Common and Preferred Stock (Details) - USD ($)		1 Months Ended		9 Months Ended
	Dec. 01, 2015	Oct. 31, 2018	Oct. 31, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Equity [Abstract]
Increase in share repurchase authorized amount	$ 300,000,000.0
Purchase of common stock (in shares)				356,590	222,000
Repurchase of shares of common stock				$ 51,660,000	$ 23,600,000
Remaining authorized repurchase amount				$ 499,300,000
Common stock, authorized (in shares)				150,000,000		150,000,000
Common stock, par value (in dollars per share)				$ 0.01		$ 0.01
Preferred stock, authorized (in shares)				5,000,000		5,000,000
Preferred stock, par value (in dollars per share)				$ 0.01		$ 0.01
Preferred stock, shares outstanding (in shares)				0		0
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Purchase of common stock			$ 1,000,000	$ 50,654,000	$ 22,650,000
Subsequent Event
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Purchase of common stock		$ 1,000,000