Commercial Mortgage, Subordinate Loans and Other Lending Assets, Net - Allocation of Carrying Value of Loan Portfolio Based on Internal Risk Ratings (Details) $ in Thousands	6 Months Ended	12 Months Ended
Jun. 30, 2021 USD ($) loan	Jun. 30, 2020 USD ($) loan	Dec. 31, 2020 USD ($) loan
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans \| loan	68	67	67
Total	$ 7,558,304	$ 6,535,079	$ 6,535,079
Mortgage loans on real estate, commercial and consumer, percentage of portfolio	100.00%	100.00%	100.00%
Year 1	$ 1,309,620	$ 469,586
Year 2	486,189	2,661,017
Year 3	2,680,262	1,398,479
Year 4	1,202,436	999,564
Year 5	926,367	204,129
Prior	953,430	802,304
General CECL Allowance	(38,199)	(38,102)	$ (38,102)
Total carrying value, net	$ 7,520,105	$ 6,496,977	$ 6,496,977
Weighted Average Risk Rating	3.1	3.1
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	$ 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%	0.50%
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	63	62
Total	$ 7,048,000	$ 6,129,541
Mortgage loans on real estate, commercial and consumer, percentage of portfolio	93.20%	93.80%
Year 1	$ 1,309,620	$ 469,586
Year 2	486,189	2,661,017
Year 3	2,680,262	1,398,479
Year 4	1,202,436	868,514
Year 5	672,655	88,710
Prior	$ 696,838	$ 643,235
4
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans \| loan	1	0
Total	$ 81,060	$ 0
Mortgage loans on real estate, commercial and consumer, percentage of portfolio	1.10%	0.00%
Year 1	$ 0	$ 0
Year 2	0	0
Year 3	0	0
Year 4	0	0
Year 5	81,060	0
Prior	$ 0	$ 0
5
Financing Receivable, Credit Quality Indicator [Line Items]
Number of Loans \| loan	3	4
Total	$ 397,244	$ 373,538
Mortgage loans on real estate, commercial and consumer, percentage of portfolio	5.30%	5.70%
Year 1	$ 0	$ 0
Year 2	0	0
Year 3	0	0
Year 4	0	131,050
Year 5	172,652	115,419
Prior	$ 224,592	$ 127,069

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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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