Secured Debt Agreements, Net - Schedule of All in Cost of Secured Credit Facilities (Detail) - Credit Facilities [Member] - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Schedule Of All In Cost Of Secured Credit Facilities [Line Items]
New Financings	$ 2,540,584	$ 898,516
Total Borrowings	$ 8,729,281	$ 7,896,863
Wtd. Avg. All-in Cost	1.78%	1.83%
Collateral	$ 13,222,033	$ 12,040,907
Wtd. Avg. All-in Yield	3.42%	3.40%
Net Interest Margin	1.64%	1.57%
1.49% or less [Member]
Schedule Of All In Cost Of Secured Credit Facilities [Line Items]
New Financings	$ 562,480	$ 0
Total Borrowings	$ 2,017,600	$ 1,377,406
Wtd. Avg. All-in Cost	1.42%	1.45%
Collateral	$ 2,520,834	$ 1,851,104
Wtd. Avg. All-in Yield	2.88%	2.82%
Net Interest Margin	1.46%	1.37%
1.50% to + 1.74% [Member]
Schedule Of All In Cost Of Secured Credit Facilities [Line Items]
New Financings	$ 901,070	$ 340,997
Total Borrowings	$ 2,836,242	$ 2,600,520
Wtd. Avg. All-in Cost	1.67%	1.65%
Collateral	$ 3,981,023	$ 4,173,632
Wtd. Avg. All-in Yield	3.32%	3.18%
Net Interest Margin	1.65%	1.53%
1.75% to + 1.99% [Member]
Schedule Of All In Cost Of Secured Credit Facilities [Line Items]
New Financings	$ 404,035	$ 35,088
Total Borrowings	$ 1,701,316	$ 1,639,137
Wtd. Avg. All-in Cost	1.84%	1.87%
Collateral	$ 2,755,559	$ 2,459,716
Wtd. Avg. All-in Yield	3.41%	3.54%
Net Interest Margin	1.57%	1.67%
2.00% or more [Member]
Schedule Of All In Cost Of Secured Credit Facilities [Line Items]
New Financings	$ 672,999	$ 522,431
Total Borrowings	$ 2,174,123	$ 2,279,800
Wtd. Avg. All-in Cost	2.21%	2.24%
Collateral	$ 3,964,617	$ 3,556,455
Wtd. Avg. All-in Yield	3.88%	3.87%
Net Interest Margin	1.67%	1.63%