Commercial Mortgage Loans - Allowance Past Due (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Financing Receivable, Past Due [Line Items]
Par Value	$ 4,226,888	$ 2,714,734
Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity
Financing Receivable, Past Due [Line Items]
Par Value	4,226,888
Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity | Current
Financing Receivable, Past Due [Line Items]
Par Value	4,112,880
Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity | 1-29 days past due
Financing Receivable, Past Due [Line Items]
Par Value	56,933
Interest income recognized	3,100
Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity | 30-59 days past due
Financing Receivable, Past Due [Line Items]
Par Value	0
Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity | 60-89 days past due
Financing Receivable, Past Due [Line Items]
Par Value	0
Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity | 90-119 days past due
Financing Receivable, Past Due [Line Items]
Par Value	0
Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity | 120+ days past due
Financing Receivable, Past Due [Line Items]
Par Value	57,075
Multifamily | Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity
Financing Receivable, Past Due [Line Items]
Par Value	2,941,220
Multifamily | Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity | Current
Financing Receivable, Past Due [Line Items]
Par Value	2,941,220
Multifamily | Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity | 1-29 days past due
Financing Receivable, Past Due [Line Items]
Par Value	0
Multifamily | Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity | 30-59 days past due
Financing Receivable, Past Due [Line Items]
Par Value	0
Multifamily | Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity | 60-89 days past due
Financing Receivable, Past Due [Line Items]
Par Value	0
Multifamily | Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity | 90-119 days past due
Financing Receivable, Past Due [Line Items]
Par Value	0
Multifamily | Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity | 120+ days past due
Financing Receivable, Past Due [Line Items]
Par Value	0
Retail | Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity
Financing Receivable, Past Due [Line Items]
Par Value	104,725
Retail | Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity | Current
Financing Receivable, Past Due [Line Items]
Par Value	104,725
Retail | Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity | 1-29 days past due
Financing Receivable, Past Due [Line Items]
Par Value	0
Retail | Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity | 30-59 days past due
Financing Receivable, Past Due [Line Items]
Par Value	0
Retail | Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity | 60-89 days past due
Financing Receivable, Past Due [Line Items]
Par Value	0
Retail | Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity | 90-119 days past due
Financing Receivable, Past Due [Line Items]
Par Value	0
Retail | Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity | 120+ days past due
Financing Receivable, Past Due [Line Items]
Par Value	0
Office | Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity
Financing Receivable, Past Due [Line Items]
Par Value	484,158
Office | Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity | Current
Financing Receivable, Past Due [Line Items]
Par Value	484,158
Office | Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity | 1-29 days past due
Financing Receivable, Past Due [Line Items]
Par Value	0
Office | Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity | 30-59 days past due
Financing Receivable, Past Due [Line Items]
Par Value	0
Office | Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity | 60-89 days past due
Financing Receivable, Past Due [Line Items]
Par Value	0
Office | Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity | 90-119 days past due
Financing Receivable, Past Due [Line Items]
Par Value	0
Office | Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity | 120+ days past due
Financing Receivable, Past Due [Line Items]
Par Value	0
Industrial | Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity
Financing Receivable, Past Due [Line Items]
Par Value	88,839
Industrial | Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity | Current
Financing Receivable, Past Due [Line Items]
Par Value	31,906
Industrial | Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity | 1-29 days past due
Financing Receivable, Past Due [Line Items]
Par Value	56,933
Industrial | Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity | 30-59 days past due
Financing Receivable, Past Due [Line Items]
Par Value	0
Industrial | Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity | 60-89 days past due
Financing Receivable, Past Due [Line Items]
Par Value	0
Industrial | Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity | 90-119 days past due
Financing Receivable, Past Due [Line Items]
Par Value	0
Industrial | Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity | 120+ days past due
Financing Receivable, Past Due [Line Items]
Par Value	0
Mixed Use | Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity
Financing Receivable, Past Due [Line Items]
Par Value	62,720
Mixed Use | Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity | Current
Financing Receivable, Past Due [Line Items]
Par Value	62,720
Mixed Use | Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity | 1-29 days past due
Financing Receivable, Past Due [Line Items]
Par Value	0
Mixed Use | Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity | 30-59 days past due
Financing Receivable, Past Due [Line Items]
Par Value	0
Mixed Use | Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity | 60-89 days past due
Financing Receivable, Past Due [Line Items]
Par Value	0
Mixed Use | Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity | 90-119 days past due
Financing Receivable, Past Due [Line Items]
Par Value	0
Mixed Use | Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity | 120+ days past due
Financing Receivable, Past Due [Line Items]
Par Value	0
Hospitality | Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity
Financing Receivable, Past Due [Line Items]
Par Value	459,859
Hospitality | Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity | Current
Financing Receivable, Past Due [Line Items]
Par Value	402,784
Hospitality | Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity | 1-29 days past due
Financing Receivable, Past Due [Line Items]
Par Value	0
Hospitality | Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity | 30-59 days past due
Financing Receivable, Past Due [Line Items]
Par Value	0
Hospitality | Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity | 60-89 days past due
Financing Receivable, Past Due [Line Items]
Par Value	0
Hospitality | Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity | 90-119 days past due
Financing Receivable, Past Due [Line Items]
Par Value	0
Hospitality | Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity | 120+ days past due
Financing Receivable, Past Due [Line Items]
Par Value	57,075
Self Storage | Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity
Financing Receivable, Past Due [Line Items]
Par Value	56,330
Self Storage | Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity | Current
Financing Receivable, Past Due [Line Items]
Par Value	56,330
Self Storage | Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity | 1-29 days past due
Financing Receivable, Past Due [Line Items]
Par Value	0
Self Storage | Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity | 30-59 days past due
Financing Receivable, Past Due [Line Items]
Par Value	0
Self Storage | Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity | 60-89 days past due
Financing Receivable, Past Due [Line Items]
Par Value	0
Self Storage | Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity | 90-119 days past due
Financing Receivable, Past Due [Line Items]
Par Value	0
Self Storage | Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity | 120+ days past due
Financing Receivable, Past Due [Line Items]
Par Value	0
Manufactured Housing | Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity
Financing Receivable, Past Due [Line Items]
Par Value	29,037
Manufactured Housing | Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity | Current
Financing Receivable, Past Due [Line Items]
Par Value	29,037
Manufactured Housing | Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity | 1-29 days past due
Financing Receivable, Past Due [Line Items]
Par Value	0
Manufactured Housing | Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity | 30-59 days past due
Financing Receivable, Past Due [Line Items]
Par Value	0
Manufactured Housing | Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity | 60-89 days past due
Financing Receivable, Past Due [Line Items]
Par Value	0
Manufactured Housing | Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity | 90-119 days past due
Financing Receivable, Past Due [Line Items]
Par Value	0
Manufactured Housing | Commercial Portfolio Segment | Financing Receivable, Held-to-Maturity | 120+ days past due
Financing Receivable, Past Due [Line Items]
Par Value	$ 0