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, 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 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 exercised	110			21			$ 89
Common stock awards and options exercised (shares)							(2,151)
Ending balance at Jun. 30, 2016	22,073	3,196	$ 504	9,767	16,686	(997)	$ (7,083)
Ending balance (shares) at Jun. 30, 2016			503,880				114,230
Beginning balance at Dec. 31, 2016	21,219	3,196	$ 504	9,782	17,459	(2,040)	$ (7,682)
Beginning balance (shares) at Dec. 31, 2016			503,880				121,941
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,122
Other comprehensive loss	770					770
Cash dividends declared:
Common stock dividends	(286)				(286)
Preferred stock cash dividend	(91)				(91)
Common stock acquired	(750)						$ (750)
Common stock acquired (shares)							9,383
Common stock awards exercised	86			21			$ 65
Common stock awards and options exercised (shares)							(1,551)
Other	(2)				(2)
Other (shares)
Ending balance at Jun. 30, 2017	$ 22,068	$ 3,196	$ 504	$ 9,803	$ 18,202	$ (1,270)	$ (8,367)
Ending balance (shares) at Jun. 30, 2017			503,880				129,773