Net Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Net Income (Loss) Available to Common Stockholders, Basic	$ 47	$ 352	$ 73	$ 583
Basic earnings per common share:
Weighted-average common shares outstanding	233.3	235.2	233.2	237.4
Net earnings attributable to common stockholders (in dollars per share)	$ 0.20	$ 1.50	$ 0.31	$ 2.45
Diluted earnings per common share:
Weighted-average common shares outstanding	233.3	235.2	233.2	237.4
Dilutive common shares—stock options (in shares)	0.2	0.9	0.3	0.9
Diluted weighted-average shares outstanding	233.5	236.1	233.5	238.3
Net earnings attributable to common stockholders diluted (in dollars per share)	$ 0.20	$ 1.49	$ 0.31	$ 2.44
Antidilutive securities excluded from computation of EPS (in shares)	4.4	0.8	4.3	0.8
Retained Earnings
Net Income (Loss) Available to Common Stockholders, Basic			$ 73	$ 583