Segment Information - Reconciliation of Consolidated Net Income to Consolidated NOI (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Segment Reporting [Abstract]
Net income	$ 6,252	$ 4,583	$ 12,876	$ 44,445	$ 10,835	$ 57,321
Plus:
Interest expense	20,516		19,301		40,873	38,834
Interest expense - amortization of deferred financing costs	666		627		1,332	1,254
Depreciation and amortization	51,667		43,958		103,111	87,490
General and administrative expenses	8,399		7,523		18,243	16,246
Equity in loss of Real Estate Ventures	1,491		358		2,849	1,183
Less:
Interest income	553		641		1,078	1,344
Income tax provision	(17)		(20)		(46)	(158)
Net loss on disposition of real estate	0		(35)		0	(35)
Net gain on sale of undepreciated real estate	250		2,837		1,251	2,859
Net gain on real estate venture transactions	1,276		0		1,535	37,263
Consolidated net operating income	$ 86,929		$ 81,220		$ 173,425	$ 161,055