Basic and Diluted Net Income per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Basic and Diluted Net Income Per Common Share
Net income available to common stockholders	$ 5,853	$ 7,896	$ 6,628	$ 13,354
Weighted Average Shares Outstanding
Basic (in shares)	50,470	50,225	50,441	50,267
Effect of dilutive securities (in shares)	41	762	58	747
Diluted (in shares)	50,511	50,987	50,499	51,014
Basic net income per common share (in dollars per share)	$ 0.12	$ 0.16	$ 0.13	$ 0.27
Diluted net income per common share (in dollars per share)	$ 0.12	$ 0.15	$ 0.13	$ 0.26
Stock based compensation awards excluded from the dilutive calculations as the effect would have been antidilutive (in shares)	2,200	1,300	2,200	1,300