Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Earnings Per Share
Net income attributable to common shares	$ 6,920	$ 3,147	$ 17,026	$ 9,763
Weighted-average common shares outstanding - basic	26,126,332	21,214,825	24,029,106	21,113,700
Effect of potentially dilutive common shares:
Stock options	238,386	338,674	329,833	360,707
Unvested awards	184,819	155,260	185,673	205,524
Weighted-average common shares outstanding - diluted	26,549,537	21,708,759	24,544,612	21,679,931
Net income per share attributable to common shares
Basic (in dollars per share)	$ 0.26	$ 0.15	$ 0.71	$ 0.46
Diluted (in dollars per share)	$ 0.26	$ 0.14	$ 0.69	$ 0.45
Weighted-average potentially dilutive securities excluded in calculation of basic and diluted income (loss) per share	40,565	146,216	157,534	187,404