Loans and ACL (Analysis of the Allowance for Credit Losses) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Provision (benefit)	$ 251	$ 592	$ 1,057
Commercial and Industrial [Member]
ACL, beginning balance	454	470	433
Charge-offs	(131)	(248)	(337)
Recoveries	42	47	17
Provision (benefit)	56	166	357
Other		19
ACL, ending balance	421	454	470
CRE Income Producing Properties [Member]
ACL, beginning balance	149	170	249
Charge-offs	(31)	(74)	(150)
Recoveries	14	20	9
Provision (benefit)	30	23	62
Other		10
ACL, ending balance	162	149	170
CRE Construction And Development [Member]
ACL, beginning balance	76	134	371
Charge-offs	(11)	(58)	(245)
Recoveries	19	31	45
Provision (benefit)	(36)	(39)	(37)
Other		8
ACL, ending balance	48	76	134
Commercial Other Lending Subsidiaries [Member]
ACL, beginning balance	15	13	11
Charge-offs	(10)	(3)	(8)
Recoveries	3	2	2
Provision (benefit)	13	3	8
Other		0
ACL, ending balance	21	15	13
Direct Retail Lending [Member]
ACL, beginning balance	209	300	232
Charge-offs	(69)	(148)	(224)
Recoveries	29	38	36
Provision (benefit)	26	15	256
Other	(85)	4
ACL, ending balance	110	209	300
Retail Revolving Credit [Member]
ACL, beginning balance	115	102	112
Charge-offs	(71)	(85)	(81)
Recoveries	19	17	18
Provision (benefit)	47	81	53
Other		0
ACL, ending balance	110	115	102
Retail Residential Mortgage-Nonguaranteed [Member]
ACL, beginning balance	269	296	318
Charge-offs	(82)	(79)	(135)
Recoveries	7	3	3
Provision (benefit)	(62)	5	110
Other	85	44
ACL, ending balance	217	269	296
Retail Residential Mortgage-Government Guaranteed [Member]
ACL, beginning balance	62	32	47
Charge-offs	(2)	(2)	(1)
Recoveries	0	0	0
Provision (benefit)	(24)	32	(14)
Other		0
ACL, ending balance	36	62	32
Retail Sales Finance [Member]
ACL, beginning balance	45	29	38
Charge-offs	(23)	(23)	(26)
Recoveries	9	9	10
Provision (benefit)	19	30	7
Other		0
ACL, ending balance	50	45	29
Retail Other Lending Subsidiaries [Member]
ACL, beginning balance	224	264	186
Charge-offs	(259)	(252)	(217)
Recoveries	30	32	24
Provision (benefit)	240	245	271
Other		(65)
ACL, ending balance	235	224	264
Acquired from FDIC [Member]
ACL, beginning balance	114	128	149
Charge-offs	(21)	(19)	(34)
Recoveries	0	0	0
Provision (benefit)	(29)	5	13
Other		0
ACL, ending balance	64	114	128
Unallocated [Member]
ACL, beginning balance		80	110
Charge-offs		0	0
Recoveries		0	0
Provision (benefit)		(33)	(30)
Other		(47)
ACL, ending balance		0	80
ALLL [Member]
ACL, beginning balance	1,732	2,018	2,256
Charge-offs	(710)	(991)	(1,458)
Recoveries	172	199	164
Provision (benefit)	280	533	1,056
Other		(27)
ACL, ending balance	1,474	1,732	2,018
RUFC [Member]
ACL, beginning balance	89	30	29
Charge-offs	0	0	0
Recoveries	0	0	0
Provision (benefit)	(29)	59	1
Other		0
ACL, ending balance	60	89	30
ACL [Member]
ACL, beginning balance	1,821	2,048	2,285
Charge-offs	(710)	(991)	(1,458)
Recoveries	172	199	164
Provision (benefit)	251	592	1,057
Other		(27)
ACL, ending balance	$ 1,534	$ 1,821	$ 2,048