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	1,404				1,404
Other comprehensive income (loss)	(594)					(594)
Preferred stock issued	742	742
Cash dividends declared:
Common stock dividends	(401)				(401)
Preferred stock cash dividend	(101)				(101)
Common stock acquired	(1,170)						$ (1,170)
Common stock acquired (shares)							15,552
Common stock awards and options exercised, including related taxes	140			(45)			$ 185
Common stock awards and options exercised, including related taxes (shares)							(4,148)
Other	(5)			(4)	(1)
Other (shares)							(2)
Ending balance (shares) at Sep. 30, 2015			503,880				100,087
Ending balance at Sep. 30, 2015	21,343	2,703	$ 504	9,742	15,638	(1,101)	$ (6,143)
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 income (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 and options exercised, including related taxes	146			32			$ 114
Common stock awards and options exercised, including related taxes (shares)							(2,765)
Other	0				(1)		$ 1
Other (shares)							(15)
Ending balance (shares) at Sep. 30, 2016			503,880				118,309
Ending balance at Sep. 30, 2016	$ 22,150	$ 3,196	$ 504	$ 9,778	$ 17,047	$ (993)	$ (7,382)