Stockholders' Equity (Details) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2013
Class of Stock [Line Items]
Increase in stockholders' equity			$ 134,000,000
Net income	$ 42,000,000	$ 46,000,000	99,000,000	$ 113,000,000
Other comprehensive income	$ (1,000,000)	$ 2,000,000	7,000,000	1,000,000
Income tax benefit related to share-based compensation			$ 28,000,000
Number of warrants issued (in shares)					13,490,236
Warrant, strike price per share (usd per share)					$ 53.8475
Trading days measurement period (in days)			160 days
Stated percentage of warrants	1.125%		1.125%
Unrecognized compensation expense	$ 38,000,000		$ 38,000,000
Weighted average period for recognition (in years)			1 year 7 months
Unrecognized compensation forfeiture rate (as a percent)			4.30%
Restricted and Performance Stock
Class of Stock [Line Items]
Fair value of restricted and performance stock awards granted			$ 33,000,000	28,000,000
Total fair value of restricted shares vested			$ 22,000,000	$ 25,000,000
Restricted Stock
Class of Stock [Line Items]
Number of nonvested shares outstanding (in shares)	603,000		603,000
Performance shares that are expected to vest (in shares)	425,000		425,000
Common Stock
Class of Stock [Line Items]
Number of common stock issued (in shares)			467,000
December 2015 Repurchase Program | Common Stock
Class of Stock [Line Items]
Authorized repurchase amount	$ 50,000,000		$ 50,000,000