CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - 3 months ended Mar. 31, 2016 - USD ($) $ in Millions	Total	Preferred Stock	Common Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock
Beginning balance at Dec. 31, 2015	$ 47,284	$ 0	$ 6	$ 29,655	$ 27,045	$ (616)	$ (8,806)
Beginning balance (shares) at Dec. 31, 2015		3,375,000	648,317,395
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income	1,588				1,013	575
Common Stock Dividends, Shares			33,871
Dividends, Common Stock	211		$ 0	2	213
Cash dividends - preferred series	(37)				(37)
Purchases of treasury stock	(970)						(970)
Issuances of common stock and restricted stock, shares, net of forfeitures			1,785,298
Issuances of common stock and restricted stock, value, net of forfeitures	30		$ 1	29
Exercise of stock options and warrants, tax effects of exercises and restricted stock vesting, shares			16,500
Exercise of stock options and warrants, tax effects of exercises and restricted stock vesting, value	(11)		$ 0	(11)
Compensation expense for restricted stock awards, restricted stock units and stock options	34			34
Ending balance at Mar. 31, 2016	$ 47,707	$ 0	$ 7	$ 29,709	$ 27,808	$ (41)	$ (9,776)
Ending balance (shares) at Mar. 31, 2016		3,375,000	650,153,064