Borrowings - Additional information (Details) € in Millions, £ in Millions, kr in Millions		1 Months Ended	12 Months Ended
	Nov. 23, 2021 USD ($)	Feb. 28, 2019 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2023 SEK (kr)	Dec. 31, 2023 GBP (£)	Dec. 31, 2023 EUR (€)	Dec. 31, 2022 SEK (kr)	Dec. 31, 2022 GBP (£)	Dec. 31, 2022 EUR (€)	Apr. 30, 2022 USD ($)	Apr. 01, 2022 USD ($)	Feb. 25, 2022 USD ($)	Nov. 04, 2021 USD ($)	Feb. 25, 2021 USD ($)	Nov. 04, 2020 USD ($)	Sep. 29, 2020 USD ($)	Sep. 24, 2020 USD ($)	Aug. 03, 2020 USD ($)
Debt Instrument [Line Items]
Borrowings under credit facilities			$ 719,914,000	$ 729,144,000
February 2019 Credit Facility | Line of Credit
Debt Instrument [Line Items]
Commitment aggregate amount		$ 800,000,000	$ 1,100,000,000	1,100,000,000								$ 1,100,000,000	$ 965,000,000	$ 875,000,000
Line of credit facility commitment aggregate value		$ 1,200,000,000										$ 1,500,000,000	$ 1,500,000,000
Debt instrument, basis spread on variable floor rate (as percent)		1.00%
Percentage of unused portion of credit facility, greater than two-third of commitments (as percent)		0.50%
Percentage of unused portion of credit facility, less than two-third of commitments (as percent)		0.375%
Debt issuance costs, financing fees		$ 6,400,000									$ 4,100,000
Effective interest rate			7.09%		7.09%	7.09%	7.09%
February 2019 Credit Facility | Line of Credit | Level 3
Debt Instrument [Line Items]
Fair value of long-term debt			$ 719,900,000	729,100,000
February 2019 Credit Facility | Line of Credit | Interest Period Of One Month
Debt Instrument [Line Items]
Debt instrument, credit spread adjustment		0.0010
February 2019 Credit Facility | Line of Credit | Interest Period Of Three Month
Debt Instrument [Line Items]
Debt instrument, credit spread adjustment		0.0015
February 2019 Credit Facility | Line of Credit | Interest Period Of Six Month
Debt Instrument [Line Items]
Debt instrument, credit spread adjustment		0.0025
February 2019 Credit Facility | Federal Funds Purchased | Line of Credit
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		0.50%
February 2019 Credit Facility | Base Rate | Line of Credit
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		1.25%
February 2019 Credit Facility | Base Rate | Line of Credit | External Credit Rating, Investment Grade
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		1.00%
February 2019 Credit Facility | SOFR | Line of Credit
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		2.25%
February 2019 Credit Facility | SOFR | Line of Credit | External Credit Rating, Investment Grade
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		2.00%
February 2019 Credit Facility | Applicable Rate | Line of Credit
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		2.00%
February 2019 Credit Facility | Applicable Rate | Line of Credit | External Credit Rating, Non Investment Grade
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		2.25%
February 2019 Credit Facility | Screen Rate | Line of Credit
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		2.20%
February 2019 Credit Facility | Screen Rate | Line of Credit | External Credit Rating, Non Investment Grade
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		2.45%
February 2019 Credit Facility | Overnight Bank Funding Rate | Line of Credit
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		0.50%
February 2019 Credit Facility | One-Month Secured Overnight Financing Rate (SOFR) | Line of Credit
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		1.00%
Debt instrument, credit spread adjustment		0.0010
Debt Denominated In U.S Dollars | Line of Credit
Debt Instrument [Line Items]
Borrowings under credit facilities			$ 489,500,000	$ 497,500,000
Effective interest rate			7.428%	6.324%	7.428%	7.428%	7.428%	6.324%	6.324%	6.324%
Debt Denominated In U.S Dollars | LIBOR | Line of Credit
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate				4.224%
Debt Denominated In U.S Dollars | One-Month Secured Overnight Financing Rate (SOFR) | Line of Credit
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate			5.328%
Debt Denominated In Swedish Kronas | Line of Credit
Debt Instrument [Line Items]
Borrowings under credit facilities			$ 1,300,000	$ 1,200,000	kr 12.8			kr 12.8
Effective interest rate			6.063%	4.375%	6.063%	6.063%	6.063%	4.375%	4.375%	4.375%
Debt Denominated In Swedish Kronas | Stockholm Interbank Offered Rate (STIBOR) | Line of Credit
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate			4.063%	2.375%
Debt Denominated In British Pounds | Line of Credit
Debt Instrument [Line Items]
Borrowings under credit facilities			$ 84,900,000	$ 82,500,000		£ 66.6			£ 68.6
Effective interest rate			7.22%	4.96%	7.22%	7.22%	7.22%	4.96%	4.96%	4.96%
Debt Denominated In British Pounds | Sterling Overnight Index Average (SONIA) | Line of Credit
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate			5.22%
Debt Denominated In British Pounds | GBP LIBOR | Line of Credit
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate				0.296%
Debt Denominated In Euro | Line of Credit
Debt Instrument [Line Items]
Borrowings under credit facilities			$ 144,300,000	$ 147,900,000			€ 130.6			€ 138.6
Effective interest rate			5.875%	3.625%	5.875%	5.875%	5.875%	3.625%	3.625%	3.625%
Debt Denominated In Euro | Euro Interbank Offered Rate (EURIBOR) | Line of Credit
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate			3.875%	1.625%
September 24, 2020 - August 2025 Notes | Notes
Debt Instrument [Line Items]
Aggregate principal amount																	$ 25,000,000	$ 25,000,000	$ 50,000,000
Fixed interest rate			4.66%		4.66%	4.66%	4.66%												4.66%
Ownership percent for immediate conversion			66.67%		66.67%	66.67%	66.67%
September 24, 2020 - August 2025 Notes | Notes | Level 3
Debt Instrument [Line Items]
Fair value of long-term debt			$ 47,800,000	$ 46,100,000
November 5, 2020 - Series B Notes | Notes
Debt Instrument [Line Items]
Aggregate principal amount																$ 62,500,000
Fixed interest rate			4.25%		4.25%	4.25%	4.25%									4.25%
November 5, 2020 - Series B Notes | Notes | Level 3
Debt Instrument [Line Items]
Fair value of long-term debt			$ 59,300,000	56,800,000
November 5, 2020 - Series C Notes | Notes
Debt Instrument [Line Items]
Aggregate principal amount																$ 112,500,000
Fixed interest rate			4.75%		4.75%	4.75%	4.75%									4.75%
November 5, 2020 - Series C Notes | Notes | Level 3
Debt Instrument [Line Items]
Fair value of long-term debt			$ 102,500,000	97,700,000
Series B And Series C Senior Unsecured Notes Due November | Notes
Debt Instrument [Line Items]
Interest rate extended																0.0075
Investment grade conditions																0.0150
February 25, 2021 Series D Notes | Notes
Debt Instrument [Line Items]
Aggregate principal amount															$ 80,000,000
Fixed interest rate			3.41%		3.41%	3.41%	3.41%								3.41%
February 25, 2021 Series D Notes | Notes | Level 3
Debt Instrument [Line Items]
Fair value of long-term debt			$ 73,400,000	69,600,000
February 25, 2021 Series E Notes | Notes
Debt Instrument [Line Items]
Aggregate principal amount															$ 70,000,000
Fixed interest rate			4.06%		4.06%	4.06%	4.06%								4.06%
February 25, 2021 Series E Notes | Notes | Level 3
Debt Instrument [Line Items]
Fair value of long-term debt			$ 61,200,000	57,800,000
Series D And Series E Senior Unsecured Notes Due February | Notes
Debt Instrument [Line Items]
Interest rate extended															0.0075
Investment grade conditions															0.0150
November 23, 2021 - November 2026 Notes | Notes
Debt Instrument [Line Items]
Aggregate principal amount	$ 350,000,000
Fixed interest rate	3.30%		3.30%		3.30%	3.30%	3.30%
Ownership percent for immediate conversion			66.67%		66.67%	66.67%	66.67%
Redemption percentage on purchase price (as percent)	100.00%
November 23, 2021 - November 2026 Notes | Notes | Level 3
Debt Instrument [Line Items]
Fair value of long-term debt			$ 311,400,000	$ 294,600,000