Earnings Per Share (EPS) - Computation of Basic and Diluted EPS Attributable to Common Stock (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Basic EPS
Net income	$ 51	$ 43	$ 163	$ 112
Weighted average shares of common stock outstanding (in shares)	70,556,877	69,498,218	70,353,597	69,016,054
Basic earnings per share (in dollars per share)	$ 0.73	$ 0.62	$ 2.32	$ 1.62
Diluted EPS
Net income	$ 51	$ 43	$ 163	$ 112
Weighted average shares of common stock outstanding (in shares)	70,556,877	69,498,218	70,353,597	69,016,054
Dilutive effect of stock options and restricted stock units (in shares)	2,000,000	2,000,000	2,000,000	2,000,000
Weighted average shares of common stock outstanding (in shares)	72,599,944	71,499,591	72,388,598	71,138,743
Diluted earnings per share (in dollars per share)	$ 0.71	$ 0.60	$ 2.25	$ 1.57
Common stock equivalents excluded from income per diluted share (in shares)	0	0	1,000,000	2,000,000