CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - 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, 2013	$ 41,632	$ 0	$ 6	$ 26,526	$ 20,292	$ (872)	$ (4,320)
Beginning balance (shares) at Dec. 31, 2013		875,000	637,151,800
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income	4,870				4,428	442
Dividends, Common Stock	(680)				(680)
Cash dividends - preferred series	(67)				(67)
Purchases of treasury stock	(2,045)						(2,045)
Issuances of common stock and restricted stock, shares, net of forfeitures			1,373,725
Issuances of common stock and restricted stock, value, net of forfeitures	100		$ 0	100
Exercise of stock options and warrants, tax effects of exercises and restricted stock vesting, shares			5,031,523
Exercise of stock options and warrants, tax effects of exercises and restricted stock vesting, value	146		$ 0	146
Stock Issued During Period, Shares, New Issues		1,000,000
Stock Issued During Period, Value, New Issues	969	$ 0		969
Compensation expense for restricted stock awards, restricted stock units and stock options	128			128
Ending balance at Dec. 31, 2014	45,053	$ 0	$ 6	27,869	23,973	(430)	(6,365)
Ending balance (shares) at Dec. 31, 2014		1,875,000	643,557,048
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income	3,864				4,050	(186)
Common Stock Dividends, Shares			46,846
Dividends, Common Stock	(816)		$ 0		(820)
Dividends, Share-based Compensation, Stock				4
Cash dividends - preferred series	(158)				(158)
Purchases of treasury stock	(2,441)						(2,441)
Issuances of common stock and restricted stock, shares, net of forfeitures			2,603,953
Issuances of common stock and restricted stock, value, net of forfeitures	111		$ 0	111
Exercise of stock options and warrants, tax effects of exercises and restricted stock vesting, shares			2,109,548
Exercise of stock options and warrants, tax effects of exercises and restricted stock vesting, value	71		$ 0	71
Stock Issued During Period, Shares, New Issues		1,500,000
Stock Issued During Period, Value, New Issues	1,472	$ 0		1,472
Compensation expense for restricted stock awards, restricted stock units and stock options	128			128
Ending balance at Dec. 31, 2015	47,284	$ 0	$ 6	29,655	27,045	(616)	(8,806)
Ending balance (shares) at Dec. 31, 2015		3,375,000	648,317,395
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income	3,418				3,751	(333)
Common Stock Dividends, Shares			52,338
Dividends, Common Stock	(812)		$ 0		(816)
Dividends, Share-based Compensation, Stock				4
Cash dividends - preferred series	(214)				(214)
Purchases of treasury stock	(3,661)						(3,661)
Issuances of common stock and restricted stock, shares, net of forfeitures			3,272,745
Issuances of common stock and restricted stock, value, net of forfeitures	131		$ 1	130
Exercise of stock options and warrants, tax effects of exercises and restricted stock vesting, shares			2,094,129
Exercise of stock options and warrants, tax effects of exercises and restricted stock vesting, value	102		$ 0	102
Stock Issued During Period, Shares, New Issues		1,100,000
Stock Issued During Period, Value, New Issues	1,066	$ 0		1,066
Compensation expense for restricted stock awards, restricted stock units and stock options	200			200
Ending balance at Dec. 31, 2016	$ 47,514	$ 0	$ 7	$ 31,157	$ 29,766	$ (949)	$ (12,467)
Ending balance (shares) at Dec. 31, 2016		4,475,000	653,736,607