Earnings Per Share (EPS) - Computation of Basic and Diluted EPS Attributable to Common Stock (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Basic EPS
Net income	$ 58	$ 40	$ 112	$ 69
Weighted average shares of common stock outstanding (in shares)	70,448,809	69,029,749	70,250,273	68,770,976
Basic earnings per share (in dollars per share)	$ 0.82	$ 0.58	$ 1.59	$ 1.00
Diluted EPS
Net income	$ 58	$ 40	$ 112	$ 69
Weighted average shares of common stock outstanding (in shares)	70,448,809	69,029,749	70,250,273	68,770,976
Dilutive effect of stock options and restricted stock units (in shares)	3,000,000	2,000,000	2,000,000	2,000,000
Weighted average shares of common stock outstanding (in shares)	72,561,891	71,167,177	72,404,539	71,101,716
Diluted earnings per share (in dollars per share)	$ 0.80	$ 0.56	$ 1.55	$ 0.97
Common stock equivalents excluded from income per diluted share (in shares)	0	0	1,000,000	0