Variable Interest Entities - Summarized Balance Sheet (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Assets:
Net Investment in Real Estate	$ 2,792,668	$ 2,705,826
Total Assets	3,110,354	2,941,062
Liabilities and Partners' Capital:
Mortgage Loans Payable, Net	299,978	450,056
Total Liabilities and Equity/Partners' Capital	3,110,354	2,941,062
Other Real Estate Partnerships
Assets:
Net Investment in Real Estate	266,260	270,708
Other Assets, Net	23,652	23,530
Total Assets	289,912	294,238
Liabilities and Partners' Capital:
Mortgage Loans Payable, Net	20,723	61,256
Other Liabilities, Net	8,425	9,283
Partners' Capital	260,764	223,699
Total Liabilities and Equity/Partners' Capital	$ 289,912	$ 294,238