Investments in Real Estate Debt - Summary of Credit Rating of Investments in Real Estate Debt (Detail) $ in Thousands	Mar. 31, 2021 USD ($) Position	Dec. 31, 2020 USD ($) Position
Schedule Of Trading Securities And Other Trading Assets [Line Items]
Number of Positions | Position	260	228
Cost Basis	$ 4,923,780	$ 4,723,514
Fair Value	$ 4,896,416	$ 4,566,306
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	87	81
Cost Basis	$ 1,409,962	$ 1,435,891
Fair Value	$ 1,404,595	$ 1,381,221
Percentage Based on Fair Value	29.00%	30.00%
Non Rated [Member]
Schedule Of Trading Securities And Other Trading Assets [Line Items]
Number of Positions | Position	43	28
Cost Basis	$ 1,203,589	$ 997,411
Fair Value	$ 1,211,332	$ 1,004,027
Percentage Based on Fair Value	25.00%	22.00%
B Credit Rating [Member]
Schedule Of Trading Securities And Other Trading Assets [Line Items]
Number of Positions | Position	63	52
Cost Basis	$ 1,212,740	$ 1,186,975
Fair Value	$ 1,182,356	$ 1,114,977
Percentage Based on Fair Value	24.00%	24.00%
BBB Credit Rating [Member]
Schedule Of Trading Securities And Other Trading Assets [Line Items]
Number of Positions | Position	48	48
Cost Basis	$ 794,027	$ 797,918
Fair Value	$ 783,062	$ 753,393
Percentage Based on Fair Value	16.00%	17.00%
A Credit Rating [Member]
Schedule Of Trading Securities And Other Trading Assets [Line Items]
Number of Positions | Position	11	11
Cost Basis	$ 260,220	$ 262,097
Fair Value	$ 268,855	$ 267,023
Percentage Based on Fair Value	5.00%	6.00%
CCC Credit Rating [Member]
Schedule Of Trading Securities And Other Trading Assets [Line Items]
Number of Positions | Position	3	3
Cost Basis	$ 32,780	$ 32,402
Fair Value	$ 35,763	$ 34,839
Percentage Based on Fair Value	1.00%	1.00%
AAA Credit Rating [Member]
Schedule Of Trading Securities And Other Trading Assets [Line Items]
Number of Positions | Position	4	4
Cost Basis	$ 9,712	$ 10,044
Fair Value	$ 9,704	$ 10,047
AA Credit Rating [Member]
Schedule Of Trading Securities And Other Trading Assets [Line Items]
Number of Positions | Position	1	1
Cost Basis	$ 750	$ 776
Fair Value	$ 749	$ 779