Equity - Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Numerator:
Net income	$ 33,008	$ 32,897	$ 24,640	$ 16,705	$ 19,370	$ 26,085	$ 26,585	$ 7,888	$ 10,964	$ 22,734	$ 25,281	$ 11,231	$ 107,250	$ 79,928	$ 70,210
Private perpetual preferred unit distributions													(936)	(936)	(476)
Net income attributable to non-controlling interests													(54,858)	(45,262)	(43,067)
Earnings allocated to unvested shares													(36)	(24)	(33)
Net income attributable to common stockholders - basic													51,420	33,706	26,634
Earnings allocated to unvested shares													(36)	(550)	(482)
Net income attributable to common stockholders - diluted													$ 106,278	$ 78,442	$ 69,252
Denominator:
Weighted average shares outstanding - basic (shares)													133,881,000	114,245,000	97,941,000
Operating partnership units (shares)													142,967,000	151,669,000	156,565,000
Effect of dilutive securities, stock-based compensation plans (shares)													454,000	707,000	0
Effect of dilutive securities, exchangeable senior notes (shares)													266,000	0	0
Weighted average shares outstanding - dilutive (in shares)													277,568,000	266,621,000	254,506,000
Basic (USD per share)													$ 0.38	$ 0.30	$ 0.27
Diluted (USD per share)													$ 0.38	$ 0.29	$ 0.27
Antidilutive securities (shares)													800,746	0	631,251