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	368				368
Other comprehensive loss	478					478
Cash dividends declared:
Common stock dividends	(135)				(135)
Preferred stock cash dividend	(49)				(49)
Common stock acquired	(325)						$ (325)
Common stock acquired (shares)							5,615
Common stock awards and options exercised	57			(7)			$ 64
Common stock awards and options exercised (shares)							(1,542)
Other	(1)						$ (1)
Other (shares)							15
Ending balance at Mar. 31, 2016	21,496	2,703	$ 504	9,739	16,233	(964)	$ (6,719)
Ending balance (shares) at Mar. 31, 2016			503,880				108,316
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
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 and options exercised	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