Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Numerator:
Net income	$ 7,798	$ 6,146	$ 5,500	$ 1,987	$ 5,881	$ 6,175	$ 8,074	$ 7,172	$ 21,431	$ 27,302	$ 36,544
Less: Net income allocated to participating securities									0	0	(277)
Net income available to common shareholders									$ 21,431	$ 27,302	$ 36,267
Denominator:
Weighted average common shares outstanding									17,109	20,577	20,922
Weighted average dilutive securities									352	461	544
Weighted average common shares outstanding, diluted									17,461	21,038	21,466
Income per common share, basic (in dollars per share)	$ 0.49	$ 0.39	$ 0.32	$ 0.10	$ 0.29	$ 0.30	$ 0.39	$ 0.35	$ 1.25	$ 1.33	$ 1.73
Income per common share, diluted (in dollars per share)	$ 0.48	$ 0.38	$ 0.31	$ 0.10	$ 0.29	$ 0.29	$ 0.38	$ 0.34	$ 1.23	$ 1.3	$ 1.69