Parent Company FInancial Statements Parent Company Financial Statements (Balance Sheets) (Details) (USD $) In Millions, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Condensed Financial Statements, Captions [Line Items]
Cash and due from subsidiary bank	$ 1,026	$ 1,140
Other short-term investments	99	112
Premises and equipment	532	594
Other assets	4,438	3,888
Total assets	69,190	65,224
Medium- and long-term debt	2,679	3,543
Other liabilities	1,507	986
Total liabilities	61,788	58,074
Common stock - $5 par value: Authorized - 325,000,000 shares; Issued - 228,164,824 shares	1,141	1,141
Capital surplus	2,188	2,179
Accumulated other comprehensive loss	(412)	(391)	(413)
Retained earnings	6,744	6,318
Less cost of common stock in treasury - 49,146,225 shares at 12/31/14 and 45,860,786 shares at 12/31/13	(2,259)	(2,097)
Total shareholders' equity	7,402	7,150	6,939	6,865
Total liabilities and shareholders' equity	69,190	65,224
Common stock, par value	$ 5	$ 5
Common stock, authorized shares	325,000,000	325,000,000
Common stock, issued shares	228,164,824	228,164,824
Shares in treasury	49,146,225	45,860,786
Parent Company
Condensed Financial Statements, Captions [Line Items]
Cash and due from subsidiary bank	0	31
Short-term investments with subsidiary bank	1,133	482
Other short-term investments	94	96
Investments in subsidiaries, principally banks	7,411	7,171
Premises and equipment	2	4
Other assets	142	139
Total assets	8,782	7,923
Medium- and long-term debt	1,212	617
Other liabilities	168	156
Total liabilities	1,380	773
Common stock - $5 par value: Authorized - 325,000,000 shares; Issued - 228,164,824 shares	1,141	1,141
Capital surplus	2,188	2,179
Accumulated other comprehensive loss	(412)	(391)
Retained earnings	6,744	6,318
Less cost of common stock in treasury - 49,146,225 shares at 12/31/14 and 45,860,786 shares at 12/31/13	(2,259)	(2,097)
Total shareholders' equity	7,402	7,150
Total liabilities and shareholders' equity	$ 8,782	$ 7,923