Condensed Consolidated Statements of Stockholders' Equity Statement - USD ($) shares in Millions, $ in Millions	Total	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Treasury Stock, at cost [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Beginning balance at Dec. 31, 2015	$ 13,402	$ 1,459	$ 15	$ 4,152	$ 11,253	$ (3,343)	$ (134)
Beginning balance (shares) at Dec. 31, 2015			1,488
Increase (Decrease) in Stockholders' Equity
Net income	864				864
Other comprehensive income (loss), net of tax	117						117
Issuance of preferred stock	730	730
Dividends declared on preferred stock	(57)				(57)
Dividends declared on common stock	(173)				(173)
Stock option exercises and other	19			(14)		33
Share-based compensation and related tax effects	76			76
Other	12			9	(5)	8
Ending balance (shares) at Jun. 30, 2016			1,488
Ending balance at Jun. 30, 2016	14,990	2,189	$ 15	4,223	11,882	(3,302)	(17)
Beginning balance at Dec. 31, 2016	16,421	2,783	$ 15	4,267	12,649	(3,130)	(163)
Beginning balance (shares) at Dec. 31, 2016			1,488
Increase (Decrease) in Stockholders' Equity
Net income	1,139				1,139
Other comprehensive income (loss), net of tax	51						51
Dividends declared on preferred stock	(78)				(78)
Dividends declared on common stock	(215)				(215)
Stock option exercises and other	72			(26)		98
Share-based compensation and related tax effects	79			79
Other	20			16		4
Ending balance (shares) at Jun. 30, 2017			1,488
Ending balance at Jun. 30, 2017	$ 17,489	$ 2,783	$ 15	$ 4,336	$ 13,495	$ (3,028)	$ (112)