Parent Company FInancial Statements Parent Company Financial Statements (Statements of Cash Flows) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Condensed Financial Statements, Captions [Line Items]
Net income	$ 593	$ 541	$ 521
Depreciation and amortization	123	122	133
Net periodic defined benefit cost	40	88	81
Share-based compensation expense	38	35	37
Provision for deferred income taxes	130	(20)	158
Excess tax benefits from share-based compensation arrangements	(7)	(3)	(1)
Other, net	(243)	(2)	(322)
Net cash provided by operating activities	639	836	692
Net change in premises and equipment	(70)	(102)	(75)
Net cash (used in) provided by investing activities	(3,743)	1,174	(3,676)
Maturities and redemptions of medium- and long-term debt	(1,406)	(1,080)	(193)
Issuances of medium- and long-term debt	596	0	0
Repurchases of common stock	(260)	(291)	(308)
Cash dividends paid on common stock	(137)	(123)	(97)
Issuances of common stock under employee stock plans	49	33	3
Excess tax benefits from share-based compensation arrangements	7	3	1
Net cash used in financing activities	2,724	(93)	3,962
Net increase in cash and cash equivalents	(380)	1,917	978
Cash and cash equivalents at beginning of period	6,451	4,534	3,556
Cash and cash equivalents at end of period	6,071	6,451	4,534
Interest paid	101	114	135
Income taxes recovered	218	115	46
Parent Company
Condensed Financial Statements, Captions [Line Items]
Net income	593	541	521
Undistributed earnings of subsidiaries, principally banks	(260)	(108)	(85)
Depreciation and amortization	1	1	1
Net periodic defined benefit cost	4	8	7
Share-based compensation expense	16	14	15
Provision for deferred income taxes	0	3	2
Excess tax benefits from share-based compensation arrangements	(7)	(3)	(1)
Other, net	16	2	(8)
Net cash provided by operating activities	363	458	452
Capital transactions with subsidiaries	0	0	(5)
Net change in premises and equipment	2	0	(1)
Net cash (used in) provided by investing activities	2	0	(6)
Maturities and redemptions of medium- and long-term debt	0	0	(30)
Issuances of medium- and long-term debt	596	0	0
Repurchases of common stock	(260)	(291)	(308)
Cash dividends paid on common stock	(137)	(123)	(97)
Issuances of common stock under employee stock plans	49	33	3
Excess tax benefits from share-based compensation arrangements	7	3	1
Net cash used in financing activities	255	(378)	(431)
Net increase in cash and cash equivalents	620	80	15
Cash and cash equivalents at beginning of period	513	433	418
Cash and cash equivalents at end of period	1,133	513	433
Interest paid	12	11	12
Income taxes recovered	$ (33)	$ (27)	$ (46)