Investments in Unconsolidated Joint Ventures - Balance Sheet footnotes (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Schedule of Equity Method Investments [Line Items]
Assets	$ 9,228,348		$ 9,228,348		$ 8,853,571
Liabilities	6,539,789		6,539,789		6,022,601
Joint Venture
Schedule of Equity Method Investments [Line Items]
Amortization of difference between cost of investments and book value of underlying equity	3,729	$ 5,271	7,728	$ 9,810
Joint Venture | PPR Portfolio | PPR Portfolio
Schedule of Equity Method Investments [Line Items]
Assets	2,900,500		2,900,500		2,932,401
Liabilities	$ 1,702,957		$ 1,702,957		$ 1,732,976