Investments in and Advances to Unconsolidated Real Estate Ventures - Condensed Combined Financial Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Combined balance sheet information:
Real estate, net	$ 2,397,644		$ 2,397,644		$ 2,106,670
Other assets, net	332,400		332,400		264,731
Total assets	2,730,044		2,730,044		2,371,401
Mortgages payable, net	1,382,143		1,382,143		1,190,201
Other liabilities, net	103,283		103,283		76,416
Total liabilities	1,485,426		1,485,426		1,266,617
Equity Method Investment, Summarized Financial Information, Noncontrolling Interest	0		0		0
Total equity	1,244,618		1,244,618		1,104,784
Total liabilities and equity	2,730,044		2,730,044		$ 2,371,401
Combined income statement information:
Total revenue	87,518	$ 18,318	160,691	$ 36,557
Operating income	12,484	6,213	16,858	11,835
Net income (loss)	$ (514)	$ 3,570	$ (5,189)	$ 5,993