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, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Basic and Diluted Net Income Per Common Share
Net income available to common stockholders	$ 6,385	$ 12,106	$ 19,739	$ 35,747
Weighted Average Shares Outstanding
Basic (in shares)	50,246	51,891	50,260	52,217
Effect of Dilutive Securities (in shares)	738	743	744	828
Diluted (in shares)	50,984	52,634	51,004	53,045
Basic net income per common share (in dollars per share)	$ 0.13	$ 0.23	$ 0.39	$ 0.68
Diluted net income per common share (in dollars per share)	$ 0.13	$ 0.23	$ 0.39	$ 0.67
Stock based compensation awards excluded from the dilutive calculations as the effect would have been antidilutive (in shares)	1,300	800	1,300	800