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 [Roll Forward]
Net income	412				412
Other comprehensive income (loss), net of tax	14						14
Issuance of preferred stock	727	727
Dividends declared on preferred stock	(16)				(16)
Dividends declared on common stock	(80)				(80)
Stock option exercises and other	7			(12)		19
Share-based compensation and related tax effects	47			47
Other	0			2	(2)	0
Ending balance (shares) at Mar. 31, 2016			1,488
Ending balance at Mar. 31, 2016	14,513	2,186	$ 15	4,189	11,567	(3,324)	(120)
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 [Roll Forward]
Net income	564				564
Other comprehensive income (loss), net of tax	31						31
Dividends declared on preferred stock	(37)				(37)
Dividends declared on common stock	(107)				(107)
Stock option exercises and other	58			(23)		81
Share-based compensation and related tax effects	49			49
Other	3			7	0	(4)
Ending balance (shares) at Mar. 31, 2017			1,488
Ending balance at Mar. 31, 2017	$ 16,982	$ 2,783	$ 15	$ 4,300	$ 13,069	$ (3,053)	$ (132)