Selected Quarterly Financial Information (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Quarterly Financial Statement Information [Line Items]
Total interest income	$ 6,009	$ 5,794	$ 5,571	$ 5,517	$ 5,384	$ 5,164	$ 4,937	$ 4,974	$ 22,891	$ 20,459	$ 19,397
Interest expense	562	517	478	461	423	404	400	398	2,018	1,625	1,579
Net interest income	5,447	5,277	5,093	5,056	4,961	4,760	4,537	4,576	20,873	18,834	17,818
Provision for loan, lease and other losses	1,752	1,588	1,592	1,527	1,380	1,092	1,129	935	6,459	4,536	3,541
Net interest income after provision for credit losses	3,695	3,689	3,501	3,529	3,581	3,668	3,408	3,641	14,414	14,298	14,277
Non-interest income	1,119	1,184	1,161	1,164	1,233	1,140	1,135	1,071	4,628	4,579	4,472
Non-interest expense	3,679	3,361	3,295	3,223	3,480	3,160	3,307	3,049	13,558	12,996	12,180
Income from continuing operations before income taxes	1,135	1,512	1,367	1,470	1,334	1,648	1,236	1,663	5,484	5,881	6,569
Income tax provision (benefit)	342	496	424	452	426	530	384	529	1,714	1,869	2,146
Income from continuing operations, net of tax	793	1,016	943	1,018	908	1,118	852	1,134	3,770	4,012	4,423
Income (loss) from discontinued operations, net of tax	(2)	(11)	(1)	(5)	12	(4)	11	19	(19)	38	5
Net income	791	1,005	942	1,013	920	1,114	863	1,153	3,751	4,050	4,428
Dividends and undistributed earnings allocated to participating securities	(6)	(6)	(6)	(6)	(4)	(6)	(4)	(6)	(24)	(20)	(18)
Preferred stock dividends	(75)	(37)	(65)	(37)	(68)	(29)	(29)	(32)	(214)	(158)	(67)
Net income available to common stockholders	$ 710	$ 962	$ 871	$ 970	$ 848	$ 1,079	$ 830	$ 1,115	$ 3,513	$ 3,872	$ 4,343
Basic earnings per common share:
Net income from continuing operations (in dollars per share)	$ 1.47	$ 1.94	$ 1.70	$ 1.86	$ 1.58	$ 2.01	$ 1.50	$ 2.00	$ 7.00	$ 7.08	$ 7.70
Income (loss) discontinued operations (in dollars per share)	0.00	(0.02)	0.00	(0.01)	0.02	(0.01)	0.02	0.03	(0.04)	0.07	0.01
Net income per basic common share (in dollars per share)	1.47	1.92	1.70	1.85	1.60	2.00	1.52	2.03	6.96	7.15	7.71
Diluted earnings per common share:
Net income from continuing operations (in dollars per share)	1.45	1.92	1.69	1.85	1.56	1.99	1.48	1.97	6.93	7.00	7.58
Income (loss) from discontinued operations (in dollars per share)	0.00	(0.02)	0.00	(0.01)	0.02	(0.01)	0.02	0.03	(0.04)	0.07	0.01
Net income per diluted common share (in dollars per share)	$ 1.45	$ 1.90	$ 1.69	$ 1.84	$ 1.58	$ 1.98	$ 1.50	$ 2.00	$ 6.89	$ 7.07	$ 7.59
Weighted average common shares outstanding:
Basic common shares	483.5	501.1	511.7	523.5	530.8	540.6	545.6	550.2	504.9	541.8	563.1
Diluted common shares	489.2	505.9	516.5	528.0	536.3	546.3	552.0	557.2	509.8	548.0	571.9
Average balance sheet data:
Loans held for investment	$ 245,586				$ 229,851				$ 245,586	$ 229,851	$ 208,316
Total assets	357,033				334,048				357,033	334,048
Interest-bearing deposits	211,266				191,874				211,266	191,874
Total deposits	236,768				217,721				236,768	217,721	205,548
Total stockholders’ equity	47,514				47,284				47,514	47,284	$ 45,053	$ 41,632
Weighted Average
Average balance sheet data:
Loans held for investment	240,027	$ 235,843	$ 230,379	$ 226,736	220,052	$ 211,227	$ 206,337	$ 205,194	240,027	220,052
Interest-earning assets	317,853	310,987	302,764	299,456	292,054	283,082	276,585	278,427	317,853	292,054
Total assets	350,225	343,153	334,479	331,919	323,354	313,822	307,206	309,401	350,225	323,354
Interest-bearing deposits	206,464	196,913	195,641	194,125	189,885	185,800	183,946	182,998	206,464	189,885
Total deposits	232,204	222,251	221,146	219,180	215,899	210,974	209,143	207,851	232,204	215,899
Borrowings	58,624	60,708	54,359	53,761	48,850	45,070	41,650	46,082	58,624	48,850
Total stockholders’ equity	$ 47,972	$ 49,033	$ 48,934	$ 49,078	$ 48,712	$ 48,456	$ 47,255	$ 46,397	$ 47,972	$ 48,712