Commercial Mortgage Loans, Subordinate Loans and Other Lending Assets, Net - Allocation of Carrying Value of Loan Portfolio Based on Internal Risk Ratings (Details) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2022 USD ($) loan	Dec. 31, 2021 USD ($) loan	Mar. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans \| loan	67	67
Total	$ 8,371,419	$ 7,890,848
Mortgage loans on real estate, commercial and consumer, percentage of portfolio	100.00%	100.00%
Year 1	$ 994,971	$ 2,622,248
Year 2	2,636,290	644,404
Year 3	669,291	2,307,948
Year 4	1,822,835	828,270
Year 5	796,136	648,727
Prior	1,451,896	839,251
General CECL Allowance(1)	(21,377)	(33,588)
Total carrying value, net	$ 8,350,042	$ 7,857,260
Weighted Average Risk Rating	3.1	3.1
Off-balance sheet, credit loss, liability	$ 3,928	$ 3,106	$ 3,794	$ 3,365
1
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans \| loan	0	0
Total	$ 0	$ 0
Mortgage loans on real estate, commercial and consumer, percentage of portfolio	0.00%	0.00%
Year 1	$ 0
Year 2	0	0
Year 3	0	0
Year 4	0	0
Year 5	0	0
Prior	$ 0	$ 0
2
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans \| loan	1	1
Total	$ 32,000	$ 32,000
Mortgage loans on real estate, commercial and consumer, percentage of portfolio	0.40%	0.40%
Year 1	$ 0	$ 0
Year 2	0	0
Year 3	0	0
Year 4	0	0
Year 5	0	0
Prior	$ 32,000	$ 32,000
3
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans \| loan	61	62
Total	$ 7,774,143	$ 7,372,081
Mortgage loans on real estate, commercial and consumer, percentage of portfolio	92.80%	93.50%
Year 1	$ 994,971	$ 2,622,248
Year 2	2,636,290	644,404
Year 3	669,291	2,307,948
Year 4	1,822,835	828,270
Year 5	796,136	389,264
Prior	$ 854,620	$ 579,947
4
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans \| loan	1	1
Total	$ 106,313	$ 81,980
Mortgage loans on real estate, commercial and consumer, percentage of portfolio	1.30%	1.00%
Year 1	$ 0	$ 0
Year 2	0	0
Year 3	0	0
Year 4	0	0
Year 5	0	81,980
Prior	$ 106,313	$ 0
5
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans \| loan	4	3
Total	$ 458,963	$ 404,787
Mortgage loans on real estate, commercial and consumer, percentage of portfolio	5.50%	5.10%
Year 1	$ 0	$ 0
Year 2	0	0
Year 3	0	0
Year 4	0	0
Year 5	0	177,483
Prior	$ 458,963	$ 227,304

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The reserve to cover probable credit losses related to specifically identified fixed maturity real estate loans as well as probable credit losses inherent in the remainder of that loan portfolio.

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Amount of financing receivable originated more than five years prior to current fiscal year.

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Amount of financing receivable originated four years prior to current fiscal year.

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Amount of financing receivable originated in current fiscal year.

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Amount of financing receivable originated three years prior to current fiscal year.

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The balance represents the amount of loans that are secured by real estate mortgages, offset by the reserve to cover probable credit losses on the loan portfolio.

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Amount, before allowance for credit loss, of financing receivable.

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Amount of expected credit loss for credit exposure on off-balance-sheet commitment, including but not limited to, loan commitment, standby letter of credit, financial guarantee not accounted for as insurance. Excludes off-balance sheet credit exposure accounted for as insurance and instrument accounted for under derivatives and hedging.

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