Equity - 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	$ 32,897	$ 26,085	$ 74,242	$ 60,558
Private perpetual preferred unit distributions	(234)	(234)	(702)	(702)
Net income attributable to non-controlling interests	(16,690)	(14,631)	(39,050)	(34,378)
Earnings allocated to unvested shares	(11)	(7)	(27)	(19)
Net income attributable to common stockholders - basic	15,962	11,213	34,463	25,459
Earnings allocated to unvested shares and LTIP units	(11)	(161)	(27)	(425)
Net income attributable to common stockholders - diluted	$ 32,652	$ 25,690	$ 73,513	$ 59,431
Denominator:
Weighted average shares outstanding - basic (in shares)	136,831,000	115,900,000	126,740,000	112,741,000
Operating partnership units (in shares)	141,908,000	149,973,000	143,648,000	153,127,000
Stock-based compensation plans (in shares)	1,090,000	0	378,000	0
Exchangeable senior notes (in shares)	785,000	0	262,000	0
Weighted average shares outstanding - diluted (in shares)	280,614,000	265,873,000	271,028,000	265,868,000
Basic (in USD per share)	$ 0.12	$ 0.10	$ 0.27	$ 0.23
Diluted (in USD per share)	$ 0.12	$ 0.10	$ 0.27	$ 0.22
Antidilutive securities (in shares)	1,033,044	802,462	757,119	692,209