Borrowings - Senior Notes (Details) - USD ($)	1 Months Ended	12 Months Ended
	Nov. 30, 2021	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Sep. 30, 2019	Sep. 30, 2018	Mar. 31, 2014	Mar. 31, 2013	Jan. 31, 2013
Debt Instrument [Line Items]
Borrowing Outstanding		$ 2,306,700,000	$ 2,296,700,000
Fair Value		6,486,500,000	5,905,200,000
Interest Expense		$ 68,900,000	68,900,000	$ 77,800,000
Senior Notes
Debt Instrument [Line Items]
Interest Expense	$ 10,100,000
3.875% Senior Notes Due 2/01/2023
Debt Instrument [Line Items]
Interest rate (percent)	3.875%
3.875% Senior Notes Due 2/01/2023 | Senior Notes
Debt Instrument [Line Items]
Interest rate (percent)		3.875%
Borrowing Outstanding	$ 250,000,000	$ 0
Fair Value		0	0
Interest Expense		$ 0	0	8,900,000
Senior notes percentage of par value									99.966%
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
3.500% Senior Notes Due 9/19/2029 | Senior Notes
Debt Instrument [Line Items]
Interest rate (percent)		3.50%
Borrowing Outstanding		$ 425,000,000.0
Fair Value		401,900,000	364,100,000
Interest Expense		$ 15,300,000	15,300,000	15,300,000
Senior notes percentage of par value					99.841%
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
5.625% Senior Notes Due 3/30/2043 | Senior Notes
Debt Instrument [Line Items]
Interest rate (percent)		5.625%
Borrowing Outstanding		$ 600,000,000.0					$ 200,000,000	$ 400,000,000
Fair Value		594,600,000	545,800,000
Interest Expense		$ 33,700,000	33,700,000	33,700,000
Senior notes percentage of par value							104.315%	99.583%
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
5.650% Senior Notes Due 9/15/2048 | Senior Notes
Debt Instrument [Line Items]
Interest rate (percent)		5.65%
Borrowing Outstanding		$ 350,000,000.0
Fair Value		336,000,000.0	322,200,000
Interest Expense		$ 19,900,000	$ 19,900,000	$ 19,900,000
Senior notes percentage of par value						99.914%