Income Taxes (tables)

12 Months Ended

Dec. 31, 2017

Income Taxes disclosure

Composition of income tax expense included in consolidated statement of income and shareholders' equity [Table Text Block]

(for the year ended December 31, in millions)	2017			2016			2015
Composition of income tax expense included in the consolidated statements of income
Current expense:
Federal	$	314		$	899		$	1,144
Impact of TCJA at enactment		21			—			—
Foreign		56			21			29
State		4			8			9
Total current tax expense		395			928			1,182
Deferred expense (benefit):
Federal		229			110			117
Impact of TCJA at enactment		108			—			—
Foreign		(58	)		1			2
Total deferred tax expense		279			111			119
Total income tax expense included in the consolidated statements of income		674			1,039			1,301
Composition of income tax expense (benefit) included in shareholders' equity
Expense (benefit) relating to share-based compensation, the changes in unrealized gain on investments, unrealized loss on foreign exchange and other items in other comprehensive income (loss)		110			(289	)		(448	)
Total income tax expense included in the consolidated financial statements	$	784		$	750		$	853

Effective tax rate [Table Text Block]

(for the year ended December 31, in millions)	2017			2016			2015
Income (loss) before income taxes
U.S.	$	2,798		$	3,946		$	4,621
Foreign		(68	)		107			119
Total income before income taxes		2,730			4,053			4,740
Effective tax rate
Statutory tax rate		35	%		35	%		35	%
Expected federal income tax expense		956			1,419			1,659
Tax effect of:
Nontaxable investment income		(297	)		(323	)		(345	)
TCJA at enactment		129			—			—
Other, net		(114	)		(57	)		(13	)
Total income tax expense	$	674		$	1,039		$	1,301
Effective tax rate		25	%		26	%		27	%

Deferred tax assets and liabilities [Table Text Block]

(at December 31, in millions)	2017		2016
Deferred tax assets
Claims and claim adjustment expense reserves	$	930	$	664
Unearned premium reserves		478		760
Compensation-related liabilities		61		268
Other		191		272
Total gross deferred tax assets		1,660		1,964
Less: valuation allowance		6		3
Adjusted gross deferred tax assets		1,654		1,961
Deferred tax liabilities
Claims and claim adjustment expense reserve discounting (transition rule)		560		—
Deferred acquisition costs		376		604
Investments		454		592
Internally developed software		97		157
Other		97		143
Total gross deferred tax liabilities		1,584		1,496
Net deferred tax asset	$	70	$	465

Net operating loss amounts by jurisdiction and year of expiration [Table Text Block]

(in millions)	Amount		Year of expiration
Brazil	$	15	None
United Kingdom	$	156	None

Reconciliation of unrecognized tax benefits [Table Text Block]

(in millions)	2017			2016
Balance at January 1	$	13		$	16
Additions for tax positions of prior years		—			3
Reductions for tax positions of prior years		(1	)		(6	)
Reductions based on tax positions related to current year		(6	)		—
Balance at December 31	$	6		$	13