Selected Quarterly Financial Data (Unaudited) (details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Selected Quarterly Financial Data (Unaudited) disclosure
Total revenues	$ 6,674	$ 6,794	$ 6,706	$ 6,626	$ 6,783	$ 6,886	$ 6,785	$ 6,708	$ 26,800	$ 27,162	$ 26,191
Total expenses	5,465	5,487	5,630	5,478	5,323	5,628	5,884	5,238	22,060	22,073	21,246
Income before income taxes	1,209	1,307	1,076	1,148	1,460	1,258	901	1,470	4,740	5,089	4,945
Income tax expense	343	379	264	315	422	339	218	418	1,301	1,397	1,272
Net income	$ 866	$ 928	$ 812	$ 833	$ 1,038	$ 919	$ 683	$ 1,052	$ 3,439	$ 3,692	$ 3,673
Net income per share, basic	$ 2.87	$ 3.00	$ 2.56	$ 2.58	$ 3.15	$ 2.72	$ 1.98	$ 2.98	$ 10.99	$ 10.82	$ 9.84
Net income per share, diluted	$ 2.83	$ 2.97	$ 2.53	$ 2.55	$ 3.11	$ 2.69	$ 1.95	$ 2.95	$ 10.88	$ 10.70	$ 9.74