Consolidated Statement of Shareholders' Equity (unaudited) - USD ($) $ in Millions	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income [Member]	Deferred Equity Compensation [Member]
Beginning balance at Dec. 31, 2014					$ 370
Increase (Decrease) in Shareholders' Equity
Net Income	$ 627
Other comprehensive income	(97)
Ending balance at Sep. 30, 2015					273
Beginning balance at Jun. 30, 2015					239
Increase (Decrease) in Shareholders' Equity
Net Income	129
Other comprehensive income	34
Ending balance at Sep. 30, 2015					273
Beginning balance (in shares) at Dec. 31, 2015		137,928,552
Beginning balance at Dec. 31, 2015	6,063	$ 1	$ 1,342	$ 4,478	237	$ 5
Increase (Decrease) in Shareholders' Equity
Net Income	684			684
Dividends ($0.39 per share)	(52)			(52)
Common stock repurchases (in shares)		(7,420,631)
Common stock repurchases	(190)		(190)
Share-based compensation and other (in shares)		464,699
Share-based compensation and other	14		14
Other comprehensive income	121				121
Ending balance (in shares) at Sep. 30, 2016		130,972,620
Ending balance at Sep. 30, 2016	6,640	$ 1	1,166	5,110	358	5
Beginning balance at Jun. 30, 2016					383
Increase (Decrease) in Shareholders' Equity
Net Income	479
Other comprehensive income	(25)
Ending balance (in shares) at Sep. 30, 2016		130,972,620
Ending balance at Sep. 30, 2016	$ 6,640	$ 1	$ 1,166	$ 5,110	$ 358	$ 5