Condensed Consolidated Statements of Changes in Stockholders' Equity Condensed Consolidated Statements of Changes in Stockholders' Equity (Unaudited) - USD ($) shares in Thousands, $ in Millions	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Treasury Stock	AOCI Attributable to Parent [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of accounting change net of income taxes				$ 0		$ 0
Adjusted balance, beginning of period				13,114		(337)
Beginning balance at Dec. 31, 2016			$ 5,247	13,114	$ (1,125)	(337)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of shares under incentive and stock compensation plans			(66)
Stock-based compensation plans expense			36
Issuance of shares for warrant exercise			40		(40)
Net Income (Loss) Attributable to Parent	$ 378			378
Dividends declared on common stock				(86)
Treasury stock acquired					(325)
Issuance of shares under incentive and stock compensation plans					72
Net shares acquired related to employee incentive and stock compensation plans					33
Total other comprehensive income						130
Ending balance at Mar. 31, 2017	17,009	$ 4	5,177	13,406	(1,371)	(207)
Common Shares Outstanding, beginning of period (in thousands) at Dec. 31, 2016		373,949
Stock Issued or Granted During Period, Share-based Compensation [Abstract]
Treasury stock acquired		6,709
Issuance of shares under incentive and stock compensation plans		1,690
Return of shares under incentive and stock compensation plans to treasury stock		674
Issuance of shares for warrant exercise		940
Common Shares Outstanding, at end of period at Mar. 31, 2017		369,196
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of accounting change net of income taxes				5		(5)
Adjusted balance, beginning of period				9,647		658
Beginning balance at Dec. 31, 2017	13,494		4,379	9,642	(1,194)	663
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of shares under incentive and stock compensation plans			(74)
Stock-based compensation plans expense			61
Issuance of shares for warrant exercise			3		(3)
Net Income (Loss) Attributable to Parent	597			597
Dividends declared on common stock				(88)
Treasury stock acquired					0
Issuance of shares under incentive and stock compensation plans					81
Net shares acquired related to employee incentive and stock compensation plans					31
Total other comprehensive income						(897)
Ending balance at Mar. 31, 2018	$ 13,143	$ 4	$ 4,363	$ 10,156	$ (1,141)	$ (239)
Common Shares Outstanding, beginning of period (in thousands) at Dec. 31, 2017		356,835
Stock Issued or Granted During Period, Share-based Compensation [Abstract]
Treasury stock acquired		0
Issuance of shares under incentive and stock compensation plans		1,770
Return of shares under incentive and stock compensation plans to treasury stock		595
Issuance of shares for warrant exercise		67
Common Shares Outstanding, at end of period at Mar. 31, 2018		358,077