CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Millions	Total	Preferred Stock	Common Stock	Additional Paid-in Capital	Retained Earnings	Treasury Stock, at Cost	Accumulated Other Comprehensive Loss
Beginning balance (in shares) at Dec. 31, 2014		0	546,000,000
Beginning balance at Dec. 31, 2014	$ 19,268	$ 0	$ 6	$ 18,676	$ 1,294	$ (336)	$ (372)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends to common stockholders	(214)				(214)
Dividends to preferred stockholders	(7)				(7)
Issuance of preferred stock (in shares)		0
Issuance of preferred stock	247	$ 247
Treasury stock purchased (in shares)			(20,000,000)
Treasury stock purchased	(500)					(500)
Share-based compensation plans (in shares)			2,000,000
Share-based compensation plans	18			40		(22)
Employee stock purchase plan shares purchased	9			9
Net income	840				840
Total comprehensive income:
Other comprehensive loss	(15)						(15)
Total comprehensive income	825				840		(15)
Ending balance (in shares) at Dec. 31, 2015		0	528,000,000
Ending balance at Dec. 31, 2015	19,646	$ 247	$ 6	18,725	1,913	(858)	(387)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends to common stockholders	(241)				(241)
Dividends to preferred stockholders	$ (14)				(14)
Treasury stock purchased (in shares)	(17,332,684)		(17,000,000)
Treasury stock purchased	$ (430)			(25)		(405)
Share-based compensation plans (in shares)			1,000,000
Share-based compensation plans	12			12		0
Employee stock purchase plan shares purchased	10			10
Net income	1,045				1,045
Total comprehensive income:
Other comprehensive loss	(281)						(281)
Total comprehensive income	764				1,045		(281)
Ending balance (in shares) at Dec. 31, 2016		0	512,000,000
Ending balance at Dec. 31, 2016	19,747	$ 247	$ 6	18,722	2,703	(1,263)	(668)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends to common stockholders	(322)				(322)
Dividends to preferred stockholders	$ (14)				(14)
Treasury stock purchased (in shares)	(22,362,401)		(22,000,000)
Treasury stock purchased	$ (820)			25		(845)
Share-based compensation plans (in shares)			1,000,000
Share-based compensation plans	22			22		0
Employee stock purchase plan shares purchased	12			12
Net income	1,652				1,652
Total comprehensive income:
Other comprehensive loss	(7)						(7)
Total comprehensive income	1,645				1,652		(7)
Ending balance (in shares) at Dec. 31, 2017		0	491,000,000
Total comprehensive income:
Reclassification of tax effects resulting from the 2017 Tax Legislation	145				145		(145)	[1]
Ending balance at Dec. 31, 2017	$ 20,270	$ 247	$ 6	$ 18,781	$ 4,164	$ (2,108)	$ (820)

[1] As of December 31, 2017, the balance of AOCI reflects the retrospective adoption of FASB ASU 2018-02, Income Statement-Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income. For further discussion, see Note 22 “Income Taxes.”