Borrowings - Additional Information (Details) € in Millions	1 Months Ended	12 Months Ended
	Nov. 30, 2021 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2023 EUR (€)	Jun. 30, 2021 USD ($)	May 31, 2021 USD ($)	Feb. 28, 2017 EUR (€)	Mar. 31, 2014 USD ($)	Mar. 31, 2013 USD ($)
Line of Credit Facility [Line Items]
Interest		$ 123,800,000	$ 110,400,000	$ 113,300,000
Debt principal amount		2,306,700,000	2,296,700,000
Interest expense		68,900,000	68,900,000	77,800,000
Fair value		6,486,500,000	5,905,200,000
Fair value of CLO assets		$ 6,800,000,000	6,200,000,000
Senior Notes
Line of Credit Facility [Line Items]
Debt redemption price percentage		100.00%
Interest expense	$ 10,100,000
CLO Term Loans
Line of Credit Facility [Line Items]
Interest		$ 24,900,000	10,700,000	5,600,000
Debt principal amount		$ 431,700,000	421,700,000
CLO Term Loan Maturing November 17, 2031
Line of Credit Facility [Line Items]
Debt principal amount | €					€ 39.9			€ 36.1
CLO Term Loan Maturing November 17, 2031 | Euribor
Line of Credit Facility [Line Items]
Interest rate at end of period		6.02%			6.02%
Master Credit Agreements - Term Loans
Line of Credit Facility [Line Items]
Outstanding borrowing		$ 86,700,000
CLO Financing Facility
Line of Credit Facility [Line Items]
Outstanding borrowing		236,500,000			€ 213.8
CBAM CLO Financing Facility
Line of Credit Facility [Line Items]
Outstanding borrowing		68,500,000			61.9
Borrowing capacity | €					€ 100.0
5.625% Senior Notes Due 3/30/2043
Line of Credit Facility [Line Items]
Debt principal amount		$ 600,000,000.0	600,000,000.0
Interest rate (percent)		5.625%			5.625%
5.625% Senior Notes Due 3/30/2043 | Senior Notes
Line of Credit Facility [Line Items]
Debt principal amount		$ 600,000,000.0							$ 200,000,000	$ 400,000,000
Interest rate (percent)		5.625%			5.625%
Interest expense		$ 33,700,000	33,700,000	33,700,000
Fair value		$ 594,600,000	545,800,000
5.625% Senior Notes Due 3/30/2043 | Treasury Rate | Senior Notes
Line of Credit Facility [Line Items]
Applicable margin over base rate		0.40%
5.650% Senior Notes Due 9/15/2048
Line of Credit Facility [Line Items]
Debt principal amount		$ 350,000,000.0	350,000,000.0
Interest rate (percent)		5.65%			5.65%
5.650% Senior Notes Due 9/15/2048 | Senior Notes
Line of Credit Facility [Line Items]
Debt principal amount		$ 350,000,000.0
Interest rate (percent)		5.65%			5.65%
Interest expense		$ 19,900,000	19,900,000	19,900,000
Fair value		$ 336,000,000.0	322,200,000
5.650% Senior Notes Due 9/15/2048 | Treasury Rate | Senior Notes
Line of Credit Facility [Line Items]
Applicable margin over base rate		0.40%
3.500% Senior Notes Due 9/19/2029
Line of Credit Facility [Line Items]
Debt principal amount		$ 425,000,000.0	425,000,000.0
Interest rate (percent)		3.50%			3.50%
3.500% Senior Notes Due 9/19/2029 | Senior Notes
Line of Credit Facility [Line Items]
Debt principal amount		$ 425,000,000.0
Interest rate (percent)		3.50%			3.50%
Interest expense		$ 15,300,000	15,300,000	15,300,000
Fair value		$ 401,900,000	364,100,000
3.500% Senior Notes Due 9/19/2029 | Treasury Rate | Senior Notes
Line of Credit Facility [Line Items]
Applicable margin over base rate		0.30%
3.875% Senior Notes Due 2/01/2023
Line of Credit Facility [Line Items]
Interest rate (percent)	3.875%
3.875% Senior Notes Due 2/01/2023 | Senior Notes
Line of Credit Facility [Line Items]
Debt principal amount	$ 250,000,000	$ 0
Interest rate (percent)		3.875%			3.875%
Interest expense		$ 0	0	$ 8,900,000
Fair value		$ 0	0
3.875% Senior Notes Due 2/01/2023 | Treasury Rate | Senior Notes
Line of Credit Facility [Line Items]
Applicable margin over base rate		0.30%
4.625% Subordinated Notes Due 5/15/2061
Line of Credit Facility [Line Items]
Interest		$ 23,500,000	23,500,000
Debt principal amount						$ 65,000,000	$ 435,000,000
Debt redemption price percentage		102.00%
Interest rate (percent)							4.625%
Period from tax redemption event that debt may be redeemed		120 days
Period from rating agency event that debt may be redeemed		90 days
Fair value		$ 411,800,000	$ 323,800,000