Borrowings - Schedule of Debt Obligations (Details) - USD ($)	Mar. 31, 2026	Dec. 31, 2025	Jun. 30, 2021	May 31, 2021
Debt Instrument [Line Items]
Borrowing Outstanding	$ 3,033,700,000	$ 3,025,100,000
Carrying Value	3,001,600,000	2,997,000,000
CLO Borrowings
Debt Instrument [Line Items]
Borrowing Outstanding	358,700,000	350,100,000
Carrying Value	$ 353,500,000	349,400,000
3.500% Senior Notes Due 9/19/2029
Debt Instrument [Line Items]
Interest rate (percent)	3.50%
Borrowing Outstanding	$ 425,000,000.0	425,000,000.0
Carrying Value	$ 423,500,000	423,400,000
5.050% Senior Notes Due 9/19/2035
Debt Instrument [Line Items]
Interest rate (percent)	5.05%
Borrowing Outstanding	$ 800,000,000.0	800,000,000.0
Carrying Value	$ 791,300,000	791,100,000
5.625% Senior Notes Due 3/30/2043
Debt Instrument [Line Items]
Interest rate (percent)	5.625%
Borrowing Outstanding	$ 600,000,000.0	600,000,000.0
Carrying Value	$ 600,500,000	600,500,000
5.650% Senior Notes Due 9/15/2048
Debt Instrument [Line Items]
Interest rate (percent)	5.65%
Borrowing Outstanding	$ 350,000,000.0	350,000,000.0
Carrying Value	$ 346,800,000	346,700,000
4.625% Subordinated Notes Due 5/15/2061
Debt Instrument [Line Items]
Interest rate (percent)	4.625%			4.625%
Borrowing Outstanding	$ 500,000,000.0	500,000,000.0	$ 65,000,000.0	$ 435,000,000.0
Carrying Value	$ 486,000,000.0	$ 485,900,000