Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Total revenues	$ 18,616	$ 19,892	$ 21,709	$ 23,862	$ 26,119	$ 29,854	$ 32,760	$ 33,567	$ 84,079	$ 122,300	$ 133,785
Income (loss) before income taxes	3,691	1,559	2,656	1,496	7,888	7,151	10,936	10,487	9,402	36,462	33,893
Net income	$ 2,541	$ 1,117	$ 1,861	$ 392	$ 5,413	$ 5,368	$ 7,992	$ 7,978	$ 5,911	$ 26,751	$ 19,989
Basic earnings per common share (in dollars per share)	$ 0.30	$ 0.13	$ 0.22	$ 0.05	$ 0.65	$ 0.64	$ 0.95	$ 0.96	$ 0.70	$ 3.20	$ 2.45
Diluted earnings per common share (in dollars per share)	$ 0.30	$ 0.13	$ 0.22	$ 0.05	$ 0.64	$ 0.62	$ 0.94	$ 0.93	$ 0.70	$ 3.13	$ 2.38