Equity - Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Numerator - Basic:
Net income	$ 31,359	$ 24,640	$ 50,504	$ 41,345
Private perpetual preferred unit distributions	(234)	(234)	(468)	(468)
Net income attributable to non-controlling interests	(14,541)	(13,317)	(23,467)	(22,360)
Earnings allocated to unvested shares	(10)	(10)	(17)	(18)
Net income attributable to common stockholders - basic	16,574	11,079	26,552	18,499
Numerator - Diluted:
Net income	31,359	24,640	50,504	41,345
Private perpetual preferred unit distributions	(234)	(234)	(468)	(468)
Earnings allocated to unvested shares	(10)	(215)	(17)	(387)
Net income attributable to common stockholders - diluted	$ 31,115	$ 24,191	$ 50,019	$ 40,490
Denominator:
Weighted average shares outstanding - basic (in shares)	157,921,000	122,502,000	157,265,000	121,640,000
Operating partnership units (in shares)	138,467,000	143,665,000	139,123,000	144,511,000
Effect of dilutive securities:
Stock-based compensation plans (in shares)	973,000	0	874,000	970,000
Exchangeable senior notes (in shares)	1,037,000	0	918,000	0
Weighted average shares outstanding - diluted (in shares)	298,398,000	266,167,000	298,180,000	267,121,000
Earnings per share:
Basic (in USD per share)	$ 0.10	$ 0.09	$ 0.17	$ 0.15
Diluted (in USD per share)	$ 0.10	$ 0.09	$ 0.17	$ 0.15
Antidilutive securities (in shares)	909,591	1,069,803	766,078	0