Equity - Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Numerator:
Net income	$ 28,720	$ 26,784	$ 18,930	$ 9,856	$ 39,781	$ 29,230	$ 30,184	$ 18,058	$ 32,260	$ 35,489	$ 31,359	$ 19,145	$ 84,290	$ 117,253	$ 118,253
Private perpetual preferred unit distributions													(1,743)	(936)	(936)
Net income attributable to non-controlling interests													(33,102)	(50,714)	(54,670)
Earnings allocated to unvested shares													(45)	(38)	(36)
Net income attributable to common stockholders - basic													49,400	65,565	62,611
Earnings allocated to unvested shares													(45)	(38)	(36)
Net income attributable to common stockholders - diluted													$ 82,502	$ 116,279	$ 117,281
Denominator:
Weighted average shares outstanding - basic (shares)													178,340,000	167,571,000	158,380,000
Operating partnership units (shares)													119,458,000	129,687,000	138,075,000
Effect of dilutive securities, stock-based compensation plans (shares)													0	1,000	775,000
Effect of dilutive securities, exchangeable senior notes (shares)													0	0	819,000
Weighted average shares outstanding - dilutive (in shares)													297,798,000	297,259,000	298,049,000
Basic (USD per share)													$ 0.28	$ 0.39	$ 0.40
Diluted (USD per share)													$ 0.28	$ 0.39	$ 0.39
Antidilutive securities (shares)													416,492	485,865	834,267