, 2014 2015 2016 2017 2018 Incurred Claims and Allocated Claims Adjustment Expenses, Net of Reinsurance Unaudited Accident Year IBNR Reserves December 31, 2018 Cumulative Number of Reported Claims 2014 $ 936 $ 860 $ 836 $ 835 $ 834 $ 6 21,568 2015 786 750 741 731 6 20,143 2016 896 863 820 22 22,267 2017 1,209 1,177 30 24,855 2018 1,093 73 21,547 Total $ 4,655 Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Unaudited Liability for Claims Accident Year And Allocated Claim 2014 $ 464 $ 710 $ 775 $ 803 $ 817 Adjustment Expenses, 2015 376 615 681 699 Net of Reinsurance 2016 441 685 745 2017 618 1,003 2014 - Before 2018 561 2018 2014 Total $ 3,825 $ 830 $ 143 Total net liability $ 973 Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Unaudited Years 1 2 3 4 5 52.9 % 31.2 % 8.0 % 2.9 % 1.7 % Commercial Multi-Peril ( dollars in millions ) For the Years Ended December 31, 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Unaudited Accident Year IBNR Reserves December 31, 2018 Cumulative Number of Reported Claims 2009 $ 1,484 $ 1,506 $ 1,501 $ 1,498 $ 1,511 $ 1,514 $ 1,514 $ 1,509 $ 1,500 $ 1,493 $ 21 103,448 2010 1,711 1,826 1,832 1,861 1,895 1,892 1,898 1,885 1,881 32 111,931 2011 2,235 2,244 2,269 2,286 2,296 2,287 2,283 2,279 38 125,743 2012 1,885 1,883 1,903 1,888 1,888 1,867 1,859 42 104,800 2013 1,615 1,623 1,620 1,609 1,591 1,600 51 83,667 2014 1,663 1,627 1,625 1,617 1,626 72 78,097 2015 1,568 1,625 1,593 1,597 110 71,242 2016 1,662 1,623 1,598 204 68,024 2017 1,872 1,928 357 69,218 2018 1,976 605 58,784 Total $ 17,837 Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Accident Year Unaudited 2009 $ 603 $ 958 $ 1,121 $ 1,264 $ 1,360 $ 1,408 $ 1,436 $ 1,449 $ 1,457 $ 1,466 2010 709 1,180 1,395 1,579 1,698 1,763 1,798 1,819 1,834 2011 1,060 1,573 1,803 1,979 2,088 2,156 2,193 2,222 2012 795 1,246 1,424 1,590 1,699 1,752 1,780 Liability for Claims 2013 644 987 1,167 1,304 1,410 1,475 And Allocated Claim 2014 628 956 1,154 1,328 1,448 Adjustment Expenses, 2015 595 970 1,144 1,310 Net of Reinsurance 2016 585 950 1,133 2017 716 1,199 2009 - Before 2018 792 2018 2009 Total $ 14,659 $ 3,178 $ 357 Total net liability $ 3,535 Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Unaudited Years 1 2 3 4 5 6 7 8 9 10 39.7 % 23.2 % 11.0 % 9.4 % 6.2 % 3.3 % 1.7 % 1.1 % 0.7 % 0.6 % Commercial Automobile ( dollars in millions ) For the Years Ended December 31, 2014 2015 2016 2017 2018 Incurred Claims and Allocated Claims Adjustment Expenses, Net of Reinsurance Unaudited Accident Year IBNR Reserves December 31, 2018 Cumulative Number of Reported Claims 2014 $ 1,156 $ 1,153 $ 1,155 $ 1,171 $ 1,193 $ 36 177,493 2015 1,188 1,202 1,234 1,283 83 173,333 2016 1,278 1,303 1,371 191 182,647 2017 1,386 1,501 401 190,126 2018 1,645 736 185,419 Total $ 6,993 Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Unaudited Liability for Claims Accident Year And Allocated Claim 2014 $ 394 $ 611 $ 812 $ 977 $ 1,089 Adjustment Expenses, 2015 405 650 885 1,058 Net of Reinsurance 2016 412 688 931 2017 456 746 2014 - Before 2018 515 2018 2014 Total $ 4,339 $ 2,654 $ 207 Total net liability $ 2,861 Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Unaudited Years 1 2 3 4 5 31.3 % 19.2 % 17.6 % 13.7 % 9.3 % Workers’ Compensation ( dollars in millions ) For the Years Ended December 31, 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Unaudited Accident Year IBNR Reserves December 31, 2018 Cumulative Number of Reported Claims 2009 $ 1,799 $ 1,778 $ 1,746 $ 1,753 $ 1,753 $ 1,766 $ 1,775 $ 1,750 $ 1,736 $ 1,728 $ 221 104,789 2010 1,886 2,042 2,035 2,056 2,049 2,052 2,055 2,021 2,003 271 117,368 2011 2,284 2,303 2,347 2,350 2,379 2,385 2,363 2,348 356 136,728 2012 2,447 2,456 2,457 2,456 2,445 2,453 2,416 404 137,922 2013 2,553 2,545 2,540 2,506 2,463 2,423 473 132,424 2014 2,554 2,553 2,547 2,476 2,430 563 124,507 2015 2,644 2,585 2,505 2,441 751 122,388 2016 2,768 2,690 2,569 863 122,493 2017 2,779 2,681 1,179 119,890 2018 2,744 1,738 109,002 Total $ 23,783 Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Accident Year Unaudited 2009 $ 288 $ 623 $ 828 $ 961 $ 1,065 $ 1,137 $ 1,193 $ 1,235 $ 1,274 $ 1,303 2010 341 750 978 1,133 1,246 1,321 1,385 1,430 1,465 2011 420 911 1,185 1,365 1,487 1,583 1,652 1,696 2012 443 940 1,217 1,394 1,536 1,629 1,689 Liability for Claims 2013 458 954 1,237 1,413 1,525 1,604 And Allocated Claim 2014 455 944 1,224 1,399 1,505 Adjustment Expenses, 2015 430 893 1,154 1,310 Net of Reinsurance 2016 421 873 1,118 2017 433 890 2009 - Before 2018 440 2018 2009 Total $ 13,020 $ 10,763 $ 5,276 Total net liability $ 16,039 Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Unaudited Years 1 2 3 4 5 6 7 8 9 10 17.4 % 19.5 % 11.2 % 7.3 % 5.3 % 3.8 % 3.0 % 2.2 % 2.0 % 1.7 % Bond & Specialty Insurance General Liability ( dollars in millions ) For the Years Ended December 31, 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Unaudited Accident Year IBNR Reserves December 31, 2018 Cumulative Number of Reported Claims 2009 $ 592 $ 624 $ 665 $ 686 $ 680 $ 660 $ 655 $ 641 $ 631 $ 626 $ 11 6,297 2010 571 612 679 679 661 668 653 653 657 18 5,673 2011 565 596 639 632 601 545 520 508 (12 ) 5,212 2012 538 591 614 605 601 599 605 97 4,853 2013 510 565 606 630 654 607 103 4,442 2014 549 571 563 518 473 67 4,335 2015 528 524 486 437 92 4,155 2016 512 511 504 153 4,235 2017 534 517 266 4,128 2018 530 406 2,894 Total $ 5,464 Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Accident Year Unaudited 2009 $ 36 $ 167 $ 310 $ 390 $ 460 $ 497 $ 563 $ 592 $ 595 $ 597 2010 33 152 291 396 482 565 597 623 631 2011 33 143 249 324 414 447 476 490 2012 38 160 255 342 383 419 436 Liability for Claims 2013 34 154 252 352 400 434 And Allocated Claim 2014 38 150 239 312 367 Adjustment Expenses, 2015 38 141 234 310 Net of Reinsurance 2016 30 141 233 2017 38 155 2009 - Before 2018 49 2018 2009 Total $ 3,702 $ 1,762 $ 71 Total net liability $ 1,833 Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Unaudited Years 1 2 3 4 5 6 7 8 9 10 6.8 % 21.4 % 19.4 % 15.3 % 11.4 % 7.3 % 6.0 % 3.7 % 0.9 % 0.2 % Fidelity and Surety ( dollars in millions ) For the Years Ended December 31, 2014 2015 2016 2017 2018 IBNR Reserves December 31, 2018 Cumulative Incurred Claims and Allocated Claims Adjustment Number of Expenses, Net of Reinsurance Reported Accident Year Unaudited Claims 2014 $ 223 $ 212 $ 165 $ 136 $ 130 $ (4 ) 1,069 2015 217 191 179 145 38 827 2016 226 239 205 12 866 2017 244 271 64 863 2018 220 121 595 Total $ 971 Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Accident Year Unaudited Liability for Claims And Allocated Claim 2014 $ 58 $ 96 $ 111 $ 127 $ 124 Adjustment Expenses, 2015 32 75 87 86 Net of Reinsurance 2016 54 121 142 2017 70 166 2014 - Before 2018 64 2018 2014 Total $ 582 $ 389 $ 30 Total net liability $ 419 Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Unaudited Years 1 2 3 4 5 29.5 % 31.8 % 9.9 % 6.1 % (2.7 )% Personal Insurance Automobile ( dollars in millions ) For the Years Ended December 31, 2014 2015 2016 2017 2018 IBNR Reserves December 31, 2018 Cumulative Incurred Claims and Allocated Claims Adjustment Number of Expenses, Net of Reinsurance Reported Accident Year Unaudited Claims 2014 $ 2,014 $ 1,994 $ 1,981 $ 1,985 $ 1,980 $ 14 670,431 2015 2,186 2,244 2,236 2,222 35 757,837 2016 2,779 2,791 2,772 126 921,479 2017 3,323 3,256 341 1,059,610 2018 3,281 825 960,293 Total $ 13,511 Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Accident Year Unaudited Liability for Claims And Allocated Claim 2014 $ 1,193 $ 1,564 $ 1,763 $ 1,879 $ 1,936 Adjustment Expenses, 2015 1,319 1,768 1,985 2,109 Net of Reinsurance 2016 1,610 2,203 2,466 2017 1,912 2,575 2014 - Before 2018 1,889 2018 2014 Total $ 10,975 $ 2,536 $ 240 Total net liability $ 2,776 Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Unaudited Years 1 2 3 4 5 58.8 % 20.2 % 9.8 % 5.7 % 2.9 % Homeowners (excluding Other) ( dollars in millions ) For the Years Ended December 31, 2014 2015 2016 2017 2018 IBNR Reserves December 31, 2018 Cumulative Incurred Claims and Allocated Claims Adjustment Number of Expenses, Net of Reinsurance Reported Accident Year Unaudited Claims 2014 $ 1,515 $ 1,450 $ 1,453 $ 1,457 $ 1,451 $ 7 151,705 2015 1,438 1,454 1,461 1,452 10 145,088 2016 1,556 1,547 1,525 27 143,797 2017 2,312 2,340 101 168,357 2018 2,610 568 165,780 Total $ 9,378 Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Accident Year Unaudited Liability for Claims And Allocated Claim 2014 $ 1,053 $ 1,338 $ 1,402 $ 1,425 $ 1,433 Adjustment Expenses, 2015 994 1,333 1,395 1,421 Net of Reinsurance 2016 1,049 1,392 1,455 2017 1,471 2,059 2014 - Before 2018 1,657 2018 2014 Total $ 8,025 $ 1,353 $ 23 Total net liability $ 1,376 Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Unaudited Years 1 2 3 4 5 67.2 % 22.7 % 4.3 % 1.7 % 0.5 % International - Canada ( dollars in millions ) For the Years Ended December 31, IBNR Reserves December 31, 2018 Cumulative 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 Number of Accident Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Reported Year Unaudited Claims 2009 $ 454 $ 442 $ 450 $ 456 $ 464 $ 456 $ 449 $ 449 $ 442 $ 440 $ — 55,162 2010 463 464 475 488 477 469 465 459 457 5 54,919 2011 436 416 424 420 412 406 401 396 4 55,783 2012 413 393 394 378 377 361 355 12 51,226 2013 461 455 446 435 422 421 14 54,231 2014 408 422 423 412 405 (3 ) 52,291 2015 343 342 342 339 16 45,201 2016 343 389 389 32 45,728 2017 329 362 26 46,545 2018 418 89 46,883 Total $ 3,982 Accident Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Year Unaudited 2009 $ 189 $ 283 $ 323 $ 350 $ 379 $ 403 $ 419 $ 430 $ 433 $ 434 2010 182 278 313 351 380 409 425 437 442 2011 167 237 266 299 332 353 370 378 2012 157 219 249 274 300 317 325 Liability for Claims 2013 184 258 289 320 351 368 And Allocated Claim 2014 180 252 287 314 344 Adjustment Expenses, 2015 154 215 241 269 Net of Reinsurance 2016 201 269 294 2017 173 244 2009 - Before 2018 208 2018 2009 Total $ 3,306 $ 676 $ 34 Total net liability $ 710 Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Unaudited Years 1 2 3 4 5 6 7 8 9 10 45.2 % 18.7 % 7.8 % 7.4 % 7.3 % 5.2 % 3.5 % 2.2 % 1.0 % 0.2 %
Historical average annual percentage payout of incurred claims by age of accident year [Table Text Block]	Business Insurance General Liability ( dollars in millions ) For the Years Ended December 31, 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Unaudited Accident Year IBNR Reserves Dec 31, 2018 Cumulative Number of Reported Claims 2009 $ 1,060 $ 1,071 $ 1,028 $ 960 $ 869 $ 837 $ 809 $ 796 $ 783 $ 775 $ 56 25,702 2010 1,028 1,031 1,021 959 927 912 918 908 911 79 27,911 2011 1,004 1,074 1,065 998 972 935 913 908 80 27,444 2012 989 985 935 913 892 905 917 98 24,801 2013 965 975 958 940 927 933 101 22,446 2014 976 989 983 948 956 177 22,108 2015 998 956 923 967 222 21,033 2016 1,075 1,058 1,087 439 19,190 2017 1,133 1,143 717 16,464 2018 1,253 1,080 13,107 Total $ 9,850 Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Accident Year Unaudited 2009 $ 35 $ 167 $ 314 $ 446 $ 543 $ 613 $ 643 $ 667 $ 689 $ 701 2010 35 139 324 487 629 702 756 781 800 2011 47 187 355 539 660 725 762 799 2012 32 150 295 489 589 699 754 Liability for Claims 2013 35 175 363 498 639 745 And Allocated Claim 2014 37 163 321 515 640 Adjustment Expenses, 2015 36 137 336 558 Net of Reinsurance 2016 35 191 421 2017 40 180 2009 - Before 2018 42 2018 2009 Total $ 5,640 $ 4,210 $ 2,949 Total net liability $ 7,159 Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Unaudited Years 1 2 3 4 5 6 7 8 9 10 3.8 % 13.6 % 19.0 % 19.1 % 13.4 % 9.5 % 5.0 % 3.2 % 2.5 % 1.5 % Commercial Property ( dollars in millions ) For the Years Ended December 31, 2014 2015 2016 2017 2018 Incurred Claims and Allocated Claims Adjustment Expenses, Net of Reinsurance Unaudited Accident Year IBNR Reserves December 31, 2018 Cumulative Number of Reported Claims 2014 $ 936 $ 860 $ 836 $ 835 $ 834 $ 6 21,568 2015 786 750 741 731 6 20,143 2016 896 863 820 22 22,267 2017 1,209 1,177 30 24,855 2018 1,093 73 21,547 Total $ 4,655 Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Unaudited Liability for Claims Accident Year And Allocated Claim 2014 $ 464 $ 710 $ 775 $ 803 $ 817 Adjustment Expenses, 2015 376 615 681 699 Net of Reinsurance 2016 441 685 745 2017 618 1,003 2014 - Before 2018 561 2018 2014 Total $ 3,825 $ 830 $ 143 Total net liability $ 973 Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Unaudited Years 1 2 3 4 5 52.9 % 31.2 % 8.0 % 2.9 % 1.7 % Commercial Multi-Peril ( dollars in millions ) For the Years Ended December 31, 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Unaudited Accident Year IBNR Reserves December 31, 2018 Cumulative Number of Reported Claims 2009 $ 1,484 $ 1,506 $ 1,501 $ 1,498 $ 1,511 $ 1,514 $ 1,514 $ 1,509 $ 1,500 $ 1,493 $ 21 103,448 2010 1,711 1,826 1,832 1,861 1,895 1,892 1,898 1,885 1,881 32 111,931 2011 2,235 2,244 2,269 2,286 2,296 2,287 2,283 2,279 38 125,743 2012 1,885 1,883 1,903 1,888 1,888 1,867 1,859 42 104,800 2013 1,615 1,623 1,620 1,609 1,591 1,600 51 83,667 2014 1,663 1,627 1,625 1,617 1,626 72 78,097 2015 1,568 1,625 1,593 1,597 110 71,242 2016 1,662 1,623 1,598 204 68,024 2017 1,872 1,928 357 69,218 2018 1,976 605 58,784 Total $ 17,837 Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Accident Year Unaudited 2009 $ 603 $ 958 $ 1,121 $ 1,264 $ 1,360 $ 1,408 $ 1,436 $ 1,449 $ 1,457 $ 1,466 2010 709 1,180 1,395 1,579 1,698 1,763 1,798 1,819 1,834 2011 1,060 1,573 1,803 1,979 2,088 2,156 2,193 2,222 2012 795 1,246 1,424 1,590 1,699 1,752 1,780 Liability for Claims 2013 644 987 1,167 1,304 1,410 1,475 And Allocated Claim 2014 628 956 1,154 1,328 1,448 Adjustment Expenses, 2015 595 970 1,144 1,310 Net of Reinsurance 2016 585 950 1,133 2017 716 1,199 2009 - Before 2018 792 2018 2009 Total $ 14,659 $ 3,178 $ 357 Total net liability $ 3,535 Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Unaudited Years 1 2 3 4 5 6 7 8 9 10 39.7 % 23.2 % 11.0 % 9.4 % 6.2 % 3.3 % 1.7 % 1.1 % 0.7 % 0.6 % Commercial Automobile ( dollars in millions ) For the Years Ended December 31, 2014 2015 2016 2017 2018 Incurred Claims and Allocated Claims Adjustment Expenses, Net of Reinsurance Unaudited Accident Year IBNR Reserves December 31, 2018 Cumulative Number of Reported Claims 2014 $ 1,156 $ 1,153 $ 1,155 $ 1,171 $ 1,193 $ 36 177,493 2015 1,188 1,202 1,234 1,283 83 173,333 2016 1,278 1,303 1,371 191 182,647 2017 1,386 1,501 401 190,126 2018 1,645 736 185,419 Total $ 6,993 Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Unaudited Liability for Claims Accident Year And Allocated Claim 2014 $ 394 $ 611 $ 812 $ 977 $ 1,089 Adjustment Expenses, 2015 405 650 885 1,058 Net of Reinsurance 2016 412 688 931 2017 456 746 2014 - Before 2018 515 2018 2014 Total $ 4,339 $ 2,654 $ 207 Total net liability $ 2,861 Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Unaudited Years 1 2 3 4 5 31.3 % 19.2 % 17.6 % 13.7 % 9.3 % Workers’ Compensation ( dollars in millions ) For the Years Ended December 31, 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Unaudited Accident Year IBNR Reserves December 31, 2018 Cumulative Number of Reported Claims 2009 $ 1,799 $ 1,778 $ 1,746 $ 1,753 $ 1,753 $ 1,766 $ 1,775 $ 1,750 $ 1,736 $ 1,728 $ 221 104,789 2010 1,886 2,042 2,035 2,056 2,049 2,052 2,055 2,021 2,003 271 117,368 2011 2,284 2,303 2,347 2,350 2,379 2,385 2,363 2,348 356 136,728 2012 2,447 2,456 2,457 2,456 2,445 2,453 2,416 404 137,922 2013 2,553 2,545 2,540 2,506 2,463 2,423 473 132,424 2014 2,554 2,553 2,547 2,476 2,430 563 124,507 2015 2,644 2,585 2,505 2,441 751 122,388 2016 2,768 2,690 2,569 863 122,493 2017 2,779 2,681 1,179 119,890 2018 2,744 1,738 109,002 Total $ 23,783 Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Accident Year Unaudited 2009 $ 288 $ 623 $ 828 $ 961 $ 1,065 $ 1,137 $ 1,193 $ 1,235 $ 1,274 $ 1,303 2010 341 750 978 1,133 1,246 1,321 1,385 1,430 1,465 2011 420 911 1,185 1,365 1,487 1,583 1,652 1,696 2012 443 940 1,217 1,394 1,536 1,629 1,689 Liability for Claims 2013 458 954 1,237 1,413 1,525 1,604 And Allocated Claim 2014 455 944 1,224 1,399 1,505 Adjustment Expenses, 2015 430 893 1,154 1,310 Net of Reinsurance 2016 421 873 1,118 2017 433 890 2009 - Before 2018 440 2018 2009 Total $ 13,020 $ 10,763 $ 5,276 Total net liability $ 16,039 Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Unaudited Years 1 2 3 4 5 6 7 8 9 10 17.4 % 19.5 % 11.2 % 7.3 % 5.3 % 3.8 % 3.0 % 2.2 % 2.0 % 1.7 % Bond & Specialty Insurance General Liability ( dollars in millions ) For the Years Ended December 31, 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Unaudited Accident Year IBNR Reserves December 31, 2018 Cumulative Number of Reported Claims 2009 $ 592 $ 624 $ 665 $ 686 $ 680 $ 660 $ 655 $ 641 $ 631 $ 626 $ 11 6,297 2010 571 612 679 679 661 668 653 653 657 18 5,673 2011 565 596 639 632 601 545 520 508 (12 ) 5,212 2012 538 591 614 605 601 599 605 97 4,853 2013 510 565 606 630 654 607 103 4,442 2014 549 571 563 518 473 67 4,335 2015 528 524 486 437 92 4,155 2016 512 511 504 153 4,235 2017 534 517 266 4,128 2018 530 406 2,894 Total $ 5,464 Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Accident Year Unaudited 2009 $ 36 $ 167 $ 310 $ 390 $ 460 $ 497 $ 563 $ 592 $ 595 $ 597 2010 33 152 291 396 482 565 597 623 631 2011 33 143 249 324 414 447 476 490 2012 38 160 255 342 383 419 436 Liability for Claims 2013 34 154 252 352 400 434 And Allocated Claim 2014 38 150 239 312 367 Adjustment Expenses, 2015 38 141 234 310 Net of Reinsurance 2016 30 141 233 2017 38 155 2009 - Before 2018 49 2018 2009 Total $ 3,702 $ 1,762 $ 71 Total net liability $ 1,833 Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Unaudited Years 1 2 3 4 5 6 7 8 9 10 6.8 % 21.4 % 19.4 % 15.3 % 11.4 % 7.3 % 6.0 % 3.7 % 0.9 % 0.2 % Fidelity and Surety ( dollars in millions ) For the Years Ended December 31, 2014 2015 2016 2017 2018 IBNR Reserves December 31, 2018 Cumulative Incurred Claims and Allocated Claims Adjustment Number of Expenses, Net of Reinsurance Reported Accident Year Unaudited Claims 2014 $ 223 $ 212 $ 165 $ 136 $ 130 $ (4 ) 1,069 2015 217 191 179 145 38 827 2016 226 239 205 12 866 2017 244 271 64 863 2018 220 121 595 Total $ 971 Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Accident Year Unaudited Liability for Claims And Allocated Claim 2014 $ 58 $ 96 $ 111 $ 127 $ 124 Adjustment Expenses, 2015 32 75 87 86 Net of Reinsurance 2016 54 121 142 2017 70 166 2014 - Before 2018 64 2018 2014 Total $ 582 $ 389 $ 30 Total net liability $ 419 Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Unaudited Years 1 2 3 4 5 29.5 % 31.8 % 9.9 % 6.1 % (2.7 )% Personal Insurance Automobile ( dollars in millions ) For the Years Ended December 31, 2014 2015 2016 2017 2018 IBNR Reserves December 31, 2018 Cumulative Incurred Claims and Allocated Claims Adjustment Number of Expenses, Net of Reinsurance Reported Accident Year Unaudited Claims 2014 $ 2,014 $ 1,994 $ 1,981 $ 1,985 $ 1,980 $ 14 670,431 2015 2,186 2,244 2,236 2,222 35 757,837 2016 2,779 2,791 2,772 126 921,479 2017 3,323 3,256 341 1,059,610 2018 3,281 825 960,293 Total $ 13,511 Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Accident Year Unaudited Liability for Claims And Allocated Claim 2014 $ 1,193 $ 1,564 $ 1,763 $ 1,879 $ 1,936 Adjustment Expenses, 2015 1,319 1,768 1,985 2,109 Net of Reinsurance 2016 1,610 2,203 2,466 2017 1,912 2,575 2014 - Before 2018 1,889 2018 2014 Total $ 10,975 $ 2,536 $ 240 Total net liability $ 2,776 Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Unaudited Years 1 2 3 4 5 58.8 % 20.2 % 9.8 % 5.7 % 2.9 % Homeowners (excluding Other) ( dollars in millions ) For the Years Ended December 31, 2014 2015 2016 2017 2018 IBNR Reserves December 31, 2018 Cumulative Incurred Claims and Allocated Claims Adjustment Number of Expenses, Net of Reinsurance Reported Accident Year Unaudited Claims 2014 $ 1,515 $ 1,450 $ 1,453 $ 1,457 $ 1,451 $ 7 151,705 2015 1,438 1,454 1,461 1,452 10 145,088 2016 1,556 1,547 1,525 27 143,797 2017 2,312 2,340 101 168,357 2018 2,610 568 165,780 Total $ 9,378 Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Accident Year Unaudited Liability for Claims And Allocated Claim 2014 $ 1,053 $ 1,338 $ 1,402 $ 1,425 $ 1,433 Adjustment Expenses, 2015 994 1,333 1,395 1,421 Net of Reinsurance 2016 1,049 1,392 1,455 2017 1,471 2,059 2014 - Before 2018 1,657 2018 2014 Total $ 8,025 $ 1,353 $ 23 Total net liability $ 1,376 Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Unaudited Years 1 2 3 4 5 67.2 % 22.7 % 4.3 % 1.7 % 0.5 % International - Canada ( dollars in millions ) For the Years Ended December 31, IBNR Reserves December 31, 2018 Cumulative 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 Number of Accident Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Reported Year Unaudited Claims 2009 $ 454 $ 442 $ 450 $ 456 $ 464 $ 456 $ 449 $ 449 $ 442 $ 440 $ — 55,162 2010 463 464 475 488 477 469 465 459 457 5 54,919 2011 436 416 424 420 412 406 401 396 4 55,783 2012 413 393 394 378 377 361 355 12 51,226 2013 461 455 446 435 422 421 14 54,231 2014 408 422 423 412 405 (3 ) 52,291 2015 343 342 342 339 16 45,201 2016 343 389 389 32 45,728 2017 329 362 26 46,545 2018 418 89 46,883 Total $ 3,982 Accident Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Year Unaudited 2009 $ 189 $ 283 $ 323 $ 350 $ 379 $ 403 $ 419 $ 430 $ 433 $ 434 2010 182 278 313 351 380 409 425 437 442 2011 167 237 266 299 332 353 370 378 2012 157 219 249 274 300 317 325 Liability for Claims 2013 184 258 289 320 351 368 And Allocated Claim 2014 180 252 287 314 344 Adjustment Expenses, 2015 154 215 241 269 Net of Reinsurance 2016 201 269 294 2017 173 244 2009 - Before 2018 208 2018 2009 Total $ 3,306 $ 676 $ 34 Total net liability $ 710 Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance Unaudited Years 1 2 3 4 5 6 7 8 9 10 45.2 % 18.7 % 7.8 % 7.4 % 7.3 % 5.2 % 3.5 % 2.2 % 1.0 % 0.2 %

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2018
Debt Disclosure [Abstract]
Debt outstanding [Table Text Block]	Debt outstanding was as follows: (at December 31, in millions) 2018 2017 Short-term: Commercial paper $ 100 $ 100 5.90% Senior notes due June 2, 2019 500 — 5.80% Senior notes due May 15, 2018 — 500 Total short-term debt 600 600 Long-term: 5.90% Senior notes due June 2, 2019 — 500 3.90% Senior notes due November 1, 2020 500 500 7.75% Senior notes due April 15, 2026 200 200 7.625% Junior subordinated debentures due December 15, 2027 125 125 6.375% Senior notes due March 15, 2033 500 500 6.75% Senior notes due June 20, 2036 400 400 6.25% Senior notes due June 15, 2037 800 800 5.35% Senior notes due November 1, 2040 750 750 4.60% Senior notes due August 1, 2043 500 500 4.30% Senior notes due August 25, 2045 400 400 8.50% Junior subordinated debentures due December 15, 2045 56 56 3.75% Senior notes due May 15, 2046 500 500 8.312% Junior subordinated debentures due July 1, 2046 73 73 4.00% Senior notes due May 30, 2047 700 700 4.05% Senior notes due March 7, 2048 500 — Total long-term debt 6,004 6,004 Total debt principal 6,604 6,604 Unamortized fair value adjustment 44 46 Unamortized debt issuance costs (84 ) (79 ) Total debt $ 6,564 $ 6,571
Merger-related unamortized fair value adjustments and the related effective interest rate [Table Text Block]	The following table presents merger-related unamortized fair value adjustments and the related effective interest rate: Unamortized Fair Value Purchase Adjustment at December 31, Effective Interest Rate to Maturity (in millions) Issue Rate Maturity Date 2018 2017 Junior subordinated debentures 7.625 % Dec. 2027 $ 12 $ 13 6.147 % 8.500 % Dec. 2045 14 15 6.362 % 8.312 % Jul. 2046 18 18 6.362 % Total $ 44 $ 46

Shareholders' Equity and Divi_2

Shareholders' Equity and Dividend Availability (Table)	12 Months Ended
	Dec. 31, 2018
Stockholders' Equity Note [Abstract]
Share repurchase activity and remaining repurchase capacity under the share repurchase authorization [Table Text Block]	The following table summarizes repurchase activity in 2018 and remaining repurchase capacity at December 31, 2018 . (in millions, except per share amounts) Quarterly Period Ending Number of shares repurchased Cost of shares repurchased Average price paid per share Remaining capacity under share repurchase authorization March 31, 2018 2.5 $ 350 $ 141.84 $ 4,206 June 30, 2018 2.7 350 129.66 3,856 September 30, 2018 3.0 400 130.22 3,456 December 31, 2018 1.4 170 125.09 3,286 Total 9.6 $ 1,270 132.33 3,286

Other Comprehensive Income an_2

Other Comprehensive Income and Accumulated Other Comprehensive Income (Tables)	12 Months Ended
	Dec. 31, 2018
Other Comprehensive Income and Accumulated Other Comprehensive Income disclosure
Changes in accumulated other comprehensive income (loss) (AOCI) [Table Text Block]	The following table presents the changes in the Company’s accumulated other comprehensive income (AOCI) for the years ended December 31, 2018 , 2017 and 2016 . Changes in Net Unrealized Gains on Investment Securities (in millions) Having No Credit Losses Recognized in the Consolidated Statement of Income Having Credit Losses Recognized in the Consolidated Statement of Income Net Benefit Plan Assets and Obligations Recognized in Shareholders’ Equity Net Unrealized Foreign Currency Translation Total Accumulated Other Comprehensive Income (Loss) Balance, December 31, 2015 $ 1,100 $ 189 $ (713 ) $ (733 ) $ (157 ) Other comprehensive income (loss) (OCI) before reclassifications (530 ) 4 (30 ) (49 ) (605 ) Amounts reclassified from AOCI, net of tax (42 ) 9 40 — 7 Net OCI, current period (572 ) 13 10 (49 ) (598 ) Balance, December 31, 2016 528 202 (703 ) (782 ) (755 ) OCI before reclassifications 367 4 (24 ) 171 518 Amounts reclassified from AOCI, net of tax (148 ) 1 41 — (106 ) Net OCI, current period 219 5 17 171 412 Balance, December 31, 2017 747 207 (686 ) (611 ) (343 ) Cumulative effect of adoption of updated accounting guidance for equity financial instruments at January 1, 2018 (34 ) — — — (34 ) Income tax benefit (12 ) — — — (12 ) Net of taxes (22 ) — — — (22 ) Reclassification of certain tax effects from accumulated other comprehensive income at January 1, 2018 145 7 (141 ) (35 ) (24 ) Total effect of adoption of new guidance at January 1, 2018, net of tax 123 7 (141 ) (35 ) (46 ) OCI before reclassifications, net of tax (1,151 ) (21 ) (114 ) (227 ) (1,513 ) Amounts reclassified from AOCI, net of tax (25 ) — 68 — 43 Net OCI, current period (1,176 ) (21 ) (46 ) (227 ) (1,470 ) Balance, December 31, 2018 $ (306 ) $ 193 $ (873 ) $ (873 ) $ (1,859 )
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). (for the year ended December 31, in millions) 2018 2017 2016 Changes in net unrealized gains on investment securities: Having no credit losses recognized in the consolidated statement of income $ (1,489 ) $ 294 $ (883 ) Income tax expense (benefit) (313 ) 75 (311 ) Net of taxes (1,176 ) 219 (572 ) Having credit losses recognized in the consolidated statement of income (27 ) 8 21 Income tax expense (benefit) (6 ) 3 8 Net of taxes (21 ) 5 13 Net changes in benefit plan assets and obligations (56 ) 29 16 Income tax expense (benefit) (10 ) 12 6 Net of taxes (46 ) 17 10 Net changes in unrealized foreign currency translation (247 ) 191 (41 ) Income tax expense (benefit) (20 ) 20 8 Net of taxes (227 ) 171 (49 ) Total other comprehensive income (loss) (1,819 ) 522 (887 ) Total income tax expense (benefit) (349 ) 110 (289 ) Total other comprehensive income (loss), net of taxes $ (1,470 ) $ 412 $ (598 )
Pre-tax and related income tax (expense) benefit components of the amounts reclassified from accumulated other comprehensive income to the consolidated statement of income [Table Text Block]	The following table presents the pre-tax and related income tax (expense) benefit components of the amounts reclassified from the Company’s AOCI to the Company’s consolidated statement of income. (for the year ended December 31, in millions) 2018 2017 2016 Reclassification adjustments related to unrealized gains on investment securities: Having no credit losses recognized in the consolidated statement of income (1) $ (32 ) $ (228 ) $ (64 ) Income tax expense (2) (7 ) (80 ) (22 ) Net of taxes (25 ) (148 ) (42 ) Having credit losses recognized in the consolidated statement of income (1) — 1 13 Income tax benefit (2) — — 4 Net of taxes — 1 9 Reclassification adjustment related to benefit plan assets and obligations: Claims and claim adjustment expenses (3) 35 32 25 General and administrative expenses (3) 51 48 37 Total 86 80 62 Income tax benefit (2) 18 39 22 Net of taxes 68 41 40 Reclassification adjustment related to foreign currency translation (1) — — — Income tax benefit (2) — — — Net of taxes — — — Total reclassifications 54 (147 ) 11 Total income tax (expense) benefit 11 (41 ) 4 Total reclassifications, net of taxes $ 43 $ (106 ) $ 7 ___________________________________________ (1) (Increases) decreases net realized investment gains on the consolidated statement of income. (2) (Increases) decreases income tax expense on the consolidated statement of income. (3) Increases (decreases) expenses on the consolidated statement of income.

Earnings per Share (Table)

Earnings per Share (Table)	12 Months Ended
	Dec. 31, 2018
Earnings Per Share Reconciliation [Abstract]
Earnings per share reconciliation [Table Text Block]	The following is a reconciliation of the income and share data used in the basic and diluted earnings per share computations: (for the year ended December 31, in millions, except per share amounts) 2018 2017 2016 Basic and Diluted Net income, as reported $ 2,523 $ 2,056 $ 3,014 Participating share-based awards — allocated income (19 ) (15 ) (22 ) Net income available to common shareholders — basic and diluted $ 2,504 $ 2,041 $ 2,992 Common Shares Basic Weighted average shares outstanding 267.4 276.0 288.1 Diluted Weighted average shares outstanding 267.4 276.0 288.1 Weighted average effects of dilutive securities: Stock options and performance shares 2.4 2.6 2.9 Total 269.8 278.6 291.0 Net income Per Common Share Basic $ 9.37 $ 7.39 $ 10.39 Diluted $ 9.28 $ 7.33 $ 10.28

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Composition of income tax expense included in consolidated statement of income and shareholders' equity [Table Text Block]	The following table presents the components of income tax expense included in the amounts reported in the Company’s consolidated financial statements: (for the year ended December 31, in millions) 2018 2017 2016 Composition of income tax expense included in the consolidated statement of income Current expense: Federal $ 424 $ 314 $ 899 Impact of TCJA at enactment — 21 — Foreign 41 56 21 State 8 4 8 Total current tax expense 473 395 928 Deferred expense (benefit): Federal (13 ) 229 110 Impact of TCJA at enactment — 108 — Foreign (22 ) (58 ) 1 Total deferred tax expense (benefit) (35 ) 279 111 Total income tax expense included in the consolidated statement of income 438 674 1,039 Composition of income tax expense (benefit) included in shareholders’ equity Expense (benefit) relating to changes in the unrealized gain (loss) on investments, unrealized loss on foreign exchange and other items in other comprehensive income (loss) (349 ) 110 (289 ) Total income tax expense included in the consolidated financial statements $ 89 $ 784 $ 750
Effective tax rate [Table Text Block]	The following is a reconciliation of income tax expense at the U.S. federal statutory income tax rate to the income tax expense reported in the Company’s consolidated statement of income: (for the year ended December 31, in millions) 2018 2017 2016 Income (loss) before income taxes U.S. $ 3,039 $ 2,798 $ 3,946 Foreign (78 ) (68 ) 107 Total income before income taxes 2,961 2,730 4,053 Effective tax rate Statutory tax rate 21 % 35 % 35 % Expected federal income tax expense 622 956 1,419 Tax effect of: Nontaxable investment income (150 ) (297 ) (323 ) TCJA at enactment — 129 — Other, net (34 ) (114 ) (57 ) Total income tax expense $ 438 $ 674 $ 1,039 Effective tax rate 15 % 25 % 26 %
Deferred tax assets and liabilities [Table Text Block]	The net deferred tax asset comprises the tax effects of temporary differences related to the following assets and liabilities: (at December 31, in millions) 2018 2017 Deferred tax assets Claims and claim adjustment expense reserves $ 571 $ 930 Unearned premium reserves 503 478 Compensation-related liabilities 92 61 Other 200 191 Total gross deferred tax assets 1,366 1,660 Less: valuation allowance 8 6 Adjusted gross deferred tax assets 1,358 1,654 Deferred tax liabilities Claims and claim adjustment expense reserve discounting (transition rule) 159 560 Deferred acquisition costs 397 376 Investments 152 454 Internally developed software 92 97 Depreciation 67 57 Other 46 40 Total gross deferred tax liabilities 913 1,584 Net deferred tax asset $ 445 $ 70
Net operating loss amounts by jurisdiction and year of expiration [Table Text Block]	The NOL amounts by jurisdiction and year of expiration are as follows: (in millions) Amount Year of expiration United States $ 2 2035 - 2036 Brazil $ 19 None Canada $ 1 2037 - 2038 United Kingdom $ 146 None
Reconciliation of unrecognized tax benefits [Table Text Block]	The following is a reconciliation of the beginning and ending amount of unrecognized tax benefits for the years ended December 31, 2018 and 2017 : (in millions) 2018 2017 Balance at January 1 $ 6 $ 13 Additions for tax positions of prior years 25 — Reductions for tax positions of prior years — (1 ) Reductions based on tax positions related to current year — (6 ) Balance at December 31 $ 31 $ 6

Share-Based Incentive Compens_2

Share-Based Incentive Compensation (Tables)	12 Months Ended
	Dec. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Assumptions used in estimating fair value of options on grant date [Table Text Block]	The following table provides information about options granted: (for the year ended December 31,) 2018 2017 2016 Assumptions used in estimating fair value of options on grant date Expected term of stock options 6 years 6 years 5 – 6 years Expected volatility of Company’s stock 14.94 % 16.50 % 15.14% – 16.80% Weighted average volatility 14.94 % 16.50 % 16.79 % Expected annual dividend per share $2.88 $2.68 $2.44 – $2.68 Risk-free rate 2.68 % 2.08 % 1.36% – 2.23% Additional information Weighted average grant-date fair value of options granted (per share) $ 20.13 $ 16.15 $ 13.29 Total intrinsic value of options exercised during the year (in millions) $ 67 $ 90 $ 167
Additional information regarding option grants [Table Text Block]	The following table provides information about options granted: (for the year ended December 31,) 2018 2017 2016 Assumptions used in estimating fair value of options on grant date Expected term of stock options 6 years 6 years 5 – 6 years Expected volatility of Company’s stock 14.94 % 16.50 % 15.14% – 16.80% Weighted average volatility 14.94 % 16.50 % 16.79 % Expected annual dividend per share $2.88 $2.68 $2.44 – $2.68 Risk-free rate 2.68 % 2.08 % 1.36% – 2.23% Additional information Weighted average grant-date fair value of options granted (per share) $ 20.13 $ 16.15 $ 13.29 Total intrinsic value of options exercised during the year (in millions) $ 67 $ 90 $ 167
Summary of stock option activity under the Company's 2014 Incentive Plan and legacy share-based incentive compensation plans [Table Text Block]	A summary of stock option activity under the 2014 Incentive Plan and the legacy plans as of and for the year ended December 31, 2018 is as follows: Stock Options Number Weighted Average Exercise Price Weighted Average Contractual Life Remaining Aggregate Intrinsic Value ($ in millions) Outstanding, beginning of year 8,712,467 $ 97.45 Original grants 1,632,361 140.85 Exercised (1,229,850 ) 83.74 Forfeited or expired (120,622 ) 117.39 Outstanding, end of year 8,994,356 $ 106.93 6.2 years $ 149 Vested at end of year (1) 5,861,909 $ 99.28 5.3 years $ 134 Exercisable at end of year 3,889,013 $ 88.83 3.9 years $ 123 ___________________________________________ (1) Represents awards for which the requisite service has been rendered, including those that are retirement eligible.
Summary of restricted stock units, deferred stock units and performance share activity [Table Text Block]	A summary of restricted stock units, deferred stock units and performance share activity under the 2014 Incentive Plan and the legacy plans as of and for the year ended December 31, 2018 is as follows: Restricted and Deferred Stock Units Performance Shares Other Equity Instruments Number Weighted Average Grant-Date Fair Value Number Weighted Average Grant-Date Fair Value Nonvested, beginning of year 1,286,970 $ 111.74 787,732 $ 112.40 Granted 559,807 139.20 319,408 140.85 Vested (554,640 ) (1) 114.77 (385,604 ) (2) 106.06 Forfeited (75,461 ) 122.29 (68,593 ) 123.01 Performance-based adjustment — — 31,946 (3) 126.29 Nonvested, end of year 1,216,676 (4) $ 122.34 684,889 $ 128.83 ___________________________________________ (1) Represents awards for which the requisite service has been rendered. (2) Reflects the number of performance shares attributable to the performance goals attained over the completed performance period ( three years ) and for which service conditions have been met. (3) Represents the current year change in estimated performance shares to reflect the attainment of performance goals for the awards that were granted in each of the years 2016 through 2018 . (4) 95,953 shares of restricted common stock were also issued outside of the 2014 Incentive Plan in 2017 in connection with the acquisition of Simply Business, of which 92,995 shares remain unvested and are not included in this table. See note 9.

Pension Plans, Retirement Ben_2

Pension Plans, Retirement Benefits and Savings Plans (Tables)	12 Months Ended
	Dec. 31, 2018
Retirement Benefits [Abstract]
Summary of the funded status, obligations and amounts recognized in the consolidated balance sheet for the Company's benefit plans [Table Text Block]	The following tables summarize the funded status, obligations and amounts recognized in the consolidated balance sheet for the Company’s benefit plans. The Company uses a December 31 measurement date for its pension and postretirement benefit plans. (at and for the year ended December 31, in millions) Qualified Domestic Pension Plan Nonqualified and Foreign Pension Plans Total 2018 2017 2018 2017 2018 2017 Change in projected benefit obligation: Benefit obligation at beginning of year $ 3,679 $ 3,367 $ 230 $ 225 $ 3,909 $ 3,592 Benefits earned 126 112 7 7 133 119 Interest cost on benefit obligation 119 120 7 7 126 127 Actuarial (gain) loss (273 ) 258 (11 ) 1 (284 ) 259 Benefits paid (207 ) (178 ) (12 ) (9 ) (219 ) (187 ) Settlement — — — (11 ) — (11 ) Foreign currency exchange rate change — — (6 ) 10 (6 ) 10 Benefit obligation at end of year $ 3,444 $ 3,679 $ 215 $ 230 $ 3,659 $ 3,909 Change in plan assets: Fair value of plan assets at beginning of year $ 3,957 $ 3,387 $ 113 $ 106 $ 4,070 $ 3,493 Actual return on plan assets (179 ) 448 (1 ) 11 (180 ) 459 Company contributions 200 300 10 7 210 307 Benefits paid (207 ) (178 ) (12 ) (9 ) (219 ) (187 ) Settlement — — — (12 ) — (12 ) Foreign currency exchange rate change — — (7 ) 10 (7 ) 10 Fair value of plan assets at end of year 3,771 3,957 103 113 3,874 4,070 Funded status of plan at end of year $ 327 $ 278 $ (112 ) $ (117 ) $ 215 $ 161 Amounts recognized in the consolidated balance sheet consist of: Accrued over-funded benefit plan assets $ 327 $ 278 $ 4 $ 6 $ 331 $ 284 Accrued under-funded benefit plan liabilities — — (116 ) (123 ) (116 ) (123 ) Total $ 327 $ 278 $ (112 ) $ (117 ) $ 215 $ 161 Amounts recognized in accumulated other comprehensive income consist of: Net actuarial loss $ 1,113 $ 1,035 $ 36 $ 47 $ 1,149 $ 1,082 Prior service benefit (5 ) (6 ) 1 — (4 ) (6 ) Total $ 1,108 $ 1,029 $ 37 $ 47 $ 1,145 $ 1,076 Postretirement Benefit Plans (at and for the year ended December 31, in millions) 2018 2017 Change in projected benefit obligation: Benefit obligation at beginning of year $ 225 $ 214 Benefits earned — — Interest cost on benefit obligation 7 7 Actuarial (gain) loss (18 ) 13 Benefits paid (10 ) (10 ) Foreign currency exchange rate change (1 ) 1 Benefit obligation at end of year $ 203 $ 225 Change in plan assets: Fair value of plan assets at beginning of year $ 13 $ 14 Actual return on plan assets — — Company contributions 9 9 Benefits paid (10 ) (10 ) Fair value of plan assets at end of year 12 13 Funded status of plan at end of year $ (191 ) $ (212 ) Amounts recognized in the consolidated balance sheet consist of: Accrued under-funded benefit plan liability $ (191 ) $ (212 ) Amounts recognized in accumulated other comprehensive income consist of: Net actuarial gain $ (17 ) $ — Prior service benefit (25 ) (28 ) Total $ (42 ) $ (28 )
Summary of the components of net periodic benefit cost and other amounts recognized in other comprehensive income related to the benefit plans [Table Text Block]	The following table summarizes the components of net periodic benefit cost and other amounts recognized in other comprehensive income related to the benefit plans. Pension Plans Postretirement Benefit Plans (for the year ended December 31, in millions) 2018 2017 2016 2018 2017 2016 Net Periodic Benefit Cost: Service cost $ 133 $ 119 $ 118 $ — $ — $ — Non-service cost: Interest cost on benefit obligation 126 127 122 7 7 8 Expected return on plan assets (264 ) (240 ) (230 ) — — — Settlement — 3 1 — — — Amortization of unrecognized: Prior service benefit (1 ) (1 ) (1 ) (4 ) (4 ) (3 ) Net actuarial loss 91 85 66 — — — Total non-service cost (benefit) (48 ) (26 ) (42 ) 3 3 5 Net periodic benefit cost 85 93 76 3 3 5 Other Changes in Benefit Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income: Prior service benefit — — — — — — Net actuarial loss (gain) 160 40 66 (18 ) 13 (17 ) Foreign currency exchange rate change (1 ) 2 (2 ) — (1 ) 1 Settlement — (2 ) (1 ) — — — Amortization of prior service benefit 1 1 1 4 4 3 Amortization of net actuarial loss (91 ) (85 ) (66 ) — — — Total other changes recognized in other comprehensive income 69 (44 ) (2 ) (14 ) 16 (13 ) Total other changes recognized in net periodic benefit cost and other comprehensive income $ 154 $ 49 $ 74 $ (11 ) $ 19 $ (8 )
Consolidated statement of income line items impacted by service costs and non-service benefit costs [Table Text Block]	The following table indicates the line items in which the respective service costs and non-service costs are presented in the consolidated statement of income for the years ended December 31, 2018 , 2017 and 2016 . Pension Plans Postretirement Benefit Plans (for the year ended December 31, in millions) 2018 2017 2016 2018 2017 2016 Service Cost: Net investment income $ 1 $ — $ — $ — $ — $ — Claims and claim adjustment expenses 54 48 48 — $ — — General and administrative expenses 78 71 70 — — — Total service cost 133 119 118 — — — Non-Service Cost: Claims and claim adjustment expenses (19 ) (11 ) (18 ) 1 1 2 General and administrative expenses (29 ) (15 ) (24 ) 2 2 3 Total non-service cost (benefit) (48 ) (26 ) (42 ) 3 3 5 Net periodic benefit cost $ 85 $ 93 $ 76 $ 3 $ 3 $ 5
Benefit obligations assumptions, net periodic benefit cost assumptions and health care cost trend rates [Table Text Block]	The following table summarizes assumptions used with regard to the Company’s qualified and nonqualified domestic pension plans and the domestic postretirement benefit plans. (at and for the year ended December 31,) 2018 2017 Assumptions used to determine benefit obligations Discount rate: Qualified domestic pension plan 4.39 % 3.71 % Nonqualified domestic pension plan 4.33 % 3.66 % Domestic postretirement benefit plan 4.26 % 3.60 % Cash balance interest crediting rate 4.01 % 4.01 % Future compensation increase rate 4.00 % 4.00 % Assumptions used to determine net periodic benefit cost Discount rate: Qualified domestic pension plan: Service cost 3.87 % 4.52 % Interest cost 3.34 % 3.55 % Nonqualified domestic pension plan: Service cost 3.73 % 4.24 % Interest cost 3.26 % 3.43 % Domestic postretirement benefit plan: Interest cost 3.21 % 3.42 % Expected long-term rate of return on assets: Pension plan 7.00 % 7.00 % Postretirement benefit plan 4.00 % 4.00 % Assumed health care cost trend rates Following year: Medical (before age 65) 7.50 % 7.50 % Medical (age 65 and older) 8.75 % 8.75 % Rate to which the cost trend rate is assumed to decline (ultimate trend rate) 4.50 % 4.50 % Year that the rate reaches the ultimate trend rate: Medical (before age 65) 2026 2026 Medical (age 65 and older) 2026 2026
Level within the fair value hierarchy at which the financial assets of the Company's pension plans are measured [Table Text Block]	The following tables present the level within the fair value hierarchy at which the financial assets of the Company’s pension plans are measured on a recurring basis. (at December 31, 2018, in millions) Total Level 1 Level 2 Level 3 Invested assets: Fixed maturities Obligations of states, municipalities and political subdivisions $ 3 $ — $ 3 $ — Debt securities issued by foreign governments 27 — 27 — Mortgage-backed securities, collateralized mortgage obligations and pass-through securities 30 — 30 — All other corporate bonds 712 — 712 — Total fixed maturities 772 — 772 — Mutual funds Equity mutual funds 1,288 1,282 6 — Bond mutual funds 760 757 3 — Total mutual funds 2,048 2,039 9 — Equity securities 783 783 — — Other investments 1 — — 1 Cash and short-term securities U.S. Treasury securities 30 30 — — Other 240 19 221 — Total cash and short-term securities 270 49 221 — Total $ 3,874 $ 2,871 $ 1,002 $ 1 (at December 31, 2017, in millions) Total Level 1 Level 2 Level 3 Invested assets: Fixed maturities Obligations of states, municipalities and political subdivisions $ 3 $ — $ 3 $ — Debt securities issued by foreign governments 16 — 16 — Mortgage-backed securities, collateralized mortgage obligations and pass-through securities 10 — 10 — All other corporate bonds 514 — 514 — Total fixed maturities 543 — 543 — Mutual funds Equity mutual funds 1,335 1,328 7 — Bond mutual funds 822 819 3 — Total mutual funds 2,157 2,147 10 — Equity securities 883 882 1 — Other investments 1 — — 1 Cash and short-term securities U.S. Treasury securities 241 241 — — Money market mutual funds 27 27 — — Other 218 27 191 — Total cash and short-term securities 486 295 191 — Total $ 4,070 $ 3,324 $ 745 $ 1
Estimated future benefit payments [Table Text Block]	The following table presents the estimated benefits expected to be paid by the Company’s pension and postretirement benefit plans for the next ten years (reflecting estimated future employee service). Benefits Expected to be Paid (in millions) Pension Plans Postretirement Benefit Plans 2019 $ 239 $ 13 2020 246 14 2021 255 15 2022 260 15 2023 268 15 2024 through 2028 1,361 72

Consolidating Financial State_2

Consolidating Financial Statements (Tables)	12 Months Ended
	Dec. 31, 2018
Consolidating Financial Statements of The Travelers Companies, Inc. and Subsidiaries (Unaudited) disclosure
Consolidating Statement of Income (Unaudited) [Table Text Block]	CONSOLIDATING STATEMENT OF INCOME (Unaudited) For the year ended December 31, 2018 (in millions) TPC Other Subsidiaries TRV Eliminations Consolidated Revenues Premiums $ 18,508 $ 8,551 $ — $ — $ 27,059 Net investment income 1,704 738 32 — 2,474 Fee income 432 — — — 432 Net realized investment gains (losses) (1) 118 9 (13 ) — 114 Other revenues 96 112 — (5 ) 203 Total revenues 20,858 9,410 19 (5 ) 30,282 Claims and expenses Claims and claim adjustment expenses 12,344 5,947 — — 18,291 Amortization of deferred acquisition costs 2,972 1,409 — — 4,381 General and administrative expenses 2,947 1,335 20 (5 ) 4,297 Interest expense 48 — 304 — 352 Total claims and expenses 18,311 8,691 324 (5 ) 27,321 Income (loss) before income taxes 2,547 719 (305 ) — 2,961 Income tax expense (benefit) 437 115 (114 ) — 438 Net income of subsidiaries — — 2,714 (2,714 ) — Net income $ 2,110 $ 604 $ 2,523 $ (2,714 ) $ 2,523 ___________________________________________ (1) Total other-than-temporary impairments (OTTI) for the year ended December 31, 2018 , and the amounts comprising total OTTI that were recognized in net realized investment gains (losses) and in other comprehensive income (OCI), were as follows: (in millions) TPC Other Subsidiaries TRV Eliminations Consolidated Total OTTI losses $ (1 ) $ — $ — $ — $ (1 ) OTTI losses recognized in net realized investment gains (losses) $ (1 ) $ — $ — $ — $ (1 ) OTTI losses recognized in OCI $ — $ — $ — $ — $ — CONSOLIDATING STATEMENT OF INCOME (Unaudited) For the year ended December 31, 2017 (in millions) TPC Other Subsidiaries TRV Eliminations Consolidated Revenues Premiums $ 17,562 $ 8,121 $ — $ — $ 25,683 Net investment income 1,627 759 24 (13 ) 2,397 Fee income 447 — — — 447 Net realized investment gains (1) 19 131 66 — 216 Other revenues 101 68 — (10 ) 159 Total revenues 19,756 9,079 90 (23 ) 28,902 Claims and expenses Claims and claim adjustment expenses 11,735 5,732 — — 17,467 Amortization of deferred acquisition costs 2,820 1,346 — — 4,166 General and administrative expenses 2,906 1,249 25 (10 ) 4,170 Interest expense 48 — 321 — 369 Total claims and expenses 17,509 8,327 346 (10 ) 26,172 Income (loss) before income taxes 2,247 752 (256 ) (13 ) 2,730 Income tax expense (benefit) 519 290 (130 ) (5 ) 674 Net income of subsidiaries — — 2,190 (2,190 ) — Net income $ 1,728 $ 462 $ 2,064 $ (2,198 ) $ 2,056 ___________________________________________ (1) Total other-than-temporary impairments (OTTI) for the year ended December 31, 2017 , and the amounts comprising total OTTI that were recognized in net realized investment gains and in other comprehensive income (OCI), were as follows: (in millions) TPC Other Subsidiaries TRV Eliminations Consolidated Total OTTI losses $ (4 ) $ (9 ) $ — $ — $ (13 ) OTTI losses recognized in net realized investment gains $ (5 ) $ (9 ) $ — $ — $ (14 ) OTTI gains recognized in OCI $ 1 $ — $ — $ — $ 1 CONSOLIDATING STATEMENT OF INCOME (Unaudited) For the year ended December 31, 2016 (in millions) TPC Other Subsidiaries TRV Eliminations Consolidated Revenues Premiums $ 16,788 $ 7,746 $ — $ — $ 24,534 Net investment income 1,569 720 13 — 2,302 Fee income 458 — — — 458 Net realized investment gains (losses) (1) 30 39 (1 ) — 68 Other revenues 248 36 — (21 ) 263 Total revenues 19,093 8,541 12 (21 ) 27,625 Claims and expenses Claims and claim adjustment expenses 10,232 4,838 — — 15,070 Amortization of deferred acquisition costs 2,702 1,283 — — 3,985 General and administrative expenses 2,928 1,242 5 (21 ) 4,154 Interest expense 48 — 315 — 363 Total claims and expenses 15,910 7,363 320 (21 ) 23,572 Income (loss) before income taxes 3,183 1,178 (308 ) — 4,053 Income tax expense (benefit) 999 208 (168 ) — 1,039 Net income of subsidiaries — — 3,154 (3,154 ) — Net income $ 2,184 $ 970 $ 3,014 $ (3,154 ) $ 3,014 ___________________________________________ (1) Total other-than-temporary impairments (OTTI) for the year ended December 31, 2016 , and the amounts comprising total OTTI that were recognized in net realized investment gains (losses) and in other comprehensive income (OCI), were as follows: (in millions) TPC Other Subsidiaries TRV Eliminations Consolidated Total OTTI losses $ (19 ) $ (20 ) $ (1 ) $ — $ (40 ) OTTI losses recognized in net realized investment gains (losses) $ (13 ) $ (15 ) $ (1 ) $ — $ (29 ) OTTI losses recognized in OCI $ (6 ) $ (5 ) $ — $ — $ (11 )
Consolidating Statement of Comprehensive Income (Unaudited) [Table Text Block]	CONSOLIDATING STATEMENT OF COMPREHENSIVE INCOME (Unaudited) For the year ended December 31, 2018 (in millions) TPC Other Subsidiaries TRV Eliminations Consolidated Net income $ 2,110 $ 604 $ 2,523 $ (2,714 ) $ 2,523 Other comprehensive loss: Changes in net unrealized gains on investment securities: Having no credit losses recognized in the consolidated statement of income (1,028 ) (461 ) — — (1,489 ) Having credit losses recognized in the consolidated statement of income (20 ) (7 ) — — (27 ) Net changes in benefit plan assets and obligations 1 (4 ) (53 ) — (56 ) Net changes in unrealized foreign currency translation (144 ) (103 ) — — (247 ) Other comprehensive loss before income taxes and other comprehensive loss of subsidiaries (1,191 ) (575 ) (53 ) — (1,819 ) Income tax benefit (231 ) (101 ) (17 ) — (349 ) Other comprehensive loss, net of taxes, before other comprehensive loss of subsidiaries (960 ) (474 ) (36 ) — (1,470 ) Other comprehensive loss of subsidiaries — — (1,434 ) 1,434 — Other comprehensive loss (960 ) (474 ) (1,470 ) 1,434 (1,470 ) Comprehensive income $ 1,150 $ 130 $ 1,053 $ (1,280 ) $ 1,053 CONSOLIDATING STATEMENT OF COMPREHENSIVE INCOME (Unaudited) For the year ended December 31, 2017 (in millions) TPC Other Subsidiaries TRV Eliminations Consolidated Net income $ 1,728 $ 462 $ 2,064 $ (2,198 ) $ 2,056 Other comprehensive income (loss): Changes in net unrealized gains on investment securities: Having no credit losses recognized in the consolidated statement of income 313 25 (44 ) — 294 Having credit losses recognized in the consolidated statement of income 6 2 — — 8 Net changes in benefit plan assets and obligations (1 ) 8 22 — 29 Net changes in unrealized foreign currency translation 83 108 — — 191 Other comprehensive income (loss) before income taxes and other comprehensive income of subsidiaries 401 143 (22 ) — 522 Income tax expense 98 10 2 — 110 Other comprehensive income (loss), net of taxes, before other comprehensive income of subsidiaries 303 133 (24 ) — 412 Other comprehensive income of subsidiaries — — 436 (436 ) — Other comprehensive income 303 133 412 (436 ) 412 Comprehensive income $ 2,031 $ 595 $ 2,476 $ (2,634 ) $ 2,468 CONSOLIDATING STATEMENT OF COMPREHENSIVE INCOME (Unaudited) For the year ended December 31, 2016 (in millions) TPC Other Subsidiaries TRV Eliminations Consolidated Net income $ 2,184 $ 970 $ 3,014 $ (3,154 ) $ 3,014 Other comprehensive loss: Changes in net unrealized gains on investment securities: Having no credit losses recognized in the consolidated statement of income (696 ) (198 ) 11 — (883 ) Having credit losses recognized in the consolidated statement of income 11 10 — — 21 Net changes in benefit plan assets and obligations 25 11 (20 ) — 16 Net changes in unrealized foreign currency translation 73 (114 ) — — (41 ) Other comprehensive loss before income taxes and other comprehensive loss of subsidiaries (587 ) (291 ) (9 ) — (887 ) Income tax benefit (222 ) (66 ) (1 ) — (289 ) Other comprehensive loss, net of taxes, before other comprehensive loss of subsidiaries (365 ) (225 ) (8 ) — (598 ) Other comprehensive loss of subsidiaries — — (590 ) 590 — Other comprehensive loss (365 ) (225 ) (598 ) 590 (598 ) Comprehensive income $ 1,819 $ 745 $ 2,416 $ (2,564 ) $ 2,416
Consolidating Balance Sheet (Unaudited) [Table Text Block]	CONSOLIDATING BALANCE SHEET (Unaudited) At December 31, 2018 (in millions) TPC Other Subsidiaries TRV Eliminations Consolidated Assets Fixed maturities, available for sale, at fair value (amortized cost $63,601) $ 43,683 $ 19,697 $ 84 $ — $ 63,464 Equity securities, at fair value (cost $382) 105 92 171 — 368 Real estate investments 2 902 — — 904 Short-term securities 1,855 759 1,371 — 3,985 Other investments 2,746 810 1 — 3,557 Total investments 48,391 22,260 1,627 — 72,278 Cash 181 192 — — 373 Investment income accrued 434 187 3 — 624 Premiums receivable 5,089 2,417 — — 7,506 Reinsurance recoverables 5,904 2,466 — — 8,370 Ceded unearned premiums 522 56 — — 578 Deferred acquisition costs 1,930 190 — — 2,120 Deferred taxes 167 302 (24 ) — 445 Contractholder receivables 3,867 918 — — 4,785 Goodwill 2,578 1,368 — (9 ) 3,937 Other intangible assets 224 121 — — 345 Investment in subsidiaries — — 26,993 (26,993 ) — Other assets 2,220 15 669 (32 ) 2,872 Total assets $ 71,507 $ 30,492 $ 29,268 $ (27,034 ) $ 104,233 Liabilities Claims and claim adjustment expense reserves $ 34,093 $ 16,575 $ — $ — $ 50,668 Unearned premium reserves 9,414 4,141 — — 13,555 Contractholder payables 3,867 918 — — 4,785 Payables for reinsurance premiums 169 120 — — 289 Debt 693 32 5,871 (32 ) 6,564 Other liabilities 4,133 849 496 — 5,478 Total liabilities 52,369 22,635 6,367 (32 ) 81,339 Shareholders’ equity Common stock (1,750.0 shares authorized; 263.7 shares issued and 263.6 shares outstanding) — 401 23,144 (401 ) 23,144 Additional paid-in capital 11,634 7,023 — (18,657 ) — Retained earnings 8,065 879 35,211 (8,951 ) 35,204 Accumulated other comprehensive loss (561 ) (446 ) (1,859 ) 1,007 (1,859 ) Treasury stock, at cost (510.9 shares) — — (33,595 ) — (33,595 ) Total shareholders’ equity 19,138 7,857 22,901 (27,002 ) 22,894 Total liabilities and shareholders’ equity $ 71,507 $ 30,492 $ 29,268 $ (27,034 ) $ 104,233 CONSOLIDATING BALANCE SHEET (Unaudited) At December 31, 2017 (in millions) TPC Other Subsidiaries TRV Eliminations Consolidated Assets Fixed maturities, available for sale, at fair value (amortized cost $61,316) $ 43,240 $ 19,372 $ 82 $ — $ 62,694 Equity securities, available for sale, at fair value (cost $440) 161 111 181 — 453 Real estate investments 54 878 — — 932 Short-term securities 2,751 914 1,230 — 4,895 Other investments 2,673 854 1 — 3,528 Total investments 48,879 22,129 1,494 — 72,502 Cash 157 187 — — 344 Investment income accrued 418 183 5 — 606 Premiums receivable 4,852 2,292 — — 7,144 Reinsurance recoverables 5,842 2,467 — — 8,309 Ceded unearned premiums 493 58 — — 551 Deferred acquisition costs 1,835 190 — — 2,025 Deferred taxes (89 ) 173 (14 ) — 70 Contractholder receivables 3,854 921 — — 4,775 Goodwill 2,592 1,368 — (9 ) 3,951 Other intangible assets 202 140 — — 342 Investment in subsidiaries — — 27,946 (27,946 ) — Other assets 2,181 (3 ) 700 (14 ) 2,864 Total assets $ 71,216 $ 30,105 $ 30,131 $ (27,969 ) $ 103,483 Liabilities Claims and claim adjustment expense reserves $ 33,386 $ 16,264 $ — $ — $ 49,650 Unearned premium reserves 8,957 3,958 — — 12,915 Contractholder payables 3,854 921 — — 4,775 Payables for reinsurance premiums 165 109 — — 274 Debt 693 14 5,878 (14 ) 6,571 Other liabilities 4,161 882 524 — 5,567 Total liabilities 51,216 22,148 6,402 (14 ) 79,752 Shareholders’ equity Common stock (1,750.0 shares authorized; 271.5 shares issued and 271.4 shares outstanding) — 390 22,886 (390 ) 22,886 Additional paid-in capital 11,634 6,972 — (18,606 ) — Retained earnings 8,036 594 33,460 (8,628 ) 33,462 Accumulated other comprehensive income (loss) 330 1 (343 ) (331 ) (343 ) Treasury stock, at cost (500.9 shares) — — (32,274 ) — (32,274 ) Total shareholders’ equity 20,000 7,957 23,729 (27,955 ) 23,731 Total liabilities and shareholders’ equity $ 71,216 $ 30,105 $ 30,131 $ (27,969 ) $ 103,483
Consolidating Statement of Cash Flows (Unaudited) [Table Text Block]	CONSOLIDATING STATEMENT OF CASH FLOWS (Unaudited) For the year ended December 31, 2018 (in millions) TPC Other Subsidiaries TRV Eliminations Consolidated Cash flows from operating activities Net income $ 2,110 $ 604 $ 2,523 $ (2,714 ) $ 2,523 Net adjustments to reconcile net income to net cash provided by operating activities 1,141 605 (363 ) 474 1,857 Net cash provided by operating activities 3,251 1,209 2,160 (2,240 ) 4,380 Cash flows from investing activities Proceeds from maturities of fixed maturities 5,158 1,906 22 — 7,086 Proceeds from sales of investments: Fixed maturities 2,449 1,096 1 — 3,546 Equity securities 65 107 6 — 178 Real estate investments 66 8 — — 74 Other investments 403 108 — — 511 Purchases of investments: Fixed maturities (9,404 ) (4,096 ) (26 ) — (13,526 ) Equity securities (8 ) (99 ) (10 ) — (117 ) Real estate investments (1 ) (73 ) — — (74 ) Other investments (454 ) (83 ) — — (537 ) Net sales (purchases) of short-term securities 895 154 (141 ) — 908 Securities transactions in course of settlement (80 ) 24 — — (56 ) Acquisition, net of cash acquired — (4 ) — — (4 ) Other (310 ) (8 ) — — (318 ) Net cash used in investing activities (1,221 ) (960 ) (148 ) — (2,329 ) Cash flows from financing activities Treasury stock acquired — share repurchase authorization — — (1,270 ) — (1,270 ) Treasury stock acquired — net employee share-based compensation — — (51 ) — (51 ) Dividends paid to shareholders — — (814 ) — (814 ) Payment of debt — — (600 ) — (600 ) Issuance of debt — 18 591 (18 ) 591 Issuance of common stock — employee share options — — 132 — 132 Dividends paid to parent company (2,003 ) (255 ) — 2,258 — Net cash used in financing activities (2,003 ) (237 ) (2,012 ) 2,240 (2,012 ) Effect of exchange rate changes on cash (3 ) (7 ) — — (10 ) Net increase in cash 24 5 — — 29 Cash at beginning of year 157 187 — — 344 Cash at end of year $ 181 $ 192 $ — $ — $ 373 Supplemental disclosure of cash flow information Income taxes paid (received) $ 437 $ 254 $ (283 ) $ — $ 408 Interest paid $ 47 $ — $ 300 $ — $ 347 CONSOLIDATING STATEMENT OF CASH FLOWS (Unaudited) For the year ended December 31, 2017 (in millions) TPC Other Subsidiaries TRV Eliminations Consolidated Cash flows from operating activities Net income $ 1,728 $ 462 $ 2,064 $ (2,198 ) $ 2,056 Net adjustments to reconcile net income to net cash provided by operating activities 1,500 701 (32 ) (77 ) 2,092 Net cash provided by operating activities 3,228 1,163 2,032 (2,275 ) 4,148 Cash flows from investing activities Proceeds from maturities of fixed maturities 6,576 2,168 6 — 8,750 Proceeds from sales of investments: Fixed maturities 1,007 846 1 — 1,854 Equity securities 97 414 254 — 765 Real estate investments — 23 — — 23 Other investments 357 124 — (13 ) 468 Purchases of investments: Fixed maturities (8,513 ) (3,697 ) (40 ) — (12,250 ) Equity securities (68 ) (133 ) (258 ) — (459 ) Real estate investments (1 ) (58 ) — — (59 ) Other investments (444 ) (97 ) — — (541 ) Net sales (purchases) of short-term securities (303 ) (120 ) 397 — (26 ) Securities transactions in course of settlement (55 ) 5 3 — (47 ) Acquisition, net of cash acquired — 25 (477 ) 13 (439 ) Other (244 ) 3 — — (241 ) Net cash used in investing activities (1,591 ) (497 ) (114 ) — (2,202 ) Cash flows from financing activities Treasury stock acquired — share repurchase authorization — — (1,378 ) — (1,378 ) Treasury stock acquired — net employee share-based compensation — — (62 ) — (62 ) Dividends paid to shareholders — — (785 ) — (785 ) Payment of debt — — (657 ) — (657 ) Issuance of debt — 14 789 (14 ) 789 Issuance of common stock — employee share options — — 173 — 173 Dividends paid to parent company (1,624 ) (665 ) — 2,289 — Net cash used in financing activities (1,624 ) (651 ) (1,920 ) 2,275 (1,920 ) Effect of exchange rate changes on cash 3 8 — — 11 Net increase (decrease) in cash 16 23 (2 ) — 37 Cash at beginning of year 141 164 2 — 307 Cash at end of year $ 157 $ 187 $ — $ — $ 344 Supplemental disclosure of cash flow information Income taxes paid (received) $ 481 $ 206 $ (173 ) $ — $ 514 Interest paid $ 47 $ — $ 320 $ — $ 367 CONSOLIDATING STATEMENT OF CASH FLOWS (Unaudited) For the year ended December 31, 2016 (in millions) TPC Other Subsidiaries TRV Eliminations Consolidated Cash flows from operating activities Net income $ 2,184 $ 970 $ 3,014 $ (3,154 ) $ 3,014 Net adjustments to reconcile net income to net cash provided by operating activities 1,282 139 (122 ) 156 1,455 Net cash provided by operating activities 3,466 1,109 2,892 (2,998 ) 4,469 Cash flows from investing activities Proceeds from maturities of fixed maturities 6,589 2,380 6 — 8,975 Proceeds from sales of investments: Fixed maturities 768 647 2 — 1,417 Equity securities 47 45 — — 92 Real estate investments — 69 — — 69 Other investments 386 180 — — 566 Purchases of investments: Fixed maturities (7,921 ) (3,676 ) (12 ) — (11,609 ) Equity securities (6 ) (42 ) (3 ) — (51 ) Real estate investments (1 ) (47 ) — — (48 ) Other investments (453 ) (127 ) — — (580 ) Net sales (purchases) of short-term securities (501 ) 383 (81 ) — (199 ) Securities transactions in course of settlement 12 (32 ) (1 ) — (21 ) Other (331 ) (10 ) 3 — (338 ) Net cash used in investing activities (1,411 ) (230 ) (86 ) — (1,727 ) Cash flows from financing activities Treasury stock acquired — share repurchase authorization — — (2,400 ) — (2,400 ) Treasury stock acquired — net employee share-based compensation — — (72 ) — (72 ) Dividends paid to shareholders — — (757 ) — (757 ) Payment of debt — — (400 ) — (400 ) Issuance of debt — — 491 — 491 Issuance of common stock — employee share options — — 332 — 332 Dividends paid to parent company (2,140 ) (858 ) — 2,998 — Net cash used in financing activities (2,140 ) (858 ) (2,806 ) 2,998 (2,806 ) Effect of exchange rate changes on cash 1 (10 ) — — (9 ) Net increase (decrease) in cash (84 ) 11 — — (73 ) Cash at beginning of year 225 153 2 — 380 Cash at end of year $ 141 $ 164 $ 2 $ — $ 307 Supplemental disclosure of cash flow information Income taxes paid (received) $ 737 $ 287 $ (132 ) $ — $ 892 Interest paid $ 47 $ — $ 311 $ — $ 358

Selected Quarterly Financial _2

Selected Quarterly Financial Data (Unaudited) (Table)	12 Months Ended
	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Selected Quarterly Financial Data (Unaudited) disclosure [Table Text Block]	2018 (in millions, except per share amounts) First Quarter Second Quarter Third Quarter Fourth Quarter Total Total revenues $ 7,286 $ 7,477 $ 7,723 $ 7,796 $ 30,282 Total expenses 6,508 6,846 6,917 7,050 27,321 Income before income taxes 778 631 806 746 2,961 Income tax expense 109 107 97 125 438 Net income $ 669 $ 524 $ 709 $ 621 $ 2,523 Net income per share (1) : Basic $ 2.45 $ 1.93 $ 2.65 $ 2.33 $ 9.37 Diluted 2.42 1.92 2.62 2.32 9.28 2017 (in millions, except per share amounts) First Second Third Fourth Total Total revenues $ 6,942 $ 7,184 $ 7,325 $ 7,451 $ 28,902 Total expenses 6,182 6,394 7,005 6,591 26,172 Income before income taxes 760 790 320 860 2,730 Income tax expense (2) 143 195 27 309 674 Net income $ 617 $ 595 $ 293 $ 551 $ 2,056 Net income per share (1) : Basic $ 2.19 $ 2.13 $ 1.06 $ 2.00 $ 7.39 Diluted 2.17 2.11 1.05 1.98 7.33 ___________________________________________ (1) Due to the use of an average number of shares for each quarter, the sum of the quarterly earnings per share may not equal the total earnings per share for the full year. (2) Income tax expense for the fourth quarter and full year of 2017 included a net charge of $129 million to reflect the change in tax laws and tax rates enacted in the U.S. on December 22, 2017 as part of the Tax Cuts and Jobs Act of 2017, resulting primarily from revaluing the Company’s deferred tax assets and liabilities and the tax imposed on accumulated foreign earnings.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Details) - Simply Business [Member] - USD ($) $ in Millions	Aug. 04, 2017	Aug. 31, 2017
Business Acquisition
Approximate purchase price including the repayment of debt and other obligations	$ 464
Restricted common stock [Member]
Business Acquisition
Share issued (in shares)	95,953	95,953
Shares issued value	$ 12	$ 12
Restricted common stock [Member] | Two years from the issuance date [Member]
Business Acquisition
Vesting percentage	50.00%	50.00%
Vesting period (in years)	2 years	2 years
Restricted common stock [Member] | Three years from the issuance date [Member]
Business Acquisition
Vesting percentage	50.00%	50.00%
Vesting period (in years)	3 years	3 years

Summary of Significant Accoun_4

Summary of Significant Accounting Policies (Details) - Updated Guidance - USD ($) $ in Millions	Jan. 01, 2018	Dec. 31, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Member]
New Accounting Pronouncements
Cumulative effect adjustment increasing (decreasing) equity	$ (22)		$ (22)
Reclassification of certain tax effects from adoption of updated accounting guidance	(24)	$ (24)
Retained earnings [Member]
New Accounting Pronouncements
Cumulative effect adjustment increasing (decreasing) equity			$ 22
Reclassification of certain tax effects from adoption of updated accounting guidance		$ 24
Accounting Standards Update 2016-01 [Member] | Accumulated Other Comprehensive Income (Loss) [Member]
New Accounting Pronouncements
Cumulative effect adjustment increasing (decreasing) equity	(22)
Accounting Standards Update 2016-01 [Member] | Retained earnings [Member]
New Accounting Pronouncements
Cumulative effect adjustment increasing (decreasing) equity	22
Accounting Standards Update 2018-02 [Member] | Accumulated Other Comprehensive Income (Loss) [Member]
New Accounting Pronouncements
Reclassification of certain tax effects from adoption of updated accounting guidance	(24)
Accounting Standards Update 2018-02 [Member] | Retained earnings [Member]
New Accounting Pronouncements
Reclassification of certain tax effects from adoption of updated accounting guidance	$ 24

Summary of Significant Accoun_5

Summary of Significant Accounting Policies (Details) - Revenue from Contracts with Customers - Accounting Standards Update 2014-09 [Member] $ in Millions	12 Months Ended
	Dec. 31, 2018USD ($)
Revenues within scope of updated accounting guidance
Revenues within scope of updated accounting guidance	$ 171
Revenues within scope of updated accounting guidance, as a percentage of total revenues (less than)	1.00%

Summary of Significant Accoun_6

Summary of Significant Accounting Policies (Details) - Lease Accounting	Jan. 01, 2019
Subsequent event [Member] | Scenario, Forecast [Member] | Accounting Standards Update 2016-02 [Member]
New Accounting Pronouncements
Right of use asset and lease liability to be recognized upon adoption of updated lease guidance as a percentage of total assets and total liabilities (less than)	1.00%

Summary of Significant Accoun_7

Summary of Significant Accounting Policies Summary of Significant Accounting Policies (Details) - Policy Details	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Maximum useful life for buildings held in real estate investments	39 years
Maximum original maturity of short-term securities	1 year
Availability of financial information provided by private equity and real estate partnerships following the date of the reporting, maximum	3 months
Availability of financial information provided by hedge funds following the date of the reporting	1 month
Estimated recovery time for securities for which the issuer is in bankruptcy	12 months
Estimated recovery time for securities for which the issuer is financially troubled but not in bankruptcy	24 months

Summary of Significant Accoun_8

Summary of Significant Accounting Policies (Details) - Additional Details $ in Millions	12 Months Ended
	Dec. 31, 2018USD ($)businessessegment	Dec. 31, 2017USD ($)	Dec. 31, 2016
Accounting Policies [Abstract]
Minimum collateral provided by borrowers of securities, as a percentage of the market value of the loaned securities plus accrued interest	102.00%
Number of reporting units for which the Company performs a review of goodwill held | segment	3
Number of operating segments | segment	3
Number of reportable segments | segment	3
Liability for guaranty fund and other insurance-related assessments | $	$ 217	$ 231
Recoverables for liability for guaranty fund and other insurance-related assessments | $	$ 16	$ 16
Minimum expected payment period for loss-based assessments and recoveries	1 year	1 year
Net written premiums for participating dividend policies as a percent of total Company net written premiums	1.00%	1.00%	1.00%
Liability accrued for policyholder dividends | $	$ 72	$ 67
Percentage of capital provided by International for its syndicate at Lloyd's	100.00%
Number of principal business units through which the Company's syndicate at Lloyd's writes business | businesses	6

Summary of Significant Accoun_9

Summary of Significant Accounting Policies (Details) - Equity Method Investment	Dec. 31, 2018
Junto - Brazilian joint venture [Member]
Equity method investment
Percent of common stock owned	49.50%
Junto Holding Latam S.A. [Member]
Equity method investment
Percent of common stock owned	49.50%

Segment Information (Details)

Segment Information (Details) $ in Millions		3 Months Ended								12 Months Ended
		Dec. 31, 2018USD ($)	Sep. 30, 2018USD ($)	Jun. 30, 2018USD ($)	Mar. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Sep. 30, 2017USD ($)	Jun. 30, 2017USD ($)	Mar. 31, 2017USD ($)	Dec. 31, 2018USD ($)segment	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Segment reporting information
Number of reportable segments | segment										3
Premiums										$ 27,059	$ 25,683	$ 24,534
Net investment income										2,474	2,397	2,302
Fee income										432	447	458
Other revenues										203	159	263
Income tax expense (benefit)		$ 125	$ 97	$ 107	$ 109	$ 309	$ 27	$ 195	$ 143	438	674	1,039
Net realized investment gains	[1]									114	216	68
Total revenues		7,796	7,723	7,477	7,286	7,451	7,325	7,184	6,942	30,282	28,902	27,625
Core income (loss)										2,430	2,043	2,967
Net realized investment gains, net of tax										93	142	47
Impact of Tax Cuts and Jobs Act of 2017 at enactment											(129)
Net income		$ 621	$ 709	$ 524	$ 669	$ 551	$ 293	$ 595	$ 617	2,523	2,056	3,014
Domestic [Member]
Segment reporting information
Total revenues										28,418	27,253	25,904
International [Member]
Segment reporting information
Total revenues										1,864	1,649	1,721
Reportable segments [Member]
Segment reporting information
Premiums										27,059	25,683	24,534
Net investment income										2,474	2,397	2,302
Fee income										432	447	458
Other revenues										201	153	252
Total segment revenues										30,166	28,680	27,546
Amortization and depreciation										5,177	4,972	4,804
Income tax expense (benefit)										499	612	1,157
Core income (loss)										2,728	2,297	3,211
Reportable segments [Member] | Business Insurance [Member]
Segment reporting information
Premiums										14,722	14,146	13,855
Net investment income										1,833	1,786	1,701
Fee income										412	430	442
Other revenues										112	69	168
Total segment revenues										17,079	16,431	16,166
Amortization and depreciation										2,943	2,852	2,783
Income tax expense (benefit)										259	448	656
Core income (loss)										1,638	1,613	1,982
Reportable segments [Member] | Business Insurance [Member] | Domestic [Member]
Segment reporting information
Premiums										13,657	13,143	12,904
Reportable segments [Member] | Business Insurance [Member] | Domestic [Member] | Workers' compensation [Member]
Segment reporting information
Premiums										3,899	3,962	3,969
Reportable segments [Member] | Business Insurance [Member] | Domestic [Member] | Automobile [Member]
Segment reporting information
Premiums										2,388	2,132	2,010
Reportable segments [Member] | Business Insurance [Member] | Domestic [Member] | Commercial property [Member]
Segment reporting information
Premiums										1,828	1,775	1,769
Reportable segments [Member] | Business Insurance [Member] | Domestic [Member] | General liability [Member]
Segment reporting information
Premiums										2,181	2,047	1,977
Reportable segments [Member] | Business Insurance [Member] | Domestic [Member] | Commercial multi-peril [Member]
Segment reporting information
Premiums										3,333	3,198	3,148
Reportable segments [Member] | Business Insurance [Member] | Domestic [Member] | Other [Member]
Segment reporting information
Premiums										28	29	31
Reportable segments [Member] | Business Insurance [Member] | International [Member]
Segment reporting information
Premiums										1,065	1,003	951
Reportable segments [Member] | Bond & Specialty Insurance [Member]
Segment reporting information
Premiums										2,420	2,307	2,260
Net investment income										233	228	239
Other revenues										23	24	21
Total segment revenues										2,676	2,559	2,520
Amortization and depreciation										515	493	491
Income tax expense (benefit)										198	208	309
Core income (loss)										793	556	712
Reportable segments [Member] | Bond & Specialty Insurance [Member] | Domestic [Member]
Segment reporting information
Premiums										2,216	2,126	2,088
Reportable segments [Member] | Bond & Specialty Insurance [Member] | Domestic [Member] | General liability [Member]
Segment reporting information
Premiums										1,004	962	946
Reportable segments [Member] | Bond & Specialty Insurance [Member] | Domestic [Member] | Fidelity and surety [Member]
Segment reporting information
Premiums										1,017	977	962
Reportable segments [Member] | Bond & Specialty Insurance [Member] | Domestic [Member] | Other [Member]
Segment reporting information
Premiums										195	187	180
Reportable segments [Member] | Bond & Specialty Insurance [Member] | International [Member]
Segment reporting information
Premiums										204	181	172
Reportable segments [Member] | Personal Insurance [Member]
Segment reporting information
Premiums										9,917	9,230	8,419
Net investment income										408	383	362
Fee income										20	17	16
Other revenues										66	60	63
Total segment revenues										10,411	9,690	8,860
Amortization and depreciation										1,719	1,627	1,530
Income tax expense (benefit)										42	(44)	192
Core income (loss)										297	128	517
Reportable segments [Member] | Personal Insurance [Member] | Domestic [Member]
Segment reporting information
Premiums										9,232	8,598	7,826
Reportable segments [Member] | Personal Insurance [Member] | Domestic [Member] | Automobile [Member]
Segment reporting information
Premiums										5,097	4,655	4,013
Reportable segments [Member] | Personal Insurance [Member] | Domestic [Member] | Homeowners and Other [Member]
Segment reporting information
Premiums										4,135	3,943	3,813
Reportable segments [Member] | Personal Insurance [Member] | International [Member]
Segment reporting information
Premiums										685	632	593
Other [Member]
Segment reporting information
Other revenues										2	6	11
Core income (loss)										(298)	(254)	(244)
After-tax interest expense										$ 278	$ 240	$ 236
[1]	Total other-than-temporary impairment (OTTI) losses were $(1) million, $(13) million and $(40) million for the years ended December 31, 2018, 2017 and 2016, respectively. Of total OTTI, credit losses of $(1) million, $(14) million and $(29) million for the years ended December 31, 2018, 2017 and 2016, respectively, were recognized in net realized investment gains. In addition, unrealized gains (losses) from other changes in total OTTI of $0 million, $1 million and $(11) million for the years ended December 31, 2018, 2017 and 2016, respectively, were recognized in other comprehensive income (loss) as part of changes in net unrealized gains (losses) on investment securities having credit losses recognized in the consolidated statement of income.

Segment Information (Details) -

Segment Information (Details) - Net Written Premiums - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment reporting information
Net written premiums	$ 27,708	$ 26,219	$ 24,958
Business Insurance [Member]
Segment reporting information
Net written premiums	14,956	14,270	13,900
Business Insurance [Member] | Domestic [Member]
Segment reporting information
Net written premiums	13,872	13,257	12,945
Business Insurance [Member] | Domestic [Member] | Select Accounts [Member]
Segment reporting information
Net written premiums	2,828	2,800	2,729
Business Insurance [Member] | Domestic [Member] | Middle Market [Member]
Segment reporting information
Net written premiums	8,214	7,756	7,379
Business Insurance [Member] | Domestic [Member] | National Accounts [Member]
Segment reporting information
Net written premiums	1,025	1,010	1,058
Business Insurance [Member] | Domestic [Member] | National Property and Other [Member]
Segment reporting information
Net written premiums	1,805	1,691	1,779
Business Insurance [Member] | International [Member]
Segment reporting information
Net written premiums	1,084	1,013	955
Bond & Specialty Insurance [Member]
Segment reporting information
Net written premiums	2,528	2,359	2,271
Bond & Specialty Insurance [Member] | Domestic [Member]
Segment reporting information
Net written premiums	2,290	2,160	2,099
Bond & Specialty Insurance [Member] | Domestic [Member] | Management Liability [Member]
Segment reporting information
Net written premiums	1,455	1,367	1,342
Bond & Specialty Insurance [Member] | Domestic [Member] | Surety [Member]
Segment reporting information
Net written premiums	835	793	757
Bond & Specialty Insurance [Member] | International [Member]
Segment reporting information
Net written premiums	238	199	172
Personal Insurance [Member]
Segment reporting information
Net written premiums	10,224	9,590	8,787
Personal Insurance [Member] | Domestic [Member]
Segment reporting information
Net written premiums	9,516	8,940	8,184
Personal Insurance [Member] | Domestic [Member] | Total Agency [Member]
Segment reporting information
Net written premiums	9,120	8,579	7,875
Personal Insurance [Member] | Domestic [Member] | Agency Automobile [Member]
Segment reporting information
Net written premiums	4,972	4,646	4,103
Personal Insurance [Member] | Domestic [Member] | Agency Homeowners and Other [Member]
Segment reporting information
Net written premiums	4,148	3,933	3,772
Personal Insurance [Member] | Domestic [Member] | Direct-to-Consumer [Member]
Segment reporting information
Net written premiums	396	361	309
Personal Insurance [Member] | International [Member]
Segment reporting information
Net written premiums	$ 708	$ 650	$ 603

Segment Information (Details)_2

Segment Information (Details) - Assets by Segment - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Assets by segment
Total assets	$ 104,233	$ 103,483
Reportable segments [Member]
Assets by segment
Total assets	103,601	102,807
Reportable segments [Member] | Business Insurance [Member]
Assets by segment
Total assets	78,965	78,082
Reportable segments [Member] | Bond & Specialty Insurance [Member]
Assets by segment
Total assets	8,693	8,776
Reportable segments [Member] | Personal Insurance [Member]
Assets by segment
Total assets	15,943	15,949
Other assets [Member]
Assets by segment
Total assets	$ 632	$ 676

Segment Information (Details)_3

Segment Information (Details) - Enterprise-Wide Disclosures - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues based on location
Benchmark percentage of revenue transactions from a single customer									10.00%	10.00%	10.00%
Total revenues	$ 7,796	$ 7,723	$ 7,477	$ 7,286	$ 7,451	$ 7,325	$ 7,184	$ 6,942	$ 30,282	$ 28,902	$ 27,625
United States [Member]
Revenues based on location
Total revenues									28,418	27,253	25,904
Non-U.S. [Member]
Revenues based on location
Total revenues									1,864	1,649	1,721
Canada
Revenues based on location
Total revenues									1,293	1,232	1,154
Other Non-U.S. [Member]
Revenues based on location
Total revenues									$ 571	$ 417	$ 567

Investments (Details) - Fixed M

Investments (Details) - Fixed Maturities - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Investment disclosure details
Fixed maturities, amortized cost	$ 63,601	$ 61,316
Gross unrealized gains	712	1,556
Gross unrealized losses	849	178
Fixed maturities, at fair value	63,464	62,694
U.S. Treasury securities and obligations of U.S. government and government agencies and authorities [Member]
Investment disclosure details
Fixed maturities, amortized cost	2,076	2,080
Gross unrealized gains	4	4
Gross unrealized losses	16	8
Fixed maturities, at fair value	2,064	2,076
Obligations of states, municipalities and political subdivisions [Member]
Investment disclosure details
Fixed maturities, amortized cost	28,329	29,996
Gross unrealized gains	489	968
Gross unrealized losses	207	49
Fixed maturities, at fair value	28,611	30,915
Obligations of states, municipalities and political subdivisions, local general obligation [Member]
Investment disclosure details
Fixed maturities, amortized cost	14,473	13,488
Gross unrealized gains	219	444
Gross unrealized losses	120	26
Fixed maturities, at fair value	14,572	13,906
Obligations of states, municipalities and political subdivisions, revenue [Member]
Investment disclosure details
Fixed maturities, amortized cost	9,755	11,307
Gross unrealized gains	172	338
Gross unrealized losses	74	19
Fixed maturities, at fair value	9,853	11,626
Obligations of states, municipalities and political subdivisions, state general obligation [Member]
Investment disclosure details
Fixed maturities, amortized cost	1,329	1,443
Gross unrealized gains	18	44
Gross unrealized losses	13	3
Fixed maturities, at fair value	1,334	1,484
Obligations of states, municipalities and political subdivisions, pre-refunded [Member]
Investment disclosure details
Fixed maturities, amortized cost	2,772	3,758
Gross unrealized gains	80	142
Gross unrealized losses		1
Fixed maturities, at fair value	2,852	3,899
Debt securities issued by foreign governments [Member]
Investment disclosure details
Fixed maturities, amortized cost	1,255	1,505
Gross unrealized gains	7	14
Gross unrealized losses	5	10
Fixed maturities, at fair value	1,257	1,509
Mortgage-backed securities, collateralized mortgage obligations and pass-through securities [Member]
Investment disclosure details
Fixed maturities, amortized cost	2,557	2,334
Gross unrealized gains	54	87
Gross unrealized losses	38	11
Fixed maturities, at fair value	2,573	2,410
All other corporate bonds [Member]
Investment disclosure details
Fixed maturities, amortized cost	29,307	25,311
Gross unrealized gains	156	478
Gross unrealized losses	583	100
Fixed maturities, at fair value	28,880	25,689
Redeemable preferred stock [Member]
Investment disclosure details
Fixed maturities, amortized cost	77	90
Gross unrealized gains	2	5
Fixed maturities, at fair value	$ 79	$ 95

Investments Investments (Detail

Investments Investments (Details) - Contractual Maturities - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Investments [Abstract]
Fixed maturities, due in one year or less, amortized cost	$ 4,489
Fixed maturities, due after 1 year through 5 years, amortized cost	17,020
Fixed maturities, due after 5 years through 10 years, amortized cost	17,030
Fixed maturities, due after 10 years, amortized cost	22,505
Fixed maturities excluding mortgage-backed securities, collateralized mortgage obligations and pass-through securities, amortized cost	61,044
Mortgage-backed securities, collateralized mortgage obligations and pass-through securities, amortized cost	2,557
Fixed maturities, amortized cost	63,601	$ 61,316
Fixed maturities, due in one year or less, fair value	4,505
Fixed maturities, due after 1 year through 5 years, fair value	17,021
Fixed maturities, due after 5 years through 10 years, fair value	16,785
Fixed maturities, due after 10 years, fair value	22,580
Fixed maturities excluding mortgage-backed securities, collateralized mortgage obligations and pass-through securities, fair value	60,891
Mortgage-backed securities, collateralized mortgage obligations and pass-through securities, fair value	2,573
Fixed maturities, at fair value	$ 63,464	$ 62,694

Investments (Details) - Fixed_2

Investments (Details) - Fixed Maturities Narrative - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Investment disclosure details
Fixed maturities, at fair value	$ 63,464	$ 62,694
Securities on loan as part of a tri-party lending agreement	367	304
Proceeds from sales of fixed maturities classified as available for sale	3,546	1,854	$ 1,417
Gross realized gains on sales of fixed maturities	51	42	79
Gross realized losses on sales of fixed maturities	18	38	$ 20
Insurance subsidiaries' securities on deposit at financial institutions in certain states pursuant to the respective states' insurance regulatory requirements	4,230	4,410
Fair value of funds deposited with third parties to be used as collateral to secure various liabilities on behalf of insureds, cedants and other creditors	37	35
Fair value of other investments pledged as collateral securing outstanding letters of credit	1	1
Subsidiary [Member]
Investment disclosure details
Fair value of owned securities pledged into a Lloyd's trust account to support capital requirements for the Company's operations at Lloyd's	115	37
TRV [Member]
Investment disclosure details
Fixed maturities, at fair value	84	82
Fair value of owned securities pledged into a Lloyd's trust account to support capital requirements for the Company's operations at Lloyd's	33	33
Obligations of states, municipalities and political subdivisions, pre-refunded [Member]
Investment disclosure details
Fixed maturities, at fair value	2,852	3,899
Mortgage-backed securities, collateralized mortgage obligations and pass-through securities [Member]
Investment disclosure details
Fixed maturities, at fair value	2,573	2,410
Residential mortgage-backed pass-through securities classified as available-for-sale, GNMA, FNMA, FHLMC and Canadian Government [Member]
Investment disclosure details
Fixed maturities, at fair value	859	804
Residential collateralized mortgage obligations [Member]
Investment disclosure details
Fixed maturities, at fair value	$ 1,710	$ 1,610
Percent guaranteed by or fully collateralized by securities issued by GNMA, FNMA or FHLMC	52.00%	55.00%
Non-guaranteed residential collateralized mortgage obligations [Member]
Investment disclosure details
Fixed maturities, at fair value	$ 828	$ 717
Commercial mortgage-backed securities [Member]
Investment disclosure details
Fixed maturities, at fair value	1,220	1,170
Commercial mortgage-backed securities, containing guarantees by the U.S. government or a government-sponsored enterprise [Member]
Investment disclosure details
Fixed maturities, at fair value	458	475
Commercial mortgage-backed securities, non-guaranteed securities [Member]
Investment disclosure details
Fixed maturities, at fair value	$ 759	$ 693

Investments (Details) - Equity

Investments (Details) - Equity Securities $ in Millions	12 Months Ended
	Dec. 31, 2018USD ($)
Investment disclosure details
Equity securities, cost	$ 382
Gross gains	10
Gross losses	24
Equity securities, at fair value	368
Net recognized losses on equity securities still held	29
Public common stock [Member]
Investment disclosure details
Equity securities, cost	338
Gross gains	2
Gross losses	24
Equity securities, at fair value	316
Non-redeemable preferred stock [Member]
Investment disclosure details
Equity securities, cost	44
Gross gains	8
Equity securities, at fair value	$ 52

Investments (Details) - Availab

Investments (Details) - Available for Sale Equity Securities - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Investment disclosure details
Equity securities available for sale, cost	$ 440
Gross gains	20
Gross losses	7
Equity securities, available for sale, at fair value	453
Proceeds from sales of equity securities classified as available for sale	765	$ 92
Equity securities [Member]
Investment disclosure details
Gross realized gains	239	17
Gross realized losses	3	$ 3
Public common stock [Member]
Investment disclosure details
Equity securities available for sale, cost	332
Gross gains	8
Gross losses	1
Equity securities, available for sale, at fair value	339
Non-redeemable preferred stock [Member]
Investment disclosure details
Equity securities available for sale, cost	108
Gross gains	12
Gross losses	6
Equity securities, available for sale, at fair value	$ 114

Investments (Details) - Additio

Investments (Details) - Additional Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Investments [Abstract]
Proceeds from sales of real estate investments	$ 74	$ 23	$ 69
Gross gains on sales of real estate investments	23	10	7
Gross losses on sales of real estate investments	0	0	$ 0
Accumulated depreciation on real estate held for investment purposes	383	364
Future minimum rental income expected on operating leases relating to the Company's real estate properties for 2019	101
Future minimum rental income expected on operating leases relating to the Company's real estate properties for 2020	90
Future minimum rental income expected on operating leases relating to the Company's real estate properties for 2021	77
Future minimum rental income expected on operating leases relating to the Company's real estate properties for 2022	62
Future minimum rental income expected on operating leases relating to the Company's real estate properties for 2023	39
Future minimum rental income expected on operating leases relating to the Company's real estate properties for 2024 and thereafter	$ 75
Combined average days to maturity of short-term securities (in days)	54 days
Amortized cost of short-term securities (which approximates fair value)	$ 3,985	$ 4,895
Minimum percentage of equity interest that must be held by the Company in order for the investment in a VIE to be considered significant	20.00%

Investments (Details) - Unreali

Investments (Details) - Unrealized Losses - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Investment disclosure details
Continuous unrealized loss position, less than 12 months, fair value		$ 9,153
Continuous unrealized loss position, less than 12 months, gross unrealized losses		68
Continuous unrealized loss position, 12 months or longer, fair value		5,870
Continuous unrealized loss position, 12 months or longer, gross unrealized losses		117
Continuous unrealized loss position, total, fair value		15,023
Continuous unrealized loss position, total, gross unrealized losses		185
Investment disclosure details
Continuous unrealized loss position, less than 12 months, fair value	$ 19,036	9,132
Continuous unrealized loss position, less than 12 months, gross unrealized losses	399	68
Continuous unrealized loss position, 12 months or longer, fair value	12,579	5,780
Continuous unrealized loss position, 12 months or longer, gross unrealized losses	450	110
Continuous unrealized loss position, total, fair value	31,615	14,912
Continuous unrealized loss position, total, gross unrealized losses	849	178
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	484	1,150
Continuous unrealized loss position, less than 12 months, gross unrealized losses	5	5
Continuous unrealized loss position, 12 months or longer, fair value	1,011	470
Continuous unrealized loss position, 12 months or longer, gross unrealized losses	11	3
Continuous unrealized loss position, total, fair value	1,495	1,620
Continuous unrealized loss position, total, gross unrealized losses	16	8
Obligations of states, municipalities and political subdivisions [Member]
Investment disclosure details
Continuous unrealized loss position, less than 12 months, fair value	5,241	505
Continuous unrealized loss position, less than 12 months, gross unrealized losses	82	2
Continuous unrealized loss position, 12 months or longer, fair value	3,298	2,959
Continuous unrealized loss position, 12 months or longer, gross unrealized losses	125	47
Continuous unrealized loss position, total, fair value	8,539	3,464
Continuous unrealized loss position, total, gross unrealized losses	207	49
Debt securities issued by foreign governments [Member]
Investment disclosure details
Continuous unrealized loss position, less than 12 months, fair value	96	394
Continuous unrealized loss position, less than 12 months, gross unrealized losses		6
Continuous unrealized loss position, 12 months or longer, fair value	328	111
Continuous unrealized loss position, 12 months or longer, gross unrealized losses	5	4
Continuous unrealized loss position, total, fair value	424	505
Continuous unrealized loss position, total, gross unrealized losses	5	10
Mortgage-backed securities, collateralized mortgage obligations and pass-through securities [Member]
Investment disclosure details
Continuous unrealized loss position, less than 12 months, fair value	593	1,021
Continuous unrealized loss position, less than 12 months, gross unrealized losses	9	7
Continuous unrealized loss position, 12 months or longer, fair value	1,070	250
Continuous unrealized loss position, 12 months or longer, gross unrealized losses	29	4
Continuous unrealized loss position, total, fair value	1,663	1,271
Continuous unrealized loss position, total, gross unrealized losses	38	11
All other corporate bonds [Member]
Investment disclosure details
Continuous unrealized loss position, less than 12 months, fair value	12,622	6,062
Continuous unrealized loss position, less than 12 months, gross unrealized losses	303	48
Continuous unrealized loss position, 12 months or longer, fair value	6,872	1,990
Continuous unrealized loss position, 12 months or longer, gross unrealized losses	280	52
Continuous unrealized loss position, total, fair value	19,494	8,052
Continuous unrealized loss position, total, gross unrealized losses	$ 583	100
Equity securities [Member]
Investment disclosure details
Continuous unrealized loss position, less than 12 months, fair value		21
Continuous unrealized loss position, 12 months or longer, fair value		90
Continuous unrealized loss position, 12 months or longer, gross unrealized losses		7
Continuous unrealized loss position, total, fair value		111
Continuous unrealized loss position, total, gross unrealized losses		7
Public common stock [Member]
Investment disclosure details
Continuous unrealized loss position, less than 12 months, fair value		18
Continuous unrealized loss position, 12 months or longer, fair value		34
Continuous unrealized loss position, 12 months or longer, gross unrealized losses		1
Continuous unrealized loss position, total, fair value		52
Continuous unrealized loss position, total, gross unrealized losses		1
Non-redeemable preferred stock [Member]
Investment disclosure details
Continuous unrealized loss position, less than 12 months, fair value		3
Continuous unrealized loss position, 12 months or longer, fair value		56
Continuous unrealized loss position, 12 months or longer, gross unrealized losses		6
Continuous unrealized loss position, total, fair value		59
Continuous unrealized loss position, total, gross unrealized losses		$ 6

Investments (Details) - Impairm

Investments (Details) - Impairment Charges - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Investment Information
Fixed maturities impairment charges	$ 1
Total investments impairment charges	1
Impairment charges		$ 14	$ 29
Fixed maturities [Member]
Investment Information
Impairment charges		4	15
All other corporate bonds [Member]
Investment Information
Fixed maturities impairment charges	$ 1
Impairment charges		4	15
Equity securities [Member]
Investment Information
Impairment charges		9	12
Public common stock [Member]
Investment Information
Impairment charges		9	9
Non-redeemable preferred stock [Member]
Investment Information
Impairment charges			3
Other investments [Member]
Investment Information
Impairment charges		$ 1	$ 2

Investments (Details) - OTTI Ro

Investments (Details) - OTTI Rollforward - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Roll-forward of the credit losses on fixed maturities recognized in the consolidated statement of income for which a portion of the other-than-temporary impairment was recognized in other comprehensive income (loss) [Roll Forward]
Cumulative OTTI credit losses recognized for securities held, beginning of period	$ 75	$ 85
Additions for OTTI Securities Where Credit Losses Have Been Previously Recognized		1
Reductions Due to Sales/Defaults of Credit- Impaired Securities	(30)	(7)
Adjustments to Book Value of Credit- Impaired Securities due to Changes in Cash Flows		(4)
Adjustments to Book Value of Credit- Impaired Securities due to Changes in Cash Flows	12
Cumulative OTTI credit losses recognized for securities still held, end of period	57	75
Mortgage-backed securities, collateralized mortgage obligations and pass-through securities [Member]
Roll-forward of the credit losses on fixed maturities recognized in the consolidated statement of income for which a portion of the other-than-temporary impairment was recognized in other comprehensive income (loss) [Roll Forward]
Cumulative OTTI credit losses recognized for securities held, beginning of period	29	31
Reductions Due to Sales/Defaults of Credit- Impaired Securities	(18)
Adjustments to Book Value of Credit- Impaired Securities due to Changes in Cash Flows		(2)
Adjustments to Book Value of Credit- Impaired Securities due to Changes in Cash Flows	4
Cumulative OTTI credit losses recognized for securities still held, end of period	15	29
All other corporate bonds [Member]
Roll-forward of the credit losses on fixed maturities recognized in the consolidated statement of income for which a portion of the other-than-temporary impairment was recognized in other comprehensive income (loss) [Roll Forward]
Cumulative OTTI credit losses recognized for securities held, beginning of period	46	54
Additions for OTTI Securities Where Credit Losses Have Been Previously Recognized		1
Reductions Due to Sales/Defaults of Credit- Impaired Securities	(12)	(7)
Adjustments to Book Value of Credit- Impaired Securities due to Changes in Cash Flows		(2)
Adjustments to Book Value of Credit- Impaired Securities due to Changes in Cash Flows	8
Cumulative OTTI credit losses recognized for securities still held, end of period	$ 42	$ 46

Investments Investments (Deta_2

Investments Investments (Details) - Concentrations and Credit Quality - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Investment disclosure details
Fixed maturities, at fair value	$ 63,464	$ 62,694
Below investment grade [Member]
Investment disclosure details
Fixed maturities, at fair value	1,480	1,670
U.S. Treasury securities and obligations of U.S. government and government agencies and authorities [Member]
Investment disclosure details
Fixed maturities, at fair value	$ 2,064	$ 2,076
Credit Concentration Risk [Member] | Shareholders' equity, total [Member] | U.S. Treasury securities and obligations of U.S. government and government agencies and authorities [Member] | Minimum [Member]
Investment disclosure details
Concentration risk as a percentage of shareholders' equity	5.00%	5.00%

Investments (Details) - Net Inv

Investments (Details) - Net Investment Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Net investment income
Gross investment income	$ 2,513	$ 2,435	$ 2,340
Investment expenses	39	38	38
Net Investment income	2,474	2,397	2,302
Fixed maturities [Member]
Net investment income
Gross investment income	1,980	1,895	1,981
Equity securities [Member]
Net investment income
Gross investment income	16	28	37
Short-term securities [Member]
Net investment income
Gross investment income	92	62	29
Real estate [Member]
Net investment income
Gross investment income	48	44	51
Other investments [Member]
Net investment income
Gross investment income	$ 377	$ 406	$ 242

Investments (Details) - Net Unr

Investments (Details) - Net Unrealized Investment Gains - USD ($) $ in Millions	Jan. 01, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Changes in net unrealized investment gains [Roll Forward]
Changes in net unrealized investment gains		$ (1,819)	$ 522	$ (887)
Income tax expense (benefit)		(349)	110	(289)
Change in net unrealized gain on investment securities, net of tax		(1,470)	412	(598)
Balance, beginning of year	$ (343)	(343)
Balance, end of year		(1,859)	(343)
Total net unrealized gains on investment securities (after-tax)			1,110
Net unrealized gains on investment securities reported in accumulated other comprehensive income (after-tax)			954
Adjustment reported in retained earnings due to the enactment of the Tax Cuts and Jobs Act of 2017			158
Accumulated Other Comprehensive Income (Loss) [Member]
Changes in net unrealized investment gains [Roll Forward]
Changes in net unrealized investment gains		(1,819)	522	(887)
Income tax expense (benefit)		(349)	110	(289)
Change in net unrealized gain on investment securities, net of tax		(1,470)	412	(598)
Cumulative effect of adoption of updated accounting guidance for equity financial instruments	(22)		(22)
Reclassification of certain tax effects from adoption of updated accounting guidance	(24)	(24)
Changes in Net Unrealized Gains on Investment Securities [Member]
Changes in net unrealized investment gains [Roll Forward]
Changes in net unrealized investment gains		(1,516)	302	(862)
Income tax expense (benefit)		(319)	78	(303)
Change in net unrealized gain on investment securities, net of tax		(1,197)	224	(559)
Cumulative effect of adoption of updated accounting guidance for equity financial instruments		(22)
Reclassification of certain tax effects from adoption of updated accounting guidance		152
Balance, beginning of year	$ 954	954	730	1,289
Balance, end of year		(113)	954	730
Changes in Net Unrealized Gains on Investment Securities [Member] | Fixed maturities [Member]
Changes in net unrealized investment gains [Roll Forward]
Changes in net unrealized investment gains		(1,515)	513	(915)
Changes in Net Unrealized Gains on Investment Securities [Member] | Equity securities [Member]
Changes in net unrealized investment gains [Roll Forward]
Changes in net unrealized investment gains			(215)	51
Changes in Net Unrealized Gains on Investment Securities [Member] | Other investments [Member]
Changes in net unrealized investment gains [Roll Forward]
Changes in net unrealized investment gains		$ (1)	$ 4	$ 2

Investments Investments (Deta_3

Investments Investments (Details) - Derivatives - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Futures [Member] | U.S. Treasury notes contracts [Member]
Derivatives
Notional value of open contracts	$ 0	$ 400,000,000

Fair Value Measurements (Detail

Fair Value Measurements (Details) - Additional Information - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Percent of fixed maturities for which a pricing service estimates fair value	99.00%	98.00%
Percent change in monthly price at which securities are further evaluated	10.00%
Fair value of the fixed maturities for which the Company used an internal pricing matrix	$ 82	$ 127
Fair value of the fixed maturities for which the Company received a broker quote	104	$ 77
Estimated fair value of put/call option	$ 10

Fair Value Measurements (Deta_2

Fair Value Measurements (Details) - Fair Value Hierarchy - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Estimated fair value of put/call option reported in other liabilities	$ 10
Recurring basis [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	63,884	$ 63,204
Other liabilities measured on a recurring basis	10
Recurring basis [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	63,464	62,694
Recurring basis [Member] | U.S. Treasury securities and obligations of U.S. government and government agencies and authorities [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	2,064	2,076
Recurring basis [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	28,611	30,915
Recurring basis [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	1,257	1,509
Recurring basis [Member] | Mortgage-backed securities, collateralized mortgage obligations and pass-through securities [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	2,573	2,410
Recurring basis [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	28,880	25,689
Recurring basis [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	79	95
Recurring basis [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	368	453
Recurring basis [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	316	339
Recurring basis [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	52	114
Recurring basis [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	52	57
Recurring basis [Member] | 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	2,429	2,493
Recurring basis [Member] | Level 1 [Member] | Fixed maturities [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	2,067	2,090
Recurring basis [Member] | Level 1 [Member] | U.S. Treasury securities and obligations of U.S. government and government agencies and authorities [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	2,064	2,076
Recurring basis [Member] | 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		11
Recurring basis [Member] | Level 1 [Member] | Redeemable preferred stock [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	3	3
Recurring basis [Member] | 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	346	384
Recurring basis [Member] | 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	316	339
Recurring basis [Member] | 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	30	45
Recurring basis [Member] | 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	16	19
Recurring basis [Member] | Level 1 [Member] | Investments in various publicly-traded securities, including mutual funds and other small holdings [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	16	19
Recurring basis [Member] | 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	61,233	60,469
Recurring basis [Member] | 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	61,211	60,400
Recurring basis [Member] | 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	28,599	30,910
Recurring basis [Member] | 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	1,257	1,509
Recurring basis [Member] | Level 2 [Member] | Mortgage-backed securities, collateralized mortgage obligations and pass-through securities [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	2,554	2,371
Recurring basis [Member] | 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	28,725	25,518
Recurring basis [Member] | 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	76	92
Recurring basis [Member] | 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	22	69
Recurring basis [Member] | 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	22	69
Recurring basis [Member] | 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	222	242
Other liabilities measured on a recurring basis	10
Estimated fair value of put/call option reported in other liabilities	10
Recurring basis [Member] | 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	186	204
Recurring basis [Member] | 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	12	5
Recurring basis [Member] | 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	19	39
Recurring basis [Member] | 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	155	160
Recurring basis [Member] | 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	36	38
Recurring basis [Member] | Level 3 [Member] | Investment in non-public common and preferred equity securities where the fair value estimate is determined either internally or by an external fund manager [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	$ 36	$ 38

Fair Value Measurements (Deta_3

Fair Value Measurements (Details) - Changes in Level 3 - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Changes in Level 3 fair value category [Roll Forward]
Level 3 fair value category, beginning balance	$ 242	$ 220
Level 3 fair value category, total realized and unrealized investment gains (losses) reported in net realized investment gains	9	(1)
Level 3 fair value category, total unrealized investment gains (losses) reported in increases in other comprehensive income (loss)	(4)	4
Level 3 fair value category purchases	149	312
Level 3 fair value category sales	(23)	(2)
Level 3 fair value category settlements/maturities	(71)	(47)
Gross transfers into Level 3	11	21
Gross transfers out of Level 3	(91)	(265)
Level 3 fair value category, ending balance	222	242
Amount of total realized investment gains (losses) for the period included in the consolidated statement of income attributable to changes in the fair value of assets still held at the reporting date		(1)
Fixed maturities [Member]
Changes in Level 3 fair value category [Roll Forward]
Level 3 fair value category, beginning balance	204	184
Level 3 fair value category, total realized and unrealized investment gains (losses) reported in net realized investment gains	2
Level 3 fair value category, total unrealized investment gains (losses) reported in increases in other comprehensive income (loss)	(4)	1
Level 3 fair value category purchases	146	312
Level 3 fair value category sales	(11)	(2)
Level 3 fair value category settlements/maturities	(71)	(47)
Gross transfers into Level 3	11	21
Gross transfers out of Level 3	(91)	(265)
Level 3 fair value category, ending balance	186	204
Other investments [Member]
Changes in Level 3 fair value category [Roll Forward]
Level 3 fair value category, beginning balance	38	36
Level 3 fair value category, total realized and unrealized investment gains (losses) reported in net realized investment gains	7	(1)
Level 3 fair value category, total unrealized investment gains (losses) reported in increases in other comprehensive income (loss)		3
Level 3 fair value category purchases	3
Level 3 fair value category sales	(12)
Level 3 fair value category, ending balance	$ 36	38
Amount of total realized investment gains (losses) for the period included in the consolidated statement of income attributable to changes in the fair value of assets still held at the reporting date		$ (1)

Fair Value Measurements (Deta_4

Fair Value Measurements (Details) - Financial Instruments - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Financial Instruments
Short-term securities	$ 3,985	$ 4,895
Commercial paper	100	100
Carrying Value [Member]
Financial Instruments
Short-term securities	3,985	4,895
Debt	6,464	6,471
Commercial paper	100	100
Fair Value [Member]
Financial Instruments
Short-term securities	3,985	4,895
Debt	7,128	7,702
Commercial paper	100	100
Fair Value [Member] | Level 1 [Member]
Financial Instruments
Short-term securities	632	1,238
Fair Value [Member] | Level 2 [Member]
Financial Instruments
Short-term securities	3,316	3,622
Debt	7,128	7,702
Commercial paper	100	100
Fair Value [Member] | Level 3 [Member]
Financial Instruments
Short-term securities	$ 37	$ 35

Reinsurance Reinsurance (Detail

Reinsurance Reinsurance (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reinsurance Disclosures [Abstract]
Percentage of residual market business written directly by the Company for mandatory pools and associations and then ceded to the mandatory pool	100.00%
Written premiums, direct	$ 28,210	$ 26,648	$ 25,567
Written premiums, assumed	1,042	1,000	928
Written premiums, ceded	(1,544)	(1,429)	(1,537)
Total net written premiums	27,708	26,219	24,958
Earned premiums, direct	27,536	26,189	25,262
Earned premiums, assumed	1,024	965	875
Earned premiums, ceded	(1,501)	(1,471)	(1,603)
Total net earned premiums	$ 27,059	$ 25,683	$ 24,534
Percentage of assumed earned premiums to net earned premiums	3.80%	3.80%	3.60%
Ceded claims and claim adjustment expenses incurred	$ 1,293	$ 1,225	$ 762
Gross reinsurance recoverables on paid and unpaid claims and claim adjustment expenses	3,485	3,303
Allowance for uncollectible reinsurance	(110)	(111)
Net reinsurance recoverables	3,375	3,192
Mandatory pools and associations	2,005	2,011
Structured settlements	2,990	3,106
Total reinsurance recoverables	8,370	$ 8,309
Terrorism Risk Insurance Program, annual aggregate industry loss minimum in order for a loss to be covered, next fiscal year	180
Terrorism Risk Insurance Program, ultimate annual aggregate industry loss minimum in order for a loss to be covered	$ 200
Terrorism Risk Insurance Program, percentage of subject losses reimbursed by the Federal Government, after insurer deductible, subject to annual cap, next fiscal year	81.00%
Terrorism Risk Insurance Program, ultimate percentage of subject losses reimbursed by the Federal Government, after insurer deductible, subject to annual cap	80.00%
Terrorism Risk Insurance Program, percentage of insurer's direct earned premiums for covered lines for the preceding calendar year at which the deductible is set	20.00%
Terrorism Risk Insurance Program, Company's estimated deductible for the next fiscal year	$ 2,520
Terrorism Risk Insurance Program, annual cap limiting amount of aggregate subject losses for all participating insurers	$ 100,000

Goodwill and Other Intangible_3

Goodwill and Other Intangible Assets (Details) - Goodwill - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Goodwill by segment
Goodwill	$ 3,937	$ 3,951
Reportable segments [Member] | Business Insurance [Member]
Goodwill by segment
Goodwill	2,585	2,585
Reportable segments [Member] | Business Insurance [Member] | Business Acquisition [Member]
Goodwill by segment
Goodwill	26
Amount of goodwill expected to be deductible for tax purposes	0
Reportable segments [Member] | Bond & Specialty Insurance [Member]
Goodwill by segment
Goodwill	550	550
Reportable segments [Member] | Personal Insurance [Member]
Goodwill by segment
Goodwill	776	790
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	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Other intangible assets by major asset class
Intangible assets subject to amortization, gross carrying amount	$ 306	$ 286
Intangible assets subject to amortization, accumulated amortization	187	171
Intangible assets subject to amortization, net	119	115
Intangible assets not subject to amortization	226	227
Total other intangible assets, gross carrying amount	532	513
Total other intangible assets, net	345	342
Amortization expense of intangible assets	17	13	$ 11
Estimated intangible asset amortization expense, 2019	16
Estimated intangible asset amortization expense, 2020	15
Estimated intangible asset amortization expense, 2021	14
Estimated intangible asset amortization expense, 2022	13
Estimated intangible asset amortization expense, 2023	12
Customer-related [Member]
Other intangible assets by major asset class
Intangible assets subject to amortization, gross carrying amount	98	77
Intangible assets subject to amortization, accumulated amortization	12	4
Intangible assets subject to amortization, net	86	73
Contract-based [Member]
Other intangible assets by major asset class
Intangible assets subject to amortization, gross carrying amount	208	209
Intangible assets subject to amortization, accumulated amortization	175	167
Intangible assets subject to amortization, net	33	$ 42
Insurance Contracts Acquired in Business Combination [Member]
Other intangible assets by major asset class
Estimated intangible asset amortization expense, 2019	6
Estimated intangible asset amortization expense, 2020	5
Estimated intangible asset amortization expense, 2021	4
Estimated intangible asset amortization expense, 2022	3
Estimated intangible asset amortization expense, 2023	$ 3

Insurance Claim Reserves (Detai

Insurance Claim Reserves (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
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	$ 49,650
Net reserves at end of year	42,471
Reinsurance recoverables on unpaid losses	8,197
Claims and claim adjustment expense reserves at end of year	50,668	$ 49,650
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	49,633	47,929	$ 48,272
Reinsurance recoverables on unpaid losses	8,123	7,981	8,449
Net reserves at beginning of year	41,510	39,948	39,823
Estimated claims and claim adjustment expenses for claims arising in the current year	18,614	17,846	15,675
Estimated decrease in claims and claim adjustment expenses for claims arising in prior years	(406)	(458)	(680)
Total increases	18,208	17,388	14,995
Claims and claim adjustment expense payments for claims arising in current year	7,697	7,335	6,220
Claims and claim adjustment expense payments for claims arising in prior years	9,363	8,708	8,576
Total payments	17,060	16,043	14,796
Unrealized foreign exchange loss (gain)	(187)	217	(74)
Net reserves at end of year	42,471	41,510	39,948
Reinsurance recoverables on unpaid losses	8,182	8,123	7,981
Claims and claim adjustment expense reserves at end of year	50,653	49,633	47,929
Amount of increase in gross claims and claim adjustment expense reserves	1,020	1,700
Amount of increase in reinsurance recoverables on unpaid losses	$ 59	$ 142
Reserves for long-term disability and annuity claim payments primarily arising from workers' compensation insurance and workers' compensation excess insurance policies, discount rate (percent)	5.00%	5.00%
Reserves for long-term disability and annuity claim payments primarily arising from workers' compensation insurance and workers' compensation excess insurance policies, net of discount	$ 2,450	$ 2,320
Discount included in reserves for long-term disability and annuity claim payments primarily arising from workers' compensation insurance and workers' compensation excess insurance policies	1,160	1,100
Accretion expense	49	50	$ 50
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	17
Reinsurance recoverables on unpaid losses	15
Claims and claim adjustment expense reserves at end of year	$ 15	$ 17

Insurance Claim Reserves (Det_2

Insurance Claim Reserves (Details) - Prior Year Reserve Development - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Asbestos reserves [Member]
Liability for claims and claim adjustment expense
Increase to asbestos and environmental claims	$ 225	$ 225	$ 225
Environmental reserves [Member]
Liability for claims and claim adjustment expense
Increase to asbestos and environmental claims	55	65	82
Property-casualty [Member]
Liability for claims and claim adjustment expense
Net favorable prior year reserve development included in estimated claims and claim adjustment expenses incurred for claims arising in prior years	406	458	680
Net favorable (unfavorable) prior year reserve development impacting the Company's results of operations	517	592	771
Property-casualty [Member] | Business Insurance [Member]
Liability for claims and claim adjustment expense
Net favorable (unfavorable) prior year reserve development impacting the Company's results of operations	142	439	424
Property-casualty [Member] | Business Insurance [Member] | Asbestos reserves [Member]
Liability for claims and claim adjustment expense
Increase to asbestos and environmental claims	225	225	225
Property-casualty [Member] | Business Insurance [Member] | Environmental reserves [Member]
Liability for claims and claim adjustment expense
Increase to asbestos and environmental claims	55	65	82
Property-casualty [Member] | 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	266	140	350
Property-casualty [Member] | Personal Insurance [Member]
Liability for claims and claim adjustment expense
Net favorable (unfavorable) prior year reserve development impacting the Company's results of operations	$ 109	$ 13	$ (3)

Insurance Claim Reserves (Det_3

Insurance Claim Reserves (Details) - Claims and Claim Adjustment Expenses Reserves Summary - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability
Net Undiscounted Claims and Claim Adjustment Expense Reserves	$ 43,559
Discount (Net of Reinsurance)	(1,088)
Subtotal: Net Claims and Claim Adjustment Expense Reserves	42,471
Reinsurance Recoverables on Unpaid Losses	8,197
Claims and Claim Adjustment Expense Reserves	50,668	$ 49,650
Discount on reinsurance recoverables for long-term disability and annuity claim payments included in discount (net of reinsurance)	70
Total reinsurance recoverables	8,370	8,309
Property-casualty [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability
Net Undiscounted Claims and Claim Adjustment Expense Reserves	43,559
Discount (Net of Reinsurance)	(1,088)
Subtotal: Net Claims and Claim Adjustment Expense Reserves	42,471	41,510	$ 39,948	$ 39,823
Reinsurance Recoverables on Unpaid Losses	8,182	8,123	7,981	8,449
Claims and Claim Adjustment Expense Reserves	50,653	49,633	$ 47,929	$ 48,272
Accident and health [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability
Reinsurance Recoverables on Unpaid Losses	15
Claims and Claim Adjustment Expense Reserves	15	$ 17
Business Insurance [Member] | General liability [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability
Net Undiscounted Claims and Claim Adjustment Expense Reserves	7,159
Business Insurance [Member] | Commercial property [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability
Net Undiscounted Claims and Claim Adjustment Expense Reserves	973
Business Insurance [Member] | Commercial multi-peril [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability
Net Undiscounted Claims and Claim Adjustment Expense Reserves	3,535
Business Insurance [Member] | Automobile [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability
Net Undiscounted Claims and Claim Adjustment Expense Reserves	2,861
Business Insurance [Member] | Workers' compensation [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability
Net Undiscounted Claims and Claim Adjustment Expense Reserves	16,039
Bond & Specialty Insurance [Member] | General liability [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability
Net Undiscounted Claims and Claim Adjustment Expense Reserves	1,833
Bond & Specialty Insurance [Member] | Fidelity and surety [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability
Net Undiscounted Claims and Claim Adjustment Expense Reserves	419
Personal Insurance [Member] | Automobile [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability
Net Undiscounted Claims and Claim Adjustment Expense Reserves	2,776
Personal Insurance [Member] | Homeowners (excluding Other) [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability
Net Undiscounted Claims and Claim Adjustment Expense Reserves	1,376
Personal Insurance [Member] | International - Canada [Member] | Property-casualty [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability
Net Undiscounted Claims and Claim Adjustment Expense Reserves	710
Reportable segments [Member] | Property-casualty [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability
Net Undiscounted Claims and Claim Adjustment Expense Reserves	37,681
Discount (Net of Reinsurance)	(1,083)
Subtotal: Net Claims and Claim Adjustment Expense Reserves	36,598
Reinsurance Recoverables on Unpaid Losses	3,056
Claims and Claim Adjustment Expense Reserves	39,654
Reportable segments [Member] | Business Insurance [Member] | General liability [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability
Net Undiscounted Claims and Claim Adjustment Expense Reserves	7,159
Discount (Net of Reinsurance)	(174)
Subtotal: Net Claims and Claim Adjustment Expense Reserves	6,985
Reinsurance Recoverables on Unpaid Losses	854
Claims and Claim Adjustment Expense Reserves	7,839
Reportable segments [Member] | Business Insurance [Member] | Commercial property [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability
Net Undiscounted Claims and Claim Adjustment Expense Reserves	973
Subtotal: Net Claims and Claim Adjustment Expense Reserves	973
Reinsurance Recoverables on Unpaid Losses	429
Claims and Claim Adjustment Expense Reserves	1,402
Reportable segments [Member] | Business Insurance [Member] | Commercial multi-peril [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability
Net Undiscounted Claims and Claim Adjustment Expense Reserves	3,535
Subtotal: Net Claims and Claim Adjustment Expense Reserves	3,535
Reinsurance Recoverables on Unpaid Losses	181
Claims and Claim Adjustment Expense Reserves	3,716
Reportable segments [Member] | Business Insurance [Member] | Automobile [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability
Net Undiscounted Claims and Claim Adjustment Expense Reserves	2,861
Subtotal: Net Claims and Claim Adjustment Expense Reserves	2,861
Reinsurance Recoverables on Unpaid Losses	226
Claims and Claim Adjustment Expense Reserves	3,087
Reportable segments [Member] | Business Insurance [Member] | Workers' compensation [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability
Net Undiscounted Claims and Claim Adjustment Expense Reserves	16,039
Discount (Net of Reinsurance)	(909)
Subtotal: Net Claims and Claim Adjustment Expense Reserves	15,130
Reinsurance Recoverables on Unpaid Losses	698
Claims and Claim Adjustment Expense Reserves	15,828
Reportable segments [Member] | Bond & Specialty Insurance [Member] | General liability [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability
Net Undiscounted Claims and Claim Adjustment Expense Reserves	1,833
Subtotal: Net Claims and Claim Adjustment Expense Reserves	1,833
Reinsurance Recoverables on Unpaid Losses	152
Claims and Claim Adjustment Expense Reserves	1,985
Reportable segments [Member] | Bond & Specialty Insurance [Member] | Fidelity and surety [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability
Net Undiscounted Claims and Claim Adjustment Expense Reserves	419
Subtotal: Net Claims and Claim Adjustment Expense Reserves	419
Reinsurance Recoverables on Unpaid Losses	7
Claims and Claim Adjustment Expense Reserves	426
Reportable segments [Member] | Personal Insurance [Member] | Automobile [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability
Net Undiscounted Claims and Claim Adjustment Expense Reserves	2,776
Subtotal: Net Claims and Claim Adjustment Expense Reserves	2,776
Reinsurance Recoverables on Unpaid Losses	480
Claims and Claim Adjustment Expense Reserves	3,256
Reportable segments [Member] | Personal Insurance [Member] | Homeowners (excluding Other) [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability
Net Undiscounted Claims and Claim Adjustment Expense Reserves	1,376
Subtotal: Net Claims and Claim Adjustment Expense Reserves	1,376
Reinsurance Recoverables on Unpaid Losses	3
Claims and Claim Adjustment Expense Reserves	1,379
Reportable segments [Member] | Personal Insurance [Member] | International - Canada [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability
Net Undiscounted Claims and Claim Adjustment Expense Reserves	710
Subtotal: Net Claims and Claim Adjustment Expense Reserves	710
Reinsurance Recoverables on Unpaid Losses	26
Claims and Claim Adjustment Expense Reserves	736
Reconciling Items [Member] | Other insurance contracts [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability
Net Undiscounted Claims and Claim Adjustment Expense Reserves	3,762
Discount (Net of Reinsurance)	(5)
Subtotal: Net Claims and Claim Adjustment Expense Reserves	3,757
Reinsurance Recoverables on Unpaid Losses	2,116
Claims and Claim Adjustment Expense Reserves	5,873
Reconciling Items [Member] | Unallocated loss adjustment expense reserves [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability
Net Undiscounted Claims and Claim Adjustment Expense Reserves	2,053
Subtotal: Net Claims and Claim Adjustment Expense Reserves	2,053
Reinsurance Recoverables on Unpaid Losses	37
Claims and Claim Adjustment Expense Reserves	2,090
Reconciling Items [Member] | Structured settlements [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability
Reinsurance Recoverables on Unpaid Losses	2,990
Claims and Claim Adjustment Expense Reserves	2,990
Reconciling Items [Member] | Other [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability
Net Undiscounted Claims and Claim Adjustment Expense Reserves	63
Subtotal: Net Claims and Claim Adjustment Expense Reserves	63
Reinsurance Recoverables on Unpaid Losses	(17)
Claims and Claim Adjustment Expense Reserves	$ 46

Insurance Claim Reserves (Det_4

Insurance Claim Reserves (Details) - Claim Development $ in Millions	Dec. 31, 2018USD ($)item	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)	Dec. 31, 2012USD ($)	Dec. 31, 2011USD ($)	Dec. 31, 2010USD ($)	Dec. 31, 2009USD ($)
Claims Development
Total net liability (Audited)	$ 43,559
Property-casualty [Member]
Claims Development
Total net liability (Audited)	43,559
Business Insurance [Member] | General liability [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	9,850
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	5,640
Liability for Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance, Disclosed Accident Years (Audited)	4,210
Liability for Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance, Before Disclosed Accident Years (Audited)	2,949
Total net liability (Audited)	7,159
Business Insurance [Member] | Commercial property [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	4,655
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	3,825
Liability for Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance, Disclosed Accident Years (Audited)	830
Liability for Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance, Before Disclosed Accident Years (Audited)	143
Total net liability (Audited)	973
Business Insurance [Member] | Commercial multi-peril [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	17,837
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	14,659
Liability for Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance, Disclosed Accident Years (Audited)	3,178
Liability for Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance, Before Disclosed Accident Years (Audited)	357
Total net liability (Audited)	3,535
Business Insurance [Member] | Automobile [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	6,993
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	4,339
Liability for Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance, Disclosed Accident Years (Audited)	2,654
Liability for Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance, Before Disclosed Accident Years (Audited)	207
Total net liability (Audited)	2,861
Business Insurance [Member] | Workers' compensation [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	23,783
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	13,020
Liability for Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance, Disclosed Accident Years (Audited)	10,763
Liability for Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance, Before Disclosed Accident Years (Audited)	5,276
Total net liability (Audited)	16,039
Bond & Specialty Insurance [Member] | General liability [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	5,464
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	3,702
Liability for Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance, Disclosed Accident Years (Audited)	1,762
Liability for Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance, Before Disclosed Accident Years (Audited)	71
Total net liability (Audited)	1,833
Bond & Specialty Insurance [Member] | Fidelity and surety [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	971
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	582
Liability for Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance, Disclosed Accident Years (Audited)	389
Liability for Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance, Before Disclosed Accident Years (Audited)	30
Total net liability (Audited)	419
Personal Insurance [Member] | Automobile [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	13,511
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	10,975
Liability for Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance, Disclosed Accident Years (Audited)	2,536
Liability for Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance, Before Disclosed Accident Years (Audited)	240
Total net liability (Audited)	2,776
Personal Insurance [Member] | Homeowners (excluding Other) [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	9,378
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	8,025
Liability for Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance, Disclosed Accident Years (Audited)	1,353
Liability for Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance, Before Disclosed Accident Years (Audited)	23
Total net liability (Audited)	1,376
Personal Insurance [Member] | International - Canada [Member] | Property-casualty [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	3,982
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	3,306
Liability for Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance, Disclosed Accident Years (Audited)	676
Liability for Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance, Before Disclosed Accident Years (Audited)	34
Total net liability (Audited)	710
Short-duration Insurance Contracts, Accident Year 2009 [Member] | Business Insurance [Member] | General liability [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	775	$ 783	$ 796	$ 809	$ 837	$ 869	$ 960	$ 1,028	$ 1,071	$ 1,060
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	701	689	667	643	613	543	446	314	167	35
IBNR Reserves Dec. 31, 2018 (Audited)	$ 56
Cumulative Number of Reported Claims (Audited) | item	25,702
Short-duration Insurance Contracts, Accident Year 2009 [Member] | Business Insurance [Member] | Commercial multi-peril [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 1,493	1,500	1,509	1,514	1,514	1,511	1,498	1,501	1,506	1,484
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	1,466	1,457	1,449	1,436	1,408	1,360	1,264	1,121	958	603
IBNR Reserves Dec. 31, 2018 (Audited)	$ 21
Cumulative Number of Reported Claims (Audited) | item	103,448
Short-duration Insurance Contracts, Accident Year 2009 [Member] | Business Insurance [Member] | Workers' compensation [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 1,728	1,736	1,750	1,775	1,766	1,753	1,753	1,746	1,778	1,799
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	1,303	1,274	1,235	1,193	1,137	1,065	961	828	623	288
IBNR Reserves Dec. 31, 2018 (Audited)	$ 221
Cumulative Number of Reported Claims (Audited) | item	104,789
Short-duration Insurance Contracts, Accident Year 2009 [Member] | Bond & Specialty Insurance [Member] | General liability [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 626	631	641	655	660	680	686	665	624	592
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	597	595	592	563	497	460	390	310	167	36
IBNR Reserves Dec. 31, 2018 (Audited)	$ 11
Cumulative Number of Reported Claims (Audited) | item	6,297
Short-duration Insurance Contracts, Accident Year 2009 [Member] | Personal Insurance [Member] | International - Canada [Member] | Property-casualty [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 440	442	449	449	456	464	456	450	442	454
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 434	433	430	419	403	379	350	323	283	$ 189
Cumulative Number of Reported Claims (Audited) | item	55,162
Short-duration Insurance Contracts, Accident Year 2010 [Member] | Business Insurance [Member] | General liability [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 911	908	918	912	927	959	1,021	1,031	1,028
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	800	781	756	702	629	487	324	139	35
IBNR Reserves Dec. 31, 2018 (Audited)	$ 79
Cumulative Number of Reported Claims (Audited) | item	27,911
Short-duration Insurance Contracts, Accident Year 2010 [Member] | Business Insurance [Member] | Commercial multi-peril [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 1,881	1,885	1,898	1,892	1,895	1,861	1,832	1,826	1,711
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	1,834	1,819	1,798	1,763	1,698	1,579	1,395	1,180	709
IBNR Reserves Dec. 31, 2018 (Audited)	$ 32
Cumulative Number of Reported Claims (Audited) | item	111,931
Short-duration Insurance Contracts, Accident Year 2010 [Member] | Business Insurance [Member] | Workers' compensation [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 2,003	2,021	2,055	2,052	2,049	2,056	2,035	2,042	1,886
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	1,465	1,430	1,385	1,321	1,246	1,133	978	750	341
IBNR Reserves Dec. 31, 2018 (Audited)	$ 271
Cumulative Number of Reported Claims (Audited) | item	117,368
Short-duration Insurance Contracts, Accident Year 2010 [Member] | Bond & Specialty Insurance [Member] | General liability [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 657	653	653	668	661	679	679	612	571
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	631	623	597	565	482	396	291	152	33
IBNR Reserves Dec. 31, 2018 (Audited)	$ 18
Cumulative Number of Reported Claims (Audited) | item	5,673
Short-duration Insurance Contracts, Accident Year 2010 [Member] | Personal Insurance [Member] | International - Canada [Member] | Property-casualty [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 457	459	465	469	477	488	475	464	463
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	442	437	425	409	380	351	313	278	$ 182
IBNR Reserves Dec. 31, 2018 (Audited)	$ 5
Cumulative Number of Reported Claims (Audited) | item	54,919
Short-duration Insurance Contracts, Accident Year 2011 [Member] | Business Insurance [Member] | General liability [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 908	913	935	972	998	1,065	1,074	1,004
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	799	762	725	660	539	355	187	47
IBNR Reserves Dec. 31, 2018 (Audited)	$ 80
Cumulative Number of Reported Claims (Audited) | item	27,444
Short-duration Insurance Contracts, Accident Year 2011 [Member] | Business Insurance [Member] | Commercial multi-peril [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 2,279	2,283	2,287	2,296	2,286	2,269	2,244	2,235
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	2,222	2,193	2,156	2,088	1,979	1,803	1,573	1,060
IBNR Reserves Dec. 31, 2018 (Audited)	$ 38
Cumulative Number of Reported Claims (Audited) | item	125,743
Short-duration Insurance Contracts, Accident Year 2011 [Member] | Business Insurance [Member] | Workers' compensation [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 2,348	2,363	2,385	2,379	2,350	2,347	2,303	2,284
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	1,696	1,652	1,583	1,487	1,365	1,185	911	420
IBNR Reserves Dec. 31, 2018 (Audited)	$ 356
Cumulative Number of Reported Claims (Audited) | item	136,728
Short-duration Insurance Contracts, Accident Year 2011 [Member] | Bond & Specialty Insurance [Member] | General liability [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 508	520	545	601	632	639	596	565
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	490	476	447	414	324	249	143	33
IBNR Reserves Dec. 31, 2018 (Audited)	$ (12)
Cumulative Number of Reported Claims (Audited) | item	5,212
Short-duration Insurance Contracts, Accident Year 2011 [Member] | Personal Insurance [Member] | International - Canada [Member] | Property-casualty [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 396	401	406	412	420	424	416	436
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	378	370	353	332	299	266	237	$ 167
IBNR Reserves Dec. 31, 2018 (Audited)	$ 4
Cumulative Number of Reported Claims (Audited) | item	55,783
Short-duration Insurance Contracts, Accident Year 2012 [Member] | Business Insurance [Member] | General liability [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 917	905	892	913	935	985	989
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	754	699	589	489	295	150	32
IBNR Reserves Dec. 31, 2018 (Audited)	$ 98
Cumulative Number of Reported Claims (Audited) | item	24,801
Short-duration Insurance Contracts, Accident Year 2012 [Member] | Business Insurance [Member] | Commercial multi-peril [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 1,859	1,867	1,888	1,888	1,903	1,883	1,885
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	1,780	1,752	1,699	1,590	1,424	1,246	795
IBNR Reserves Dec. 31, 2018 (Audited)	$ 42
Cumulative Number of Reported Claims (Audited) | item	104,800
Short-duration Insurance Contracts, Accident Year 2012 [Member] | Business Insurance [Member] | Workers' compensation [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 2,416	2,453	2,445	2,456	2,457	2,456	2,447
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	1,689	1,629	1,536	1,394	1,217	940	443
IBNR Reserves Dec. 31, 2018 (Audited)	$ 404
Cumulative Number of Reported Claims (Audited) | item	137,922
Short-duration Insurance Contracts, Accident Year 2012 [Member] | Bond & Specialty Insurance [Member] | General liability [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 605	599	601	605	614	591	538
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	436	419	383	342	255	160	38
IBNR Reserves Dec. 31, 2018 (Audited)	$ 97
Cumulative Number of Reported Claims (Audited) | item	4,853
Short-duration Insurance Contracts, Accident Year 2012 [Member] | Personal Insurance [Member] | International - Canada [Member] | Property-casualty [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 355	361	377	378	394	393	413
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	325	317	300	274	249	219	$ 157
IBNR Reserves Dec. 31, 2018 (Audited)	$ 12
Cumulative Number of Reported Claims (Audited) | item	51,226
Short-duration Insurance Contracts, Accident Year 2013 [Member] | Business Insurance [Member] | General liability [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 933	927	940	958	975	965
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	745	639	498	363	175	35
IBNR Reserves Dec. 31, 2018 (Audited)	$ 101
Cumulative Number of Reported Claims (Audited) | item	22,446
Short-duration Insurance Contracts, Accident Year 2013 [Member] | Business Insurance [Member] | Commercial multi-peril [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 1,600	1,591	1,609	1,620	1,623	1,615
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	1,475	1,410	1,304	1,167	987	644
IBNR Reserves Dec. 31, 2018 (Audited)	$ 51
Cumulative Number of Reported Claims (Audited) | item	83,667
Short-duration Insurance Contracts, Accident Year 2013 [Member] | Business Insurance [Member] | Workers' compensation [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 2,423	2,463	2,506	2,540	2,545	2,553
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	1,604	1,525	1,413	1,237	954	458
IBNR Reserves Dec. 31, 2018 (Audited)	$ 473
Cumulative Number of Reported Claims (Audited) | item	132,424
Short-duration Insurance Contracts, Accident Year 2013 [Member] | Bond & Specialty Insurance [Member] | General liability [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 607	654	630	606	565	510
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	434	400	352	252	154	34
IBNR Reserves Dec. 31, 2018 (Audited)	$ 103
Cumulative Number of Reported Claims (Audited) | item	4,442
Short-duration Insurance Contracts, Accident Year 2013 [Member] | Personal Insurance [Member] | International - Canada [Member] | Property-casualty [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 421	422	435	446	455	461
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	368	351	320	289	258	$ 184
IBNR Reserves Dec. 31, 2018 (Audited)	$ 14
Cumulative Number of Reported Claims (Audited) | item	54,231
Short-duration Insurance Contracts, Accident Year 2014 [Member] | Business Insurance [Member] | General liability [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 956	948	983	989	976
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	640	515	321	163	37
IBNR Reserves Dec. 31, 2018 (Audited)	$ 177
Cumulative Number of Reported Claims (Audited) | item	22,108
Short-duration Insurance Contracts, Accident Year 2014 [Member] | Business Insurance [Member] | Commercial property [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 834	835	836	860	936
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	817	803	775	710	464
IBNR Reserves Dec. 31, 2018 (Audited)	$ 6
Cumulative Number of Reported Claims (Audited) | item	21,568
Short-duration Insurance Contracts, Accident Year 2014 [Member] | Business Insurance [Member] | Commercial multi-peril [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 1,626	1,617	1,625	1,627	1,663
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	1,448	1,328	1,154	956	628
IBNR Reserves Dec. 31, 2018 (Audited)	$ 72
Cumulative Number of Reported Claims (Audited) | item	78,097
Short-duration Insurance Contracts, Accident Year 2014 [Member] | Business Insurance [Member] | Automobile [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 1,193	1,171	1,155	1,153	1,156
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	1,089	977	812	611	394
IBNR Reserves Dec. 31, 2018 (Audited)	$ 36
Cumulative Number of Reported Claims (Audited) | item	177,493
Short-duration Insurance Contracts, Accident Year 2014 [Member] | Business Insurance [Member] | Workers' compensation [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 2,430	2,476	2,547	2,553	2,554
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	1,505	1,399	1,224	944	455
IBNR Reserves Dec. 31, 2018 (Audited)	$ 563
Cumulative Number of Reported Claims (Audited) | item	124,507
Short-duration Insurance Contracts, Accident Year 2014 [Member] | Bond & Specialty Insurance [Member] | General liability [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 473	518	563	571	549
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	367	312	239	150	38
IBNR Reserves Dec. 31, 2018 (Audited)	$ 67
Cumulative Number of Reported Claims (Audited) | item	4,335
Short-duration Insurance Contracts, Accident Year 2014 [Member] | Bond & Specialty Insurance [Member] | Fidelity and surety [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 130	136	165	212	223
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	124	127	111	96	58
IBNR Reserves Dec. 31, 2018 (Audited)	$ (4)
Cumulative Number of Reported Claims (Audited) | item	1,069
Short-duration Insurance Contracts, Accident Year 2014 [Member] | Personal Insurance [Member] | Automobile [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 1,980	1,985	1,981	1,994	2,014
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	1,936	1,879	1,763	1,564	1,193
IBNR Reserves Dec. 31, 2018 (Audited)	$ 14
Cumulative Number of Reported Claims (Audited) | item	670,431
Short-duration Insurance Contracts, Accident Year 2014 [Member] | Personal Insurance [Member] | Homeowners (excluding Other) [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 1,451	1,457	1,453	1,450	1,515
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	1,433	1,425	1,402	1,338	1,053
IBNR Reserves Dec. 31, 2018 (Audited)	$ 7
Cumulative Number of Reported Claims (Audited) | item	151,705
Short-duration Insurance Contracts, Accident Year 2014 [Member] | Personal Insurance [Member] | International - Canada [Member] | Property-casualty [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 405	412	423	422	408
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	344	314	287	252	$ 180
IBNR Reserves Dec. 31, 2018 (Audited)	$ (3)
Cumulative Number of Reported Claims (Audited) | item	52,291
Short-duration Insurance Contracts, Accident Year 2015 [Member] | Business Insurance [Member] | General liability [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 967	923	956	998
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	558	336	137	36
IBNR Reserves Dec. 31, 2018 (Audited)	$ 222
Cumulative Number of Reported Claims (Audited) | item	21,033
Short-duration Insurance Contracts, Accident Year 2015 [Member] | Business Insurance [Member] | Commercial property [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 731	741	750	786
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	699	681	615	376
IBNR Reserves Dec. 31, 2018 (Audited)	$ 6
Cumulative Number of Reported Claims (Audited) | item	20,143
Short-duration Insurance Contracts, Accident Year 2015 [Member] | Business Insurance [Member] | Commercial multi-peril [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 1,597	1,593	1,625	1,568
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	1,310	1,144	970	595
IBNR Reserves Dec. 31, 2018 (Audited)	$ 110
Cumulative Number of Reported Claims (Audited) | item	71,242
Short-duration Insurance Contracts, Accident Year 2015 [Member] | Business Insurance [Member] | Automobile [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 1,283	1,234	1,202	1,188
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	1,058	885	650	405
IBNR Reserves Dec. 31, 2018 (Audited)	$ 83
Cumulative Number of Reported Claims (Audited) | item	173,333
Short-duration Insurance Contracts, Accident Year 2015 [Member] | Business Insurance [Member] | Workers' compensation [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 2,441	2,505	2,585	2,644
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	1,310	1,154	893	430
IBNR Reserves Dec. 31, 2018 (Audited)	$ 751
Cumulative Number of Reported Claims (Audited) | item	122,388
Short-duration Insurance Contracts, Accident Year 2015 [Member] | Bond & Specialty Insurance [Member] | General liability [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 437	486	524	528
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	310	234	141	38
IBNR Reserves Dec. 31, 2018 (Audited)	$ 92
Cumulative Number of Reported Claims (Audited) | item	4,155
Short-duration Insurance Contracts, Accident Year 2015 [Member] | Bond & Specialty Insurance [Member] | Fidelity and surety [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 145	179	191	217
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	86	87	75	32
IBNR Reserves Dec. 31, 2018 (Audited)	$ 38
Cumulative Number of Reported Claims (Audited) | item	827
Short-duration Insurance Contracts, Accident Year 2015 [Member] | Personal Insurance [Member] | Automobile [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 2,222	2,236	2,244	2,186
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	2,109	1,985	1,768	1,319
IBNR Reserves Dec. 31, 2018 (Audited)	$ 35
Cumulative Number of Reported Claims (Audited) | item	757,837
Short-duration Insurance Contracts, Accident Year 2015 [Member] | Personal Insurance [Member] | Homeowners (excluding Other) [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 1,452	1,461	1,454	1,438
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	1,421	1,395	1,333	994
IBNR Reserves Dec. 31, 2018 (Audited)	$ 10
Cumulative Number of Reported Claims (Audited) | item	145,088
Short-duration Insurance Contracts, Accident Year 2015 [Member] | Personal Insurance [Member] | International - Canada [Member] | Property-casualty [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 339	342	342	343
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	269	241	215	$ 154
IBNR Reserves Dec. 31, 2018 (Audited)	$ 16
Cumulative Number of Reported Claims (Audited) | item	45,201
Short-duration Insurance Contracts, Accident Year 2016 [Member] | Business Insurance [Member] | General liability [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 1,087	1,058	1,075
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	421	191	35
IBNR Reserves Dec. 31, 2018 (Audited)	$ 439
Cumulative Number of Reported Claims (Audited) | item	19,190
Short-duration Insurance Contracts, Accident Year 2016 [Member] | Business Insurance [Member] | Commercial property [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 820	863	896
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	745	685	441
IBNR Reserves Dec. 31, 2018 (Audited)	$ 22
Cumulative Number of Reported Claims (Audited) | item	22,267
Short-duration Insurance Contracts, Accident Year 2016 [Member] | Business Insurance [Member] | Commercial multi-peril [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 1,598	1,623	1,662
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	1,133	950	585
IBNR Reserves Dec. 31, 2018 (Audited)	$ 204
Cumulative Number of Reported Claims (Audited) | item	68,024
Short-duration Insurance Contracts, Accident Year 2016 [Member] | Business Insurance [Member] | Automobile [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 1,371	1,303	1,278
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	931	688	412
IBNR Reserves Dec. 31, 2018 (Audited)	$ 191
Cumulative Number of Reported Claims (Audited) | item	182,647
Short-duration Insurance Contracts, Accident Year 2016 [Member] | Business Insurance [Member] | Workers' compensation [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 2,569	2,690	2,768
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	1,118	873	421
IBNR Reserves Dec. 31, 2018 (Audited)	$ 863
Cumulative Number of Reported Claims (Audited) | item	122,493
Short-duration Insurance Contracts, Accident Year 2016 [Member] | Bond & Specialty Insurance [Member] | General liability [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 504	511	512
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	233	141	30
IBNR Reserves Dec. 31, 2018 (Audited)	$ 153
Cumulative Number of Reported Claims (Audited) | item	4,235
Short-duration Insurance Contracts, Accident Year 2016 [Member] | Bond & Specialty Insurance [Member] | Fidelity and surety [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 205	239	226
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	142	121	54
IBNR Reserves Dec. 31, 2018 (Audited)	$ 12
Cumulative Number of Reported Claims (Audited) | item	866
Short-duration Insurance Contracts, Accident Year 2016 [Member] | Personal Insurance [Member] | Automobile [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 2,772	2,791	2,779
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	2,466	2,203	1,610
IBNR Reserves Dec. 31, 2018 (Audited)	$ 126
Cumulative Number of Reported Claims (Audited) | item	921,479
Short-duration Insurance Contracts, Accident Year 2016 [Member] | Personal Insurance [Member] | Homeowners (excluding Other) [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 1,525	1,547	1,556
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	1,455	1,392	1,049
IBNR Reserves Dec. 31, 2018 (Audited)	$ 27
Cumulative Number of Reported Claims (Audited) | item	143,797
Short-duration Insurance Contracts, Accident Year 2016 [Member] | Personal Insurance [Member] | International - Canada [Member] | Property-casualty [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 389	389	343
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	294	269	$ 201
IBNR Reserves Dec. 31, 2018 (Audited)	$ 32
Cumulative Number of Reported Claims (Audited) | item	45,728
Short-duration Insurance Contracts, Accident Year 2017 [Member] | Business Insurance [Member] | General liability [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 1,143	1,133
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	180	40
IBNR Reserves Dec. 31, 2018 (Audited)	$ 717
Cumulative Number of Reported Claims (Audited) | item	16,464
Short-duration Insurance Contracts, Accident Year 2017 [Member] | Business Insurance [Member] | Commercial property [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 1,177	1,209
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	1,003	618
IBNR Reserves Dec. 31, 2018 (Audited)	$ 30
Cumulative Number of Reported Claims (Audited) | item	24,855
Short-duration Insurance Contracts, Accident Year 2017 [Member] | Business Insurance [Member] | Commercial multi-peril [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 1,928	1,872
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	1,199	716
IBNR Reserves Dec. 31, 2018 (Audited)	$ 357
Cumulative Number of Reported Claims (Audited) | item	69,218
Short-duration Insurance Contracts, Accident Year 2017 [Member] | Business Insurance [Member] | Automobile [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 1,501	1,386
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	746	456
IBNR Reserves Dec. 31, 2018 (Audited)	$ 401
Cumulative Number of Reported Claims (Audited) | item	190,126
Short-duration Insurance Contracts, Accident Year 2017 [Member] | Business Insurance [Member] | Workers' compensation [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 2,681	2,779
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	890	433
IBNR Reserves Dec. 31, 2018 (Audited)	$ 1,179
Cumulative Number of Reported Claims (Audited) | item	119,890
Short-duration Insurance Contracts, Accident Year 2017 [Member] | Bond & Specialty Insurance [Member] | General liability [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 517	534
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	155	38
IBNR Reserves Dec. 31, 2018 (Audited)	$ 266
Cumulative Number of Reported Claims (Audited) | item	4,128
Short-duration Insurance Contracts, Accident Year 2017 [Member] | Bond & Specialty Insurance [Member] | Fidelity and surety [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 271	244
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	166	70
IBNR Reserves Dec. 31, 2018 (Audited)	$ 64
Cumulative Number of Reported Claims (Audited) | item	863
Short-duration Insurance Contracts, Accident Year 2017 [Member] | Personal Insurance [Member] | Automobile [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 3,256	3,323
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	2,575	1,912
IBNR Reserves Dec. 31, 2018 (Audited)	$ 341
Cumulative Number of Reported Claims (Audited) | item	1,059,610
Short-duration Insurance Contracts, Accident Year 2017 [Member] | Personal Insurance [Member] | Homeowners (excluding Other) [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 2,340	2,312
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	2,059	1,471
IBNR Reserves Dec. 31, 2018 (Audited)	$ 101
Cumulative Number of Reported Claims (Audited) | item	168,357
Short-duration Insurance Contracts, Accident Year 2017 [Member] | Personal Insurance [Member] | International - Canada [Member] | Property-casualty [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 362	329
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	244	$ 173
IBNR Reserves Dec. 31, 2018 (Audited)	$ 26
Cumulative Number of Reported Claims (Audited) | item	46,545
Short-duration Insurance Contracts, Accident Year 2018 [Member] | Business Insurance [Member] | General liability [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 1,253
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	42
IBNR Reserves Dec. 31, 2018 (Audited)	$ 1,080
Cumulative Number of Reported Claims (Audited) | item	13,107
Short-duration Insurance Contracts, Accident Year 2018 [Member] | Business Insurance [Member] | Commercial property [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 1,093
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	561
IBNR Reserves Dec. 31, 2018 (Audited)	$ 73
Cumulative Number of Reported Claims (Audited) | item	21,547
Short-duration Insurance Contracts, Accident Year 2018 [Member] | Business Insurance [Member] | Commercial multi-peril [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 1,976
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	792
IBNR Reserves Dec. 31, 2018 (Audited)	$ 605
Cumulative Number of Reported Claims (Audited) | item	58,784
Short-duration Insurance Contracts, Accident Year 2018 [Member] | Business Insurance [Member] | Automobile [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 1,645
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	515
IBNR Reserves Dec. 31, 2018 (Audited)	$ 736
Cumulative Number of Reported Claims (Audited) | item	185,419
Short-duration Insurance Contracts, Accident Year 2018 [Member] | Business Insurance [Member] | Workers' compensation [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 2,744
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	440
IBNR Reserves Dec. 31, 2018 (Audited)	$ 1,738
Cumulative Number of Reported Claims (Audited) | item	109,002
Short-duration Insurance Contracts, Accident Year 2018 [Member] | Bond & Specialty Insurance [Member] | General liability [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 530
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	49
IBNR Reserves Dec. 31, 2018 (Audited)	$ 406
Cumulative Number of Reported Claims (Audited) | item	2,894
Short-duration Insurance Contracts, Accident Year 2018 [Member] | Bond & Specialty Insurance [Member] | Fidelity and surety [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 220
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	64
IBNR Reserves Dec. 31, 2018 (Audited)	$ 121
Cumulative Number of Reported Claims (Audited) | item	595
Short-duration Insurance Contracts, Accident Year 2018 [Member] | Personal Insurance [Member] | Automobile [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 3,281
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	1,889
IBNR Reserves Dec. 31, 2018 (Audited)	$ 825
Cumulative Number of Reported Claims (Audited) | item	960,293
Short-duration Insurance Contracts, Accident Year 2018 [Member] | Personal Insurance [Member] | Homeowners (excluding Other) [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 2,610
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	1,657
IBNR Reserves Dec. 31, 2018 (Audited)	$ 568
Cumulative Number of Reported Claims (Audited) | item	165,780
Short-duration Insurance Contracts, Accident Year 2018 [Member] | Personal Insurance [Member] | International - Canada [Member] | Property-casualty [Member]
Claims Development
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	$ 418
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Audited for 2018)	208
IBNR Reserves Dec. 31, 2018 (Audited)	$ 89
Cumulative Number of Reported Claims (Audited) | item	46,883

Insurance Claim Reserves (Det_5

Insurance Claim Reserves (Details) - Historical Claim Duration	Dec. 31, 2018
Business Insurance [Member] | General liability [Member]
Historical Claims Duration
Short-duration Insurance Contracts, Historical Claims Duration, Year One	3.80%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two	13.60%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three	19.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four	19.10%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five	13.40%
Short-duration Insurance Contracts, Historical Claims Duration, Year Six	9.50%
Short-duration Insurance Contracts, Historical Claims Duration, Year Seven	5.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Eight	3.20%
Short-duration Insurance Contracts, Historical Claims Duration, Year Nine	2.50%
Short-duration Insurance Contracts, Historical Claims Duration, Year Ten	1.50%
Business Insurance [Member] | Commercial property [Member]
Historical Claims Duration
Short-duration Insurance Contracts, Historical Claims Duration, Year One	52.90%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two	31.20%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three	8.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four	2.90%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five	1.70%
Business Insurance [Member] | Commercial multi-peril [Member]
Historical Claims Duration
Short-duration Insurance Contracts, Historical Claims Duration, Year One	39.70%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two	23.20%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three	11.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four	9.40%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five	6.20%
Short-duration Insurance Contracts, Historical Claims Duration, Year Six	3.30%
Short-duration Insurance Contracts, Historical Claims Duration, Year Seven	1.70%
Short-duration Insurance Contracts, Historical Claims Duration, Year Eight	1.10%
Short-duration Insurance Contracts, Historical Claims Duration, Year Nine	0.70%
Short-duration Insurance Contracts, Historical Claims Duration, Year Ten	0.60%
Business Insurance [Member] | Automobile [Member]
Historical Claims Duration
Short-duration Insurance Contracts, Historical Claims Duration, Year One	31.30%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two	19.20%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three	17.60%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four	13.70%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five	9.30%
Business Insurance [Member] | Workers' compensation [Member]
Historical Claims Duration
Short-duration Insurance Contracts, Historical Claims Duration, Year One	17.40%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two	19.50%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three	11.20%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four	7.30%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five	5.30%
Short-duration Insurance Contracts, Historical Claims Duration, Year Six	3.80%
Short-duration Insurance Contracts, Historical Claims Duration, Year Seven	3.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Eight	2.20%
Short-duration Insurance Contracts, Historical Claims Duration, Year Nine	2.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Ten	1.70%
Bond & Specialty Insurance [Member] | General liability [Member]
Historical Claims Duration
Short-duration Insurance Contracts, Historical Claims Duration, Year One	6.80%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two	21.40%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three	19.40%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four	15.30%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five	11.40%
Short-duration Insurance Contracts, Historical Claims Duration, Year Six	7.30%
Short-duration Insurance Contracts, Historical Claims Duration, Year Seven	6.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Eight	3.70%
Short-duration Insurance Contracts, Historical Claims Duration, Year Nine	0.90%
Short-duration Insurance Contracts, Historical Claims Duration, Year Ten	0.20%
Bond & Specialty Insurance [Member] | Fidelity and surety [Member]
Historical Claims Duration
Short-duration Insurance Contracts, Historical Claims Duration, Year One	29.50%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two	31.80%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three	9.90%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four	6.10%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five	(2.70%)
Personal Insurance [Member] | Automobile [Member]
Historical Claims Duration
Short-duration Insurance Contracts, Historical Claims Duration, Year One	58.80%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two	20.20%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three	9.80%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four	5.70%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five	2.90%
Personal Insurance [Member] | Homeowners (excluding Other) [Member]
Historical Claims Duration
Short-duration Insurance Contracts, Historical Claims Duration, Year One	67.20%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two	22.70%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three	4.30%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four	1.70%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five	0.50%
Personal Insurance [Member] | International - Canada [Member] | Property-casualty [Member]
Historical Claims Duration
Short-duration Insurance Contracts, Historical Claims Duration, Year One	45.20%
Short-duration Insurance Contracts, Historical Claims Duration, Year Two	18.70%
Short-duration Insurance Contracts, Historical Claims Duration, Year Three	7.80%
Short-duration Insurance Contracts, Historical Claims Duration, Year Four	7.40%
Short-duration Insurance Contracts, Historical Claims Duration, Year Five	7.30%
Short-duration Insurance Contracts, Historical Claims Duration, Year Six	5.20%
Short-duration Insurance Contracts, Historical Claims Duration, Year Seven	3.50%
Short-duration Insurance Contracts, Historical Claims Duration, Year Eight	2.20%
Short-duration Insurance Contracts, Historical Claims Duration, Year Nine	1.00%
Short-duration Insurance Contracts, Historical Claims Duration, Year Ten	0.20%

Insurance Claim Reserves Insura

Insurance Claim Reserves Insurance Claim Reserves (Details) - Asbestos and Environmental Reserves - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Liability for claims and claim adjustment expense
Asbestos and environmental claims reserves, balance	$ 1,620	$ 1,640
Asbestos reserves [Member]
Liability for claims and claim adjustment expense
Increase to asbestos and environmental claims	225	225	$ 225
Net losses paid	$ 225	$ 271	$ 708
Percent of total asbestos net paid losses related to policyholders with whom the Company had entered into settlement agreements limiting the Company's liability	9.00%	4.00%	69.00%
Asbestos reserves [Member] | PPG Industries, Inc Litigation [Member]
Liability for claims and claim adjustment expense
Settlement amount paid			$ 458
Environmental reserves [Member]
Liability for claims and claim adjustment expense
Increase to asbestos and environmental claims	$ 55	$ 65	$ 82

Debt (Details)

Debt (Details) - USD ($) $ in Millions	Dec. 31, 2018	May 15, 2018	Mar. 07, 2018	Dec. 31, 2017	May 22, 2017	May 11, 2016
Schedule of debt
Commercial paper	$ 100			$ 100
Total short-term debt	600			600
Total long-term debt	6,004			6,004
Total debt principal	6,604			6,604
Unamortized fair value adjustment	44			46
Unamortized debt issuance costs	(84)			(79)
Total debt	6,564			6,571
Senior Notes [Member] | 5.90% Senior notes due June 2, 2019 [Member]
Schedule of debt
Current maturities of long-term debt	$ 500
Total long-term debt				$ 500
Interest rate (percent)	5.90%			5.90%
Senior Notes [Member] | 5.80% Senior Notes due May 15, 2018 [Member]
Schedule of debt
Current maturities of long-term debt				$ 500
Interest rate (percent)		5.80%		5.80%
Senior Notes [Member] | 3.90% Senior notes due November 1, 2020 [Member]
Schedule of debt
Total long-term debt	$ 500			$ 500
Interest rate (percent)	3.90%			3.90%
Senior Notes [Member] | 7.75% Senior notes due April 15, 2026 [Member]
Schedule of debt
Total long-term debt	$ 200			$ 200
Interest rate (percent)	7.75%			7.75%
Senior Notes [Member] | 6.375% Senior notes due March 15, 2033 [Member]
Schedule of debt
Total long-term debt	$ 500			$ 500
Interest rate (percent)	6.375%			6.375%
Senior Notes [Member] | 6.75% Senior notes due June 20, 2036 [Member]
Schedule of debt
Total long-term debt	$ 400			$ 400
Interest rate (percent)	6.75%			6.75%
Senior Notes [Member] | 6.25% Senior notes due June 15, 2037 [Member]
Schedule of debt
Total long-term debt	$ 800			$ 800
Interest rate (percent)	6.25%			6.25%
Senior Notes [Member] | 5.35% Senior notes due November 1, 2040 [Member]
Schedule of debt
Total long-term debt	$ 750			$ 750
Interest rate (percent)	5.35%			5.35%
Senior Notes [Member] | 4.60% Senior notes due August 1, 2043 [Member]
Schedule of debt
Total long-term debt	$ 500			$ 500
Interest rate (percent)	4.60%			4.60%
Senior Notes [Member] | 4.30% Senior notes due August 25, 2045 [Member]
Schedule of debt
Total long-term debt	$ 400			$ 400
Interest rate (percent)	4.30%			4.30%
Senior Notes [Member] | 3.75% Senior notes due May 15, 2046 [Member]
Schedule of debt
Total long-term debt	$ 500			$ 500
Interest rate (percent)	3.75%			3.75%		3.75%
Senior Notes [Member] | 4.00% Senior notes due May 30, 2047 [Member]
Schedule of debt
Total long-term debt	$ 700			$ 700
Interest rate (percent)	4.00%			4.00%	4.00%
Senior Notes [Member] | 4.05% Senior notes due March 7, 2048 [Member]
Schedule of debt
Total long-term debt	$ 500
Interest rate (percent)	4.05%		4.05%
Junior Subordinated Debt [Member] | 7.625% Junior subordinated debentures due December 15, 2027 [Member]
Schedule of debt
Total long-term debt	$ 125			$ 125
Unamortized fair value adjustment	$ 12			$ 13
Interest rate (percent)	7.625%			7.625%
Junior Subordinated Debt [Member] | 8.50% Junior subordinated debentures due December 15, 2045 [Member]
Schedule of debt
Total long-term debt	$ 56			$ 56
Unamortized fair value adjustment	$ 14			$ 15
Interest rate (percent)	8.50%			8.50%
Junior Subordinated Debt [Member] | 8.312% Junior subordinated debentures due July 1, 2046 [Member]
Schedule of debt
Total long-term debt	$ 73			$ 73
Unamortized fair value adjustment	$ 18			$ 18
Interest rate (percent)	8.312%			8.312%

Debt (Details) - Debt Issuance

Debt (Details) - Debt Issuance - USD ($) $ in Millions	Mar. 07, 2018	May 22, 2017	May 11, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument
Net proceeds of issuance, after the deduction of the underwriting discount and expenses				$ 591	$ 789	$ 491
Senior Notes [Member] | 4.05% Senior notes due March 7, 2048 [Member]
Debt Instrument
Debt, principal amount	$ 500
Interest rate (percent)	4.05%			4.05%
Net proceeds of issuance, after the deduction of the underwriting discount and expenses	$ 491
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%
Senior Notes [Member] | 4.00% Senior notes due May 30, 2047 [Member]
Debt Instrument
Debt, principal amount		$ 700
Interest rate (percent)		4.00%		4.00%	4.00%
Net proceeds of issuance, after the deduction of the underwriting discount and expenses		$ 689
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%
Senior Notes [Member] | 3.75% Senior notes due May 15, 2046 [Member]
Debt Instrument
Debt, principal amount			$ 500
Interest rate (percent)			3.75%	3.75%	3.75%
Net proceeds of issuance, after the deduction of the underwriting discount and expenses			$ 491
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			0.20%

Debt (Details) - Repayment

Debt (Details) - Repayment - USD ($) $ in Millions	May 15, 2018	Dec. 15, 2017	Jun. 02, 2017	Jun. 20, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument
Debt, principal amount repaid					$ 600	$ 657	$ 400
Senior Notes [Member] | 5.80% Senior Notes due May 15, 2018 [Member]
Debt Instrument
Debt, principal amount repaid	$ 500
Interest rate (percent)	5.80%					5.80%
Senior Notes [Member] | 5.75% Senior notes due December 15, 2017 [Member]
Debt Instrument
Debt, principal amount repaid		$ 450
Interest rate (percent)		5.75%
Senior Notes [Member] | 6.25% Senior notes due June 20, 2016 [Member]
Debt Instrument
Debt, principal amount repaid				$ 400
Interest rate (percent)				6.25%
Junior Subordinated Debt [Member] | 6.25% Fixed-to-floating rate junior subordinated debentures due March 15, 2067 [Member]
Debt Instrument
Debt, principal amount repaid			$ 107
Interest rate (percent)			6.25%
Percentage of principal amount at which redemption price was set			100.00%

Debt (Details) - Commercial Pap

Debt (Details) - Commercial Paper - Commercial Paper [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Line of Credit Facility
Credit agreement, maximum borrowing capacity	$ 800
Minimum [Member]
Line of Credit Facility
Interest rate on commercial paper	1.47%	0.65%
Maximum [Member]
Line of Credit Facility
Interest rate on commercial paper	2.37%	1.17%

Debt (Details) - Junior Subordi

Debt (Details) - Junior Subordinated Debt $ in Millions	12 Months Ended
	Dec. 31, 2018USD ($)trustsdebenture_instruments	Dec. 31, 2017USD ($)
Debt Instrument
Unamortized fair value adjustment	$ 44	$ 46
Amount of certain debt obligations of Travelers Property Casualty Corp. (TPC) and Travelers Insurance Group Holdings, Inc. (TIGHI) that are fully and unconditionally guaranteed by The Travelers Companies, Inc.	$ 700
Junior Subordinated Debt [Member]
Debt Instrument
Number of junior subordinated debentures that are all similar in nature | debenture_instruments	3
Number of separate trusts that issued preferred securities and used proceeds to purchase the Company's subordinated debentures | trusts	3
Impact of amortization of the fair value adjustment on interest expense	$ 2	$ 1
Junior Subordinated Debt [Member] | 7.625% Junior subordinated debentures due December 15, 2027 [Member]
Debt Instrument
Interest rate (percent)	7.625%	7.625%
Effective interest rate (percent)	6.147%
Unamortized fair value adjustment	$ 12	$ 13
Junior Subordinated Debt [Member] | 8.50% Junior subordinated debentures due December 15, 2045 [Member]
Debt Instrument
Interest rate (percent)	8.50%	8.50%
Effective interest rate (percent)	6.362%
Unamortized fair value adjustment	$ 14	$ 15
Junior Subordinated Debt [Member] | 8.312% Junior subordinated debentures due July 1, 2046 [Member]
Debt Instrument
Interest rate (percent)	8.312%	8.312%
Effective interest rate (percent)	6.362%
Unamortized fair value adjustment	$ 18	$ 18
Senior Notes [Member] | 7.75% Senior notes due April 15, 2026 [Member]
Debt Instrument
Interest rate (percent)	7.75%	7.75%
Amount of certain debt obligations of Travelers Property Casualty Corp. (TPC) and Travelers Insurance Group Holdings, Inc. (TIGHI) that are fully and unconditionally guaranteed by The Travelers Companies, Inc.	$ 200
Senior Notes [Member] | 6.375% Senior notes due March 15, 2033 [Member]
Debt Instrument
Interest rate (percent)	6.375%	6.375%
Amount of certain debt obligations of Travelers Property Casualty Corp. (TPC) and Travelers Insurance Group Holdings, Inc. (TIGHI) that are fully and unconditionally guaranteed by The Travelers Companies, Inc.	$ 500

Debt (Details) - Maturities

Debt (Details) - Maturities $ in Millions	Dec. 31, 2018USD ($)
Maturities of long-term debt
Amount of debt obligations, other than commercial paper, due in 2019	$ 500
Amount of debt obligations, other than commercial paper, due in 2020	500
Amount of debt obligations, other than commercial paper, due in 2021	0
Amount of debt obligations, other than commercial paper, due in 2022	0
Amount of debt obligations, other than commercial paper, due in 2023	$ 0

Debt (Details) - Line of Credit

Debt (Details) - Line of Credit - Line of credit [Member] - USD ($) $ in Millions	Jun. 04, 2018	Jun. 03, 2018	Dec. 31, 2018
Revolving Credit Agreement Entered Into on June 4, 2018 [Member]
Line of Credit Facility
Credit agreement, term (in years)	5 years
Credit agreement, maximum borrowing capacity	$ 1,000
Credit agreement, covenant terms			Pursuant to the credit agreement covenants, the Company must maintain a minimum consolidated net worth, defined as shareholders’ equity determined in accordance with GAAP (excluding accumulated other comprehensive income (loss)) plus (a) trust preferred securities (not to exceed 15% of total capital) and (b) mandatorily convertible securities (combined with trust preferred securities, not to exceed 25% of total capital) less goodwill and other intangible assets.  The threshold is adjusted downward by an amount equal to 70% of the aggregate amount of common stock repurchased by the Company after March 31, 2018, up to a maximum deduction of $1.75 billion. The threshold was $13.60 billion at December 31, 2018 and could decline to a minimum of $12.494 billion during the term of the credit agreement, subject to the Company repurchasing an additional $1.58 billion of its common stock. In addition, the credit agreement contains other customary restrictive covenants as well as certain customary events of default, including with respect to a change in control, which is defined to include the acquisition of 35% or more of the Company’s voting stock and certain changes in the composition of the Company’s board of directors.
Maximum percentage of trust preferred securities relative to total capital in determining consolidated net worth			15.00%
Maximum percentage of trust preferred securities and mandatorily convertible securities relative to total capital in determining consolidated net worth			25.00%
Credit agreement, threshold of consolidated net worth			$ 13,600
Percentage of aggregate amount of common stock repurchased by the Company after March 31, 2018 by which the threshold is adjusted downward			70.00%
Maximum downward adjustment to threshold relative to common stock repurchases			$ 1,750
Common stock repurchases required during the term of the credit agreement to reduce threshold net worth to minimum amount reported			$ 1,580
Credit agreement, compliance			At December 31, 2018, the Company was in compliance with these covenants.
Revolving Credit Agreement Entered Into on June 4, 2018 [Member] | Minimum [Member]
Line of Credit Facility
Credit agreement, threshold of consolidated net worth			$ 12,494
Percentage of Company's voting stock acquired by outside entity that would be considered a change in control			35.00%
Revolving Credit Agreement Entered Into on June 4, 2018 [Member] | LIBOR [Member]
Line of Credit Facility
Credit agreement, cost of borrowing, basis points above LIBOR			1.00%
Revolving Credit Agreement Entered Into on June 4, 2018 [Member] | LIBOR [Member] | Minimum [Member]
Line of Credit Facility
Credit agreement, cost of borrowing, basis points above LIBOR			0.75%
Revolving Credit Agreement Entered Into on June 4, 2018 [Member] | LIBOR [Member] | Maximum [Member]
Line of Credit Facility
Credit agreement, cost of borrowing, basis points above LIBOR			1.375%
Revolving Credit Agreement Due to Expire on June 7, 2018 [Member]
Line of Credit Facility
Credit agreement, term (in years)		5 years
Credit agreement, maximum borrowing capacity		$ 1,000

Shareholders' Equity and Divi_3

Shareholders' Equity and Dividend Availability Shareholders' Equity and Dividend Availability (Details) - USD ($)	3 Months Ended				12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Apr. 30, 2017
Stockholders' Equity Note [Abstract]
Number of authorized shares (in shares)	1,755,000,000				1,755,000,000
Number of authorized shares, preferred shares (in shares)	5,000,000				5,000,000
Number of authorized shares, voting common stock (in shares)	1,745,000,000				1,745,000,000
Number of shares authorized, undesignated shares (in shares)	5,000,000				5,000,000
Additional share repurchase authorization							$ 5,000,000,000
Number of shares purchased (in shares)	1,400,000	3,000,000	2,700,000	2,500,000	9,600,000
Cost of shares repurchased	$ 170,000,000	$ 400,000,000	$ 350,000,000	$ 350,000,000	$ 1,270,000,000
Average price paid per share (in dollars per share)	$ 125.09	$ 130.22	$ 129.66	$ 141.84	$ 132.33
Remaining capacity under share repurchase authorization	$ 3,286,000,000	$ 3,456,000,000	$ 3,856,000,000	$ 4,206,000,000	$ 3,286,000,000
Cost of shares acquired to cover tax withholding costs and exercise costs					$ 51,000,000	$ 62,000,000

Shareholders' Equity and Divi_4

Shareholders' Equity and Dividend Availability (Details) - Business Acquisition - Simply Business [Member] - Restricted common stock [Member] - USD ($) $ in Millions	Aug. 04, 2017	Aug. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Business Acquisition
Share issued (in shares)	95,953	95,953
Shares issued value	$ 12	$ 12
Shares outstanding and unvested			92,995	95,953
Two years from the issuance date [Member]
Business Acquisition
Vesting percentage	50.00%	50.00%
Vesting period (in years)	2 years	2 years
Three years from the issuance date [Member]
Business Acquisition
Vesting percentage	50.00%	50.00%
Vesting period (in years)	3 years	3 years

Shareholders' Equity and Divi_5

Shareholders' Equity and Dividend Availability (Details) - Dividend Availability $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2018USD ($)item$ / shares	Dec. 31, 2017USD ($)item$ / shares	Dec. 31, 2016USD ($)item$ / shares
Statutory accounting principles
Dividends received by TRV and its two non-insurance holding companies from their U.S. insurance subsidiaries	$ 2,300	$ 2,330	$ 3,050
Cash dividends paid	814	785	757
Insurance subsidiaries [Member]
Statutory accounting principles
Statutory net income of the Company's domestic and international insurance subsidiaries	2,610	2,300	$ 3,200
Statutory capital and surplus of the Company's domestic and international insurance subsidiaries	$ 20,770	$ 20,450
Travelers [Member]
Statutory accounting principles
Number of non-insurance holding companies underneath TRV | item	2	2	2
Cash dividends declared per common share (in dollars per share) | $ / shares	$ 3.03	$ 2.83	$ 2.62
Cash dividends paid	$ 814	$ 785	$ 757
Connecticut Insurance Department [Member] | Insurance subsidiaries [Member]
Statutory accounting principles
Maximum amount of dividends available to be paid by subsidiaries to their parent without prior approval of the Connecticut Insurance Department	$ 2,520

Other Comprehensive Income an_3

Other Comprehensive Income and Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	Jan. 01, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accumulated other comprehensive income [Roll Forward]
Balance, beginning of year	$ 23,731	$ 23,731	$ 23,221
Other comprehensive income (loss), net of taxes		(1,470)	412	$ (598)
Balance, end of year		22,894	23,731	23,221
Pre-tax components of other comprehensive income (loss) and related tax expense (benefit)
Other comprehensive income (loss) before income taxes		(1,819)	522	(887)
Income tax expense (benefit)		(349)	110	(289)
Other comprehensive income (loss), net of taxes		(1,470)	412	(598)
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated other comprehensive income [Roll Forward]
Balance, beginning of year	(343)	(343)	(755)	(157)
Cumulative effect of adoption of updated accounting guidance for equity financial instruments, pre-tax	(34)
Cumulative effect of adoption of updated accounting guidance for equity financial instruments, tax	(12)
Cumulative effect of adoption of updated accounting guidance for equity financial instruments, net of income taxes	(22)		(22)
Reclassification of certain tax effects from adoption of updated accounting guidance	(24)	(24)
Effect of adoption of updated accounting guidance, net of tax, total	(46)
Other comprehensive income (loss) before reclassifications		(1,513)	518	(605)
Amounts reclassified from accumulated other comprehensive income		43	(106)	7
Other comprehensive income (loss), net of taxes		(1,470)	412	(598)
Balance, end of year		(1,859)	(343)	(755)
Pre-tax components of other comprehensive income (loss) and related tax expense (benefit)
Other comprehensive income (loss) before income taxes		(1,819)	522	(887)
Income tax expense (benefit)		(349)	110	(289)
Other comprehensive income (loss), net of taxes		(1,470)	412	(598)
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 year	747	747	528	1,100
Cumulative effect of adoption of updated accounting guidance for equity financial instruments, pre-tax	(34)
Cumulative effect of adoption of updated accounting guidance for equity financial instruments, tax	(12)
Cumulative effect of adoption of updated accounting guidance for equity financial instruments, net of income taxes	(22)
Reclassification of certain tax effects from adoption of updated accounting guidance	145
Effect of adoption of updated accounting guidance, net of tax, total	123
Other comprehensive income (loss) before reclassifications		(1,151)	367	(530)
Amounts reclassified from accumulated other comprehensive income		(25)	(148)	(42)
Other comprehensive income (loss), net of taxes		(1,176)	219	(572)
Balance, end of year		(306)	747	528
Pre-tax components of other comprehensive income (loss) and related tax expense (benefit)
Other comprehensive income (loss) before income taxes		(1,489)	294	(883)
Income tax expense (benefit)		(313)	75	(311)
Other comprehensive income (loss), net of taxes		(1,176)	219	(572)
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 year	207	207	202	189
Reclassification of certain tax effects from adoption of updated accounting guidance	7
Effect of adoption of updated accounting guidance, net of tax, total	7
Other comprehensive income (loss) before reclassifications		(21)	4	4
Amounts reclassified from accumulated other comprehensive income			1	9
Other comprehensive income (loss), net of taxes		(21)	5	13
Balance, end of year		193	207	202
Pre-tax components of other comprehensive income (loss) and related tax expense (benefit)
Other comprehensive income (loss) before income taxes		(27)	8	21
Income tax expense (benefit)		(6)	3	8
Other comprehensive income (loss), net of taxes		(21)	5	13
Net Benefit Plan Assets and Obligations Recognized in Shareholders’ Equity [Member]
Accumulated other comprehensive income [Roll Forward]
Balance, beginning of year	(686)	(686)	(703)	(713)
Reclassification of certain tax effects from adoption of updated accounting guidance	(141)
Effect of adoption of updated accounting guidance, net of tax, total	(141)
Other comprehensive income (loss) before reclassifications		(114)	(24)	(30)
Amounts reclassified from accumulated other comprehensive income		68	41	40
Other comprehensive income (loss), net of taxes		(46)	17	10
Balance, end of year		(873)	(686)	(703)
Pre-tax components of other comprehensive income (loss) and related tax expense (benefit)
Other comprehensive income (loss) before income taxes		(56)	29	16
Income tax expense (benefit)		(10)	12	6
Other comprehensive income (loss), net of taxes		(46)	17	10
Net Unrealized Foreign Currency Translation [Member]
Accumulated other comprehensive income [Roll Forward]
Balance, beginning of year	(611)	(611)	(782)	(733)
Reclassification of certain tax effects from adoption of updated accounting guidance	(35)
Effect of adoption of updated accounting guidance, net of tax, total	$ (35)
Other comprehensive income (loss) before reclassifications		(227)	171	(49)
Other comprehensive income (loss), net of taxes		(227)	171	(49)
Balance, end of year		(873)	(611)	(782)
Pre-tax components of other comprehensive income (loss) and related tax expense (benefit)
Other comprehensive income (loss) before income taxes		(247)	191	(41)
Income tax expense (benefit)		(20)	20	8
Other comprehensive income (loss), net of taxes		$ (227)	$ 171	$ (49)

Other Comprehensive Income an_4

Other Comprehensive Income and Accumulated Other Comprehensive Income (Details) - Reclassifications - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Reclassification adjustment impacting realized gains on the income statement	[1]									$ (114)	$ (216)	$ (68)
Reclassification adjustment impacting claims and claim adjustment expenses on the income statement										18,291	17,467	15,070
Reclassification adjustment impacting general and administrative expense on the income statement										4,297	4,170	4,154
Total reclassifications		$ (746)	$ (806)	$ (631)	$ (778)	$ (860)	$ (320)	$ (790)	$ (760)	(2,961)	(2,730)	(4,053)
Income tax (expense) benefit		(125)	(97)	(107)	(109)	(309)	(27)	(195)	(143)	(438)	(674)	(1,039)
Amounts reclassified from accumulated other comprehensive income, net of taxes		$ (621)	$ (709)	$ (524)	$ (669)	$ (551)	$ (293)	$ (595)	$ (617)	(2,523)	(2,056)	(3,014)
Accumulated Other Comprehensive Income (Loss) [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Total reclassifications										54	(147)	11
Income tax (expense) benefit										11	(41)	4
Amounts reclassified from accumulated other comprehensive income, net of taxes										43	(106)	7
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 realized gains on the income statement										(32)	(228)	(64)
Income tax (expense) benefit										(7)	(80)	(22)
Amounts reclassified from accumulated other comprehensive income, net of taxes										(25)	(148)	(42)
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 realized gains on the income statement											1	13
Income tax (expense) benefit												4
Amounts reclassified from accumulated other comprehensive income, net of taxes											1	9
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										35	32	25
Reclassification adjustment impacting general and administrative expense on the income statement										51	48	37
Total reclassifications										86	80	62
Income tax (expense) benefit										18	39	22
Amounts reclassified from accumulated other comprehensive income, net of taxes										$ 68	$ 41	$ 40
[1]	Total other-than-temporary impairment (OTTI) losses were $(1) million, $(13) million and $(40) million for the years ended December 31, 2018, 2017 and 2016, respectively. Of total OTTI, credit losses of $(1) million, $(14) million and $(29) million for the years ended December 31, 2018, 2017 and 2016, respectively, were recognized in net realized investment gains. In addition, unrealized gains (losses) from other changes in total OTTI of $0 million, $1 million and $(11) million for the years ended December 31, 2018, 2017 and 2016, respectively, were recognized in other comprehensive income (loss) as part of changes in net unrealized gains (losses) on investment securities having credit losses recognized in the consolidated statement of income.

Earnings per Share (Details)

Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Earnings Per Share Reconciliation [Abstract]
Net income	$ 621	$ 709	$ 524	$ 669	$ 551	$ 293	$ 595	$ 617	$ 2,523	$ 2,056	$ 3,014
Participating share-based awards — allocated income									(19)	(15)	(22)
Net income available to common shareholders — basic									2,504	2,041	2,992
Net income available to common shareholders — diluted									$ 2,504	$ 2,041	$ 2,992
Weighted average shares outstanding, basic (in shares)									267.4	276	288.1
Weighted average effects of dilutive securities, stock options and performance shares (in shares)									2.4	2.6	2.9
Weighted average shares outstanding, diluted (in shares)									269.8	278.6	291
Net income per common share, basic (in dollars per share)	$ 2.33	$ 2.65	$ 1.93	$ 2.45	$ 2	$ 1.06	$ 2.13	$ 2.19	$ 9.37	$ 7.39	$ 10.39
Net income per common share, diluted (in dollars per share)	$ 2.32	$ 2.62	$ 1.92	$ 2.42	$ 1.98	$ 1.05	$ 2.11	$ 2.17	$ 9.28	$ 7.33	$ 10.28

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Net charge included in total income tax expense related to TCJA at the date of enactment										$ 129
Current income tax expense included in consolidated statement of income, federal									$ 424		$ 899
Current income tax expense included in consolidated statement of income, federal (excluding impact of TCJA)										314
Current income tax expense included in consolidated statement of income, impact of TCJA at enactment										21
Current income tax expense included in consolidated statement of income, foreign									41	56	21
Current income tax expense included in consolidated statement of income, state									8	4	8
Total current tax expense									473	395	928
Deferred income tax expense included in consolidated statement of income, federal									(13)	337	110
Deferred income tax expense included in consolidated statement of income, federal (excluding impact of TCJA)										229
Deferred income tax expense included in consolidated statement of income, impact of TCJA at enactment										108
Deferred income tax expense included in consolidated statement of income, foreign									(22)	(58)	1
Total deferred tax expense (benefit)									(35)	279	111
Total income tax expense included in the consolidated statement of income	$ 125	$ 97	$ 107	$ 109	$ 309	$ 27	$ 195	$ 143	438	674	1,039
Expense (benefit) relating to changes in the unrealized gain (loss) on investments, unrealized loss on foreign exchange and other items in other comprehensive income (loss)									(349)	110	(289)
Total income tax expense included in the consolidated financial statements									$ 89	$ 784	$ 750

Income Taxes (Details) - Effect

Income Taxes (Details) - Effective Tax Rate - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Nov. 30, 2018	Oct. 31, 2018
Income Tax Disclosure [Abstract]
U.S. income before income taxes									$ 3,039	$ 2,798	$ 3,946
Foreign income (loss) before income taxes									(78)	(68)	107
Income before income taxes	$ 746	$ 806	$ 631	$ 778	$ 860	$ 320	$ 790	$ 760	$ 2,961	$ 2,730	$ 4,053
Statutory tax rate (percent)									21.00%	35.00%	35.00%
Expected federal income tax expense									$ 622	$ 956	$ 1,419
Tax effect of nontaxable investment income									(150)	(297)	(323)
Tax effect of TCJA at enactment										129
Tax effect of other, net									(34)	(114)	(57)
Total income tax expense included in the consolidated statement of income	125	$ 97	$ 107	$ 109	309	$ 27	$ 195	$ 143	$ 438	$ 674	$ 1,039
Effective tax rate (percent)									15.00%	25.00%	26.00%
Income taxes paid									$ 408	$ 514	$ 892
Current income tax receivable	12				$ 65				12	$ 65
Estimated additional annual tax payments relating to the discounted reserves transitional adjustment associated with TCJA	$ 23								$ 23			$ 23	$ 70

Income Taxes (Details) - Deferr

Income Taxes (Details) - Deferred Tax Asset and Liability - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Nov. 30, 2018	Oct. 31, 2018
Income Tax Disclosure [Abstract]
Deferred tax assets, claims and claim adjustment expense reserves	$ 571	$ 930
Deferred tax assets, unearned premium reserves	503	478
Deferred tax assets, compensation-related liabilities	92	61
Deferred tax assets, other	200	191
Total gross deferred tax assets	1,366	1,660
Less: valuation allowance	8	6
Adjusted gross deferred tax assets	1,358	1,654
Deferred tax liabilities, claims and claim adjustment expense reserve discounting (transition rule)	159	560
Deferred tax liabilities, deferred acquisition costs	397	376
Deferred tax liabilities, investments	152	454
Deferred tax liabilities, internally developed software	92	97
Deferred tax liabilities, depreciation	67	57
Deferred tax liabilities, other	46	40
Total gross deferred tax liabilities	913	1,584
Net deferred tax asset	445	70
Increase in valuation allowance	2
Tax expense recognized resulting from deemed repatriation of foreign earnings (part of net charge to record effect of TCJA)		41
Net charge included in total income tax expense related to TCJA at the date of enactment		$ 129
Estimated additional annual tax payments relating to the discounted reserves transitional adjustment associated with TCJA	$ 23		$ 23	$ 70

Income Taxes (Details) - NOL Ca

Income Taxes (Details) - NOL Carryforwards $ in Millions	Dec. 31, 2018USD ($)
United States [Member]
Net Operating Loss Carryforward
Net operating loss carryforward	$ 2
Brazil [Member]
Net Operating Loss Carryforward
Net operating loss carryforward	19
Canada [Member]
Net Operating Loss Carryforward
Net operating loss carryforward	1
United Kingdom [Member]
Net Operating Loss Carryforward
Net operating loss carryforward	$ 146

Income Taxes (Details) - Unreco

Income Taxes (Details) - Unrecognized Tax Benefits - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reconciliation of unrecognized tax benefits [Roll Forward]
Unrecognized tax benefits, balance at January 1	$ 6	$ 13
Additions for tax positions of prior years	25
Reductions for tax positions of prior years		(1)
Reductions based on tax positions related to current year		(6)
Unrecognized tax benefits, balance at December 31	31	6	$ 13
Unrecognized tax benefits that, if recognized, would affect the annual effective tax rate	29	3
Amount of unrecognized tax benefits that are tax positions for which the ultimate deductibility is certain, but for which there is uncertainty about the timing of deductibility	2	3
Amount of interest benefit recognized on unrecognized tax benefits in income taxes	(10)	(33)
Amount of interest recognized on unrecognized tax benefits in income taxes			$ 31
Accrued payment of interest balance for unrecognized tax benefits	$ 14	$ 25

Share-Based Incentive Compens_3

Share-Based Incentive Compensation Share-based Incentive Compensation (Details) - USD ($) $ / shares in Units, $ in Millions	Feb. 05, 2019	May 31, 2017	May 31, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Summary of stock option activity [Roll Forward]
Stock options outstanding, beginning of year, number (in shares)				8,712,467
Stock options granted, number (in shares)				1,632,361
Stock options exercised, number (in shares)				(1,229,850)
Stock options forfeited or expired, number (in shares)				(120,622)
Stock options outstanding, end of year, number (in shares)				8,994,356	8,712,467
Stock options outstanding, beginning of year, weighted average exercise price (in dollars per share)				$ 97.45
Stock options granted, weighted average exercise price (in dollars per share)				140.85
Stock options exercised, weighted average exercise price (in dollars per share)				83.74
Stock options forfeited or expired, weighted average exercise price (in dollars per share)				117.39
Stock options outstanding, end of year, weighted average exercise price (in dollars per share)				$ 106.93	$ 97.45
Stock options outstanding, weighted average contractual life remaining (in years)				6 years 2 months 12 days
Stock options outstanding, aggregate intrinsic value				$ 149
Stock options vested at end of year, number (in shares)				5,861,909
Stock options vested at end of year, weighted average exercise price (in dollars per share)				$ 99.28
Stock options vested at end of year, weighted average contractual life remaining (in years)				5 years 3 months 18 days
Stock options vested at end of year, aggregate intrinsic value				$ 134
Stock options exercisable at end of year, number (in shares)				3,889,013
Stock options exercisable at end of year, weighted average exercise price (in dollars per share)				$ 88.83
Stock options exercisable at end of year, weighted average contractual life remaining (in years)				3 years 10 months 24 days
Stock options exercisable at end of year, aggregate intrinsic value				$ 123
Stock option grants [Member]
Assumptions used in estimating fair value of options
Expected term of stock options				6 years	6 years
Expected volatility of Company’s stock (percent)				14.94%	16.50%
Weighted average volatility (percent)				14.94%	16.50%	16.79%
Expected annual dividend per share (in dollars per share)				$ 2.88	$ 2.68
Risk-free rate				2.68%	2.08%
Stock options granted, weighted average grant-date fair value of options granted (in dollars per share)				$ 20.13	$ 16.15	$ 13.29
Total intrinsic value of options exercised during the year				$ 67	$ 90	$ 167
Stock option grants [Member] | Minimum [Member]
Assumptions used in estimating fair value of options
Expected term of stock options						5 years
Expected volatility of Company’s stock (percent)						15.14%
Expected annual dividend per share (in dollars per share)						$ 2.44
Risk-free rate						1.36%
Stock option grants [Member] | Maximum [Member]
Assumptions used in estimating fair value of options
Expected term of stock options						6 years
Expected volatility of Company’s stock (percent)						16.80%
Expected annual dividend per share (in dollars per share)						$ 2.68
Risk-free rate						2.23%
The Travelers Companies, Inc 2014 Stock Incentive Plan [Member]
Share-based compensation plan description
Number of shares of the Company's common stock originally authorized for grant under the 2014 Incentive Plan (in shares)				10,000,000
Additional number of shares of the Company' common stock authorized for grant under the 2014 Incentive plan (in shares)		2,500,000	4,400,000
Number of shares of the Company's common stock authorized for grant under the 2014 Incentive Plan, total (in shares)				16,900,000
The Travelers Companies, Inc 2014 Stock Incentive Plan [Member] | Stock option grants [Member]
Share-based compensation plan description
Option term				10 years
Award vesting period				3 years
The Travelers Companies, Inc 2014 Stock Incentive Plan [Member] | Stock option grants [Member] | Subsequent event [Member]
Assumptions used in estimating fair value of options
Stock options granted, weighted average grant-date fair value of options granted (in dollars per share)	$ 16.65
Summary of stock option activity [Roll Forward]
Stock options granted, number (in shares)	2,051,673
Stock options granted, weighted average exercise price (in dollars per share)	$ 126.18
The Travelers Companies, Inc 2014 Stock Incentive Plan [Member] | Director deferred stock awards [Member]
Share-based compensation plan description
Number of days prior to date of annual meeting in year following date of grant in which annual deferred stock awards vest in full				1 day
Number of months after termination of service as a director before distributions of deferred stock awards begin				6 months

Share-Based Incentive Compens_4

Share-Based Incentive Compensation Share-Based Incentive Compensation (Details) - Restricted Stock - USD ($) $ / shares in Units, $ in Millions	Feb. 05, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Restricted stock units, deferred stock units and performance share awards [Member]
Share-based compensation
Fair value of shares that vested during the year		$ 135	$ 166	$ 175
Restricted stock units, deferred stock units and performance share awards [Member] | Subsequent event [Member]
Summary of other equity instruments [Roll Forward]
Other equity instruments, granted, number (in shares)	929,391
Other equity instruments, granted, weighted average grant date fair value (in dollars per share)	$ 126.18
Restricted and deferred stock units [Member]
Summary of other equity instruments [Roll Forward]
Other equity instruments, nonvested, number, beginning of year (in shares)		1,286,970
Other equity instruments, granted, number (in shares)		559,807
Other equity instruments, vested, number (in shares)		(554,640)
Other equity instruments, forfeited, number (in shares)		(75,461)
Other equity instruments, nonvested, number, end of year (in shares)		1,216,676	1,286,970
Other equity instruments, nonvested, weighted average grant-date fair value, beginning of year (in dollars per share)		$ 111.74
Other equity instruments, granted, weighted average grant date fair value (in dollars per share)		139.20
Other equity instruments, vested, weighted average grant date fair value (in dollars per share)		114.77
Other equity instruments, forfeited, weighted average grant date fair value (in dollars per share)		122.29
Other equity instruments, nonvested, weighted average grant-date fair value, end of year (in dollars per share)		$ 122.34	$ 111.74
Other equity instruments, nonvested dividend equivalents, number, beginning of year (in shares)		379
Other equity instruments, nonvested dividend equivalents, number, end of year (in shares)		329	379
Restricted and deferred stock units [Member] | Subsequent event [Member]
Summary of other equity instruments [Roll Forward]
Other equity instruments, granted, number (in shares)	557,637
Restricted stock units [Member]
Share-based compensation
Award vesting period		3 years
Performance shares [Member]
Share-based compensation
Award vesting period		3 years
Performance period		3 years
Summary of other equity instruments [Roll Forward]
Other equity instruments, nonvested, number, beginning of year (in shares)		787,732
Other equity instruments, granted, number (in shares)		319,408
Other equity instruments, vested, number (in shares)		(385,604)
Other equity instruments, forfeited, number (in shares)		(68,593)
Other equity instruments, performance-based adjustment, number (in shares)		31,946
Other equity instruments, nonvested, number, end of year (in shares)		684,889	787,732
Other equity instruments, nonvested, weighted average grant-date fair value, beginning of year (in dollars per share)		$ 112.40
Other equity instruments, granted, weighted average grant date fair value (in dollars per share)		140.85
Other equity instruments, vested, weighted average grant date fair value (in dollars per share)		106.06
Other equity instruments, forfeited, weighted average grant date fair value (in dollars per share)		123.01
Other equity instruments, performance-based adjustment, weighted average grant date fair value (in dollars per share)		126.29
Other equity instruments, nonvested, weighted average grant-date fair value, end of year (in dollars per share)		$ 128.83	$ 112.40
Other equity instruments, nonvested dividend equivalents, number, beginning of year (in shares)		26,584
Other equity instruments, nonvested dividend equivalents, number, end of year (in shares)		24,876	26,584
Performance shares [Member] | Subsequent event [Member]
Summary of other equity instruments [Roll Forward]
Other equity instruments, granted, number (in shares)	371,754
Performance shares [Member] | February 2017, 2018 and 2019 Awards [Member]] | Minimum [Member]
Share-based compensation
Percentage of performance shares to vest		50.00%
Performance shares [Member] | February 2017, 2018 and 2019 Awards [Member]] | Maximum [Member]
Share-based compensation
Percentage of performance shares to vest		150.00%
Restricted common stock [Member] | Simply Business [Member]
Summary of other equity instruments [Roll Forward]
Other equity instruments, nonvested, number, beginning of year (in shares)		95,953
Other equity instruments, nonvested, number, end of year (in shares)		92,995	95,953

Share-Based Incentive Compensta

Share-Based Incentive Compenstaion (Details) - Cost Recognition - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based compensation
Total compensation cost recognized in earnings for all share-based incentive compensation awards	$ 140	$ 136	$ 155
Tax benefit recognized in earnings related to compensation costs	26	45	52
Total unrecognized compensation cost related to all nonvested share-based incentive compensation awards	$ 141
Weighted-average period of recognition for unrecognized compensation cost (in years)	1 year 9 months 18 days
Cash received from the exercise of employee stock options under share-based compensation plans	$ 132	173	332
Tax benefit for tax deductions from employee stock options exercised	$ 14	31
Minimum [Member]
Share-based compensation
Estimated annual forfeiture rate reflected in share-based compensation cost (percent)	3.50%
Maximum [Member]
Share-based compensation
Estimated annual forfeiture rate reflected in share-based compensation cost (percent)	4.50%
Performance shares [Member]
Share-based compensation
Estimated attainment of performance shares at grant date (percent)	100.00%
Compensation cost adjustments for the updated estimate of performance shares due to attaining certain performance levels	$ 3	$ 3	$ 11

Pension Plans, Retirement Ben_3

Pension Plans, Retirement Benefits and Savings Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Pension Plans [Member]
Change in projected benefit obligation [Roll Forward]
Benefit obligation, balance, beginning of year	$ 3,909	$ 3,592
Benefits earned	133	119	$ 118
Interest cost on benefit obligation	126	127	122
Actuarial (gain) loss	(284)	259
Benefits paid	(219)	(187)
Settlement		(11)
Foreign currency exchange rate change, change in projected benefit obligation	(6)	10
Benefit obligation, balance, end of year	3,659	3,909	3,592
Change in plan assets [Roll Forward]
Fair value of plan assets, balance, beginning of year	4,070	3,493
Actual return on plan assets	(180)	459
Company contributions	210	307
Benefits paid	(219)	(187)
Settlement		(12)
Foreign currency exchange rate change, change in plan assets	(7)	10
Fair value of plan assets, balance, end of year	3,874	4,070	3,493
Funded status of plan at end of year	215	161
Amounts recognized in the consolidated balance sheet consist of:
Accrued over-funded benefit plan assets	331	284
Accrued under-funded benefit plan liabilities	(116)	(123)
Total amount recognized in the consolidated balance sheet	215	161
Amounts recognized in accumulated other comprehensive income consist of:
Net actuarial loss (gain)	1,149	1,082
Prior service benefit	(4)	(6)
Total amount recognized in accumulated other comprehensive income	1,145	1,076
Pension Plans [Member] | United States [Member] | Qualified Plan [Member]
Change in projected benefit obligation [Roll Forward]
Benefit obligation, balance, beginning of year	3,679	3,367
Benefits earned	126	112
Interest cost on benefit obligation	119	120
Actuarial (gain) loss	(273)	258
Benefits paid	(207)	(178)
Benefit obligation, balance, end of year	3,444	3,679	3,367
Change in plan assets [Roll Forward]
Fair value of plan assets, balance, beginning of year	3,957	3,387
Actual return on plan assets	(179)	448
Company contributions	200	300	200
Benefits paid	(207)	(178)
Fair value of plan assets, balance, end of year	3,771	3,957	3,387
Funded status of plan at end of year	327	278
Amounts recognized in the consolidated balance sheet consist of:
Accrued over-funded benefit plan assets	327	278
Total amount recognized in the consolidated balance sheet	327	278
Amounts recognized in accumulated other comprehensive income consist of:
Net actuarial loss (gain)	1,113	1,035
Prior service benefit	(5)	(6)
Total amount recognized in accumulated other comprehensive income	1,108	1,029
Nonqualified and Foreign Pension Plans [Member]
Change in projected benefit obligation [Roll Forward]
Benefit obligation, balance, beginning of year	230	225
Benefits earned	7	7
Interest cost on benefit obligation	7	7
Actuarial (gain) loss	(11)	1
Benefits paid	(12)	(9)
Settlement		(11)
Foreign currency exchange rate change, change in projected benefit obligation	(6)	10
Benefit obligation, balance, end of year	215	230	225
Change in plan assets [Roll Forward]
Fair value of plan assets, balance, beginning of year	113	106
Actual return on plan assets	(1)	11
Company contributions	10	7
Benefits paid	(12)	(9)
Settlement		(12)
Foreign currency exchange rate change, change in plan assets	(7)	10
Fair value of plan assets, balance, end of year	103	113	106
Funded status of plan at end of year	(112)	(117)
Amounts recognized in the consolidated balance sheet consist of:
Accrued over-funded benefit plan assets	4	6
Accrued under-funded benefit plan liabilities	(116)	(123)
Total amount recognized in the consolidated balance sheet	(112)	(117)
Amounts recognized in accumulated other comprehensive income consist of:
Net actuarial loss (gain)	36	47
Prior service benefit	1
Total amount recognized in accumulated other comprehensive income	37	47
Postretirement Benefit Plans [Member]
Change in projected benefit obligation [Roll Forward]
Benefit obligation, balance, beginning of year	225	214
Interest cost on benefit obligation	7	7	8
Actuarial (gain) loss	(18)	13
Benefits paid	(10)	(10)
Foreign currency exchange rate change, change in projected benefit obligation	(1)	1
Benefit obligation, balance, end of year	203	225	214
Change in plan assets [Roll Forward]
Fair value of plan assets, balance, beginning of year	13	14
Company contributions	9	9
Benefits paid	(10)	(10)
Fair value of plan assets, balance, end of year	12	13	$ 14
Funded status of plan at end of year	(191)	(212)
Amounts recognized in the consolidated balance sheet consist of:
Accrued under-funded benefit plan liabilities	(191)	(212)
Total amount recognized in the consolidated balance sheet	(191)	(212)
Amounts recognized in accumulated other comprehensive income consist of:
Net actuarial loss (gain)	(17)
Prior service benefit	(25)	(28)
Total amount recognized in accumulated other comprehensive income	$ (42)	$ (28)

Pension Plans, Retirement Ben_4

Pension Plans, Retirement Benefits and Savings Plans (Details) - Additional Pension Disclosures - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Other changes in benefit plan assets and benefit obligations recognized in other comprehensive income
Total other changes in benefit plan assets and benefit obligations recognized in other comprehensive income	$ 56	$ (29)	$ (16)
Pension Plans [Member]
Defined benefit plan disclosure
Total accumulated benefit obligation	3,530	3,770
Aggregate projected benefit obligation for plans with a projected benefit obligation in excess of plan assets	203	183
Aggregate plan assets for plans with a projected benefit obligation in excess of plan assets	87	60
Aggregate accumulated benefit obligation for plans with an accumulated benefit obligation in excess of plan assets	195	174
Aggregate plan assets for plans with an accumulated benefit obligation in excess of plan assets	87	60
Actuarial gain (loss)	284	(259)
Company contributions	210	307
Components of net periodic benefit cost
Service cost	133	119	118
Interest cost on benefit obligation	126	127	122
Expected return on plan assets	(264)	(240)	(230)
Net periodic benefit cost, settlement		3	1
Net periodic benefit cost, amortization of unrecognized prior service benefit	(1)	(1)	(1)
Net periodic benefit cost, amortization of unrecognized net actuarial loss	91	85	66
Total non-service cost (benefit)	(48)	(26)	(42)
Net periodic benefit cost	85	93	76
Other changes in benefit plan assets and benefit obligations recognized in other comprehensive income
Other changes in benefit plan assets and benefit obligations recognized in other comprehensive income, net actuarial loss (gain)	160	40	66
Other changes in benefit plan assets and benefit obligations recognized in other comprehensive income, foreign currency exchange rate change	(1)	2	(2)
Other changes in benefit plan assets and benefit obligations recognized in other comprehensive income, settlement		(2)	(1)
Other changes in benefit plan assets and benefit obligations recognized in other comprehensive income, amortization of prior service benefit	1	1	1
Other changes in benefit plan assets and benefit obligations recognized in other comprehensive income, amortization of net actuarial loss	(91)	(85)	(66)
Total other changes in benefit plan assets and benefit obligations recognized in other comprehensive income	69	(44)	(2)
Total other changes recognized in net periodic benefit cost and other comprehensive income	154	49	74
Pension Plans [Member] | Net investment income [Member]
Components of net periodic benefit cost
Service cost	1
Pension Plans [Member] | Claims and claim adjustment expenses [Member]
Components of net periodic benefit cost
Service cost	54	48	48
Total non-service cost (benefit)	(19)	(11)	(18)
Pension Plans [Member] | General and administrative expense [Member]
Components of net periodic benefit cost
Service cost	78	71	70
Total non-service cost (benefit)	(29)	(15)	(24)
Pension Plans [Member] | United States [Member] | Qualified Plan [Member]
Defined benefit plan disclosure
Total accumulated benefit obligation	3,320	3,550
Actuarial gain (loss)	273	(258)
Required contributions made	0	0	0
Company contributions	200	300	200
Required contributions during next fiscal year	0
Components of net periodic benefit cost
Service cost	126	112
Interest cost on benefit obligation	119	120
Nonqualified and Foreign Pension Plans [Member]
Defined benefit plan disclosure
Total accumulated benefit obligation	210	220
Actuarial gain (loss)	11	(1)
Company contributions	10	7
Components of net periodic benefit cost
Service cost	7	7
Interest cost on benefit obligation	7	7
Postretirement Benefit Plans [Member]
Defined benefit plan disclosure
Aggregate accumulated benefit obligation for plans with an accumulated benefit obligation in excess of plan assets	203	225
Aggregate plan assets for plans with an accumulated benefit obligation in excess of plan assets	12	13
Actuarial gain (loss)	18	(13)
Company contributions	9	9
Components of net periodic benefit cost
Interest cost on benefit obligation	7	7	8
Net periodic benefit cost, amortization of unrecognized prior service benefit	(4)	(4)	(3)
Total non-service cost (benefit)	3	3	5
Net periodic benefit cost	3	3	5
Other changes in benefit plan assets and benefit obligations recognized in other comprehensive income
Other changes in benefit plan assets and benefit obligations recognized in other comprehensive income, net actuarial loss (gain)	(18)	13	(17)
Other changes in benefit plan assets and benefit obligations recognized in other comprehensive income, foreign currency exchange rate change		(1)	1
Other changes in benefit plan assets and benefit obligations recognized in other comprehensive income, amortization of prior service benefit	4	4	3
Total other changes in benefit plan assets and benefit obligations recognized in other comprehensive income	(14)	16	(13)
Total other changes recognized in net periodic benefit cost and other comprehensive income	(11)	19	(8)
Postretirement Benefit Plans [Member] | Claims and claim adjustment expenses [Member]
Components of net periodic benefit cost
Total non-service cost (benefit)	1	1	2
Postretirement Benefit Plans [Member] | General and administrative expense [Member]
Components of net periodic benefit cost
Total non-service cost (benefit)	$ 2	$ 2	$ 3

Pension Plans, Retirement Ben_5

Pension Plans, Retirement Benefits and Savings Plans (Details) - Assumptions - United States [Member]	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Pension Plans [Member]
Defined benefit plan disclosure
Assumptions used to determine benefit obligations, cash balance interest crediting rate (percent)	4.01%	4.01%
Assumptions used to determine benefit obligations, future compensation increase rate (percent)	4.00%	4.00%
Assumptions used to determine net periodic benefit cost, expected long-term rate of return on assets (percent)	7.00%	7.00%
Pension Plans [Member] | Qualified Plan [Member]
Defined benefit plan disclosure
Assumptions used to determine benefit obligations, discount rate (percent)	4.39%	3.71%
Assumptions used to determine net periodic benefit cost, discount rate used to measure service cost (percent)	3.87%	4.52%
Assumptions used to determine net periodic benefit cost, discount rate used to measure interest cost (percent)	3.34%	3.55%
Pension Plans [Member] | Nonqualified Plan [Member]
Defined benefit plan disclosure
Assumptions used to determine benefit obligations, discount rate (percent)	4.33%	3.66%
Assumptions used to determine net periodic benefit cost, discount rate used to measure service cost (percent)	3.73%	4.24%
Assumptions used to determine net periodic benefit cost, discount rate used to measure interest cost (percent)	3.26%	3.43%
Postretirement Benefit Plans [Member]
Defined benefit plan disclosure
Assumptions used to determine benefit obligations, discount rate (percent)	4.26%	3.60%
Assumptions used to determine net periodic benefit cost, discount rate used to measure interest cost (percent)	3.21%	3.42%
Assumptions used to determine net periodic benefit cost, expected long-term rate of return on assets (percent)	4.00%	4.00%
Assumed health care cost trend rates, rate to which the cost trend rate is assumed to decline (ultimate trend rate) (percent)	4.50%	4.50%
Postretirement Benefit Plan Before Age 65 [Member]
Defined benefit plan disclosure
Assumed health care cost trend rates, medical, following year (percent)	7.50%	7.50%
Assumed health care cost trend rates, medical, year that the rate reaches the ultimate trend rate	2,026	2,026
Postretirement Benefit Plan Age 65 and Older [Member]
Defined benefit plan disclosure
Assumed health care cost trend rates, medical, following year (percent)	8.75%	8.75%
Assumed health care cost trend rates, medical, year that the rate reaches the ultimate trend rate	2,026	2,026

Pension Plans, Retirement Ben_6

Pension Plans, Retirement Benefits and Savings Plans Pension Plans, Retirement Benefits and Savings Plans (Details) - Additional Information	Dec. 31, 2018
Pension Plans [Member] | United States [Member] | Qualified Plan [Member] | Equity securities [Member] | Minimum [Member]
Defined benefit plan disclosure
Investment in class of securities (as a percentage)	55.00%
Pension Plans [Member] | United States [Member] | Qualified Plan [Member] | Equity securities [Member] | Maximum [Member]
Defined benefit plan disclosure
Investment in class of securities (as a percentage)	65.00%
Pension Plans [Member] | United States [Member] | Qualified Plan [Member] | Fixed income securities [Member] | Minimum [Member]
Defined benefit plan disclosure
Investment in class of securities (as a percentage)	20.00%
Pension Plans [Member] | United States [Member] | Qualified Plan [Member] | Fixed income securities [Member] | Maximum [Member]
Defined benefit plan disclosure
Investment in class of securities (as a percentage)	40.00%
Pension Plans [Member] | United States [Member] | Qualified Plan [Member] | Long-term growth [Member] | Minimum [Member]
Defined benefit plan disclosure
Investment in class of securities (as a percentage)	85.00%
Pension Plans [Member] | United States [Member] | Qualified Plan [Member] | Long-term growth [Member] | Maximum [Member]
Defined benefit plan disclosure
Investment in class of securities (as a percentage)	90.00%
Pension Plans [Member] | United States [Member] | Qualified Plan [Member] | Near-term benefit payments [Member] | Minimum [Member]
Defined benefit plan disclosure
Investment in class of securities (as a percentage)	10.00%
Pension Plans [Member] | United States [Member] | Qualified Plan [Member] | Near-term benefit payments [Member] | Maximum [Member]
Defined benefit plan disclosure
Investment in class of securities (as a percentage)	15.00%
Postretirement Benefit Plans [Member] | Fixed income securities [Member] | Minimum [Member]
Defined benefit plan disclosure
Investment in class of securities (as a percentage)	25.00%
Postretirement Benefit Plans [Member] | Fixed income securities [Member] | Maximum [Member]
Defined benefit plan disclosure
Investment in class of securities (as a percentage)	75.00%
Postretirement Benefit Plans [Member] | Long-term growth [Member] | Minimum [Member]
Defined benefit plan disclosure
Investment in class of securities (as a percentage)	35.00%
Postretirement Benefit Plans [Member] | Long-term growth [Member] | Maximum [Member]
Defined benefit plan disclosure
Investment in class of securities (as a percentage)	65.00%
Postretirement Benefit Plans [Member] | Near-term benefit payments [Member] | Minimum [Member]
Defined benefit plan disclosure
Investment in class of securities (as a percentage)	35.00%
Postretirement Benefit Plans [Member] | Near-term benefit payments [Member] | Maximum [Member]
Defined benefit plan disclosure
Investment in class of securities (as a percentage)	60.00%

Pension Plans, Retirement Ben_7

Pension Plans, Retirement Benefits and Savings Plans (Details) - Fair Value - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Pension Plans [Member]
Defined benefit plan disclosure
Fair value of plan assets	$ 3,874	$ 4,070	$ 3,493
Pension Plans [Member] | Level 1 [Member]
Defined benefit plan disclosure
Fair value of plan assets	2,871	3,324
Pension Plans [Member] | Level 2 [Member]
Defined benefit plan disclosure
Fair value of plan assets	1,002	745
Pension Plans [Member] | Level 3 [Member]
Defined benefit plan disclosure
Fair value of plan assets	1	1
Pension Plans [Member] | Fixed maturities [Member]
Defined benefit plan disclosure
Fair value of plan assets	772	543
Pension Plans [Member] | Fixed maturities [Member] | Level 2 [Member]
Defined benefit plan disclosure
Fair value of plan assets	772	543
Pension Plans [Member] | Obligations of states, municipalities and political subdivisions [Member]
Defined benefit plan disclosure
Fair value of plan assets	3	3
Pension Plans [Member] | Obligations of states, municipalities and political subdivisions [Member] | Level 2 [Member]
Defined benefit plan disclosure
Fair value of plan assets	3	3
Pension Plans [Member] | Debt securities issued by foreign governments [Member]
Defined benefit plan disclosure
Fair value of plan assets	27	16
Pension Plans [Member] | Debt securities issued by foreign governments [Member] | Level 2 [Member]
Defined benefit plan disclosure
Fair value of plan assets	27	16
Pension Plans [Member] | Mortgage-backed securities, collateralized mortgage obligations and pass-through securities [Member]
Defined benefit plan disclosure
Fair value of plan assets	30	10
Pension Plans [Member] | Mortgage-backed securities, collateralized mortgage obligations and pass-through securities [Member] | Level 2 [Member]
Defined benefit plan disclosure
Fair value of plan assets	30	10
Pension Plans [Member] | All other corporate bonds [Member]
Defined benefit plan disclosure
Fair value of plan assets	712	514
Pension Plans [Member] | All other corporate bonds [Member] | Level 2 [Member]
Defined benefit plan disclosure
Fair value of plan assets	712	514
Pension Plans [Member] | Total mutual funds [Member]
Defined benefit plan disclosure
Fair value of plan assets	2,048	2,157
Pension Plans [Member] | Total mutual funds [Member] | Level 1 [Member]
Defined benefit plan disclosure
Fair value of plan assets	2,039	2,147
Pension Plans [Member] | Total mutual funds [Member] | Level 2 [Member]
Defined benefit plan disclosure
Fair value of plan assets	9	10
Pension Plans [Member] | Equity mutual funds [Member]
Defined benefit plan disclosure
Fair value of plan assets	1,288	1,335
Pension Plans [Member] | Equity mutual funds [Member] | Level 1 [Member]
Defined benefit plan disclosure
Fair value of plan assets	1,282	1,328
Pension Plans [Member] | Equity mutual funds [Member] | Level 2 [Member]
Defined benefit plan disclosure
Fair value of plan assets	6	7
Pension Plans [Member] | Bond mutual funds [Member]
Defined benefit plan disclosure
Fair value of plan assets	760	822
Pension Plans [Member] | Bond mutual funds [Member] | Level 1 [Member]
Defined benefit plan disclosure
Fair value of plan assets	757	819
Pension Plans [Member] | Bond mutual funds [Member] | Level 2 [Member]
Defined benefit plan disclosure
Fair value of plan assets	3	3
Pension Plans [Member] | Equity securities [Member]
Defined benefit plan disclosure
Fair value of plan assets	783	883
Pension Plans [Member] | Equity securities [Member] | Level 1 [Member]
Defined benefit plan disclosure
Fair value of plan assets	783	882
Pension Plans [Member] | Equity securities [Member] | Level 2 [Member]
Defined benefit plan disclosure
Fair value of plan assets		1
Pension Plans [Member] | Other investments [Member]
Defined benefit plan disclosure
Fair value of plan assets	1	1
Pension Plans [Member] | Other investments [Member] | Level 3 [Member]
Defined benefit plan disclosure
Fair value of plan assets	1	1
Pension Plans [Member] | Cash and short-term securities [Member]
Defined benefit plan disclosure
Fair value of plan assets	270	486
Pension Plans [Member] | Cash and short-term securities [Member] | Level 1 [Member]
Defined benefit plan disclosure
Fair value of plan assets	49	295
Pension Plans [Member] | Cash and short-term securities [Member] | Level 2 [Member]
Defined benefit plan disclosure
Fair value of plan assets	221	191
Pension Plans [Member] | Cash and short-term securities, U.S. Treasury securities [Member]
Defined benefit plan disclosure
Fair value of plan assets	30	241
Pension Plans [Member] | Cash and short-term securities, U.S. Treasury securities [Member] | Level 1 [Member]
Defined benefit plan disclosure
Fair value of plan assets	30	241
Pension Plans [Member] | Money market mutual funds [Member]
Defined benefit plan disclosure
Fair value of plan assets		27
Pension Plans [Member] | Money market mutual funds [Member] | Level 1 [Member]
Defined benefit plan disclosure
Fair value of plan assets		27
Pension Plans [Member] | Cash and short-term securities, other [Member]
Defined benefit plan disclosure
Fair value of plan assets	240	218
Pension Plans [Member] | Cash and short-term securities, other [Member] | Level 1 [Member]
Defined benefit plan disclosure
Fair value of plan assets	19	27
Pension Plans [Member] | Cash and short-term securities, other [Member] | Level 2 [Member]
Defined benefit plan disclosure
Fair value of plan assets	221	191
Postretirement Benefit Plans [Member]
Defined benefit plan disclosure
Fair value of plan assets	12	13	$ 14
Postretirement Benefit Plans [Member] | Level 2 [Member]
Defined benefit plan disclosure
Fair value of plan assets	$ 12	$ 13

Pension Plans, Retirement Ben_8

Pension Plans, Retirement Benefits and Savings Plans (Details) - Future Payments $ in Millions	Dec. 31, 2018USD ($)
Pension Plans [Member]
Estimated Future Benefit Payments
Benefits expected to be paid, 2019	$ 239
Benefits expected to be paid, 2020	246
Benefits expected to be paid, 2021	255
Benefits expected to be paid, 2022	260
Benefits expected to be paid, 2023	268
Benefits expected to be paid, 2024 through 2028	1,361
Postretirement Benefit Plans [Member]
Estimated Future Benefit Payments
Benefits expected to be paid, 2019	13
Benefits expected to be paid, 2020	14
Benefits expected to be paid, 2021	15
Benefits expected to be paid, 2022	15
Benefits expected to be paid, 2023	15
Benefits expected to be paid, 2024 through 2028	$ 72

Pension Plans, Retirement Ben_9

Pension Plans, Retirement Benefits and Savings Plans (Details) - Savings Plan - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Savings Plan
Expense related to all savings plans	$ 118,000,000	$ 119,000,000	$ 114,000,000
The Travelers 401(k) Savings Plan [Member]
Savings Plan
Maximum annual match	$ 6,500
Vesting percentage of employer match after vesting period	100.00%
Vesting period	3 years
The Travelers 401(k) Savings Plan [Member] | Maximum [Member]
Savings Plan
Matching contribution as a percent of eligible pay	5.00%

Leases (Details)

Leases (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Leases [Abstract]
Rent expense	$ 185	$ 188	$ 197
Future minimum annual rental payments due for 2019	127
Future minimum annual rental payments due for 2020	105
Future minimum annual rental payments due for 2021	89
Future minimum annual rental payments due for 2022	61
Future minimum annual rental payments due for 2023	41
Future minimum annual rental payments due for 2024 and thereafter	77
Approximate aggregate future sublease rental income that will partially offset the lease commitments	$ 1

Contingencies, Commitments an_2

Contingencies, Commitments and Guarantees (Details) - Gain Contingency $ in Millions	3 Months Ended	79 Months Ended
	Dec. 31, 2016USD ($)	Mar. 31, 2017USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Jun. 30, 2017USD ($)	May 01, 2017defendant	Nov. 07, 2016USD ($)defendant	Nov. 06, 2016USD ($)	Aug. 17, 2010issue
Gain Contingencies
Reinsurance recoverables			$ 8,370	$ 8,309
United States Fidelity & Guaranty Company v. American Re-Insurance Company, et al. [Member]
Gain Contingencies
Number of discrete issues for which the Court of Appeals remanded the case for trial | issue									2
Number of reinsurers with whom the Company reached a settlement agreeement | defendant						2	1
Number of reinsurer defendants | defendant						2	3
Gain from payment received from settlement (pre-tax)	$ 126
Gain from payment received from settlement (after-tax)	$ 82
Reinsurance recoverables		$ 31			$ 0		$ 31	$ 238
Total settlement amount		71
Settlement amount, reinsurance recoverables		31
Interest related to settlement award		$ 40

Contingencies, Commitments an_3

Contingencies, Commitments and Guarantees (Details) - Commitments - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Contingencies, Commitments and Guarantees [Abstract]
Unfunded commitments to private equity limited partnerships and real estate partnerships	$ 1,600	$ 1,560

Contingencies, Commitments an_4

Contingencies, Commitments and Guarantees (Details) - Guarantees $ in Millions	Dec. 31, 2018USD ($)
Indemnifications related to the sale of businesses [Member]
Guarantor obligations
Maximum amount of contingent obligation	$ 358
Amount recognized on balance sheet for contingent obligation	2
Guarantees of certain investments and third-party loans [Member]
Guarantor obligations
Maximum amount of contingent obligation	45
Amount indemnified by a third party	23
Guarantees of certain insurance policy obligations [Member]
Guarantor obligations
Maximum amount of contingent obligation	480
Amount indemnified by a third party	$ 480

Consolidating Financial State_3

Consolidating Financial Statements (Details) - Additional Information $ in Millions	Dec. 31, 2018USD ($)
Consolidating Financial Statements of The Travelers Companies, Inc. and Subsidiaries (Unaudited) disclosure
Amount of certain debt obligations of Travelers Property Casualty Corp. (TPC) and Travelers Insurance Group Holdings, Inc. (TIGHI) that are fully and unconditionally guaranteed by The Travelers Companies, Inc.	$ 700

Consolidating Financial State_4

Consolidating Financial Statements (Details) - Consolidating Statement of Income (Unaudited) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Consolidating Statement of Income
Premiums										$ 27,059	$ 25,683	$ 24,534
Net investment income										2,474	2,397	2,302
Fee income										432	447	458
Net realized investment gains (losses)	[1]									114	216	68
Other revenues										203	159	263
Total revenues		$ 7,796	$ 7,723	$ 7,477	$ 7,286	$ 7,451	$ 7,325	$ 7,184	$ 6,942	30,282	28,902	27,625
Claims and claim adjustment expenses										18,291	17,467	15,070
Amortization of deferred acquisition costs										4,381	4,166	3,985
General and administrative expenses										4,297	4,170	4,154
Interest expense										352	369	363
Total claims and expenses		7,050	6,917	6,846	6,508	6,591	7,005	6,394	6,182	27,321	26,172	23,572
Income before income taxes		746	806	631	778	860	320	790	760	2,961	2,730	4,053
Income tax expense (benefit)		125	97	107	109	309	27	195	143	438	674	1,039
Net income		$ 621	$ 709	$ 524	$ 669	$ 551	$ 293	$ 595	$ 617	2,523	2,056	3,014
Total other-than-temporary impairment losses										(1)	(13)	(40)
Other-than-temporary impairment losses recognized in net realized investment gains (losses)										(1)
Other-than-temporary impairment losses recognized in net realized investment gains (losses)											(14)	(29)
Other-than-temporary impairment losses recognized in other comprehensive income (loss)										0		(11)
Other-than-temporary impairment gains recognized in other comprehensive income (loss)											1
TRV [Member]
Consolidating Statement of Income
Net investment income										32	24	13
Net realized investment gains (losses)										(13)	66	(1)
Total revenues										19	90	12
General and administrative expenses										20	25	5
Interest expense										304	321	315
Total claims and expenses										324	346	320
Income before income taxes										(305)	(256)	(308)
Income tax expense (benefit)										(114)	(130)	(168)
Net income of subsidiaries										2,714	2,190	3,154
Net income										2,523	2,064	3,014
Other-than-temporary impairment losses recognized in net realized investment gains (losses)										0
Other-than-temporary impairment losses recognized in net realized investment gains (losses)											0	(1)
Other-than-temporary impairment losses recognized in other comprehensive income (loss)										0		0
Other-than-temporary impairment gains recognized in other comprehensive income (loss)											0
Reportable Legal Entities [Member] | TPC [Member]
Consolidating Statement of Income
Premiums										18,508	17,562	16,788
Net investment income										1,704	1,627	1,569
Fee income										432	447	458
Net realized investment gains (losses)										118	19	30
Other revenues										96	101	248
Total revenues										20,858	19,756	19,093
Claims and claim adjustment expenses										12,344	11,735	10,232
Amortization of deferred acquisition costs										2,972	2,820	2,702
General and administrative expenses										2,947	2,906	2,928
Interest expense										48	48	48
Total claims and expenses										18,311	17,509	15,910
Income before income taxes										2,547	2,247	3,183
Income tax expense (benefit)										437	519	999
Net income										2,110	1,728	2,184
Total other-than-temporary impairment losses										(1)	(4)	(19)
Other-than-temporary impairment losses recognized in net realized investment gains (losses)										(1)
Other-than-temporary impairment losses recognized in net realized investment gains (losses)											(5)	(13)
Other-than-temporary impairment losses recognized in other comprehensive income (loss)												(6)
Other-than-temporary impairment gains recognized in other comprehensive income (loss)											1
Reportable Legal Entities [Member] | Other Subsidiaries [Member]
Consolidating Statement of Income
Premiums										8,551	8,121	7,746
Net investment income										738	759	720
Net realized investment gains (losses)										9	131	39
Other revenues										112	68	36
Total revenues										9,410	9,079	8,541
Claims and claim adjustment expenses										5,947	5,732	4,838
Amortization of deferred acquisition costs										1,409	1,346	1,283
General and administrative expenses										1,335	1,249	1,242
Total claims and expenses										8,691	8,327	7,363
Income before income taxes										719	752	1,178
Income tax expense (benefit)										115	290	208
Net income										604	462	970
Total other-than-temporary impairment losses											(9)	(20)
Other-than-temporary impairment losses recognized in net realized investment gains (losses)											(9)	(15)
Other-than-temporary impairment losses recognized in other comprehensive income (loss)												(5)
Reportable Legal Entities [Member] | TRV [Member]
Consolidating Statement of Income
Net investment income										32	24	13
Net realized investment gains (losses)										(13)	66	(1)
Total revenues										19	90	12
General and administrative expenses										20	25	5
Interest expense										304	321	315
Total claims and expenses										324	346	320
Income before income taxes										(305)	(256)	(308)
Income tax expense (benefit)										(114)	(130)	(168)
Net income of subsidiaries										2,714	2,190	3,154
Net income										2,523	2,064	3,014
Total other-than-temporary impairment losses												(1)
Other-than-temporary impairment losses recognized in net realized investment gains (losses)												(1)
Eliminations [Member]
Consolidating Statement of Income
Net investment income											(13)
Other revenues										(5)	(10)	(21)
Total revenues										(5)	(23)	(21)
General and administrative expenses										(5)	(10)	(21)
Total claims and expenses										(5)	(10)	(21)
Income before income taxes											(13)
Income tax expense (benefit)											(5)
Net income of subsidiaries										(2,714)	(2,190)	(3,154)
Net income										$ (2,714)	$ (2,198)	$ (3,154)
[1]	Total other-than-temporary impairment (OTTI) losses were $(1) million, $(13) million and $(40) million for the years ended December 31, 2018, 2017 and 2016, respectively. Of total OTTI, credit losses of $(1) million, $(14) million and $(29) million for the years ended December 31, 2018, 2017 and 2016, respectively, were recognized in net realized investment gains. In addition, unrealized gains (losses) from other changes in total OTTI of $0 million, $1 million and $(11) million for the years ended December 31, 2018, 2017 and 2016, respectively, were recognized in other comprehensive income (loss) as part of changes in net unrealized gains (losses) on investment securities having credit losses recognized in the consolidated statement of income.

Consolidating Financial State_5

Consolidating Financial Statements (Details) - Consolidating Statement of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Consolidating Statement of Comprehensive Income
Net income	$ 621	$ 709	$ 524	$ 669	$ 551	$ 293	$ 595	$ 617	$ 2,523	$ 2,056	$ 3,014
Changes in net unrealized gains on investment securities having no credit losses recognized in the consolidated statement of income									(1,489)	294	(883)
Changes in net unrealized gains on investment securities having credit losses recognized in the consolidated statement of income									(27)	8	21
Net changes in benefit plan assets and obligations									(56)	29	16
Net changes in unrealized foreign currency translation									(247)	191	(41)
Other comprehensive income (loss) before income taxes									(1,819)	522	(887)
Income tax expense (benefit)									(349)	110	(289)
Other comprehensive income (loss), net of taxes, before other comprehensive income (loss) of subsidiaries									(1,470)	412	(598)
Other comprehensive income (loss), net of taxes									(1,470)	412	(598)
Comprehensive income									1,053	2,468	2,416
TRV [Member]
Consolidating Statement of Comprehensive Income
Net income									2,523	2,064	3,014
Changes in net unrealized gains on investment securities having no credit losses recognized in the consolidated statement of income										(44)	11
Net changes in benefit plan assets and obligations									(53)	22	(20)
Other comprehensive income (loss) before income taxes									(53)	(22)	(9)
Income tax expense (benefit)									(17)	2	(1)
Other comprehensive income (loss), net of taxes, before other comprehensive income (loss) of subsidiaries									(36)	(24)	(8)
Other comprehensive income (loss) of subsidiaries									(1,434)	436	(590)
Other comprehensive income (loss), net of taxes									(1,470)	412	(598)
Comprehensive income									1,053	2,476	2,416
Reportable Legal Entities [Member] | TPC [Member]
Consolidating Statement of Comprehensive Income
Net income									2,110	1,728	2,184
Changes in net unrealized gains on investment securities having no credit losses recognized in the consolidated statement of income									(1,028)	313	(696)
Changes in net unrealized gains on investment securities having credit losses recognized in the consolidated statement of income									(20)	6	11
Net changes in benefit plan assets and obligations									1	(1)	25
Net changes in unrealized foreign currency translation									(144)	83	73
Other comprehensive income (loss) before income taxes									(1,191)	401	(587)
Income tax expense (benefit)									(231)	98	(222)
Other comprehensive income (loss), net of taxes, before other comprehensive income (loss) of subsidiaries									(960)	303	(365)
Other comprehensive income (loss), net of taxes									(960)	303	(365)
Comprehensive income									1,150	2,031	1,819
Reportable Legal Entities [Member] | Other Subsidiaries [Member]
Consolidating Statement of Comprehensive Income
Net income									604	462	970
Changes in net unrealized gains on investment securities having no credit losses recognized in the consolidated statement of income									(461)	25	(198)
Changes in net unrealized gains on investment securities having credit losses recognized in the consolidated statement of income									(7)	2	10
Net changes in benefit plan assets and obligations									(4)	8	11
Net changes in unrealized foreign currency translation									(103)	108	(114)
Other comprehensive income (loss) before income taxes									(575)	143	(291)
Income tax expense (benefit)									(101)	10	(66)
Other comprehensive income (loss), net of taxes, before other comprehensive income (loss) of subsidiaries									(474)	133	(225)
Other comprehensive income (loss), net of taxes									(474)	133	(225)
Comprehensive income									130	595	745
Reportable Legal Entities [Member] | TRV [Member]
Consolidating Statement of Comprehensive Income
Net income									2,523	2,064	3,014
Changes in net unrealized gains on investment securities having no credit losses recognized in the consolidated statement of income										(44)	11
Net changes in benefit plan assets and obligations									(53)	22	(20)
Other comprehensive income (loss) before income taxes									(53)	(22)	(9)
Income tax expense (benefit)									(17)	2	(1)
Other comprehensive income (loss), net of taxes, before other comprehensive income (loss) of subsidiaries									(36)	(24)	(8)
Other comprehensive income (loss) of subsidiaries									(1,434)	436	(590)
Other comprehensive income (loss), net of taxes									(1,470)	412	(598)
Comprehensive income									1,053	2,476	2,416
Eliminations [Member]
Consolidating Statement of Comprehensive Income
Net income									(2,714)	(2,198)	(3,154)
Other comprehensive income (loss) of subsidiaries									1,434	(436)	590
Other comprehensive income (loss), net of taxes									1,434	(436)	590
Comprehensive income									$ (1,280)	$ (2,634)	$ (2,564)

Consolidating Financial State_6

Consolidating Financial Statements (Details) - Consolidating Balance Sheet (Unaudited) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Consolidating Balance Sheet
Fixed maturities, at fair value	$ 63,464	$ 62,694
Equity securities, at fair value	368
Equity securities, available for sale, at fair value		453
Real estate investments	904	932
Short-term securities	3,985	4,895
Other investments	3,557	3,528
Total investments	72,278	72,502
Cash	373	344	$ 307	$ 380
Investment income accrued	624	606
Premiums receivable	7,506	7,144
Reinsurance recoverables	8,370	8,309
Ceded unearned premiums	578	551
Deferred acquisition costs	2,120	2,025
Deferred taxes	445	70
Contractholder receivables	4,785	4,775
Goodwill	3,937	3,951
Other intangible assets	345	342
Other assets	2,872	2,864
Total assets	104,233	103,483
Claims and claim adjustment expense reserves	50,668	49,650
Unearned premium reserves	13,555	12,915
Contractholder payables	4,785	4,775
Payables for reinsurance premiums	289	274
Debt	6,564	6,571
Other liabilities	5,478	5,567
Total liabilities	81,339	79,752
Common stock	23,144	22,886
Retained earnings	35,204	33,462
Accumulated other comprehensive income (loss)	(1,859)	(343)
Treasury stock, at cost	(33,595)	(32,274)
Total shareholders’ equity	22,894	23,731	23,221
Total liabilities and shareholders’ equity	104,233	103,483
Fixed maturities, available for sale, amortized cost	63,601	61,316
Equity securities, cost	$ 382
Equity securities, available for sale, cost		$ 440
Common stock, shares authorized (in shares)	1,750,000,000	1,750,000,000
Common stock, shares issued (in shares)	263,700,000	271,500,000
Common stock, shares outstanding (in shares)	263,600,000	271,400,000
Treasury stock, at cost, shares (in shares)	510,900,000	500,900,000
TRV [Member]
Consolidating Balance Sheet
Fixed maturities, at fair value	$ 84	$ 82
Equity securities, at fair value	171
Equity securities, available for sale, at fair value		181
Short-term securities	1,371	1,230
Cash			2	2
Investment in subsidiaries	26,993	27,946
Total assets	29,268	30,131
Debt	5,871	5,878
Total liabilities	6,367	6,402
Common stock	23,144	22,886
Retained earnings	35,211	33,460
Accumulated other comprehensive income (loss)	(1,859)	(343)
Treasury stock, at cost	(33,595)	(32,274)
Total shareholders’ equity	22,901	23,729
Total liabilities and shareholders’ equity	$ 29,268	$ 30,131
Common stock, shares authorized (in shares)	1,750,000,000	1,750,000,000
Common stock, shares issued (in shares)	263,700,000	271,500,000
Common stock, shares outstanding (in shares)	263,600,000	271,400,000
Treasury stock, at cost, shares (in shares)	510,900,000	500,900,000
Reportable Legal Entities [Member] | TPC [Member]
Consolidating Balance Sheet
Fixed maturities, at fair value	$ 43,683	$ 43,240
Equity securities, at fair value	105
Equity securities, available for sale, at fair value		161
Real estate investments	2	54
Short-term securities	1,855	2,751
Other investments	2,746	2,673
Total investments	48,391	48,879
Cash	181	157	141	225
Investment income accrued	434	418
Premiums receivable	5,089	4,852
Reinsurance recoverables	5,904	5,842
Ceded unearned premiums	522	493
Deferred acquisition costs	1,930	1,835
Deferred taxes	167	(89)
Contractholder receivables	3,867	3,854
Goodwill	2,578	2,592
Other intangible assets	224	202
Other assets	2,220	2,181
Total assets	71,507	71,216
Claims and claim adjustment expense reserves	34,093	33,386
Unearned premium reserves	9,414	8,957
Contractholder payables	3,867	3,854
Payables for reinsurance premiums	169	165
Debt	693	693
Other liabilities	4,133	4,161
Total liabilities	52,369	51,216
Additional paid-in capital	11,634	11,634
Retained earnings	8,065	8,036
Accumulated other comprehensive income (loss)	(561)	330
Total shareholders’ equity	19,138	20,000
Total liabilities and shareholders’ equity	71,507	71,216
Reportable Legal Entities [Member] | Other Subsidiaries [Member]
Consolidating Balance Sheet
Fixed maturities, at fair value	19,697	19,372
Equity securities, at fair value	92
Equity securities, available for sale, at fair value		111
Real estate investments	902	878
Short-term securities	759	914
Other investments	810	854
Total investments	22,260	22,129
Cash	192	187	164	153
Investment income accrued	187	183
Premiums receivable	2,417	2,292
Reinsurance recoverables	2,466	2,467
Ceded unearned premiums	56	58
Deferred acquisition costs	190	190
Deferred taxes	302	173
Contractholder receivables	918	921
Goodwill	1,368	1,368
Other intangible assets	121	140
Other assets	15	(3)
Total assets	30,492	30,105
Claims and claim adjustment expense reserves	16,575	16,264
Unearned premium reserves	4,141	3,958
Contractholder payables	918	921
Payables for reinsurance premiums	120	109
Debt	32	14
Other liabilities	849	882
Total liabilities	22,635	22,148
Common stock	401	390
Additional paid-in capital	7,023	6,972
Retained earnings	879	594
Accumulated other comprehensive income (loss)	(446)	1
Total shareholders’ equity	7,857	7,957
Total liabilities and shareholders’ equity	30,492	30,105
Reportable Legal Entities [Member] | TRV [Member]
Consolidating Balance Sheet
Fixed maturities, at fair value	84	82
Equity securities, at fair value	171
Equity securities, available for sale, at fair value		181
Short-term securities	1,371	1,230
Other investments	1	1
Total investments	1,627	1,494
Cash			$ 2	$ 2
Investment income accrued	3	5
Deferred taxes	(24)	(14)
Investment in subsidiaries	26,993	27,946
Other assets	669	700
Total assets	29,268	30,131
Debt	5,871	5,878
Other liabilities	496	524
Total liabilities	6,367	6,402
Common stock	23,144	22,886
Retained earnings	35,211	33,460
Accumulated other comprehensive income (loss)	(1,859)	(343)
Treasury stock, at cost	(33,595)	(32,274)
Total shareholders’ equity	22,901	23,729
Total liabilities and shareholders’ equity	29,268	30,131
Eliminations [Member]
Consolidating Balance Sheet
Goodwill	(9)	(9)
Investment in subsidiaries	(26,993)	(27,946)
Other assets	(32)	(14)
Total assets	(27,034)	(27,969)
Debt	(32)	(14)
Total liabilities	(32)	(14)
Common stock	(401)	(390)
Additional paid-in capital	(18,657)	(18,606)
Retained earnings	(8,951)	(8,628)
Accumulated other comprehensive income (loss)	1,007	(331)
Total shareholders’ equity	(27,002)	(27,955)
Total liabilities and shareholders’ equity	$ (27,034)	$ (27,969)

Consolidating Financial State_7

Consolidating Financial Statements (Details) - Consolidating Statement of Cash Flows (Unaudited) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Consolidating Statement of Cash Flows
Net income	$ 621	$ 709	$ 524	$ 669	$ 551	$ 293	$ 595	$ 617	$ 2,523	$ 2,056	$ 3,014
Net adjustments to reconcile net income to net cash provided by operating activities									1,857	2,092	1,455
Net cash provided by operating activities									4,380	4,148	4,469
Proceeds from maturities of fixed maturities									7,086	8,750	8,975
Proceeds from sales of investments:
Fixed maturities									3,546	1,854	1,417
Equity securities									178
Equity securities										765	92
Real estate investments									74	23	69
Other investments									511	468	566
Purchases of investments:
Fixed maturities									(13,526)	(12,250)	(11,609)
Equity securities									(117)
Equity securities										(459)	(51)
Real estate investments									(74)	(59)	(48)
Other investments									(537)	(541)	(580)
Net sales (purchases) of short-term securities									908	(26)	(199)
Securities transactions in the course of settlement									(56)	(47)	(21)
Acquisition, net of cash acquired									(4)	(439)
Other investing activities									(318)	(241)	(338)
Net cash used in investing activities									(2,329)	(2,202)	(1,727)
Treasury stock acquired — share repurchase authorization									(1,270)	(1,378)	(2,400)
Treasury stock acquired — net employee share-based compensation									(51)	(62)	(72)
Dividends paid to shareholders									(814)	(785)	(757)
Payment of debt									(600)	(657)	(400)
Issuance of debt									591	789	491
Issuance of common stock -- employee share options									132	173	332
Net cash used in financing activities									(2,012)	(1,920)	(2,806)
Effect of exchange rate changes on cash									(10)	11	(9)
Net increase (decrease) in cash									29	37	(73)
Cash at beginning of year				344				307	344	307	380
Cash at end of year	373				344				373	344	307
Income taxes paid (received)									408	514	892
Interest paid									347	367	358
TRV [Member]
Consolidating Statement of Cash Flows
Net income									2,523	2,064	3,014
Net cash provided by operating activities									2,160	2,032	2,892
Purchases of investments:
Net sales (purchases) of short-term securities									(141)	397	(81)
Acquisition, net of cash acquired										(477)
Net cash used in investing activities									(148)	(114)	(86)
Treasury stock acquired — share repurchase authorization									(1,270)	(1,378)	(2,400)
Treasury stock acquired — net employee share-based compensation									(51)	(62)	(72)
Dividends paid to shareholders									(814)	(785)	(757)
Payment of debt									(600)	(657)	(400)
Issuance of debt									591	789	491
Issuance of common stock -- employee share options									132	173	332
Net cash used in financing activities									(2,012)	(1,920)	(2,806)
Net increase (decrease) in cash										(2)
Cash at beginning of year								2		2	2
Cash at end of year											2
Income taxes paid (received)									(283)	(173)	(132)
Interest paid									300	320	311
Reportable Legal Entities [Member] | TPC [Member]
Consolidating Statement of Cash Flows
Net income									2,110	1,728	2,184
Net adjustments to reconcile net income to net cash provided by operating activities									1,141	1,500	1,282
Net cash provided by operating activities									3,251	3,228	3,466
Proceeds from maturities of fixed maturities									5,158	6,576	6,589
Proceeds from sales of investments:
Fixed maturities									2,449	1,007	768
Equity securities									65
Equity securities										97	47
Real estate investments									66
Other investments									403	357	386
Purchases of investments:
Fixed maturities									(9,404)	(8,513)	(7,921)
Equity securities									(8)
Equity securities										(68)	(6)
Real estate investments									(1)	(1)	(1)
Other investments									(454)	(444)	(453)
Net sales (purchases) of short-term securities									895	(303)	(501)
Securities transactions in the course of settlement									(80)	(55)	12
Other investing activities									(310)	(244)	(331)
Net cash used in investing activities									(1,221)	(1,591)	(1,411)
Dividends paid to parent company									(2,003)	(1,624)	(2,140)
Net cash used in financing activities									(2,003)	(1,624)	(2,140)
Effect of exchange rate changes on cash									(3)	3	1
Net increase (decrease) in cash									24	16	(84)
Cash at beginning of year				157				141	157	141	225
Cash at end of year	181				157				181	157	141
Income taxes paid (received)									437	481	737
Interest paid									47	47	47
Reportable Legal Entities [Member] | Other Subsidiaries [Member]
Consolidating Statement of Cash Flows
Net income									604	462	970
Net adjustments to reconcile net income to net cash provided by operating activities									605	701	139
Net cash provided by operating activities									1,209	1,163	1,109
Proceeds from maturities of fixed maturities									1,906	2,168	2,380
Proceeds from sales of investments:
Fixed maturities									1,096	846	647
Equity securities									107
Equity securities										414	45
Real estate investments									8	23	69
Other investments									108	124	180
Purchases of investments:
Fixed maturities									(4,096)	(3,697)	(3,676)
Equity securities									(99)
Equity securities										(133)	(42)
Real estate investments									(73)	(58)	(47)
Other investments									(83)	(97)	(127)
Net sales (purchases) of short-term securities									154	(120)	383
Securities transactions in the course of settlement									24	5	(32)
Acquisition, net of cash acquired									(4)	25
Other investing activities									(8)	3	(10)
Net cash used in investing activities									(960)	(497)	(230)
Issuance of debt									18	14
Dividends paid to parent company									(255)	(665)	(858)
Net cash used in financing activities									(237)	(651)	(858)
Effect of exchange rate changes on cash									(7)	8	(10)
Net increase (decrease) in cash									5	23	11
Cash at beginning of year				$ 187				164	187	164	153
Cash at end of year	$ 192				$ 187				192	187	164
Income taxes paid (received)									254	206	287
Reportable Legal Entities [Member] | TRV [Member]
Consolidating Statement of Cash Flows
Net income									2,523	2,064	3,014
Net adjustments to reconcile net income to net cash provided by operating activities									(363)	(32)	(122)
Net cash provided by operating activities									2,160	2,032	2,892
Proceeds from maturities of fixed maturities									22	6	6
Proceeds from sales of investments:
Fixed maturities									1	1	2
Equity securities									6
Equity securities										254
Purchases of investments:
Fixed maturities									(26)	(40)	(12)
Equity securities									(10)
Equity securities										(258)	(3)
Net sales (purchases) of short-term securities									(141)	397	(81)
Securities transactions in the course of settlement										3	(1)
Acquisition, net of cash acquired										(477)
Other investing activities											3
Net cash used in investing activities									(148)	(114)	(86)
Treasury stock acquired — share repurchase authorization									(1,270)	(1,378)	(2,400)
Treasury stock acquired — net employee share-based compensation									(51)	(62)	(72)
Dividends paid to shareholders									(814)	(785)	(757)
Payment of debt									(600)	(657)	(400)
Issuance of debt									591	789	491
Issuance of common stock -- employee share options									132	173	332
Net cash used in financing activities									(2,012)	(1,920)	(2,806)
Net increase (decrease) in cash										(2)
Cash at beginning of year								$ 2		2	2
Cash at end of year											2
Income taxes paid (received)									(283)	(173)	(132)
Interest paid									300	320	311
Eliminations [Member]
Consolidating Statement of Cash Flows
Net income									(2,714)	(2,198)	(3,154)
Net adjustments to reconcile net income to net cash provided by operating activities									474	(77)	156
Net cash provided by operating activities									(2,240)	(2,275)	(2,998)
Proceeds from sales of investments:
Other investments										(13)
Purchases of investments:
Acquisition, net of cash acquired										13
Issuance of debt									(18)	(14)
Dividends paid to parent company									2,258	2,289	2,998
Net cash used in financing activities									$ 2,240	$ 2,275	$ 2,998

Selected Quarterly Financial _3

Selected Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Total revenues	$ 7,796	$ 7,723	$ 7,477	$ 7,286	$ 7,451	$ 7,325	$ 7,184	$ 6,942	$ 30,282	$ 28,902	$ 27,625
Total expenses	7,050	6,917	6,846	6,508	6,591	7,005	6,394	6,182	27,321	26,172	23,572
Income before income taxes	746	806	631	778	860	320	790	760	2,961	2,730	4,053
Income tax expense	125	97	107	109	309	27	195	143	438	674	1,039
Net income	$ 621	$ 709	$ 524	$ 669	$ 551	$ 293	$ 595	$ 617	$ 2,523	$ 2,056	$ 3,014
Net income per common share, basic (in dollars per share)	$ 2.33	$ 2.65	$ 1.93	$ 2.45	$ 2	$ 1.06	$ 2.13	$ 2.19	$ 9.37	$ 7.39	$ 10.39
Net income per common share, diluted (in dollars per share)	$ 2.32	$ 2.62	$ 1.92	$ 2.42	$ 1.98	$ 1.05	$ 2.11	$ 2.17	$ 9.28	$ 7.33	$ 10.28
Net charge included in total income tax expense related to TCJA at the date of enactment										$ 129

Schedule II (Details) - Condens

Schedule II (Details) - Condensed Income Statement - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Condensed Statement of Income
Net investment income										$ 2,474	$ 2,397	$ 2,302
Net realized investment gains (losses)	[1]									114	216	68
Total revenues		$ 7,796	$ 7,723	$ 7,477	$ 7,286	$ 7,451	$ 7,325	$ 7,184	$ 6,942	30,282	28,902	27,625
Interest expense										352	369	363
Expenses, other										4,297	4,170	4,154
Total claims and expenses		7,050	6,917	6,846	6,508	6,591	7,005	6,394	6,182	27,321	26,172	23,572
Income before income taxes		746	806	631	778	860	320	790	760	2,961	2,730	4,053
Income tax expense (benefit)		125	97	107	109	309	27	195	143	438	674	1,039
Net income		$ 621	$ 709	$ 524	$ 669	$ 551	$ 293	$ 595	$ 617	2,523	2,056	3,014
Other-than-temporary impairment losses recognized in net realized investment gains (losses)										(1)
Other-than-temporary impairment losses recognized in net realized investment gains (losses)											(14)	(29)
Other-than-temporary impairment losses recognized in other comprehensive income (loss)										0		(11)
Other-than-temporary impairment gains recognized in other comprehensive income (loss)											1
Travelers [Member]
Condensed Statement of Income
Net investment income										32	24	13
Net realized investment gains (losses)										(13)	66	(1)
Total revenues										19	90	12
Interest expense										304	321	315
Expenses, other										20	25	5
Total claims and expenses										324	346	320
Income before income taxes										(305)	(256)	(308)
Income tax expense (benefit)										(114)	(130)	(168)
Loss before net income of subsidiaries										(191)	(126)	(140)
Net income of subsidiaries										2,714	2,190	3,154
Net income										2,523	2,064	3,014
Other-than-temporary impairment losses recognized in net realized investment gains (losses)										0
Other-than-temporary impairment losses recognized in net realized investment gains (losses)											0	(1)
Other-than-temporary impairment losses recognized in other comprehensive income (loss)										$ 0		$ 0
Other-than-temporary impairment gains recognized in other comprehensive income (loss)											$ 0
[1]	Total other-than-temporary impairment (OTTI) losses were $(1) million, $(13) million and $(40) million for the years ended December 31, 2018, 2017 and 2016, respectively. Of total OTTI, credit losses of $(1) million, $(14) million and $(29) million for the years ended December 31, 2018, 2017 and 2016, respectively, were recognized in net realized investment gains. In addition, unrealized gains (losses) from other changes in total OTTI of $0 million, $1 million and $(11) million for the years ended December 31, 2018, 2017 and 2016, respectively, were recognized in other comprehensive income (loss) as part of changes in net unrealized gains (losses) on investment securities having credit losses recognized in the consolidated statement of income.

Schedule II (Details) - Conde_2

Schedule II (Details) - Condensed Statement of Comprehensive Income - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Condensed Statement of Comprehensive Income
Net income	$ 621	$ 709	$ 524	$ 669	$ 551	$ 293	$ 595	$ 617	$ 2,523	$ 2,056	$ 3,014
Changes in net unrealized gains on investment securities having no credit losses recognized in the consolidated statement of income									(1,489)	294	(883)
Net changes in benefit plan assets and obligations									(56)	29	16
Other comprehensive income (loss) before income taxes									(1,819)	522	(887)
Income tax expense (benefit)									(349)	110	(289)
Other comprehensive income (loss), net of taxes, before other comprehensive income (loss) of subsidiaries									(1,470)	412	(598)
Other comprehensive income (loss), net of taxes									(1,470)	412	(598)
Comprehensive income									1,053	2,468	2,416
Travelers [Member]
Condensed Statement of Comprehensive Income
Net income									2,523	2,064	3,014
Changes in net unrealized gains on investment securities having no credit losses recognized in the consolidated statement of income										(44)	11
Net changes in benefit plan assets and obligations									(53)	22	(20)
Other comprehensive income (loss) before income taxes									(53)	(22)	(9)
Income tax expense (benefit)									(17)	2	(1)
Other comprehensive income (loss), net of taxes, before other comprehensive income (loss) of subsidiaries									(36)	(24)	(8)
Other comprehensive income (loss) of subsidiaries									(1,434)	436	(590)
Other comprehensive income (loss), net of taxes									(1,470)	412	(598)
Comprehensive income									$ 1,053	$ 2,476	$ 2,416

Schedule II (Details) - Conde_3

Schedule II (Details) - Condensed Balance Sheet - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Condensed Balance Sheet
Fixed maturities, at fair value	$ 63,464	$ 62,694
Equity securities, at fair value	368
Equity securities, available for sale, at fair value		453
Short-term securities	3,985	4,895
Total assets	104,233	103,483
Debt	6,564	6,571
Total liabilities	81,339	79,752
Common stock (1,750.0 shares authorized; 263.7 and 271.5 shares issued, 263.6 and 271.4 shares outstanding)	23,144	22,886
Retained earnings	35,204	33,462
Accumulated other comprehensive loss	(1,859)	(343)
Treasury stock, at cost (510.9 and 500.9 shares)	(33,595)	(32,274)
Total shareholders’ equity	22,894	23,731	$ 23,221
Total liabilities and shareholders’ equity	$ 104,233	$ 103,483
Common stock, shares authorized (in shares)	1,750,000,000	1,750,000,000
Common stock, shares issued (in shares)	263,700,000	271,500,000
Common stock, shares outstanding (in shares)	263,600,000	271,400,000
Treasury stock, at cost, shares (in shares)	510,900,000	500,900,000
Travelers [Member]
Condensed Balance Sheet
Fixed maturities, at fair value	$ 84	$ 82
Equity securities, at fair value	171
Equity securities, available for sale, at fair value		181
Short-term securities	1,371	1,230
Investment in subsidiaries	26,993	27,946
Other assets	649	692
Total assets	29,268	30,131
Debt	5,871	5,878
Other liabilities	496	524
Total liabilities	6,367	6,402
Common stock (1,750.0 shares authorized; 263.7 and 271.5 shares issued, 263.6 and 271.4 shares outstanding)	23,144	22,886
Retained earnings	35,211	33,460
Accumulated other comprehensive loss	(1,859)	(343)
Treasury stock, at cost (510.9 and 500.9 shares)	(33,595)	(32,274)
Total shareholders’ equity	22,901	23,729
Total liabilities and shareholders’ equity	$ 29,268	$ 30,131
Common stock, shares authorized (in shares)	1,750,000,000	1,750,000,000
Common stock, shares issued (in shares)	263,700,000	271,500,000
Common stock, shares outstanding (in shares)	263,600,000	271,400,000
Treasury stock, at cost, shares (in shares)	510,900,000	500,900,000

Schedule II (Details) - Conde_4

Schedule II (Details) - Condensed Statement of Cash Flows - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Condensed Statement of Cash Flows
Net income	$ 621	$ 709	$ 524	$ 669	$ 551	$ 293	$ 595	$ 617	$ 2,523	$ 2,056	$ 3,014
Deferred federal income tax expense									(13)	337	110
Other operating activities									190	43	456
Net cash provided by operating activities									4,380	4,148	4,469
Net sales (purchases) of short-term securities									908	(26)	(199)
Acquisition, net of cash acquired									(4)	(439)
Net cash used in investing activities									(2,329)	(2,202)	(1,727)
Treasury stock acquired — share repurchase authorization									(1,270)	(1,378)	(2,400)
Treasury stock acquired — net employee share-based compensation									(51)	(62)	(72)
Dividends paid to shareholders									(814)	(785)	(757)
Payment of debt									(600)	(657)	(400)
Issuance of debt									591	789	491
Issuance of common stock -- employee share options									132	173	332
Net cash used in financing activities									(2,012)	(1,920)	(2,806)
Net increase (decrease) in cash									29	37	(73)
Cash at beginning of year				$ 344				307	344	307	380
Cash at end of year	$ 373				$ 344				373	344	307
Cash received during the year for taxes									(408)	(514)	(892)
Cash paid during the year for interest									347	367	358
Travelers [Member]
Condensed Statement of Cash Flows
Net income									2,523	2,064	3,014
Equity in net income of subsidiaries									(2,714)	(2,190)	(3,154)
Dividends received from consolidated subsidiaries									2,258	2,289	2,998
Deferred federal income tax expense									28	40	12
Change in income taxes payable									100	3	(48)
Other operating activities									(35)	(174)	70
Net cash provided by operating activities									2,160	2,032	2,892
Net sales (purchases) of short-term securities									(141)	397	(81)
Other investments, net									(7)	(34)	(5)
Acquisition, net of cash acquired										(477)
Net cash used in investing activities									(148)	(114)	(86)
Treasury stock acquired — share repurchase authorization									(1,270)	(1,378)	(2,400)
Treasury stock acquired — net employee share-based compensation									(51)	(62)	(72)
Dividends paid to shareholders									(814)	(785)	(757)
Payment of debt									(600)	(657)	(400)
Issuance of debt									591	789	491
Issuance of common stock -- employee share options									132	173	332
Net cash used in financing activities									(2,012)	(1,920)	(2,806)
Net increase (decrease) in cash										(2)
Cash at beginning of year								$ 2		2	2
Cash at end of year											2
Cash received during the year for taxes									283	173	132
Cash paid during the year for interest									$ 300	$ 320	$ 311

Schedule II (Details) - Guarant

Schedule II (Details) - Guarantees	12 Months Ended
	Dec. 31, 2018
Condensed Financial Information Disclosure [Abstract]
Schedule II Guarantees Footnote	GUARANTEES The Travelers Companies, Inc. (TRV) fully and unconditionally guarantees the payment of all principal, premiums, if any, and interest on certain debt obligations of its subsidiaries TPC and TIGHI. The guarantees pertain to the $200 million 7.75% notes due 2026 and the $500 million 6.375% notes due 2033. TRV also has contingent obligations for guarantees in connection with the selling of businesses to third parties, certain insurance obligations of a subsidiary and various indemnifications including indemnifications to service providers in the normal course of business. The guarantees and indemnification clauses are often standard contractual terms and include indemnifications for breaches of representations and warranties and in some cases obligations arising from certain liabilities. The terms of these provisions vary in duration and nature. Certain of the guarantees and indemnifications described above have no stated or notional amounts or limitation to the maximum potential future payments. Accordingly, TRV is unable to provide an estimate of the maximum potential payments for such arrangements, and the likelihood for any payment under these guarantees is remote.

Schedule II (Details) - Guara_2

Schedule II (Details) - Guarantees Schedule - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Guarantor obligations
Amount of certain debt obligations of Travelers Property Casualty Corp. (TPC) and Travelers Insurance Group Holdings, Inc. (TIGHI) that are fully and unconditionally guaranteed by The Travelers Companies, Inc.	$ 700
Senior Notes [Member] | 7.75% Senior notes due April 15, 2026 [Member]
Guarantor obligations
Amount of certain debt obligations of Travelers Property Casualty Corp. (TPC) and Travelers Insurance Group Holdings, Inc. (TIGHI) that are fully and unconditionally guaranteed by The Travelers Companies, Inc.	$ 200
Interest rate (percent)	7.75%	7.75%
Senior Notes [Member] | 6.375% Senior notes due March 15, 2033 [Member]
Guarantor obligations
Amount of certain debt obligations of Travelers Property Casualty Corp. (TPC) and Travelers Insurance Group Holdings, Inc. (TIGHI) that are fully and unconditionally guaranteed by The Travelers Companies, Inc.	$ 500
Interest rate (percent)	6.375%	6.375%
Guarantees on payment of principal, premiums and interest on certain debt obligations [Member] | Travelers [Member] | Senior Notes [Member] | 7.75% Senior notes due April 15, 2026 [Member]
Guarantor obligations
Amount of certain debt obligations of Travelers Property Casualty Corp. (TPC) and Travelers Insurance Group Holdings, Inc. (TIGHI) that are fully and unconditionally guaranteed by The Travelers Companies, Inc.	$ 200
Interest rate (percent)	7.75%
Guarantees on payment of principal, premiums and interest on certain debt obligations [Member] | Travelers [Member] | Senior Notes [Member] | 6.375% Senior notes due March 15, 2033 [Member]
Guarantor obligations
Amount of certain debt obligations of Travelers Property Casualty Corp. (TPC) and Travelers Insurance Group Holdings, Inc. (TIGHI) that are fully and unconditionally guaranteed by The Travelers Companies, Inc.	$ 500
Interest rate (percent)	6.375%

Schedule III (Details)

Schedule III (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Schedule III
Deferred acquisition costs	$ 2,120	$ 2,025	$ 1,923
Claims and claim adjustment expense reserves	50,668	49,650	47,949
Unearned premiums	13,555	12,915	12,329
Earned premiums	27,059	25,683	24,534
Net investment income	2,474	2,397	2,302
Claims and claim adjustment expenses	18,291	17,467	15,070
Amortization of deferred acquisition costs	4,381	4,166	3,985
Other operating expenses	4,649	4,539	4,517
Net written premiums	27,708	26,219	24,958
Reportable segments [Member]
Schedule III
Deferred acquisition costs	2,120	2,025	1,923
Claims and claim adjustment expense reserves	50,653	49,633	47,929
Unearned premiums	13,555	12,915	12,329
Earned premiums	27,059	25,683	24,534
Net investment income	2,474	2,397	2,302
Claims and claim adjustment expenses	18,291	17,467	15,070
Amortization of deferred acquisition costs	4,381	4,166	3,985
Other operating expenses	4,267	4,138	4,123
Net written premiums	27,708	26,219	24,958
Reportable segments [Member] | Business Insurance [Member]
Schedule III
Deferred acquisition costs	1,102	1,060	1,026
Claims and claim adjustment expense reserves	41,132	40,352	39,555
Unearned premiums	7,112	6,857	6,725
Earned premiums	14,722	14,146	13,855
Net investment income	1,833	1,786	1,701
Claims and claim adjustment expenses	10,171	9,521	8,753
Amortization of deferred acquisition costs	2,388	2,286	2,221
Other operating expenses	2,623	2,563	2,554
Net written premiums	14,956	14,270	13,900
Reportable segments [Member] | Bond & Specialty Insurance [Member]
Schedule III
Deferred acquisition costs	277	258	246
Claims and claim adjustment expense reserves	3,255	3,421	3,323
Unearned premiums	1,619	1,515	1,444
Earned premiums	2,420	2,307	2,260
Net investment income	233	228	239
Claims and claim adjustment expenses	772	899	633
Amortization of deferred acquisition costs	454	432	421
Other operating expenses	459	464	445
Net written premiums	2,528	2,359	2,271
Reportable segments [Member] | Personal Insurance [Member]
Schedule III
Deferred acquisition costs	741	707	651
Claims and claim adjustment expense reserves	6,266	5,860	5,051
Unearned premiums	4,824	4,543	4,160
Earned premiums	9,917	9,230	8,419
Net investment income	408	383	362
Claims and claim adjustment expenses	7,348	7,047	5,684
Amortization of deferred acquisition costs	1,539	1,448	1,343
Other operating expenses	1,185	1,111	1,124
Net written premiums	10,224	9,590	8,787
Other [Member]
Schedule III
Claims and claim adjustment expense reserves	15	17	20
Other operating expenses	$ 382	$ 401	$ 394

Schedule V (Details)

Schedule V (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reinsurance recoverables [Member]
Schedule V [Roll Forward]
Valuation and qualifying accounts, balance at beginning of period	$ 111	$ 116	$ 157
Valuation and qualifying accounts, deductions	1	5	41
Valuation and qualifying accounts, balance at end of period	110	111	116
Allowance for uncollectible premiums receivable from underwriting activities [Member]
Schedule V [Roll Forward]
Valuation and qualifying accounts, balance at beginning of period	58	61	65
Valuation and qualifying accounts, charged to costs and expenses	50	38	35
Valuation and qualifying accounts, deductions	54	41	39
Valuation and qualifying accounts, balance at end of period	54	58	61
Allowance for uncollectible deductibles [Member]
Schedule V [Roll Forward]
Valuation and qualifying accounts, balance at beginning of period	26	34	35
Valuation and qualifying accounts, charged to costs and expenses	(1)	(2)	5
Valuation and qualifying accounts, deductions	1	6	6
Valuation and qualifying accounts, balance at end of period	$ 24	$ 26	$ 34

Schedule VI (Details)

Schedule VI (Details) - Consolidated Property and Casualty Insurance Entity [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Supplementary Information Concerning Property-Casualty Insurance Operations
Deferred acquisition costs	$ 2,120	$ 2,025	$ 1,923
Claims and claim adjustment expense reserves	50,653	49,633	47,929
Discount from reserves for unpaid claims	1,158	1,102	1,083
Unearned premiums	13,555	12,915	12,329
Earned premiums	27,059	25,683	24,534
Net investment income	2,474	2,397	2,302
Claims and claim adjustment expenses incurred related to current year	18,614	17,846	15,675
Claims and claim adjustment expenses incurred related to prior year	(406)	(458)	(680)
Amortization of deferred acquisition costs	4,381	4,166	3,985
Paid claims and claim adjustment expenses	17,060	16,043	14,796
Net written premiums	$ 27,708	$ 26,219	$ 24,958