Consolidated Statements Of Operations and Comprehensive Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Revenues
Net premiums written	$ 10,510	$ 9,078	$ 28,718	$ 25,410
Increase in unearned premiums	(510)	(313)	(1,684)	(723)
Net premiums earned	10,000	8,765	27,034	24,687
Net investment income	866	840	2,613	2,528
Realized Investment Gains (Losses)	(21)	(141)	833	(1,069)
Total revenues	10,845	9,464	30,480	26,146
Expenses
Losses and loss expenses	6,629	5,835	16,688	16,897
Policy benefits	151	198	503	550
Policy acquisition costs	1,778	1,645	5,141	4,853
Administrative expenses	806	733	2,325	2,201
Interest expense	122	130	366	390
Other (income) expense	(763)	(485)	(2,030)	(372)
Amortization of purchased intangibles	71	72	216	217
Total expenses	8,794	8,128	23,209	24,736
Income before income tax	2,051	1,336	7,271	1,410
Income tax expense (includes $(3), $7, $(5), and $(35) on unrealized gains and losses reclassified from AOCI)	218	142	873	295
Net income	1,833	1,194	6,398	1,115
Other comprehensive income (loss)
Unrealized appreciation (depreciation)	(564)	687	(2,151)	1,456
Reclassification adjustment for net realized (gains) losses included in net income	10	(49)	(26)	303
Unrealized appreciation (Depreciation) after reclassification adjustment	(554)	638	(2,177)	1,759
Change in:
Cumulative foreign currency translation adjustment	(414)	246	(84)	(168)
Postretirement benefit liability adjustment	4	(23)	(33)	(59)
Other comprehensive income (loss), before income tax	(964)	861	(2,294)	1,532
Income tax (expense) benefit related to OCI items	120	(103)	403	(295)
Other comprehensive income (loss)	(844)	758	(1,891)	1,237
Comprehensive income	$ 989	$ 1,952	$ 4,507	$ 2,352
Earnings per share
Basic earnings per share	$ 4.21	$ 2.64	$ 14.42	$ 2.47
Diluted earnings per share	$ 4.18	$ 2.63	$ 14.33	$ 2.46