Fair Value Measurements - Summary of Fair Value of Financial Assets and Liabilities (Details) - USD ($)	Jun. 30, 2023	Dec. 31, 2022
Financial assets
Total unpaid principal balance	$ 4,567,250,000	$ 5,004,798,000
Financial liabilities
Principal balance	3,705,887,000	4,179,211,000
Estimate of Fair Value Measurement \| Fair Value Measurements Nonrecurring \| Loans held for investment
Financial assets
Fair value of financial assets	4,297,350,000	4,781,402,000
Total unpaid principal balance	4,567,250,000	5,004,798,000
Estimate of Fair Value Measurement \| Fair Value Measurements Nonrecurring \| Collateralized loan obligations
Financial liabilities
Fair value of financial liabilities	2,136,382,000	2,452,212,000
Principal balance	2,142,939,000	2,461,170,000
Estimate of Fair Value Measurement \| Fair Value Measurements Nonrecurring \| Secured credit agreements
Financial liabilities
Fair value of financial liabilities	1,035,634,000	1,105,151,000
Principal balance	1,039,185,000	1,108,386,000
Estimate of Fair Value Measurement \| Fair Value Measurements Nonrecurring \| Asset-specific financing arrangements
Financial liabilities
Fair value of financial liabilities	490,581,000	561,017,000
Principal balance	492,563,000	565,376,000
Estimate of Fair Value Measurement \| Fair Value Measurements Nonrecurring \| Secured revolving credit facility
Financial liabilities
Fair value of financial liabilities		42,137,000
Estimate of Fair Value Measurement \| Fair Value Measurements Nonrecurring \| Mortgage loan payable
Financial liabilities
Fair value of financial liabilities	30,475,000
Principal balance	31,200,000	44,279,000
Estimate of Fair Value Measurement \| Fair Value Measurements Nonrecurring \| Level I \| Loans held for investment
Financial assets
Fair value of financial assets	0	0
Estimate of Fair Value Measurement \| Fair Value Measurements Nonrecurring \| Level I \| Collateralized loan obligations
Financial liabilities
Fair value of financial liabilities	0	0
Estimate of Fair Value Measurement \| Fair Value Measurements Nonrecurring \| Level I \| Secured credit agreements
Financial liabilities
Fair value of financial liabilities	0	0
Estimate of Fair Value Measurement \| Fair Value Measurements Nonrecurring \| Level I \| Asset-specific financing arrangements
Financial liabilities
Fair value of financial liabilities	0	0
Estimate of Fair Value Measurement \| Fair Value Measurements Nonrecurring \| Level I \| Secured revolving credit facility
Financial liabilities
Fair value of financial liabilities		0
Estimate of Fair Value Measurement \| Fair Value Measurements Nonrecurring \| Level I \| Mortgage loan payable
Financial liabilities
Fair value of financial liabilities	0
Estimate of Fair Value Measurement \| Fair Value Measurements Nonrecurring \| Level II \| Loans held for investment
Financial assets
Fair value of financial assets	0	0
Estimate of Fair Value Measurement \| Fair Value Measurements Nonrecurring \| Level II \| Collateralized loan obligations
Financial liabilities
Fair value of financial liabilities	0	0
Estimate of Fair Value Measurement \| Fair Value Measurements Nonrecurring \| Level II \| Secured credit agreements
Financial liabilities
Fair value of financial liabilities	0	0
Estimate of Fair Value Measurement \| Fair Value Measurements Nonrecurring \| Level II \| Asset-specific financing arrangements
Financial liabilities
Fair value of financial liabilities	0	0
Estimate of Fair Value Measurement \| Fair Value Measurements Nonrecurring \| Level II \| Secured revolving credit facility
Financial liabilities
Fair value of financial liabilities		0
Estimate of Fair Value Measurement \| Fair Value Measurements Nonrecurring \| Level II \| Mortgage loan payable
Financial liabilities
Fair value of financial liabilities	0
Estimate of Fair Value Measurement \| Fair Value Measurements Nonrecurring \| Level III \| Loans held for investment
Financial assets
Fair value of financial assets	4,479,223,000	4,922,290,000
Estimate of Fair Value Measurement \| Fair Value Measurements Nonrecurring \| Level III \| Collateralized loan obligations
Financial liabilities
Fair value of financial liabilities	2,020,326,000	2,498,853,000
Estimate of Fair Value Measurement \| Fair Value Measurements Nonrecurring \| Level III \| Secured credit agreements
Financial liabilities
Fair value of financial liabilities	1,028,114,000	1,128,847,000
Estimate of Fair Value Measurement \| Fair Value Measurements Nonrecurring \| Level III \| Asset-specific financing arrangements
Financial liabilities
Fair value of financial liabilities	490,877,000	571,097,000
Estimate of Fair Value Measurement \| Fair Value Measurements Nonrecurring \| Level III \| Secured revolving credit facility
Financial liabilities
Fair value of financial liabilities		$ 42,137,000
Estimate of Fair Value Measurement \| Fair Value Measurements Nonrecurring \| Level III \| Mortgage loan payable
Financial liabilities
Fair value of financial liabilities	$ 31,200,000

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Amortized cost, before allowance for credit loss, fee, and loan in process, of financing receivable. Excludes financing receivable covered under loss sharing agreement and net investment in lease.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
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Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
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Fair value of financial and nonfinancial obligations.

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