Basic and Diluted Net Income per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Basic and Diluted Net Income Per Common Share
Net income available to common stockholders	$ 5,111	$ 6,385	$ 11,739	$ 19,739
Weighted Average Shares Outstanding
Basic (in shares)	50,489	50,246	50,457	50,260
Effect of dilutive securities (in shares)	135	738	84	744
Diluted (in shares)	50,624	50,984	50,541	51,004
Basic net income per common share (in dollars per share)	$ 0.10	$ 0.13	$ 0.23	$ 0.39
Diluted net income per common share (in dollars per share)	$ 0.10	$ 0.13	$ 0.23	$ 0.39
Stock based compensation awards excluded from the dilutive calculations as the effect would have been antidilutive (in shares)	1,600	1,300	1,600	1,300