Debt - Unsecured Notes Payable - Additional Information (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Apr. 06, 2022	Dec. 31, 2021
Debt Instrument [Line Items]
Long-term debt outstanding	$ 1,822,801		$ 1,819,738
Maximum borrowing capacity	900,000		0
Remaining borrowing capacity	150,000
Letters of credit, outstanding amount	11,000		19,700
Fund Portfolio | Fund II
Debt Instrument [Line Items]
Long-term debt outstanding	256,468		255,978
Unsecured Notes Payable | Unsecured Debt
Debt Instrument [Line Items]
Debt available balance	146,700		16,300
Unsecured Notes Payable | Unsecured Debt | Fund Portfolio | Fund II
Debt Instrument [Line Items]
Long-term debt outstanding	40,000		40,000
$175 Million Term Loan
Debt Instrument [Line Items]
Maximum borrowing capacity	175,000	$ 175,000
Remaining borrowing capacity	175,000
$400 Million Term Loan | Unsecured Debt
Debt Instrument [Line Items]
Long-term debt outstanding	400,000
Maximum borrowing capacity	400,000
$400 Million Term Loan | Unsecured Debt | Core Portfolio
Debt Instrument [Line Items]
Long-term debt outstanding			400,000
Term Loan Maturing In September 2020 | Secured Debt | Fund II
Debt Instrument [Line Items]
Maximum borrowing capacity	40,000
Long-term line of credit, noncurrent	40,000		40,000
Remaining borrowing capacity	0		0
Subscription Line | Unsecured Debt | Fund IV
Debt Instrument [Line Items]
Maximum borrowing capacity	5,000
Long-term line of credit, noncurrent	0		5,000
Remaining borrowing capacity	5,000		0
Subscription Line | Unsecured Debt | Fund V
Debt Instrument [Line Items]
Maximum borrowing capacity	135,000
Subscription Line | Unsecured Debt | Fund V | Letter of Credit
Debt Instrument [Line Items]
Letters of credit, outstanding amount	7,000		15,700
Subscription Line | Unsecured Debt | Fund Portfolio | Fund V
Debt Instrument [Line Items]
Long-term debt outstanding	3,303		118,028
Remaining borrowing capacity	$ 124,700		16,300
Subscription Line | Secured Bridge Facility | Fund IV
Debt Instrument [Line Items]
Remaining borrowing capacity			$ 0