Equity - Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Numerator:
Net income	$ 26,085	$ 22,734	$ 60,558	$ 59,246
Private perpetual preferred unit distributions	(234)	(241)	(702)	(241)
Net income attributable to non-controlling interests	(14,631)	(14,171)	(34,378)	(36,480)
Earnings allocated to unvested shares	(7)	(8)	(19)	(27)
Net income attributable to common stockholders - basic	11,213	8,314	25,459	22,498
Earnings allocated to unvested shares and LTIP units	(161)	(127)	(425)	(374)
Net income attributable to common stockholders - diluted	$ 25,690	$ 22,366	$ 59,431	$ 58,631
Denominator:
Weighted average shares outstanding - basic	115,900,000	97,729,000	112,741,000	96,226,000
Operating partnership units	149,973,000	165,312,000	153,127,000	154,470,000
Weighted average shares outstanding - diluted	265,873,000	263,041,000	265,868,000	250,696,000
Basic (USD per share)	$ 0.10	$ 0.09	$ 0.23	$ 0.23
Diluted (USD pre share)	$ 0.10	$ 0.09	$ 0.22	$ 0.23
Antidilutive securities, shares	802,462	674,642	692,209	607,654