Variable Interest Entities - Summarized Balance Sheet (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Assets:
Net Investment in Real Estate	$ 2,755,571	$ 2,705,826
Total Assets	3,044,595	2,941,062
Liabilities and Partners' Capital:
Mortgage Loans Payable, Net	301,661	450,056
Total Liabilities and Equity/Partners' Capital	3,044,595	2,941,062
Other Real Estate Partnerships
Assets:
Net Investment in Real Estate	268,442	270,708
Other Assets, Net	24,966	23,530
Total Assets	293,408	294,238
Liabilities and Partners' Capital:
Mortgage Loans Payable, Net	20,833	61,256
Other Liabilities, Net	8,434	9,283
Partners’ Capital	264,141	223,699
Total Liabilities and Equity/Partners' Capital	$ 293,408	$ 294,238