Net Income Per Share (Details) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Earnings Per Share [Abstract]
Net income	$ 6,339	$ 11,950	$ 7,314	$ 13,787	$ 8,164	$ 8,385	$ 1,891	$ 9,564	$ 39,390	$ 28,004	$ 32,032
Less distributed and undistributed earnings allocated to participating securities									981	2,002	916
Net income allocated to common shares									$ 38,409	$ 26,002	$ 31,116
Weighted average common shares outstanding									24,308	24,708	24,850
Incremental shares from assumed conversions of common stock options									7	4	22
Adjusted weighted average common shares outstanding									24,315	24,712	24,872
Potentially dilutive securities not included in weighted average share calculation due to anti-dilutive effect									0	4	8