Consolidated Statements Of Operations and Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues
Net premiums written	$ 30,579	$ 29,244	$ 28,145
(Increase) decrease in unearned premiums	(515)	(210)	604
Net premiums earned	30,064	29,034	28,749
Net investment income	3,305	3,125	2,865
Net realized gains (losses):
Other-than-temporary impairment (OTTI) losses gross	(52)	(46)	(111)
Portion of OTTI losses recognized in other comprehensive income (OCI)	3	1	8
Net OTTI losses recognized in income	49
Net OTTI losses recognized in income		45	103
Net realized, Gain (Loss), Excluding Other-than-temporary Impairment Loss	(603)
Net realized gains (losses) excluding OTTI losses		129	(42)
Total net realized gains (losses) (includes ($302) reclassified from AOCI)	(652)
Net Realized Investment Gains (Losses) (includes $(15), and $(119) reclassified from AOCI)		84	(145)
Total revenues	32,717	32,243	31,469
Expenses
Losses and loss expenses	18,067	18,454	16,052
Policy benefits	590	676	588
Policy Acquisition Costs	5,912	5,781	5,904
Administrative expenses	2,886	2,833	3,081
Interest expense	641	607	605
Other (income) expense	(434)	(400)	(222)
Amortization of Purchased Intangibles	339	260	19
Chubb integration expenses	59	310	492
Total expenses	28,060	28,521	26,519
Income before income tax	4,657	3,722	4,950
Income tax expense (benefit) (includes $(41), $(13), and $28 on reclassified unrealized gains and losses)	695	(139)	815
Net income	3,962	3,861	4,135
Other comprehensive income (loss)
Unrealized appreciation (depreciation)	(2,298)	618	(35)
Reclassification adjustment for net realized (gains) losses included in net income	302	15	119
Other comprehensive income (loss) after reclassification for net realized gains included in net income	(1,996)	633	84
Change in:
Cumulative foreign currency translation adjustment	(802)	471	(154)
Postretirement benefit liability adjustment	(321)	(16)	545
Other comprehensive income (loss), before income tax	(3,119)	1,088	475
Income tax (expense) benefit related to OCI items	399	(231)	(54)
Other comprehensive income (loss)	(2,720)	857	421
Comprehensive income	$ 1,242	$ 4,718	$ 4,556
Earnings per share
Basic earnings per share	$ 8.55	$ 8.26	$ 8.94
Diluted earnings per share	$ 8.49	$ 8.19	$ 8.87