Selected Quarterly Financial Information (Details) - USD ($) $ / shares in Units, shares in Millions, $ 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	Dec. 31, 2012
Quarterly Financial Statement Information [Line Items]
Total interest income	$ 5,384	$ 5,164	$ 4,937	$ 4,974	$ 5,045	$ 4,887	$ 4,712	$ 4,753	$ 20,459	$ 19,397	$ 19,898
Interest expense	423	404	400	398	389	390	397	403	1,625	1,579	1,792
Net interest income	4,961	4,760	4,537	4,576	4,656	4,497	4,315	4,350	18,834	17,818	18,106
Provision for Loan, lease and Other losses	1,380	1,092	1,129	935	1,109	993	704	735	4,536	3,541	3,453
Net interest income after provision for credit losses	3,581	3,668	3,408	3,641	3,547	3,504	3,611	3,615	14,298	14,277	14,653
Non-interest income	1,233	1,140	1,135	1,071	1,157	1,142	1,153	1,020	4,579	4,472	4,278
Non-interest expense	3,480	3,160	3,307	3,049	3,284	2,985	2,979	2,932	12,996	12,180	12,353
Income from continuing operations before income taxes	1,334	1,648	1,236	1,663	1,420	1,661	1,785	1,703	5,881	6,569	6,578
Income tax provision (benefit)	426	530	384	529	450	536	581	579	1,869	2,146	2,224
Income from continuing operations, net of tax	908	1,118	852	1,134	970	1,125	1,204	1,124	4,012	4,423	4,354
Income (loss) from discontinued operations, net of tax	12	(4)	11	19	29	(44)	(10)	30	38	5	(233)
Net income	920	1,114	863	1,153	999	1,081	1,194	1,154	4,050	4,428	4,121
Dividends and undistributed earnings allocated to participating securities	(4)	(6)	(4)	(6)	(4)	(5)	(4)	(5)	(20)	(18)	(17)
Preferred stock dividends	(68)	(29)	(29)	(32)	(21)	(20)	(13)	(13)	(158)	(67)	(53)
Net income available to common stockholders	$ 848	$ 1,079	$ 830	$ 1,115	$ 974	$ 1,056	$ 1,177	$ 1,136	$ 3,872	$ 4,343	$ 4,051
Basic earnings per common share:
Net income from continuing operations (in dollars per share)	$ 1.58	$ 2.01	$ 1.50	$ 2.00	$ 1.71	$ 1.97	$ 2.09	$ 1.94	$ 7.08	$ 7.70	$ 7.39
Income (loss) discontinued operations (in dollars per share)	0.02	(0.01)	0.02	0.03	0.05	(0.08)	(0.02)	0.05	0.07	0.01	(0.40)
Net income per basic common share (in dollars per share)	1.60	2.00	1.52	2.03	1.76	1.89	2.07	1.99	7.15	7.71	6.99
Diluted earnings per common share:
Net income from continuing operations (in dollars per share)	1.56	1.99	1.48	1.97	1.68	1.94	2.06	1.91	7.00	7.58	7.28
Income (loss) from discontinued operations (in dollars per share)	0.02	(0.01)	0.02	0.03	0.05	(0.08)	(0.02)	0.05	0.07	0.01	(0.39)
Net income per diluted common share (in dollars per share)	$ 1.58	$ 1.98	$ 1.50	$ 2.00	$ 1.73	$ 1.86	$ 2.04	$ 1.96	$ 7.07	$ 7.59	$ 6.89
Weighted average common shares outstanding:
Basic common shares	530.8	540.6	545.6	550.2	554.3	559.9	567.5	571.0	541.8	563.1	579.7
Diluted common shares	536.3	546.3	552.0	557.2	561.8	567.9	577.6	580.3	548.0	571.9	587.6
Average balance sheet data:
Loans held for investment	$ 229,851				$ 208,316				$ 229,851	$ 208,316	$ 197,199
Total assets	334,048				308,167				334,048	308,167
Interest-bearing deposits	191,874				180,467				191,874	180,467
Total deposits	217,721				205,548				217,721	205,548	204,523
Total stockholders’ equity	47,284				45,053				47,284	45,053	$ 41,632	$ 40,425
Weighted Average
Average balance sheet data:
Loans held for investment	220,052	$ 211,227	$ 206,337	$ 205,194	203,436	$ 199,422	$ 194,996	$ 193,722	220,052	203,436
Interest-earning assets	292,054	283,082	276,585	278,427	273,436	268,890	263,570	262,659	292,054	273,436
Total assets	323,354	313,822	307,206	309,401	304,153	298,913	294,089	293,551	323,354	304,153
Interest-bearing deposits	189,885	185,800	183,946	182,998	179,401	179,928	182,053	184,183	189,885	179,401
Total deposits	215,899	210,974	209,143	207,851	205,355	205,199	206,315	205,842	215,899	205,355
Borrowings	48,850	45,070	41,650	46,082	43,479	40,314	35,658	35,978	48,850	43,479
Total stockholders’ equity	$ 48,712	$ 48,456	$ 47,255	$ 46,397	$ 45,576	$ 44,827	$ 43,767	$ 42,859	$ 48,712	$ 45,576