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	1,122				1,122
Other comprehensive income (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 vested	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
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	1,395				1,395
Other comprehensive income (loss)	(479)					(479)
Cash dividends declared:
Common stock dividends	(307)				(307)
Preferred stock cash dividend	(91)				91
Common stock acquired	(350)						$ (350)
Common stock acquired (shares)							3,324
Common stock awards vested	83			21			$ 62
Common stock awards and options exercised (shares)							(1,498)
Other	3				3
Other (shares)							(4)
Ending balance at Jun. 30, 2018	$ 22,571	$ 3,196	$ 504	$ 9,820	$ 19,856	$ (1,488)	$ (9,317)
Ending balance (shares) at Jun. 30, 2018			503,880				138,052