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
Numerator:
Net income (loss) attributable to common shareholders	$ (43,897)	$ 31,631	$ 32,618	$ 52,290
Less: dividends paid on unvested share-based compensation	(121)	(109)	(362)	(323)
Undistributed Earnings Attributable to Share-Based Compensation	0	(45)	0	0
Net income (loss) available to common shareholders	$ (44,018)	$ 31,477	$ 32,256	$ 51,967
Denominator:
Weighted-average number of common shares-basic	71,922,904	71,735,129	71,894,313	71,709,380
Effect of dilutive share-based compensation	0	716,181	482,036	783,533
Weighted-average number of common shares-diluted	71,922,904	72,451,310	72,376,349	72,492,913
Net income (loss) per share available to common shareholders, basic (in usd per share)	$ (0.61)	$ 0.44	$ 0.45	$ 0.72
Net income (loss) per share available to common shareholders, diluted (in usd per share)	$ (0.61)	$ 0.43	$ 0.45	$ 0.72
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount (in shares)	31,311	10,533	117,201	0