Investment Securities, Gross Unrealized Losses and Fair Value (Details) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Available-for-sale securities:
Less than 12 months, Gross unrealized losses, available-for-sale	$ (1,101)	$ (485)
Less than 12 months, Fair value, available-for-sale	72,385	37,490
12 months or more, Gross unrealized losses, available-for-sale	(1,016)	(1,437)
12 months or more, Fair value, available-for-sale	26,969	55,107
Total, Gross unrealized losses, available-for-sale	(2,117)	(1,922)
Total, Fair value, available-for-sale	99,354	92,597
Held-to-maturity securities:
Less than 12 months, Gross unrealized losses, held-to-maturity	(118)	(21)
Less than 12 months, Fair value, held-to-maturity	20,544	3,280
12 months or more, Gross unrealized losses, held-to-maturity	(3)	0
12 months or more, Fair value, held-to-maturity	233	0
Total, Gross unrealized losses, held-to-maturity	(121)	(21)
Total, Fair value, held-to-maturity	20,777	3,280
Total investment securities:
Less than 12 months, Gross unrealized losses, investment securities	(1,219)	(506)
Less than 12 months, Fair value, investment securities	92,929	40,770
12 months or more, Gross unrealized losses, investment securities	(1,019)	(1,437)
12 months or more, Fair value, investment securities	27,202	55,107
Total, Gross unrealized losses, investment securities	(2,238)	(1,943)
Total, Fair value, investment securities	120,131	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	72,287	37,357
12 months or more, Gross unrealized losses, available-for-sale	(1,002)	(1,369)
12 months or more, Fair value, available-for-sale	26,848	54,474
Total, Gross unrealized losses, available-for-sale	(2,096)	(1,850)
Total, Fair value, available-for-sale	99,135	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	(4)	(16)
Less than 12 months, Fair value, available-for-sale	1,332	7,138
12 months or more, Gross unrealized losses, available-for-sale	(6)	(122)
12 months or more, Fair value, available-for-sale	2,020	5,719
Total, Gross unrealized losses, available-for-sale	(10)	(138)
Total, Fair value, available-for-sale	3,352	12,857
Held-to-maturity securities:
Less than 12 months, Gross unrealized losses, held-to-maturity	(12)	(8)
Less than 12 months, Fair value, held-to-maturity	2,434	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	(12)	(8)
Total, Fair value, held-to-maturity	2,434	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	(559)	(198)
Less than 12 months, Fair value, available-for-sale	19,812	10,228
12 months or more, Gross unrealized losses, available-for-sale	(528)	(301)
12 months or more, Fair value, available-for-sale	6,242	3,725
Total, Gross unrealized losses, available-for-sale	(1,087)	(499)
Total, Fair value, available-for-sale	26,054	13,953
Held-to-maturity securities:
Less than 12 months, Gross unrealized losses, held-to-maturity	(3)
Less than 12 months, Fair value, held-to-maturity	454
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	(3)
Total, Fair value, held-to-maturity	454
Mortgage-backed securities: [Member]
Available-for-sale securities:
Less than 12 months, Gross unrealized losses, available-for-sale	(209)	(43)
Less than 12 months, Fair value, available-for-sale	26,573	4,854
12 months or more, Gross unrealized losses, available-for-sale	(247)	(789)
12 months or more, Fair value, available-for-sale	12,723	39,530
Total, Gross unrealized losses, available-for-sale	(456)	(832)
Total, Fair value, available-for-sale	39,296	44,384
Federal agencies [Member]
Available-for-sale securities:
Less than 12 months, Gross unrealized losses, available-for-sale	(173)	(16)
Less than 12 months, Fair value, available-for-sale	21,559	1,706
12 months or more, Gross unrealized losses, available-for-sale	(194)	(735)
12 months or more, Fair value, available-for-sale	10,421	37,854
Total, Gross unrealized losses, available-for-sale	(367)	(751)
Total, Fair value, available-for-sale	31,980	39,560
Held-to-maturity securities:
Less than 12 months, Gross unrealized losses, held-to-maturity	(92)
Less than 12 months, Fair value, held-to-maturity	16,498
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	(92)
Total, Fair value, held-to-maturity	16,498
Residential [Member]
Available-for-sale securities:
Less than 12 months, Gross unrealized losses, available-for-sale	(13)	(18)
Less than 12 months, Fair value, available-for-sale	980	946
12 months or more, Gross unrealized losses, available-for-sale	(6)	(6)
12 months or more, Fair value, available-for-sale	272	144
Total, Gross unrealized losses, available-for-sale	(19)	(24)
Total, Fair value, available-for-sale	1,252	1,090
Commercial [Member]
Available-for-sale securities:
Less than 12 months, Gross unrealized losses, available-for-sale	(23)	(9)
Less than 12 months, Fair value, available-for-sale	4,034	2,202
12 months or more, Gross unrealized losses, available-for-sale	(47)	(48)
12 months or more, Fair value, available-for-sale	2,030	1,532
Total, Gross unrealized losses, available-for-sale	(70)	(57)
Total, Fair value, available-for-sale	6,064	3,734
Corporate debt securities [Member]
Available-for-sale securities:
Less than 12 months, Gross unrealized losses, available-for-sale	(179)	(102)
Less than 12 months, Fair value, available-for-sale	3,963	1,674
12 months or more, Gross unrealized losses, available-for-sale	(132)	(68)
12 months or more, Fair value, available-for-sale	967	1,265
Total, Gross unrealized losses, available-for-sale	(311)	(170)
Total, Fair value, available-for-sale	4,930	2,939
Collateralized loan and other debt obligations [Member]
Available-for-sale securities:
Less than 12 months, Gross unrealized losses, available-for-sale	(116)	(99)
Less than 12 months, Fair value, available-for-sale	18,075	12,755
12 months or more, Gross unrealized losses, available-for-sale	(66)	(85)
12 months or more, Fair value, available-for-sale	4,375	3,958
Total, Gross unrealized losses, available-for-sale	(182)	(184)
Total, Fair value, available-for-sale	22,450	16,713
Held-to-maturity securities:
Less than 12 months, Gross unrealized losses, held-to-maturity	(11)	(13)
Less than 12 months, Fair value, held-to-maturity	1,158	1,391
12 months or more, Gross unrealized losses, held-to-maturity	(3)	0
12 months or more, Fair value, held-to-maturity	233	0
Total, Gross unrealized losses, held-to-maturity	(14)	(13)
Total, Fair value, held-to-maturity	1,391	1,391
Other [Member]
Available-for-sale securities:
Less than 12 months, Gross unrealized losses, available-for-sale	(27)	(23)
Less than 12 months, Fair value, available-for-sale	2,532	708
12 months or more, Gross unrealized losses, available-for-sale	(23)	(4)
12 months or more, Fair value, available-for-sale	521	277
Total, Gross unrealized losses, available-for-sale	(50)	(27)
Total, Fair value, available-for-sale	3,053	985
Total marketable equity securities [Member]
Available-for-sale securities:
Less than 12 months, Gross unrealized losses, available-for-sale	(7)	(4)
Less than 12 months, Fair value, available-for-sale	98	133
12 months or more, Gross unrealized losses, available-for-sale	(14)	(68)
12 months or more, Fair value, available-for-sale	121	633
Total, Gross unrealized losses, available-for-sale	(21)	(72)
Total, Fair value, available-for-sale	219	766
Perpetual preferred securities [Member]
Available-for-sale securities:
Less than 12 months, Gross unrealized losses, available-for-sale	(1)	(2)
Less than 12 months, Fair value, available-for-sale	45	92
12 months or more, Gross unrealized losses, available-for-sale	(14)	(68)
12 months or more, Fair value, available-for-sale	121	633
Total, Gross unrealized losses, available-for-sale	(15)	(70)
Total, Fair value, available-for-sale	166	725
Other marketable equity securities [Member]
Available-for-sale securities:
Less than 12 months, Gross unrealized losses, available-for-sale	(6)	(2)
Less than 12 months, Fair value, available-for-sale	53	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	(6)	(2)
Total, Fair value, available-for-sale	$ 53	$ 41