Commercial Loans - Commercial loans held (Details) - Securitized commercial loans - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Mar. 31, 2020	Jun. 30, 2019
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Coupon  Rate		65.50%
CRE LLC And CRE Mezz
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Principal  Balance	$ 259,426
Fair Value	248,624
RSBC Trust
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Principal  Balance	73,150
Fair Value	71,684
CRE 2 | Hotel | CRE LLC And CRE Mezz | Interest-Only First Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Principal  Balance	30,000
Fair Value	$ 28,779
Coupon  Rate	65.00%
CRE 4 | Nursing Facilities | CRE LLC And CRE Mezz | Principal & Interest First Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Principal  Balance	$ 50,000
Fair Value	$ 48,665
Coupon  Rate	75.00%
CRE 5 | Entertainment and Retail | CRE LLC And CRE Mezz | Interest-Only Mezzanine Loan
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Principal  Balance	$ 90,000
Fair Value	$ 85,763
Coupon  Rate	58.00%
CRE 6 | Retail | CRE LLC And CRE Mezz | Interest-Only First Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Principal  Balance	$ 40,000
Fair Value	$ 38,402
Coupon  Rate	63.00%
CRE 7 | Hotel | CRE LLC And CRE Mezz | Interest-Only First Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Principal  Balance	$ 24,535
Fair Value	$ 23,251
Coupon  Rate	62.00%
CRE 8 | Hotel | CRE LLC And CRE Mezz | Interest-Only First Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Principal  Balance	$ 13,207
Fair Value	$ 12,516
Coupon  Rate	62.00%
CRE 9 | Hotel | CRE LLC And CRE Mezz | Interest-Only First Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Principal  Balance	$ 7,259
Fair Value	$ 6,879
Coupon  Rate	62.00%
CRE 10 | Assisted Living | CRE LLC And CRE Mezz | Interest-Only First Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Principal  Balance	$ 4,425
Fair Value	$ 4,369
Coupon  Rate	79.00%
SBC 1 | Nursing Facilities | RSBC Trust | Interest-Only First Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Principal  Balance	$ 45,188
Fair Value	$ 44,314
Coupon  Rate	74.00%
SBC 4 | Apartment Complex | RSBC Trust | Interest-Only First Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Principal  Balance	$ 13,600
Fair Value	$ 13,275
Coupon  Rate	84.00%
SBC 5 | Nursing Facilities | RSBC Trust | Interest-Only First Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Principal  Balance	$ 14,362
Fair Value	$ 14,095
Coupon  Rate	49.00%
London Interbank Offered Rate (LIBOR) Floor | SBC 1 | Nursing Facilities | RSBC Trust | Interest-Only First Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Coupon  Rate	1.25%
London Interbank Offered Rate (LIBOR) Floor | SBC 4 | Apartment Complex | RSBC Trust | Interest-Only First Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Coupon  Rate	2.00%
London Interbank Offered Rate (LIBOR) | CRE 2 | Hotel | CRE LLC And CRE Mezz | Interest-Only First Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Coupon  Rate	450.00%
London Interbank Offered Rate (LIBOR) | CRE 4 | Nursing Facilities | CRE LLC And CRE Mezz | Principal & Interest First Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Coupon  Rate	475.00%
London Interbank Offered Rate (LIBOR) | CRE 5 | Entertainment and Retail | CRE LLC And CRE Mezz | Interest-Only Mezzanine Loan
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Coupon  Rate	925.00%
London Interbank Offered Rate (LIBOR) | CRE 6 | Retail | CRE LLC And CRE Mezz | Interest-Only First Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Coupon  Rate	302.00%
London Interbank Offered Rate (LIBOR) | CRE 7 | Hotel | CRE LLC And CRE Mezz | Interest-Only First Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Coupon  Rate	375.00%
London Interbank Offered Rate (LIBOR) | CRE 8 | Hotel | CRE LLC And CRE Mezz | Interest-Only First Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Coupon  Rate	375.00%
London Interbank Offered Rate (LIBOR) | CRE 9 | Hotel | CRE LLC And CRE Mezz | Interest-Only First Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Coupon  Rate	375.00%
London Interbank Offered Rate (LIBOR) | CRE 10 | Assisted Living | CRE LLC And CRE Mezz | Interest-Only First Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Coupon  Rate	485.00%
London Interbank Offered Rate (LIBOR) | SBC 1 | Nursing Facilities | RSBC Trust | Interest-Only First Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Coupon  Rate	425.00%
London Interbank Offered Rate (LIBOR) | SBC 4 | Apartment Complex | RSBC Trust | Interest-Only First Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Coupon  Rate	400.00%
London Interbank Offered Rate (LIBOR) | SBC 5 | Nursing Facilities | RSBC Trust | Interest-Only First Mortgage
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Coupon  Rate	410.00%