Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Computation of Basic and Diluted Shares
Net income	$ 2,897	$ 4,132	$ 6,896	$ 6,064	$ 7,577	$ 5,887	$ 5,661	$ 3,522	$ 19,989	$ 22,647	$ 27,105
Weighted average shares outstanding – basic (in shares)									8,147,742	7,961,891	7,756,647
Dilutive potential shares from unvested restricted shares (in shares)									252,280	182,979	350,755
Dilutive potential shares from contingent consideration (in shares)									0	20,605	41,997
Weighted average shares outstanding – diluted (in shares)									8,400,022	8,165,475	8,149,399
Earnings per share:
Basic (in dollars per share)	$ 0.35	$ 0.51	$ 0.84	$ 0.75	$ 0.95	$ 0.74	$ 0.71	$ 0.45	$ 2.45	$ 2.84	$ 3.49
Diluted (in dollars per share)	$ 0.34	$ 0.49	$ 0.83	$ 0.73	$ 0.92	$ 0.72	$ 0.69	$ 0.44	$ 2.38	$ 2.77	$ 3.33