Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
BASIC
Net income (loss) attributable to common shareholders	$ 3,916	$ (26,975)	$ 49,832	$ 74,718
Weighted-average number of common shares outstanding - basic	237,989,098	234,207,396	237,632,572	233,151,600
Income (loss) per common share:
Net income (loss) attributable to common shares outstanding - basic (in dollars per share)	$ 0.02	$ (0.12)	$ 0.21	$ 0.32
DILUTED
Impact of assumed conversions	$ (173)	$ 0	$ (192)	$ (845)
Net income (loss) attributable to common shareholders	$ 3,743	$ (26,975)	$ 49,640	$ 73,873
Effect of dilutive securities:
Share options (in shares)	66,748	0	95,788	246,166
OP Units (in shares)	3,646,869	0	3,713,867	3,818,117
Weighted-average common shares outstanding (in shares)	241,702,715	234,207,396	241,442,227	237,215,883
Income (loss) per common share:
Net income (loss) attributable to common shareholders - per common share diluted (in dollars per share)	$ 0.02	$ (0.12)	$ 0.21	$ 0.31