Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Numerator:
Net income (loss) attributable to common shareholders	$ 16,428	$ 31,631	$ 20,004	$ 655	$ 9,462	$ 23,737	$ 16,591	$ (2,003)	$ 68,718	$ 47,787	$ 19,965
Less: dividends paid on unvested share-based compensation									(432)	(459)	(328)
Undistributed Earnings Attributable to Share-Based Compensation									0	0	0
Net income (loss) available to common shareholders									$ 68,286	$ 47,328	$ 19,637
Denominator:
Weighted-average number of common shares-basic									71,715,870	65,646,712	61,498,389
Effect of dilutive share-based compensation									668,419	617,406	338,352
Weighted-average number of common shares-diluted									72,384,289	66,264,118	61,836,741
Net income (loss) per share available to common shareholders-basic (in dollars per share)	$ 0.23	$ 0.44	$ 0.28	$ 0.01					$ 0.95	$ 0.72	$ 0.32
Net income (loss) per share available to common shareholders-diluted (in dollars per share)	$ 0.23	$ 0.43	$ 0.27	$ 0.01					$ 0.94	$ 0.71	$ 0.32