Consolidated Statement of Changes In Shareholders' Equity - USD ($) shares in Thousands, $ in Millions	Total	PREFERRED STOCK	COMMON STOCK	Surplus	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	TREASURY STOCK
Beginning balance at Dec. 31, 2014	$ 21,328	$ 1,961	$ 504	$ 9,791	$ 14,737	$ (507)	$ (5,158)
Beginning balance (shares) at Dec. 31, 2014			503,880				88,685
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	823				823
Other comprehensive income (loss)	(504)					(504)
Preferred stock issued	742	742
Cash dividends declared:
Common stock dividends	(262)				(262)
Preferred stock cash dividend	(60)				(60)
Common stock acquired	(820)						$ (820)
Common stock acquired (shares)							10,719
Common stock awards and options exercised, including related taxes	107			(41)			$ 148
Common stock awards and options exercised, including related taxes (shares)							(3,274)
Other	(7)			(6)	(1)
Other (shares)							(4)
Ending balance (shares) at Jun. 30, 2015			503,880				96,126
Ending balance at Jun. 30, 2015	21,347	2,703	$ 504	9,744	15,237	(1,011)	$ (5,830)
Beginning balance at Dec. 31, 2015	21,103	2,703	$ 504	9,746	16,049	(1,442)	$ (6,457)
Beginning balance (shares) at Dec. 31, 2015			503,880				104,228
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	987				987
Other comprehensive income (loss)	445					445
Preferred stock issued	493	493
Cash dividends declared:
Common stock dividends	(268)				(268)
Preferred stock cash dividend	(82)				(82)
Common stock acquired	(715)						$ (715)
Common stock acquired (shares)							12,153
Common stock awards and options exercised, including related taxes	110			21			$ 89
Common stock awards and options exercised, including related taxes (shares)							(2,151)
Ending balance (shares) at Jun. 30, 2016			503,880				114,230
Ending balance at Jun. 30, 2016	$ 22,073	$ 3,196	$ 504	$ 9,767	$ 16,686	$ (997)	$ (7,083)