Consolidated Statement of Shareholders' Equity - 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 (in shares) at Dec. 31, 2013		182,177,866
Beginning balance at Dec. 31, 2013	$ 5,115	$ 2	$ 2,466	$ 2,482	$ 160	$ 5
Increase (Decrease) in Shareholders' Equity
Net Income	1,088			1,088
Dividends (2014 $0.44, 2015 $0.48, 2016 $0.52 per share)	(76)			(76)
Common stock repurchases (in shares)		(24,413,781)
Common stock repurchases	(590)		(590)
Share-based compensation and other (in shares)		542,576
Share-based compensation and other	11		11
Other comprehensive loss	210				210
Ending balance (in shares) at Dec. 31, 2014		158,306,661
Ending balance at Dec. 31, 2014	5,758	$ 2	1,887	3,494	370	5
Increase (Decrease) in Shareholders' Equity
Net Income	1,056			1,056
Dividends (2014 $0.44, 2015 $0.48, 2016 $0.52 per share)	(72)			(72)
Common stock repurchases (in shares)		(20,995,419)
Common stock repurchases	(555)	$ (1)	(554)
Share-based compensation and other (in shares)		617,310
Share-based compensation and other	9		9
Other comprehensive loss	(133)				(133)
Ending balance (in shares) at Dec. 31, 2015		137,928,552
Ending balance at Dec. 31, 2015	6,063	$ 1	1,342	4,478	237	5
Increase (Decrease) in Shareholders' Equity
Net Income	881			881
Dividends (2014 $0.44, 2015 $0.48, 2016 $0.52 per share)	(70)			(70)
Common stock repurchases (in shares)		(10,721,248)
Common stock repurchases	(306)		(306)
Share-based compensation and other (in shares)		780,926
Share-based compensation and other	24		24
Other comprehensive loss	(88)				(88)
Ending balance (in shares) at Dec. 31, 2016		127,988,230
Ending balance at Dec. 31, 2016	$ 6,504	$ 1	$ 1,060	$ 5,289	$ 149	$ 5