Investments in Real Estate Debt - Summary of Credit Rating of Investments in Real Estate Debt (Detail) $ in Thousands	Jun. 30, 2020 USD ($) Position	Dec. 31, 2019 USD ($) Position
Schedule Of Trading Securities And Other Trading Assets [Line Items]
Number of Positions | Position	217	203
Cost Basis	$ 5,168,122	$ 4,493,288
Fair Value	$ 4,649,372	$ 4,523,260
Percentage Based on Fair Value	100.00%	100.00%
BB Credit Rating [Member]
Schedule Of Trading Securities And Other Trading Assets [Line Items]
Number of Positions | Position	77	72
Cost Basis	$ 1,618,201	$ 1,598,930
Fair Value	$ 1,424,508	$ 1,610,643
Percentage Based on Fair Value	31.00%	36.00%
Non Rated [Member]
Schedule Of Trading Securities And Other Trading Assets [Line Items]
Number of Positions | Position	37	33
Cost Basis	$ 1,181,728	$ 764,941
Fair Value	$ 1,120,701	$ 773,791
Percentage Based on Fair Value	24.00%	17.00%
B Credit Rating [Member]
Schedule Of Trading Securities And Other Trading Assets [Line Items]
Number of Positions | Position	43	40
Cost Basis	$ 1,179,950	$ 906,609
Fair Value	$ 1,047,446	$ 909,587
Percentage Based on Fair Value	23.00%	20.00%
BBB Credit Rating [Member]
Schedule Of Trading Securities And Other Trading Assets [Line Items]
Number of Positions | Position	46	45
Cost Basis	$ 838,409	$ 885,891
Fair Value	$ 739,296	$ 891,272
Percentage Based on Fair Value	16.00%	20.00%
A Credit Rating [Member]
Schedule Of Trading Securities And Other Trading Assets [Line Items]
Number of Positions | Position	8	10
Cost Basis	$ 304,669	$ 319,031
Fair Value	$ 278,945	$ 320,140
Percentage Based on Fair Value	6.00%	7.00%
CCC Credit Rating [Member]
Schedule Of Trading Securities And Other Trading Assets [Line Items]
Number of Positions | Position	3
Cost Basis	$ 35,624
Fair Value	$ 28,941
AAA Credit Rating [Member]
Schedule Of Trading Securities And Other Trading Assets [Line Items]
Number of Positions | Position	2	2
Cost Basis	$ 8,713	$ 9,554
Fair Value	$ 8,708	$ 9,550
AA Credit Rating [Member]
Schedule Of Trading Securities And Other Trading Assets [Line Items]
Number of Positions | Position	1	1
Cost Basis	$ 828	$ 8,332
Fair Value	$ 827	$ 8,277