Commercial Mortgage Loans - Allowance Past Due (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Financing Receivable, Past Due [Line Items]
Loans, gross	$ 5,328,273	$ 4,226,888
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment
Financing Receivable, Past Due [Line Items]
Loans, gross	5,328,273
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Current
Financing Receivable, Past Due [Line Items]
Loans, gross	5,165,700
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	162,573
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Multifamily
Financing Receivable, Past Due [Line Items]
Loans, gross	3,977,421
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Multifamily | Current
Financing Receivable, Past Due [Line Items]
Loans, gross	3,977,421
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	0
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Retail
Financing Receivable, Past Due [Line Items]
Loans, gross	168,512
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Retail | Current
Financing Receivable, Past Due [Line Items]
Loans, gross	63,014
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	105,498
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Office
Financing Receivable, Past Due [Line Items]
Loans, gross	456,137
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Office | Current
Financing Receivable, Past Due [Line Items]
Loans, gross	456,137
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	0
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Industrial
Financing Receivable, Past Due [Line Items]
Loans, gross	92,658
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Industrial | Current
Financing Receivable, Past Due [Line Items]
Loans, gross	92,658
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	52,372
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Mixed Use | Current
Financing Receivable, Past Due [Line Items]
Loans, gross	52,372
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	501,791
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Hospitality | Current
Financing Receivable, Past Due [Line Items]
Loans, gross	444,716
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	57,075
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Self Storage
Financing Receivable, Past Due [Line Items]
Loans, gross	44,822
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Self Storage | Current
Financing Receivable, Past Due [Line Items]
Loans, gross	44,822
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	34,560
Financing Receivable, Held-to-Maturity | Commercial Portfolio Segment | Manufactured Housing | Current
Financing Receivable, Past Due [Line Items]
Loans, gross	34,560
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