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Loans Receivable - Collective Pool Basis (Details) $ in Thousands	1 Months Ended	3 Months Ended
	Mar. 31, 2020 USD ($) loan	Mar. 31, 2021 USD ($) loan	Mar. 31, 2020 USD ($) loan	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Financing Receivable, Allowance for Credit Loss [Line Items]
Loan Carrying Value		$ 954,748
Allowance for Credit Loss	$ (80,571)	(224,146)	$ (80,571)	$ (224,036)	$ (68,372)
Real estate loans receivable, net of credit allowance		$ 730,602
No. of Loans \| loan		52
Provision for loan losses	$ 6,898	$ 1,383	$ 7,072
Triple-net
Financing Receivable, Allowance for Credit Loss [Line Items]
No. of Loans \| loan	1		1
Deteriorated loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Loan Carrying Value		241,012
Allowance for Credit Loss		(211,191)
Real estate loans receivable, net of credit allowance		$ 29,821
No. of Loans \| loan		6
Collective loan pool
Financing Receivable, Allowance for Credit Loss [Line Items]
Loan Carrying Value		$ 259,913
Allowance for Credit Loss		(5,061)
Real estate loans receivable, net of credit allowance		$ 254,852
No. of Loans \| loan		18
Collective loan pool
Financing Receivable, Allowance for Credit Loss [Line Items]
Loan Carrying Value		$ 126,746
Allowance for Credit Loss		(1,488)
Real estate loans receivable, net of credit allowance		$ 125,258
No. of Loans \| loan		7
Collective loan pool
Financing Receivable, Allowance for Credit Loss [Line Items]
Loan Carrying Value		$ 20,620
Allowance for Credit Loss		(404)
Real estate loans receivable, net of credit allowance		$ 20,216
No. of Loans \| loan		1
Collective loan pool
Financing Receivable, Allowance for Credit Loss [Line Items]
Loan Carrying Value		$ 47,045
Allowance for Credit Loss		(923)
Real estate loans receivable, net of credit allowance		$ 46,122
No. of Loans \| loan		7
Collective loan pool
Financing Receivable, Allowance for Credit Loss [Line Items]
Loan Carrying Value		$ 229,219
Allowance for Credit Loss		(4,488)
Real estate loans receivable, net of credit allowance		$ 224,731
No. of Loans \| loan		11
Collective loan pool
Financing Receivable, Allowance for Credit Loss [Line Items]
Loan Carrying Value		$ 30,193
Allowance for Credit Loss		(591)
Real estate loans receivable, net of credit allowance		$ 29,602
No. of Loans \| loan		2