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Loans Receivable - Collective Pool Basis (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2020 USD ($) loan	Dec. 31, 2019 USD ($)	Jun. 30, 2019 USD ($)	Dec. 31, 2018 USD ($)
Financing Receivable, Allowance for Credit Loss [Line Items]
Loan Carrying Value	$ 680,691
Allowance for Credit Loss	(81,985)	$ (68,372)	$ (68,372)	$ (68,372)
Real estate loans receivable, net of credit allowance	$ 598,706
No. of Loans \| loan	41
Accrued expenses and other liabilities
Financing Receivable, Allowance for Credit Loss [Line Items]
Deferred gains	$ 62,819
Deteriorated loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Loan Carrying Value	186,584
Allowance for Credit Loss	(76,695)
Real estate loans receivable, net of credit allowance	$ 109,889
No. of Loans \| loan	5
Collective loan pool
Financing Receivable, Allowance for Credit Loss [Line Items]
Loan Carrying Value	$ 128,447
Allowance for Credit Loss	(1,866)
Real estate loans receivable, net of credit allowance	$ 126,581
No. of Loans \| loan	15
Collective loan pool
Financing Receivable, Allowance for Credit Loss [Line Items]
Loan Carrying Value	$ 184,620
Allowance for Credit Loss	(1,572)
Real estate loans receivable, net of credit allowance	$ 183,048
No. of Loans \| loan	6
Collective loan pool
Financing Receivable, Allowance for Credit Loss [Line Items]
Loan Carrying Value	$ 119,662
Allowance for Credit Loss	(999)
Real estate loans receivable, net of credit allowance	$ 118,663
No. of Loans \| loan	7
Collective loan pool
Financing Receivable, Allowance for Credit Loss [Line Items]
Loan Carrying Value	$ 15,399
Allowance for Credit Loss	(224)
Real estate loans receivable, net of credit allowance	$ 15,175
No. of Loans \| loan	1
Collective loan pool
Financing Receivable, Allowance for Credit Loss [Line Items]
Loan Carrying Value	$ 45,979
Allowance for Credit Loss	(629)
Real estate loans receivable, net of credit allowance	$ 45,350
No. of Loans \| loan	7