Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Earnings Per Share
Net income attributable to common shares	$ 12,180	$ 6,920	$ 35,476	$ 17,026
Weighted-average common shares outstanding - basic	33,425,762	26,126,332	31,906,000	24,029,106
Effect of potentially dilutive common shares:
Stock options	192,272	238,386	197,166	329,833
Unvested awards	294,121	184,819	258,201	185,673
Weighted-average common shares outstanding - diluted	33,912,155	26,549,537	32,361,367	24,544,612
Net income per share attributable to common shares
Basic (in dollars per share)	$ 0.36	$ 0.26	$ 1.11	$ 0.71
Diluted (in dollars per share)	$ 0.36	$ 0.26	$ 1.10	$ 0.69
Weighted-average potentially dilutive securities excluded in calculation of basic and diluted income (loss) per share	7,757	40,565	113,920	157,534