Earnings Per Share (Details) - USD ($) $ / shares in Units, $ 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
Earnings Per Share
Net income attributable to common shares	$ 14,895	$ 12,180	$ 12,035	$ 11,261	$ 9,342	$ 6,920	$ 5,538	$ 4,568	$ 50,371	$ 26,368	$ 14,427
Weighted-average common shares outstanding - basic									32,289,414	25,218,500	21,161,614
Effect of potentially dilutive common shares:
Stock options									192,464	302,264	349,533
Unvested awards									250,181	185,804	229,560
Weighted-average common shares outstanding - diluted									32,732,059	25,706,568	21,740,707
Net income per share attributable to common shares
Basic (in dollars per share)	$ 0.45	$ 0.36	$ 0.38	$ 0.37	$ 0.32	$ 0.26	$ 0.23	$ 0.21	$ 1.56	$ 1.05	$ 0.68
Diluted (in dollars per share)	$ 0.44	$ 0.36	$ 0.37	$ 0.37	$ 0.32	$ 0.26	$ 0.22	$ 0.21	$ 1.54	$ 1.03	$ 0.66
Weighted-average potentially dilutive securities excluded in calculation of basic and diluted income (loss) per share									29,618	117,048	180,020