Earnings per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Earnings Per Share [Abstract]
Less: Undistributed earnings attributable to unvested restricted shares	$ 0	$ 27
Numerator:
Net income attributable to common shareholders	25,298	47,850
Less: Dividends paid on unvested restricted shares	(413)	(279)
Less: Undistributed earnings attributable to unvested restricted shares	0	27
Net income attributable to common shareholders excluding amounts attributable to unvested restricted shares	$ 24,885	$ 47,544
Denominator:
Weighted-average number of common shares - basic (in shares)	123,739,823	131,272,611
Unvested restricted shares (in shares)	402,001	281,980
Unvested performance units (in shares)	0	731,951
Weighted-average number of common shares - diluted (in shares)	124,141,824	132,286,542
Net income per share attributable to common shareholders - basic (in dollars per share)	$ 0.20	$ 0.36
Net income per share attributable to common shareholders - diluted (in dollars per share)	$ 0.20	$ 0.36