Consolidated Statement of Income (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Revenues
Premiums									$ 22,090	$ 21,432	$ 21,418
Net investment income									2,879	3,059	2,776
Fee income									296	287	306
Net realized investment gains									55	264	17
Other revenues									126	70	163
Total revenues	6,373	6,407	6,388	6,278	6,332	6,482	6,179	6,119	25,446	25,112	24,680
Claims and expenses
Claims and claim adjustment expenses									16,276	13,210	12,408
Amortization of deferred acquisition costs									3,876	3,802	3,813
General and administrative expenses									3,556	3,406	3,366
Interest expense									386	388	382
Total claims and expenses	5,595	6,075	7,115	5,309	5,135	5,111	5,298	5,262	24,094	20,806	19,969
Income before income taxes	778	332	(727)	969	1,197	1,371	881	857	1,352	4,306	4,711
Income tax expense (benefit)	160	(1)	(363)	130	303	366	211	210	(74)	1,090	1,089
Net income	618	333	(364)	839	894	1,005	670	647	1,426	3,216	3,622
Net income per share
Net income per share, basic	$ 1.52	$ 0.80	$ (0.88)	$ 1.94	$ 1.98	$ 2.14	$ 1.37	$ 1.26	$ 3.40	$ 6.69	$ 6.38
Net income per share, diluted	$ 1.51	$ 0.79	$ (0.88)	$ 1.92	$ 1.95	$ 2.11	$ 1.35	$ 1.25	$ 3.36	$ 6.62	$ 6.33
Weighted average number of common shares outstanding
Weighted average number of common shares outstanding, basic									415.8	476.5	563.2
Weighted average number of common shares outstanding, diluted									420.5	482.5	568.6
Other-than-temporary impairment losses:
Other-than-temporary impairment losses, total gains (losses)									30	7	(323)
Other-than-temporary impairment losses, non-credit component of impairments recognized in accumulated other changes in equity from nonowner sources									(55)	(33)	65
Other-than-temporary impairment losses									(25)	(26)	(258)
Other net realized investment gains									80	290	275
Net realized investment gains									$ 55	$ 264	$ 17