Selected Quarterly Financial Data (Unaudited) (details) (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
Selected Quarterly Financial Data (Unaudited) disclosure
Total revenues	$ 6,373	$ 6,407	$ 6,388	$ 6,278	$ 6,332	$ 6,482	$ 6,179	$ 6,119	$ 25,446	$ 25,112	$ 24,680
Total 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 (loss) 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 (loss) 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