Stockholders' Equity (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Jun. 10, 2016
Equity, Class of Treasury Stock [Line Items]
Stock Repurchase Program, Authorized Amount			$ 150,000
Stock Repurchased and Retired During Period, Value	$ (58,070)	$ (43,091)
Common Stock [Member]
Equity, Class of Treasury Stock [Line Items]
Stock Repurchased and Retired During Period, Shares	(1,229,249)	(1,133,553)
Stock Repurchased and Retired During Period, Value	$ (12)	$ (11)
Additional Paid-in Capital [Member]
Equity, Class of Treasury Stock [Line Items]
Stock Repurchased and Retired During Period, Value	(13,229)	(11,885)
Retained Earnings [Member]
Equity, Class of Treasury Stock [Line Items]
Stock Repurchased and Retired During Period, Value	$ (44,829)	$ (31,195)