Earnings Per Common Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Earnings Per Share [Abstract]
Net income		$ 618	$ 503	$ 1,757	$ 1,367
Preferred stock dividends and other	[1]	(43)	(33)	(127)	(99)
Net Income Available to Common Stockholders		$ 575	$ 470	$ 1,630	$ 1,268
Weighted-average common shares outstanding — basic (shares)		1,339	1,324	1,338	1,322
Common stock equivalent shares related to stock incentive plans (shares)		14	10	14	10
Weighted-average common shares outstanding — diluted (shares)	[2]	1,353	1,334	1,352	1,332
Basic EPS (USD per share)		$ 0.43	$ 0.36	$ 1.22	$ 0.96
Diluted EPS (USD per share)		$ 0.42	$ 0.35	$ 1.21	$ 0.95
Antidilutive stock options and restricted stock awards excluded from the calculation of diluted EPS (in shares)		9	17	10	21

[1] Includes preferred stock dividends and undistributed earnings and dividends allocated to non-vested restricted stock units.

[2] Antidilutive stock options and restricted stock awards excluded from the calculation of diluted EPS totaled 9 million and 17 million shares for the third quarters of 2017 and 2016, respectively, and 10 million and 21 million shares for the first nine months of 2017 and 2016, respectively.