Borrowings - Additional Information (Details) € in Millions	1 Months Ended	3 Months Ended			6 Months Ended
	Aug. 31, 2023 USD ($)	Jun. 30, 2024 USD ($)	Jun. 30, 2024 EUR (€)	Jun. 30, 2023 USD ($)	Jun. 30, 2024 USD ($)	Jun. 30, 2023 USD ($)	Jun. 30, 2024 EUR (€)	Dec. 31, 2023 USD ($)	Jul. 31, 2023 USD ($)	Jun. 30, 2021 USD ($)	May 31, 2021 USD ($)	Feb. 28, 2017 EUR (€)	Mar. 31, 2014 USD ($)	Mar. 31, 2013 USD ($)
Debt Instrument [Line Items]
Borrowings under credit facilities					$ 10,400,000	$ 0
Interest expense		$ 30,400,000		$ 30,700,000	61,200,000	60,400,000
Borrowings		2,259,300,000			2,259,300,000			$ 2,306,700,000
Fair value of collateralized loan obligation assets		8,700,000,000			$ 8,700,000,000			6,800,000,000
Senior Notes
Debt Instrument [Line Items]
Debt redemption price percentage (percent)					100.00%
CLO Borrowings
Debt Instrument [Line Items]
Interest expense		6,200,000		5,900,000	$ 13,000,000	11,100,000
Borrowings		384,300,000			384,300,000			431,700,000
CLO Term Loan February 2017 Maturing September 2029
Debt Instrument [Line Items]
Borrowings		$ 29,700,000			$ 29,700,000							€ 27.7
CLO Term Loan February 2017 Maturing September 2029 | Euribor
Debt Instrument [Line Items]
Interest rate under credit facility		6.34%			6.34%		6.34%
Master Credit Agreements - Term Loans
Debt Instrument [Line Items]
Outstanding borrowings		$ 68,700,000			$ 68,700,000
CLO Financing Facility
Debt Instrument [Line Items]
Outstanding borrowings		218,900,000			218,900,000		€ 204.3
CBAM CLO Financing Facility
Debt Instrument [Line Items]
Borrowing capacity | €							100.0
Outstanding borrowings		66,600,000			66,600,000		€ 62.2
5.650% Senior Notes Due 9/15/2048
Debt Instrument [Line Items]
Borrowings		$ 350,000,000.0			$ 350,000,000.0			350,000,000.0
Interest rate (percent)		5.65%			5.65%		5.65%
5.650% Senior Notes Due 9/15/2048 | Senior Notes
Debt Instrument [Line Items]
Borrowings		$ 350,000,000.0			$ 350,000,000.0
Fair value of debt		343,300,000			$ 343,300,000			336,000,000.0
5.650% Senior Notes Due 9/15/2048 | Treasury rate | Senior Notes
Debt Instrument [Line Items]
Discount rate, spread on variable rate					0.40%
5.625% Senior Notes Due 3/30/2043
Debt Instrument [Line Items]
Borrowings		$ 600,000,000.0			$ 600,000,000.0			600,000,000.0
Interest rate (percent)		5.625%			5.625%		5.625%
5.625% Senior Notes Due 3/30/2043 | Senior Notes
Debt Instrument [Line Items]
Borrowings		$ 600,000,000.0			$ 600,000,000.0								$ 200,000,000.0	$ 400,000,000.0
Fair value of debt		582,900,000			$ 582,900,000			594,600,000
5.625% Senior Notes Due 3/30/2043 | Treasury rate | Senior Notes
Debt Instrument [Line Items]
Discount rate, spread on variable rate					0.40%
3.500% Senior Notes Due 9/19/2029
Debt Instrument [Line Items]
Borrowings		$ 425,000,000.0			$ 425,000,000.0			425,000,000.0
Interest rate (percent)		3.50%			3.50%		3.50%
3.500% Senior Notes Due 9/19/2029 | Senior Notes
Debt Instrument [Line Items]
Borrowings		$ 425,000,000.0			$ 425,000,000.0
Interest rate (percent)		3.50%			3.50%		3.50%
Fair value of debt		$ 395,600,000			$ 395,600,000			401,900,000
3.500% Senior Notes Due 9/19/2029 | Treasury rate | Senior Notes
Debt Instrument [Line Items]
Discount rate, spread on variable rate					0.30%
4.625% Subordinated Notes Due 5/15/2061
Debt Instrument [Line Items]
Interest expense		5,900,000		$ 5,900,000	$ 11,800,000	$ 11,800,000
Borrowings		$ 500,000,000.0			$ 500,000,000.0			500,000,000.0		$ 65,000,000	$ 435,000,000
Debt redemption price percentage (percent)					102.00%
Interest rate (percent)		4.625%			4.625%		4.625%				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 of debt		$ 364,000,000			$ 364,000,000			411,800,000
Revolving Credit Facility
Debt Instrument [Line Items]
Borrowing capacity		$ 1,000,000,000			$ 1,000,000,000
Interest rate under credit facility		6.44%			6.44%		6.44%
Borrowings under credit facilities		$ 0			$ 0
Outstanding borrowings		0			0
Fair value of debt		177,700,000			$ 177,700,000			$ 177,900,000
Revolving Credit Facility | Base rate
Debt Instrument [Line Items]
Margin spread on interest rate (percent)					0.50%
Revolving Credit Facility | SOFR
Debt Instrument [Line Items]
Margin spread on interest rate (percent)					0.10%
Revolving Credit Facility | SOFR | Maximum
Debt Instrument [Line Items]
Margin spread on interest rate (percent)					1.50%
Revolving Credit Facility | Global Credit Revolving Credit Facility
Debt Instrument [Line Items]
Borrowing capacity	$ 300,000,000	200,000,000			$ 200,000,000				$ 250,000,000
Borrowings under credit facilities		5,000,000	€ 5.0
Outstanding borrowings		$ 0			$ 0
Revolving Credit Facility | Global Credit Revolving Credit Facility | Base rate
Debt Instrument [Line Items]
Margin spread on interest rate (percent)	1.00%
Revolving Credit Facility | Global Credit Revolving Credit Facility | SOFR
Debt Instrument [Line Items]
Margin spread on interest rate (percent)	2.00%