Borrowings - Cabot Securitisation Senior Facility (Details) $ in Thousands		3 Months Ended		9 Months Ended
	Sep. 18, 2023 GBP (£)	Sep. 30, 2023 USD ($)	Sep. 30, 2022	Sep. 30, 2023 USD ($)	Sep. 30, 2022	Sep. 30, 2023 GBP (£)	Dec. 31, 2022 USD ($)
Debt Instrument [Line Items]
Book value | $		$ 4,760,288		$ 4,760,288			$ 4,508,360
United Kingdom, Pounds
Debt Instrument [Line Items]
Foreign currency exchange rate, translation		0.82		0.82		0.82
Cabot securitisation senior facility
Debt Instrument [Line Items]
Maximum borrowing capacity		$ 408,700		$ 408,700		£ 350,000,000
Book value		$ 437,000		$ 437,000		358,200,000
Weighted average interest rate (as a percent)		5.35%	4.67%	5.28%	4.02%
Cabot securitisation senior facility | Senior Facility | Credit Facility
Debt Instrument [Line Items]
Maximum borrowing capacity						350,000,000
Repayment of borrowings	£ 15,000,000.0
Remaining borrowing capacity						£ 335,000,000.0
Cabot securitisation senior facility | Sterling Overnight Index Average (SONIA) | Debt Instrument, Redemption, Period One
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)				3.00%
Cabot securitisation senior facility | Minimum | Sterling Overnight Index Average (SONIA) | Debt Instrument, Redemption, Period Two
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)				0.00%
Cabot securitisation senior facility | Maximum | Sterling Overnight Index Average (SONIA) | Debt Instrument, Redemption, Period Two
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)				1.00%