Commercial Loans - Commercial loans held (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Sep. 07, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Principal balance	$ 2,572,727
Fair Value	$ 2,515,310		$ 2,938,556	$ 2,691,532	$ 2,493,238
Securitized Commercial Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Coupon rate	59.70%
CRE LLC And CRE Mezz | Securitized Commercial Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Principal balance	$ 177,797
Fair Value	116,210
CRE LLC And CRE Mezz | Securitized Commercial Loans | CRE 2
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Principal balance		$ 46,800
RSBC Trust Commercial Loans, at Fair Value | Securitized Commercial Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Principal balance	14,362
Fair Value	14,362
Hotel | CRE LLC And CRE Mezz | Securitized Commercial Loans | Interest-Only First Mortgage | CRE 5
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Principal balance	24,535
Fair Value	$ 24,212
Coupon rate	62.00%
Hotel | CRE LLC And CRE Mezz | Securitized Commercial Loans | Interest-Only First Mortgage | CRE 6
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Principal balance	$ 13,207
Fair Value	$ 13,033
Coupon rate	62.00%
Hotel | CRE LLC And CRE Mezz | Securitized Commercial Loans | Interest-Only First Mortgage | CRE 7
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Principal balance	$ 7,259
Fair Value	$ 7,163
Coupon rate	62.00%
Nursing Facilities | RSBC Trust Commercial Loans, at Fair Value | Securitized Commercial Loans | Interest-Only First Mortgage | SBC 3
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Principal balance	$ 14,362
Fair Value	$ 14,362
Coupon rate	49.00%
Entertainment and Retail | CRE LLC And CRE Mezz | Securitized Commercial Loans | Interest-Only Mezzanine loan | CRE 3
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Principal balance	$ 90,000
Fair Value	$ 29,113
Coupon rate	58.00%
Retail | CRE LLC And CRE Mezz | Securitized Commercial Loans | Interest-Only First Mortgage | CRE 4
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Principal balance	$ 38,367
Fair Value	$ 38,267
Coupon rate	63.00%
Assisted Living | CRE LLC And CRE Mezz | Securitized Commercial Loans | Interest-Only First Mortgage | CRE 8
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Principal balance	$ 4,429
Fair Value	$ 4,422
Coupon rate	79.00%
London Interbank Offered Rate (LIBOR) | Hotel | CRE LLC And CRE Mezz | Securitized Commercial Loans | Interest-Only First Mortgage | CRE 5
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Coupon rate	3.75%
London Interbank Offered Rate (LIBOR) | Hotel | CRE LLC And CRE Mezz | Securitized Commercial Loans | Interest-Only First Mortgage | CRE 6
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Coupon rate	3.75%
London Interbank Offered Rate (LIBOR) | Hotel | CRE LLC And CRE Mezz | Securitized Commercial Loans | Interest-Only First Mortgage | CRE 7
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Coupon rate	3.75%
London Interbank Offered Rate (LIBOR) | Nursing Facilities | RSBC Trust Commercial Loans, at Fair Value | Securitized Commercial Loans | Interest-Only First Mortgage | SBC 3
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Coupon rate	4.10%
London Interbank Offered Rate (LIBOR) | Entertainment and Retail | CRE LLC And CRE Mezz | Securitized Commercial Loans | Interest-Only Mezzanine loan | CRE 3
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Coupon rate	9.25%
London Interbank Offered Rate (LIBOR) | Retail | CRE LLC And CRE Mezz | Securitized Commercial Loans | Interest-Only First Mortgage | CRE 4
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Coupon rate	3.02%
London Interbank Offered Rate (LIBOR) | Assisted Living | CRE LLC And CRE Mezz | Securitized Commercial Loans | Interest-Only First Mortgage | CRE 8
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Coupon rate	4.85%