Condensed Consolidated Statement of Changes in Equity - USD ($) $ in Millions	Total	Common stock and paid-in capital [Member]	Preferred stock [Member]	Retained Earnings [Member]	Accumulated other comprehensive (loss) income [Member]	Treasury stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Net of Tax	$ (231)				$ (231)
Stockholders' Equity Attributable to Parent at Dec. 31, 2015	13,439	$ 21,100	$ 696	$ (8,110)		$ (16)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss) Attributable to Parent	819			819
Dividends, Preferred Stock, Cash	(30)			(30)
Stock Repurchased During Period, Value	(696)		(696)
Adjustments to Additional Paid in Capital, Income Tax Benefit from Share-based Compensation	49	49
Other Comprehensive Income (Loss), Net of Tax	262				262
Treasury Stock, Value, Acquired, Cost Method	(173)					(173)
Dividends, Common Stock, Cash	(40)			(40)
Stockholders' Equity Attributable to Parent at Sep. 30, 2016	$ 13,630	21,149	0	(7,361)		(189)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common Stock, Dividends, Per Share, Declared	$ 0.08
Accumulated Other Comprehensive Income (Loss), Net of Tax	$ 31				31
Accumulated Other Comprehensive Income (Loss), Net of Tax	(341)				(341)
Stockholders' Equity Attributable to Parent at Dec. 31, 2016	13,317	21,166	0	(7,151)		(357)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss) Attributable to Parent	748			748
Dividends, Preferred Stock, Cash	0
Adjustments to Additional Paid in Capital, Income Tax Benefit from Share-based Compensation	57	57
Other Comprehensive Income (Loss), Net of Tax	144				144
Treasury Stock, Value, Acquired, Cost Method	(563)					(563)
Dividends, Common Stock, Cash	(130)			(130)
Stockholders' Equity Attributable to Parent at Sep. 30, 2017	$ 13,573	$ 21,223	$ 0	$ (6,533)		$ (920)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common Stock, Dividends, Per Share, Declared	$ 0.28
Accumulated Other Comprehensive Income (Loss), Net of Tax	$ (197)				$ (197)