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	610			610
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	36	36
Other Comprehensive Income (Loss), Net of Tax					266
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	266
Treasury Stock, Value, Acquired, Cost Method	(14)					(14)
Stockholders' Equity Attributable to Parent at Jun. 30, 2016	$ 13,611	21,136	0	(7,530)		(30)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common Stock, Dividends, Per Share, Declared	$ 0.00
Accumulated Other Comprehensive Income (Loss), Net of Tax	$ 35				35
Treasury Stock, Value, Acquired, Cost Method	(699)
Stockholders' Equity Attributable to Parent at Jun. 30, 2017	13,473	21,208	0	(6,760)		(730)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
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	466			466
Dividends, Preferred Stock, Cash	0
Adjustments to Additional Paid in Capital, Income Tax Benefit from Share-based Compensation	42	42
Other Comprehensive Income (Loss), Net of Tax					96
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	96
Treasury Stock, Value, Acquired, Cost Method	(373)					(373)
Dividends, Common Stock, Cash	(75)			(75)
Stockholders' Equity Attributable to Parent at Jun. 30, 2017	$ 13,473	$ 21,208	$ 0	$ (6,760)		$ (730)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common Stock, Dividends, Per Share, Declared	$ 0.16
Accumulated Other Comprehensive Income (Loss), Net of Tax	$ (245)				$ (245)