Equity - Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Numerator:
Net income	$ 26,585	$ 25,281	$ 34,473	$ 36,512
Private perpetual preferred unit distributions	(234)	0	(468)	0
Net income attributable to non-controlling interests	(15,231)	(15,447)	(19,747)	(22,309)
Earnings allocated to unvested shares	(7)	(9)	(13)	(19)
Net income attributable to common stockholders - basic	11,113	9,825	14,245	14,184
Earnings allocated to unvested shares and LTIP units	(161)	(108)	(284)	(247)
Net income attributable to common stockholders - diluted	$ 26,190	$ 25,173	$ 33,721	$ 36,265
Denominator:
Weighted average shares outstanding - basic	112,852,000	95,466,000	111,136,000	95,466,000
Operating partnership units	153,015,000	148,970,000	154,730,000	148,965,000
Weighted average shares outstanding - diluted	265,867,000	244,436,000	265,866,000	244,431,000
Basic (USD per share)	$ 0.10	$ 0.10	$ 0.13	$ 0.15
Diluted (USD pre share)	$ 0.10	$ 0.10	$ 0.13	$ 0.15
Antidilutive securities, shares	744,007	677,605	628,935	576,975