Consolidated Statements Of Operations and Comprehensive Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenues
Net premiums written	$ 8,110	$ 7,902	$ 23,229	$ 22,193
Increase in unearned premiums	(202)	(95)	(630)	(377)
Net premiums earned	7,908	7,807	22,599	21,816
Net investment income	823	813	2,457	2,328
Net realized gains (losses):
Other-than-temporary impairment (OTTI) losses gross	(14)	(8)	(19)	(36)
OTTI on fixed maturities recognized in OCI (pre-tax)	3	0	3	1
Net OTTI losses recognized in income	(11)	(8)	(16)	(35)
Net realized gains (losses) excluding OTTI losses	30	(2)	51	119
Total net realized gains (losses) (includes $(38), $10, $(142) and $27 reclassified from AOCI)	19	(10)	35	84
Total revenues	8,750	8,610	25,091	24,228
Expenses
Losses and loss expenses	4,868	6,247	13,457	14,182
Policy benefits	127	169	428	500
Policy acquisition costs	1,504	1,488	4,432	4,334
Administrative expenses	719	714	2,158	2,096
Interest expense	164	150	488	451
Other (income) expense	(145)	(118)	(307)	(333)
Amortization of purchased intangibles	83	65	253	194
Chubb integration expenses	16	50	39	233
Total expenses	7,336	8,765	20,948	21,657
Income (loss) before income tax	1,414	(155)	4,143	2,571
Income tax expense (benefit) (includes $(4), nil, $(19) and $3 on reclassified unrealized gains and losses)	183	(85)	536	243
Net income (loss)	1,231	(70)	3,607	2,328
Other comprehensive income (loss)
Unrealized appreciation (depreciation)	(251)	153	(2,063)	919
Reclassification adjustment for net realized (gains) losses included in net income	38	(10)	142	(27)
Unrealized appreciation (Depreciation) after reclassification adjustment	(213)	143	(1,921)	892
Change in:
Cumulative foreign currency translation adjustment	(482)	665	(659)	901
Postretirement benefit liability adjustment	(21)	(63)	(61)	(118)
Other comprehensive income (loss), before income tax	(716)	745	(2,641)	1,675
Income tax (expense) benefit related to OCI items	77	(46)	356	(292)
Other comprehensive income (loss)	(639)	699	(2,285)	1,383
Comprehensive income	$ 592	$ 629	$ 1,322	$ 3,711
Earnings (loss) per share
Basic earnings (loss) per share	$ 2.66	$ (0.15)	$ 7.76	$ 4.98
Diluted earnings (loss) per share	$ 2.64	$ (0.15)	$ 7.71	$ 4.94