Consolidated Variable Interest Entities, Schedule of Variable Interest Entities (Details) - USD ($) $ in Thousands	3 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Variable Interest Entity [Line Items]
Payments to Acquire Additional Interest in Subsidiaries	$ 100
Investment property, net	5,573,825	$ 5,469,481
Other assets, net (including $1,638 and $3,054 for consolidated variable interest entities at September 30, 2017 and December 31, 2016; see Note 6)	141,047	146,450
Mortgage loans payable (including $42,177 and $62,111 for consolidated variable interest entities at September 30, 2017 and December 31, 2016; see Note 6)	2,822,640	2,819,567
Other liabilities (including $1,258 and $1,998 for consolidated variable interest entities at September 30, 2017 and December 31, 2016; see Note 6)	291,074	279,667
Consolidated variable interest entities	$ 3,841	$ (2,982)
VIE as a Percentage of Consolidated Assets	0.80%	1.60%
VIE as a Percentage of Consolidated Liabilities	1.30%	1.90%
VIE as a Percentage of Total Equity	1.00%	100.00%
Noncontrolling Interest, Ownership Percentage by Parent	100.00%
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Investment property, net	$ 50,655	$ 88,987
Other assets, net (including $1,638 and $3,054 for consolidated variable interest entities at September 30, 2017 and December 31, 2016; see Note 6)	1,638	3,054
Total Assets	52,293	92,041
Mortgage loans payable (including $42,177 and $62,111 for consolidated variable interest entities at September 30, 2017 and December 31, 2016; see Note 6)	42,177	62,111
Other liabilities (including $1,258 and $1,998 for consolidated variable interest entities at September 30, 2017 and December 31, 2016; see Note 6)	1,258	1,998
Total Liabilities and Stockholder's Equity	$ 47,276	$ 61,127