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	1,550				1,550
Other comprehensive loss	449					449
Preferred stock issued	493	493
Cash dividends declared:
Common stock dividends	(414)				(414)
Preferred stock cash dividend	(137)				(137)
Common stock acquired	(1,040)						$ (1,040)
Common stock acquired (shares)							16,861
Common stock awards exercised	146			32			$ 114
Common stock awards and options exercised (shares)							(2,765)
Other	0				(1)		$ 1
Other (shares)							(15)
Ending balance at Sep. 30, 2016	22,150	3,196	$ 504	9,778	17,047	(993)	$ (7,382)
Ending balance (shares) at Sep. 30, 2016			503,880				118,309
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	1,807				1,807
Other comprehensive loss	1,056					1,056
Cash dividends declared:
Common stock dividends	(442)				(442)
Preferred stock cash dividend	(146)				(146)
Common stock acquired	(1,100)						$ (1,100)
Common stock acquired (shares)							13,131
Common stock awards exercised	106			21			$ 85
Common stock awards and options exercised (shares)							(2,033)
Other	(3)				(3)
Other (shares)
Ending balance at Sep. 30, 2017	$ 22,497	$ 3,196	$ 504	$ 9,803	$ 18,675	$ (984)	$ (8,697)
Ending balance (shares) at Sep. 30, 2017			503,880				133,039