Consolidated Statements Of Operations and Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenues
Net premiums written	$ 28,145	$ 17,713	$ 17,799
Decrease (increase) in unearned premiums	604	(500)	(373)
Net premiums earned	28,749	17,213	17,426
Net investment income	2,865	2,194	2,252
Net realized gains (losses):
Other-than-temporary impairment (OTTI) losses gross	(111)	(151)	(75)
Portion of OTTI losses recognized in other comprehensive income (OCI)	8	39	7
Net OTTI losses recognized in income	(103)	(112)	(68)
Net realized gains (losses) excluding OTTI losses	(42)	(308)	(439)
Total Net realized gains (losses) including OTTI	(145)	(420)	(507)
Total revenues	31,469	18,987	19,171
Expenses
Losses and loss expenses	16,052	9,484	9,649
Policy benefits	588	543	517
Policy Acquisition Costs	5,904	2,941	3,075
Administrative expenses	3,081	2,270	2,245
Interest expense	605	300	280
Other (income) expense	(222)	(51)	(190)
Amortization of Purchased Intangibles	19	171	108
Chubb integration expenses	492	33	0
Total expenses	26,519	15,691	15,684
Income before income tax	4,950	3,296	3,487
Income tax expense	815	462	634
Net income	4,135	2,834	2,853
Other comprehensive income (loss)
Unrealized appreciation (depreciation)	(35)	(1,280)	820
Reclassification adjustment for net realized (gains) losses included in net income	119	151	24
Other comprehensive income (loss) after reclassification for net realized gains included in net income	84	(1,129)	844
Change in:
Cumulative foreign currency translation adjustment	(154)	(958)	(632)
Postretirement benefit liability adjustment	545	15	2
Other comprehensive income (loss), before income tax	475	(2,072)	214
Income tax (expense) benefit related to OCI items	(54)	146	(175)
Other comprehensive income (loss)	421	(1,926)	39
Comprehensive income	$ 4,556	$ 908	$ 2,892
Earnings per share
Basic earnings per share	$ 8.94	$ 8.71	$ 8.50
Diluted earnings per share	$ 8.87	$ 8.62	$ 8.42