Investment Securities, Contractual Maturities (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2015	Dec. 31, 2014
Available-for-sale securities:
Contractual maturities, Total amount, available-for-sale	$ 258,180	$ 253,766
Weighted average yield contractual maturities, Total, available-for-sale	3.55%	3.60%
Due within 1 year, Contractual maturities, available-for-sale	$ 3,866	$ 4,647
Percentage of weighted average yield, Due within 1 year, available-for-sale	2.23%	2.03%
Due in 1-5 years, Contractual maturities, available-for-sale	$ 49,416	$ 39,775
Percentage of weighted average yield, Due in 1-5 years, available-for-sale	2.09%	2.20%
Due in 5-10 years, Contractual maturities, available-for-sale	$ 26,126	$ 22,310
Percentage of weighted average yield, Due In 5-10 years, available-for-sale	2.92%	3.12%
Due in 10 years or more, Contractual maturities, available-for-sale	$ 178,772	$ 187,034
Percentage of weighted average yield, Due after 10 years, available-for-sale	4.07%	3.99%
Held-to-maturity securities:
Amortized Cost	$ 80,102	$ 55,483
Weighted average yield contractual maturities, Total, held-to-maturity, cost	2.65%	2.37%
Due within 1 year, Contractual maturities, held-to-maturity, cost	$ 183	$ 192
Percentage of weighted average yield, Due In 1 year, held-to-maturity, cost	1.64%	1.61%
Held-to-maturity Securities, Debt Maturities, after One Through Five Years, Net Carrying Amount	$ 2,911	$ 4,214
Percentage of weighted average yield, Due In 1-5 years, held-to-maturity, cost	1.68%	1.72%
Due in 5-10 years, Contractual maturities, held-to-maturity, cost	$ 45,917	$ 42,244
Percentage of weighted average yield, Due In 5-10 years, held-to-maturity, cost	2.11%	2.10%
Due in 10 years or more, Contractual maturities, held-to-maturity, cost	$ 31,091	$ 8,833
Percentage of weighted average yield, Due after 10 years, held-to-maturity, cost	3.56%	3.96%
Held-to-maturity securities, fair value: [Abstract]
Contractual maturities, Total amount, held-to-maturity, fair value	$ 80,315	$ 56,359
Total debt securities [Member]
Held-to-maturity securities, fair value: [Abstract]
Contractual maturities, Total amount, held-to-maturity, fair value	80,315	56,359
Due within 1 year, Contractual maturities, held-to-maturity, fair value	183	193
Due in 1-5 years, Contractual maturities, held-to-maturity, fair value	2,929	4,239
Due in 5-10 years, Contractual maturities, held-to-maturity, fair value	46,372	42,915
Due in 10 years or more, Contractual maturities, held-to-maturity, fair value	30,831	9,012
Securities of U.S. Treasury and federal agencies [Member]
Available-for-sale securities:
Contractual maturities, Total amount, available-for-sale	$ 35,944	$ 25,804
Weighted average yield contractual maturities, Total, available-for-sale	1.50%	1.49%
Due within 1 year, Contractual maturities, available-for-sale	$ 120	$ 181
Percentage of weighted average yield, Due within 1 year, available-for-sale	0.67%	1.47%
Due in 1-5 years, Contractual maturities, available-for-sale	$ 31,348	$ 22,348
Percentage of weighted average yield, Due in 1-5 years, available-for-sale	1.46%	1.44%
Due in 5-10 years, Contractual maturities, available-for-sale	$ 4,476	$ 3,275
Percentage of weighted average yield, Due In 5-10 years, available-for-sale	1.83%	1.83%
Due in 10 years or more, Contractual maturities, available-for-sale	$ 0	$ 0
Percentage of weighted average yield, Due after 10 years, available-for-sale	0.00%	0.00%
Held-to-maturity securities:
Amortized Cost	$ 44,645	$ 40,886
Weighted average yield contractual maturities, Total, held-to-maturity, cost	2.12%	2.12%
Due within 1 year, Contractual maturities, held-to-maturity, cost	$ 0	$ 0
Percentage of weighted average yield, Due In 1 year, held-to-maturity, cost	0.00%	0.00%
Held-to-maturity Securities, Debt Maturities, after One Through Five Years, Net Carrying Amount	$ 0	$ 0
Percentage of weighted average yield, Due In 1-5 years, held-to-maturity, cost	0.00%	0.00%
Due in 5-10 years, Contractual maturities, held-to-maturity, cost	$ 44,645	$ 40,886
Percentage of weighted average yield, Due In 5-10 years, held-to-maturity, cost	2.12%	2.12%
Due in 10 years or more, Contractual maturities, held-to-maturity, cost	$ 0	$ 0
Percentage of weighted average yield, Due after 10 years, held-to-maturity, cost	0.00%	0.00%
Held-to-maturity securities, fair value: [Abstract]
Contractual maturities, Total amount, held-to-maturity, fair value	$ 45,092	$ 41,548
Due within 1 year, Contractual maturities, held-to-maturity, fair value	0	0
Due in 1-5 years, Contractual maturities, held-to-maturity, fair value	0	0
Due in 5-10 years, Contractual maturities, held-to-maturity, fair value	45,092	41,548
Due in 10 years or more, Contractual maturities, held-to-maturity, fair value	0	0
Securities of U.S. states and political subdivisions [Member]
Available-for-sale securities:
Contractual maturities, Total amount, available-for-sale	$ 48,298	$ 44,944
Weighted average yield contractual maturities, Total, available-for-sale	5.69%	5.66%
Due within 1 year, Contractual maturities, available-for-sale	$ 2,733	$ 3,568
Percentage of weighted average yield, Due within 1 year, available-for-sale	1.73%	1.71%
Due in 1-5 years, Contractual maturities, available-for-sale	$ 7,550	$ 7,050
Percentage of weighted average yield, Due in 1-5 years, available-for-sale	2.14%	2.19%
Due in 5-10 years, Contractual maturities, available-for-sale	$ 3,062	$ 3,235
Percentage of weighted average yield, Due In 5-10 years, available-for-sale	5.37%	5.13%
Due in 10 years or more, Contractual maturities, available-for-sale	$ 34,953	$ 31,091
Percentage of weighted average yield, Due after 10 years, available-for-sale	6.79%	6.96%
Held-to-maturity securities:
Amortized Cost	$ 2,174	$ 1,962
Weighted average yield contractual maturities, Total, held-to-maturity, cost	5.71%	5.60%
Due within 1 year, Contractual maturities, held-to-maturity, cost	$ 0	$ 0
Percentage of weighted average yield, Due In 1 year, held-to-maturity, cost	0.00%	0.00%
Held-to-maturity Securities, Debt Maturities, after One Through Five Years, Net Carrying Amount	$ 0	$ 0
Percentage of weighted average yield, Due In 1-5 years, held-to-maturity, cost	0.00%	0.00%
Due in 5-10 years, Contractual maturities, held-to-maturity, cost	$ 65	$ 9
Percentage of weighted average yield, Due In 5-10 years, held-to-maturity, cost	7.70%	6.60%
Due in 10 years or more, Contractual maturities, held-to-maturity, cost	$ 2,109	$ 1,953
Percentage of weighted average yield, Due after 10 years, held-to-maturity, cost	5.65%	5.59%
Held-to-maturity securities, fair value: [Abstract]
Contractual maturities, Total amount, held-to-maturity, fair value	$ 2,150	$ 1,989
Due within 1 year, Contractual maturities, held-to-maturity, fair value	0	0
Due in 1-5 years, Contractual maturities, held-to-maturity, fair value	0	0
Due in 5-10 years, Contractual maturities, held-to-maturity, fair value	64	9
Due in 10 years or more, Contractual maturities, held-to-maturity, fair value	2,086	1,980
Mortgage-backed securities: [Member]
Available-for-sale securities:
Contractual maturities, Total amount, available-for-sale	$ 123,848	$ 136,352
Weighted average yield contractual maturities, Total, available-for-sale	3.61%	3.59%
Due within 1 year, Contractual maturities, available-for-sale	$ 5	$ 1
Percentage of weighted average yield, Due within 1 year, available-for-sale	6.51%	0.28%
Due in 1-5 years, Contractual maturities, available-for-sale	$ 458	$ 347
Percentage of weighted average yield, Due in 1-5 years, available-for-sale	2.12%	2.88%
Due in 5-10 years, Contractual maturities, available-for-sale	$ 857	$ 1,099
Percentage of weighted average yield, Due In 5-10 years, available-for-sale	4.09%	3.54%
Due in 10 years or more, Contractual maturities, available-for-sale	$ 122,528	$ 134,905
Percentage of weighted average yield, Due after 10 years, available-for-sale	3.62%	3.59%
Federal agencies [Member]
Available-for-sale securities:
Contractual maturities, Total amount, available-for-sale	$ 100,078	$ 110,089
Weighted average yield contractual maturities, Total, available-for-sale	3.29%	3.27%
Due within 1 year, Contractual maturities, available-for-sale	$ 5	$ 0
Percentage of weighted average yield, Due within 1 year, available-for-sale	6.51%	0.00%
Due in 1-5 years, Contractual maturities, available-for-sale	$ 368	$ 276
Percentage of weighted average yield, Due in 1-5 years, available-for-sale	1.80%	2.86%
Due in 5-10 years, Contractual maturities, available-for-sale	$ 807	$ 1,011
Percentage of weighted average yield, Due In 5-10 years, available-for-sale	3.98%	3.38%
Due in 10 years or more, Contractual maturities, available-for-sale	$ 98,898	$ 108,802
Percentage of weighted average yield, Due after 10 years, available-for-sale	3.29%	3.27%
Held-to-maturity securities:
Amortized Cost	$ 27,577	$ 5,476
Weighted average yield contractual maturities, Total, held-to-maturity, cost	3.48%	3.89%
Due within 1 year, Contractual maturities, held-to-maturity, cost	$ 0	$ 0
Percentage of weighted average yield, Due In 1 year, held-to-maturity, cost	0.00%	0.00%
Held-to-maturity Securities, Debt Maturities, after One Through Five Years, Net Carrying Amount	$ 0	$ 0
Percentage of weighted average yield, Due In 1-5 years, held-to-maturity, cost	0.00%	0.00%
Due in 5-10 years, Contractual maturities, held-to-maturity, cost	$ 0	$ 0
Percentage of weighted average yield, Due In 5-10 years, held-to-maturity, cost	0.00%	0.00%
Due in 10 years or more, Contractual maturities, held-to-maturity, cost	$ 27,577	$ 5,476
Percentage of weighted average yield, Due after 10 years, held-to-maturity, cost	3.48%	3.89%
Held-to-maturity securities, fair value: [Abstract]
Contractual maturities, Total amount, held-to-maturity, fair value	$ 27,338	$ 5,641
Due within 1 year, Contractual maturities, held-to-maturity, fair value	0	0
Due in 1-5 years, Contractual maturities, held-to-maturity, fair value	0	0
Due in 5-10 years, Contractual maturities, held-to-maturity, fair value	0	0
Due in 10 years or more, Contractual maturities, held-to-maturity, fair value	27,338	5,641
Residential [Member]
Available-for-sale securities:
Contractual maturities, Total amount, available-for-sale	$ 8,461	$ 9,269
Weighted average yield contractual maturities, Total, available-for-sale	4.47%	4.50%
Due within 1 year, Contractual maturities, available-for-sale	$ 0	$ 0
Percentage of weighted average yield, Due within 1 year, available-for-sale	0.00%	0.00%
Due in 1-5 years, Contractual maturities, available-for-sale	$ 30	$ 9
Percentage of weighted average yield, Due in 1-5 years, available-for-sale	5.05%	4.81%
Due in 5-10 years, Contractual maturities, available-for-sale	$ 50	$ 83
Percentage of weighted average yield, Due In 5-10 years, available-for-sale	5.87%	5.63%
Due in 10 years or more, Contractual maturities, available-for-sale	$ 8,381	$ 9,177
Percentage of weighted average yield, Due after 10 years, available-for-sale	4.46%	4.49%
Commercial [Member]
Available-for-sale securities:
Contractual maturities, Total amount, available-for-sale	$ 15,309	$ 16,994
Weighted average yield contractual maturities, Total, available-for-sale	5.23%	5.16%
Due within 1 year, Contractual maturities, available-for-sale	$ 0	$ 1
Percentage of weighted average yield, Due within 1 year, available-for-sale	0.00%	0.28%
Due in 1-5 years, Contractual maturities, available-for-sale	$ 60	$ 62
Percentage of weighted average yield, Due in 1-5 years, available-for-sale	2.64%	2.71%
Due in 5-10 years, Contractual maturities, available-for-sale	$ 0	$ 5
Percentage of weighted average yield, Due In 5-10 years, available-for-sale	0.00%	1.30%
Due in 10 years or more, Contractual maturities, available-for-sale	$ 15,249	$ 16,926
Percentage of weighted average yield, Due after 10 years, available-for-sale	5.24%	5.17%
Corporate debt securities [Member]
Available-for-sale securities:
Contractual maturities, Total amount, available-for-sale	$ 14,974	$ 14,786
Weighted average yield contractual maturities, Total, available-for-sale	4.84%	4.90%
Due within 1 year, Contractual maturities, available-for-sale	$ 728	$ 600
Percentage of weighted average yield, Due within 1 year, available-for-sale	4.63%	4.32%
Due in 1-5 years, Contractual maturities, available-for-sale	$ 8,023	$ 7,634
Percentage of weighted average yield, Due in 1-5 years, available-for-sale	4.58%	4.54%
Due in 5-10 years, Contractual maturities, available-for-sale	$ 4,902	$ 5,209
Percentage of weighted average yield, Due In 5-10 years, available-for-sale	5.09%	5.30%
Due in 10 years or more, Contractual maturities, available-for-sale	$ 1,321	$ 1,343
Percentage of weighted average yield, Due after 10 years, available-for-sale	5.59%	5.70%
Collateralized loan and other debt obligations [Member]
Available-for-sale securities:
Contractual maturities, Total amount, available-for-sale	$ 29,323	$ 25,361
Weighted average yield contractual maturities, Total, available-for-sale	1.96%	1.83%
Due within 1 year, Contractual maturities, available-for-sale	$ 0	$ 23
Percentage of weighted average yield, Due within 1 year, available-for-sale	0.00%	1.95%
Due in 1-5 years, Contractual maturities, available-for-sale	$ 862	$ 944
Percentage of weighted average yield, Due in 1-5 years, available-for-sale	0.76%	0.71%
Due in 5-10 years, Contractual maturities, available-for-sale	$ 11,946	$ 8,472
Percentage of weighted average yield, Due In 5-10 years, available-for-sale	1.85%	1.67%
Due in 10 years or more, Contractual maturities, available-for-sale	$ 16,515	$ 15,922
Percentage of weighted average yield, Due after 10 years, available-for-sale	2.11%	1.99%
Held-to-maturity securities:
Amortized Cost	$ 1,405	$ 1,404
Weighted average yield contractual maturities, Total, held-to-maturity, cost	2.00%	1.96%
Due within 1 year, Contractual maturities, held-to-maturity, cost	$ 0	$ 0
Percentage of weighted average yield, Due In 1 year, held-to-maturity, cost	0.00%	0.00%
Held-to-maturity Securities, Debt Maturities, after One Through Five Years, Net Carrying Amount	$ 0	$ 0
Percentage of weighted average yield, Due In 1-5 years, held-to-maturity, cost	0.00%	0.00%
Due in 5-10 years, Contractual maturities, held-to-maturity, cost	$ 0	$ 0
Percentage of weighted average yield, Due In 5-10 years, held-to-maturity, cost	0.00%	0.00%
Due in 10 years or more, Contractual maturities, held-to-maturity, cost	$ 1,405	$ 1,404
Percentage of weighted average yield, Due after 10 years, held-to-maturity, cost	2.00%	1.96%
Held-to-maturity securities, fair value: [Abstract]
Contractual maturities, Total amount, held-to-maturity, fair value	$ 1,407	$ 1,391
Due within 1 year, Contractual maturities, held-to-maturity, fair value	0	0
Due in 1-5 years, Contractual maturities, held-to-maturity, fair value	0	0
Due in 5-10 years, Contractual maturities, held-to-maturity, fair value	0	0
Due in 10 years or more, Contractual maturities, held-to-maturity, fair value	1,407	1,391
Other [Member]
Available-for-sale securities:
Contractual maturities, Total amount, available-for-sale	$ 5,793	$ 6,519
Weighted average yield contractual maturities, Total, available-for-sale	1.71%	1.79%
Due within 1 year, Contractual maturities, available-for-sale	$ 280	$ 274
Percentage of weighted average yield, Due within 1 year, available-for-sale	1.52%	1.55%
Due in 1-5 years, Contractual maturities, available-for-sale	$ 1,175	$ 1,452
Percentage of weighted average yield, Due in 1-5 years, available-for-sale	2.50%	2.56%
Due in 5-10 years, Contractual maturities, available-for-sale	$ 883	$ 1,020
Percentage of weighted average yield, Due In 5-10 years, available-for-sale	1.39%	1.32%
Due in 10 years or more, Contractual maturities, available-for-sale	$ 3,455	$ 3,773
Percentage of weighted average yield, Due after 10 years, available-for-sale	1.54%	1.64%
Held-to-maturity securities:
Amortized Cost	$ 4,301	$ 5,755
Weighted average yield contractual maturities, Total, held-to-maturity, cost	1.60%	1.64%
Due within 1 year, Contractual maturities, held-to-maturity, cost	$ 183	$ 192
Percentage of weighted average yield, Due In 1 year, held-to-maturity, cost	1.64%	1.61%
Held-to-maturity Securities, Debt Maturities, after One Through Five Years, Net Carrying Amount	$ 2,911	$ 4,214
Percentage of weighted average yield, Due In 1-5 years, held-to-maturity, cost	1.68%	1.72%
Due in 5-10 years, Contractual maturities, held-to-maturity, cost	$ 1,207	$ 1,349
Percentage of weighted average yield, Due In 5-10 years, held-to-maturity, cost	1.40%	1.41%
Due in 10 years or more, Contractual maturities, held-to-maturity, cost	$ 0	$ 0
Percentage of weighted average yield, Due after 10 years, held-to-maturity, cost	0.00%	0.00%
Held-to-maturity securities, fair value: [Abstract]
Contractual maturities, Total amount, held-to-maturity, fair value	$ 4,328	$ 5,790
Due within 1 year, Contractual maturities, held-to-maturity, fair value	183	193
Due in 1-5 years, Contractual maturities, held-to-maturity, fair value	2,929	4,239
Due in 5-10 years, Contractual maturities, held-to-maturity, fair value	1,216	1,358
Due in 10 years or more, Contractual maturities, held-to-maturity, fair value	$ 0	$ 0