Investment Securities, Gross Unrealized Losses and Fair Value (Details) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Available-for-sale securities:
Less than 12 months, Gross unrealized losses, available-for-sale	$ (1,096)	$ (485)
Less than 12 months, Fair value, available-for-sale	63,919	37,490
12 months or more, Gross unrealized losses, available-for-sale	(840)	(1,437)
12 months or more, Fair value, available-for-sale	25,482	55,107
Total, Gross unrealized losses, available-for-sale	(1,936)	(1,922)
Total, Fair value, available-for-sale	89,401	92,597
Held-to-maturity securities:
Less than 12 months, Gross unrealized losses, held-to-maturity	(493)	(21)
Less than 12 months, Fair value, held-to-maturity	32,383	3,280
12 months or more, Gross unrealized losses, held-to-maturity	0	0
12 months or more, Fair value, held-to-maturity	0	0
Total, Gross unrealized losses, held-to-maturity	(493)	(21)
Total, Fair value, held-to-maturity	32,383	3,280
Total investment securities:
Less than 12 months, Gross unrealized losses, investment securities	(1,589)	(506)
Less than 12 months, Fair value, investment securities	96,302	40,770
12 months or more, Gross unrealized losses, investment securities	(840)	(1,437)
12 months or more, Fair value, investment securities	25,482	55,107
Total, Gross unrealized losses, investment securities	(2,429)	(1,943)
Total, Fair value, investment securities	121,784	95,877
Total debt securities [Member]
Available-for-sale securities:
Less than 12 months, Gross unrealized losses, available-for-sale	(1,094)	(481)
Less than 12 months, Fair value, available-for-sale	63,875	37,357
12 months or more, Gross unrealized losses, available-for-sale	(828)	(1,369)
12 months or more, Fair value, available-for-sale	25,358	54,474
Total, Gross unrealized losses, available-for-sale	(1,922)	(1,850)
Total, Fair value, available-for-sale	89,233	91,831
Securities of U.S. Treasury and federal agencies [Member]
Available-for-sale securities:
Less than 12 months, Gross unrealized losses, available-for-sale	(78)	(16)
Less than 12 months, Fair value, available-for-sale	11,458	7,138
12 months or more, Gross unrealized losses, available-for-sale	(50)	(122)
12 months or more, Fair value, available-for-sale	3,994	5,719
Total, Gross unrealized losses, available-for-sale	(128)	(138)
Total, Fair value, available-for-sale	15,452	12,857
Held-to-maturity securities:
Less than 12 months, Gross unrealized losses, held-to-maturity	(97)	(8)
Less than 12 months, Fair value, held-to-maturity	7,137	1,889
12 months or more, Gross unrealized losses, held-to-maturity	0	0
12 months or more, Fair value, held-to-maturity	0	0
Total, Gross unrealized losses, held-to-maturity	(97)	(8)
Total, Fair value, held-to-maturity	7,137	1,889
Securities of U.S. states and political subdivisions [Member]
Available-for-sale securities:
Less than 12 months, Gross unrealized losses, available-for-sale	(312)	(198)
Less than 12 months, Fair value, available-for-sale	13,364	10,228
12 months or more, Gross unrealized losses, available-for-sale	(284)	(301)
12 months or more, Fair value, available-for-sale	3,668	3,725
Total, Gross unrealized losses, available-for-sale	(596)	(499)
Total, Fair value, available-for-sale	17,032	13,953
Held-to-maturity securities:
Less than 12 months, Gross unrealized losses, held-to-maturity	(26)
Less than 12 months, Fair value, held-to-maturity	1,731
12 months or more, Gross unrealized losses, held-to-maturity	0
12 months or more, Fair value, held-to-maturity	0
Total, Gross unrealized losses, held-to-maturity	(26)
Total, Fair value, held-to-maturity	1,731
Mortgage-backed securities: [Member]
Available-for-sale securities:
Less than 12 months, Gross unrealized losses, available-for-sale	(568)	(43)
Less than 12 months, Fair value, available-for-sale	29,849	4,854
12 months or more, Gross unrealized losses, available-for-sale	(385)	(789)
12 months or more, Fair value, available-for-sale	12,843	39,530
Total, Gross unrealized losses, available-for-sale	(953)	(832)
Total, Fair value, available-for-sale	42,692	44,384
Federal agencies [Member]
Available-for-sale securities:
Less than 12 months, Gross unrealized losses, available-for-sale	(549)	(16)
Less than 12 months, Fair value, available-for-sale	25,808	1,706
12 months or more, Gross unrealized losses, available-for-sale	(339)	(735)
12 months or more, Fair value, available-for-sale	11,040	37,854
Total, Gross unrealized losses, available-for-sale	(888)	(751)
Total, Fair value, available-for-sale	36,848	39,560
Held-to-maturity securities:
Less than 12 months, Gross unrealized losses, held-to-maturity	(369)
Less than 12 months, Fair value, held-to-maturity	22,509
12 months or more, Gross unrealized losses, held-to-maturity	0
12 months or more, Fair value, held-to-maturity	0
Total, Gross unrealized losses, held-to-maturity	(369)
Total, Fair value, held-to-maturity	22,509
Residential [Member]
Available-for-sale securities:
Less than 12 months, Gross unrealized losses, available-for-sale	(5)	(18)
Less than 12 months, Fair value, available-for-sale	754	946
12 months or more, Gross unrealized losses, available-for-sale	(8)	(6)
12 months or more, Fair value, available-for-sale	256	144
Total, Gross unrealized losses, available-for-sale	(13)	(24)
Total, Fair value, available-for-sale	1,010	1,090
Commercial [Member]
Available-for-sale securities:
Less than 12 months, Gross unrealized losses, available-for-sale	(14)	(9)
Less than 12 months, Fair value, available-for-sale	3,287	2,202
12 months or more, Gross unrealized losses, available-for-sale	(38)	(48)
12 months or more, Fair value, available-for-sale	1,547	1,532
Total, Gross unrealized losses, available-for-sale	(52)	(57)
Total, Fair value, available-for-sale	4,834	3,734
Corporate debt securities [Member]
Available-for-sale securities:
Less than 12 months, Gross unrealized losses, available-for-sale	(113)	(102)
Less than 12 months, Fair value, available-for-sale	2,953	1,674
12 months or more, Gross unrealized losses, available-for-sale	(63)	(68)
12 months or more, Fair value, available-for-sale	797	1,265
Total, Gross unrealized losses, available-for-sale	(176)	(170)
Total, Fair value, available-for-sale	3,750	2,939
Collateralized loan and other debt obligations [Member]
Available-for-sale securities:
Less than 12 months, Gross unrealized losses, available-for-sale	(12)	(99)
Less than 12 months, Fair value, available-for-sale	5,233	12,755
12 months or more, Gross unrealized losses, available-for-sale	(43)	(85)
12 months or more, Fair value, available-for-sale	3,779	3,958
Total, Gross unrealized losses, available-for-sale	(55)	(184)
Total, Fair value, available-for-sale	9,012	16,713
Held-to-maturity securities:
Less than 12 months, Gross unrealized losses, held-to-maturity	(1)	(13)
Less than 12 months, Fair value, held-to-maturity	1,006	1,391
12 months or more, Gross unrealized losses, held-to-maturity	0	0
12 months or more, Fair value, held-to-maturity	0	0
Total, Gross unrealized losses, held-to-maturity	(1)	(13)
Total, Fair value, held-to-maturity	1,006	1,391
Other [Member]
Available-for-sale securities:
Less than 12 months, Gross unrealized losses, available-for-sale	(11)	(23)
Less than 12 months, Fair value, available-for-sale	1,018	708
12 months or more, Gross unrealized losses, available-for-sale	(3)	(4)
12 months or more, Fair value, available-for-sale	277	277
Total, Gross unrealized losses, available-for-sale	(14)	(27)
Total, Fair value, available-for-sale	1,295	985
Total marketable equity securities [Member]
Available-for-sale securities:
Less than 12 months, Gross unrealized losses, available-for-sale	(2)	(4)
Less than 12 months, Fair value, available-for-sale	44	133
12 months or more, Gross unrealized losses, available-for-sale	(12)	(68)
12 months or more, Fair value, available-for-sale	124	633
Total, Gross unrealized losses, available-for-sale	(14)	(72)
Total, Fair value, available-for-sale	168	766
Perpetual preferred securities [Member]
Available-for-sale securities:
Less than 12 months, Gross unrealized losses, available-for-sale	0	(2)
Less than 12 months, Fair value, available-for-sale	0	92
12 months or more, Gross unrealized losses, available-for-sale	(12)	(68)
12 months or more, Fair value, available-for-sale	124	633
Total, Gross unrealized losses, available-for-sale	(12)	(70)
Total, Fair value, available-for-sale	124	725
Other marketable equity securities [Member]
Available-for-sale securities:
Less than 12 months, Gross unrealized losses, available-for-sale	(2)	(2)
Less than 12 months, Fair value, available-for-sale	44	41
12 months or more, Gross unrealized losses, available-for-sale	0	0
12 months or more, Fair value, available-for-sale	0	0
Total, Gross unrealized losses, available-for-sale	(2)	(2)
Total, Fair value, available-for-sale	$ 44	$ 41