Consolidated Statements of Stockholders' Equity - 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, 2014	$ 11,803	$ 872	$ 15	$ 4,050	$ 10,198	$ (3,497)	$ 165
Beginning Balance (in shares) at Dec. 31, 2014			1,488
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,447				1,447
Other comprehensive income (loss), net of tax	(299)						(299)
Issuance of preferred stock, net	587	587
Dividends declared on preferred stock	(69)				(69)
Dividends declared on common stock	(318)				(318)
Stock option exercises and other	90			(87)		177
Share-based compensation and related tax effects	172			172
Other	(11)			17	(5)	(23)
Ending Balance (in shares) at Dec. 31, 2015			1,488
Ending Balance at Dec. 31, 2015	13,402	1,459	$ 15	4,152	11,253	(3,343)	(134)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,889				1,889
Other comprehensive income (loss), net of tax	(29)						(29)
Issuance of preferred stock, net	1,324	1,324
Dividends declared on preferred stock	(126)				(126)
Dividends declared on common stock	(360)				(360)
Stock option exercises and other	144			(80)		224
Share-based compensation and related tax effects	177			177
Other	0			18	(7)	(11)
Ending Balance (in shares) at Dec. 31, 2016			1,488
Ending Balance at Dec. 31, 2016	16,421	2,783	$ 15	4,267	12,649	(3,130)	(163)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	2,354				2,354
Other comprehensive income (loss), net of tax	11						11
Issuance of preferred stock, net	492	492
Redemption of preferred stock	(485)	(482)			(3)
Dividends declared on preferred stock	(161)				(161)
Dividends declared on common stock	(431)				(431)
Stock option exercises and other	171			(88)		259
Share-based compensation and related tax effects	144			144
Other	9			30	0	(21)
Ending Balance (in shares) at Dec. 31, 2017			1,488
Ending Balance at Dec. 31, 2017	$ 18,525	$ 2,793	$ 15	$ 4,353	$ 14,408	$ (2,892)	$ (152)