Goodwill and Other Intangible Assets (Changes in Carrying Amounts of Goodwill Attributable to Each Operating Segment) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Goodwill, beginning balance	$ 6,814	$ 6,804	$ 6,078
Acquisitions	41		721
Contingent consideration	14	6	3
Other adjustments	0	4	2
Goodwill, ending balance	6,869	6,814	6,804
Community Banking [Member]
Goodwill, beginning balance	4,924	4,900	4,542
Acquisitions	29		358
Contingent consideration	0	0	0
Other adjustments	(319)	24	0
Goodwill, ending balance	4,634	4,924	4,900
Residential Mortgage Banking [Member]
Goodwill, beginning balance	7	7	7
Acquisitions	0		0
Contingent consideration	0	0	0
Other adjustments	319	0	0
Goodwill, ending balance	326	7	7
Dealer Financial Services [Member]
Goodwill, beginning balance	111	111	111
Acquisitions	0		0
Contingent consideration	0	0	0
Other adjustments	0	0	0
Goodwill, ending balance	111	111	111
Specialized Lending [Member]
Goodwill, beginning balance	88	99	94
Acquisitions	0		5
Contingent consideration	0	0	0
Other adjustments	0	(11)	0
Goodwill, ending balance	88	88	99
Insurance Services [Member]
Goodwill, beginning balance	1,492	1,495	1,132
Acquisitions	12		358
Contingent consideration	14	6	3
Other adjustments	0	(9)	2
Goodwill, ending balance	1,518	1,492	1,495
Financial Services [Member]
Goodwill, beginning balance	192	192	192
Acquisitions	0		0
Contingent consideration	0	0	0
Other adjustments	0	0	0
Goodwill, ending balance	$ 192	$ 192	$ 192