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, 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	564	[1]				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)
Increase (Decrease) in Stockholders' Equity
Adoption of accounting standards (Note 2) | Accounting Standards Update 2014-09 and 2018-02 [Member]	167					200		(33)
Beginning balance at Dec. 31, 2017	18,525		2,793	$ 15	4,353	14,408	(2,892)	(152)
Beginning balance (shares) at Dec. 31, 2017				1,488
Increase (Decrease) in Stockholders' Equity
Net income	783					783
Other comprehensive income (loss), net of tax	(75)							(75)
Dividends declared on preferred stock	(34)					(34)
Dividends declared on common stock	(135)					(135)
Stock option exercises and other	49				(12)		61
Share-based compensation and related tax effects	47				47
Other	3				9		(6)
Ending balance (shares) at Mar. 31, 2018				1,488
Ending balance at Mar. 31, 2018	$ 19,330		$ 2,793	$ 15	$ 4,397	$ 15,222	$ (2,837)	$ (260)

[1] Adjusted for the retrospective adoption of ASU 2016-18. See Note 2.