Commercial Mortgage Loans - Past Due (Details) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2023	Jul. 31, 2023	Dec. 31, 2022
Financing Receivable, Past Due [Line Items]
Loans, gross	$ 5,062,511		$ 5,269,776
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment
Financing Receivable, Past Due [Line Items]
Loans, gross	5,062,511
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Current
Financing Receivable, Past Due [Line Items]
Loans, gross	5,036,552
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | 1-29 days past due
Financing Receivable, Past Due [Line Items]
Loans, gross	0
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | 30-59 days past due
Financing Receivable, Past Due [Line Items]
Loans, gross	0
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | 60-89 days past due
Financing Receivable, Past Due [Line Items]
Loans, gross	0
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | 90-119 days past due
Financing Receivable, Past Due [Line Items]
Loans, gross	0
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | 120+ days past due
Financing Receivable, Past Due [Line Items]
Loans, gross	25,959
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Multifamily
Financing Receivable, Past Due [Line Items]
Loans, gross	3,935,724
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Multifamily | Current
Financing Receivable, Past Due [Line Items]
Loans, gross	3,930,149
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Multifamily | 1-29 days past due
Financing Receivable, Past Due [Line Items]
Loans, gross	0
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Multifamily | 30-59 days past due
Financing Receivable, Past Due [Line Items]
Loans, gross	0
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Multifamily | 60-89 days past due
Financing Receivable, Past Due [Line Items]
Loans, gross	0
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Multifamily | 90-119 days past due
Financing Receivable, Past Due [Line Items]
Loans, gross	0
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Multifamily | 120+ days past due
Financing Receivable, Past Due [Line Items]
Loans, gross	5,575
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Multifamily | 120+ days past due | Subsequent Event
Financing Receivable, Past Due [Line Items]
Loans, gross		$ 5,600
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Retail
Financing Receivable, Past Due [Line Items]
Loans, gross	29,616
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Retail | Current
Financing Receivable, Past Due [Line Items]
Loans, gross	29,616
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Retail | 1-29 days past due
Financing Receivable, Past Due [Line Items]
Loans, gross	0
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Retail | 30-59 days past due
Financing Receivable, Past Due [Line Items]
Loans, gross	0
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Retail | 60-89 days past due
Financing Receivable, Past Due [Line Items]
Loans, gross	0
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Retail | 90-119 days past due
Financing Receivable, Past Due [Line Items]
Loans, gross	0
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Retail | 120+ days past due
Financing Receivable, Past Due [Line Items]
Loans, gross	0
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Office
Financing Receivable, Past Due [Line Items]
Loans, gross	334,016
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Office | Current
Financing Receivable, Past Due [Line Items]
Loans, gross	313,632
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Office | 1-29 days past due
Financing Receivable, Past Due [Line Items]
Loans, gross	0
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Office | 30-59 days past due
Financing Receivable, Past Due [Line Items]
Loans, gross	0
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Office | 60-89 days past due
Financing Receivable, Past Due [Line Items]
Loans, gross	0
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Office | 90-119 days past due
Financing Receivable, Past Due [Line Items]
Loans, gross	0
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Office | 120+ days past due
Financing Receivable, Past Due [Line Items]
Loans, gross	20,384
Interest income recognized	0
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Industrial
Financing Receivable, Past Due [Line Items]
Loans, gross	77,865
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Industrial | Current
Financing Receivable, Past Due [Line Items]
Loans, gross	77,865
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Industrial | 1-29 days past due
Financing Receivable, Past Due [Line Items]
Loans, gross	0
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Industrial | 30-59 days past due
Financing Receivable, Past Due [Line Items]
Loans, gross	0
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Industrial | 60-89 days past due
Financing Receivable, Past Due [Line Items]
Loans, gross	0
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Industrial | 90-119 days past due
Financing Receivable, Past Due [Line Items]
Loans, gross	0
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Industrial | 120+ days past due
Financing Receivable, Past Due [Line Items]
Loans, gross	0
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Mixed Use
Financing Receivable, Past Due [Line Items]
Loans, gross	52,463
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Mixed Use | Current
Financing Receivable, Past Due [Line Items]
Loans, gross	52,463
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Mixed Use | 1-29 days past due
Financing Receivable, Past Due [Line Items]
Loans, gross	0
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Mixed Use | 30-59 days past due
Financing Receivable, Past Due [Line Items]
Loans, gross	0
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Mixed Use | 60-89 days past due
Financing Receivable, Past Due [Line Items]
Loans, gross	0
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Mixed Use | 90-119 days past due
Financing Receivable, Past Due [Line Items]
Loans, gross	0
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Mixed Use | 120+ days past due
Financing Receivable, Past Due [Line Items]
Loans, gross	0
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Hospitality
Financing Receivable, Past Due [Line Items]
Loans, gross	576,766
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Hospitality | Current
Financing Receivable, Past Due [Line Items]
Loans, gross	576,766
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Hospitality | 1-29 days past due
Financing Receivable, Past Due [Line Items]
Loans, gross	0
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Hospitality | 30-59 days past due
Financing Receivable, Past Due [Line Items]
Loans, gross	0
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Hospitality | 60-89 days past due
Financing Receivable, Past Due [Line Items]
Loans, gross	0
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Hospitality | 90-119 days past due
Financing Receivable, Past Due [Line Items]
Loans, gross	0
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Hospitality | 120+ days past due
Financing Receivable, Past Due [Line Items]
Loans, gross	0
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Self Storage
Financing Receivable, Past Due [Line Items]
Loans, gross	29,885
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Self Storage | Current
Financing Receivable, Past Due [Line Items]
Loans, gross	29,885
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Self Storage | 1-29 days past due
Financing Receivable, Past Due [Line Items]
Loans, gross
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Self Storage | 30-59 days past due
Financing Receivable, Past Due [Line Items]
Loans, gross	0
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Self Storage | 60-89 days past due
Financing Receivable, Past Due [Line Items]
Loans, gross	0
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Self Storage | 90-119 days past due
Financing Receivable, Past Due [Line Items]
Loans, gross	0
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Self Storage | 120+ days past due
Financing Receivable, Past Due [Line Items]
Loans, gross	0
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Manufactured Housing
Financing Receivable, Past Due [Line Items]
Loans, gross	26,176
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Manufactured Housing | Current
Financing Receivable, Past Due [Line Items]
Loans, gross	26,176
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Manufactured Housing | 1-29 days past due
Financing Receivable, Past Due [Line Items]
Loans, gross	0
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Manufactured Housing | 30-59 days past due
Financing Receivable, Past Due [Line Items]
Loans, gross	0
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Manufactured Housing | 60-89 days past due
Financing Receivable, Past Due [Line Items]
Loans, gross	0
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Manufactured Housing | 90-119 days past due
Financing Receivable, Past Due [Line Items]
Loans, gross	0
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Manufactured Housing | 120+ days past due
Financing Receivable, Past Due [Line Items]
Loans, gross	$ 0