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, 2014	$ 21,328	$ 1,961	$ 504	$ 9,791	$ 14,737	$ (507)	$ (5,158)
Beginning balance (shares) at Dec. 31, 2014			503,880				88,685
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,980
Other comprehensive loss	(935)
Preferred stock issued	742	742
Cash dividends declared:
Common stock dividends	(536)				(536)
Preferred stock cash dividend	(130)				(130)
Common stock acquired	(1,520)						$ (1,520)
Common stock acquired (shares)							20,521
Common stock awards exercised	180			(41)			$ 221
Common stock awards and options exercised (shares)							(4,976)
Other	(6)			(4)	(2)
Other (shares)							(2)
Ending balance at Dec. 31, 2015	21,103	2,703	$ 504	9,746	16,049	(1,442)	$ (6,457)
Ending balance (shares) at Dec. 31, 2015			503,880				104,228
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	2,143				2,143
Other comprehensive loss	(598)					(598)
Preferred stock issued	493	493
Cash dividends declared:
Common stock dividends	(559)				(559)
Preferred stock cash dividend	(173)				(173)
Common stock acquired	(1,365)						$ (1,365)
Common stock acquired (shares)							21,098
Common stock awards exercised	175			36			$ 139
Common stock awards and options exercised (shares)							(3,369)
Other	0				(1)		$ 1
Other (shares)							(16)
Ending balance at Dec. 31, 2016	21,219	3,196	$ 504	9,782	17,459	(2,040)	$ (7,682)
Ending balance (shares) at Dec. 31, 2016			503,880				121,941
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	2,177				2,177
Other comprehensive loss	1,031					1,031
Preferred stock issued	0
Cash dividends declared:
Common stock dividends	(596)				(596)
Preferred stock cash dividend	(182)				(182)
Common stock acquired	(1,450)						$ (1,450)
Common stock acquired (shares)							16,788
Common stock awards exercised	120			16			$ 104
Common stock awards and options exercised (shares)							(2,503)
Other	(2)			1	(2)		$ (1)
Other (shares)							(4)
Ending balance at Dec. 31, 2017	$ 22,317	$ 3,196	$ 504	$ 9,799	$ 18,856	$ (1,009)	$ (9,029)
Ending balance (shares) at Dec. 31, 2017			503,880				136,230