Earnings Per Share (Details) - USD ($) $ / shares in Units, 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
Numerator:
Net income	$ 5,881	$ 6,175	$ 8,074	$ 7,172	$ 14,127	$ 8,404	$ 7,741	$ 6,272	$ 27,302	$ 36,544	$ 34,759
Less: Net income allocated to participating securities									0	(277)	(336)
Net income available to common shareholders									$ 27,302	$ 36,267	$ 34,423
Denominator:
Weighted average common shares outstanding									20,577	20,922	20,821
Weighted average dilutive securities									461	544	610
Weighted average common shares outstanding, diluted									21,038	21,466	21,431
Income per common share, basic (in dollars per share)	$ 0.29	$ 0.3	$ 0.39	$ 0.35	$ 0.68	$ 0.4	$ 0.36	$ 0.3	$ 1.33	$ 1.73	$ 1.65
Income per common share, diluted (in dollars per share)	$ 0.29	$ 0.29	$ 0.38	$ 0.34	$ 0.66	$ 0.39	$ 0.36	$ 0.29	$ 1.30	$ 1.69	$ 1.61