Quarterly Consolidated Financial Information - Unaudited (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, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Consolidated Financial Information (Unaudited)
Total revenue	$ 63,189	$ 65,861	$ 67,844	$ 77,946	$ 55,476	$ 51,461	$ 49,618	$ 50,719	$ 55,186	$ 57,730	$ 43,810	$ 41,336	$ 274,840	$ 207,274	$ 198,062
Net income (loss) attributable to common shareholders	$ 41,864	$ 4,939	$ 5,657	$ 7,839	$ 2,418	$ 3,985	$ 3,366	$ 4,011	$ 3,037	$ 2,551	$ (486)	$ 1,358	$ 60,299	$ 13,780	$ 6,460
Basic earnings (loss) per common share (in dollars per share)	$ 6.87	$ 0.82	$ 0.94	$ 1.28	$ 0.40	$ 0.63	$ 0.50	$ 0.57	$ 0.39	$ 0.33	$ (0.06)	$ 0.17	$ 9.93	$ 2.10	$ 0.83
Diluted earnings (loss) per common share (in dollars per share)	$ 6.75	$ 0.80	$ 0.92	$ 1.25	$ 0.39	$ 0.62	$ 0.49	$ 0.55	$ 0.38	$ 0.32	$ (0.06)	$ 0.17	$ 9.69	$ 2.05	$ 0.81
Basic weighted average common shares outstanding	6,090,000	6,055,000	6,036,000	6,114,000	6,149,000	6,307,000	6,685,000	7,149,000	7,739,000	7,839,000	7,841,000	7,848,000	6,074,000	6,570,000	7,817,000
Diluted average common shares outstanding (in shares)	6,201,000	6,173,000	6,142,000	6,240,000	6,275,000	6,448,000	6,819,000	7,272,000	7,872,000	7,963,000	7,841,000	8,044,000	6,220,000	6,714,000	7,987,000
Adjustment impacted diluted earnings per common share				$ 0.01
Adjustment impacted diluted weighted average common shares outstanding				23,000