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, 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	502				502
Other comprehensive loss	235					235
Cash dividends declared:
Common stock dividends	(144)				(144)
Preferred stock cash dividend	(55)				(55)
Common stock acquired	(523)						$ (523)
Common stock acquired (shares)							6,671
Common stock awards vested	60			14			$ 46
Common stock awards and options exercised (shares)							(1,091)
Other	0
Other (shares)							(1)
Ending balance at Mar. 31, 2017	21,294	3,196	$ 504	9,796	17,762	(1,805)	$ (8,159)
Ending balance (shares) at Mar. 31, 2017			503,880				127,520
Beginning balance at Dec. 31, 2017	22,317	3,196	$ 504	9,799	18,856	(1,009)	$ (9,029)
Beginning balance (shares) at Dec. 31, 2017			503,880				136,230
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	661				661
Other comprehensive loss	(65)					(65)
Cash dividends declared:
Common stock dividends	(154)				(154)
Preferred stock cash dividend	(55)				55
Common stock acquired	(350)						$ (350)
Common stock acquired (shares)							3,324
Common stock awards vested	42			(3)			$ 45
Common stock awards and options exercised (shares)							(1,075)
Other	3			0	3		$ 0
Other (shares)							(7)
Ending balance at Mar. 31, 2018	$ 22,399	$ 3,196	$ 504	$ 9,796	$ 19,311	$ (1,074)	$ (9,334)
Ending balance (shares) at Mar. 31, 2018			503,880				138,472