Borrowings - Senior Notes (Details) - USD ($)	1 Months Ended			8 Months Ended	12 Months Ended
	Nov. 30, 2021	Mar. 31, 2013	Jan. 31, 2013	Dec. 31, 2021	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Jun. 30, 2021	May 31, 2021	Sep. 30, 2019	Sep. 30, 2018	Mar. 31, 2014
Debt Instrument [Line Items]
Borrowing Outstanding				$ 2,097,600,000	$ 2,296,700,000	$ 2,097,600,000
Fair Value				5,811,000,000	5,491,600,000	5,811,000,000
Interest Expense					68,900,000	77,800,000	$ 78,900,000
Interest					$ 110,400,000	113,300,000	94,000,000.0
Senior Notes
Debt Instrument [Line Items]
Interest Expense	$ 10,100,000
Debt redemption price percentage					100.00%
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	0
Interest Expense					$ 0	8,900,000	9,900,000
Senior notes percentage of par value			99.966%
3.875% Senior Notes Due 2/01/2023 | Senior Notes | Treasury Rate
Debt Instrument [Line Items]
Applicable margin over base rate			0.30%
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	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		$ 400,000,000			$ 600,000,000.0							$ 200,000,000
Fair Value				795,500,000	545,800,000	795,500,000
Interest Expense					$ 33,700,000	33,700,000	33,800,000
Senior notes percentage of par value		99.583%										104.315%
5.625% Senior Notes Due 3/30/2043 | Senior Notes | Treasury Rate
Debt Instrument [Line Items]
Applicable margin over base rate		0.40%
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	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				484,700,000	322,200,000	484,700,000
Interest Expense					$ 19,900,000	19,900,000	19,900,000
Senior notes percentage of par value										99.841%	99.914%
5.650% Senior Notes Due 9/15/2048 | Senior Notes | Treasury Rate
Debt Instrument [Line Items]
Applicable margin over base rate		0.40%
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	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				457,400,000	364,100,000	457,400,000
Interest Expense					15,300,000	15,300,000	$ 15,300,000
3.500% Senior Notes Due 9/19/2029 | Senior Notes | Treasury Rate
Debt Instrument [Line Items]
Applicable margin over base rate			0.30%
4.625% Subordinated Notes Due 5/15/2061
Debt Instrument [Line Items]
Interest rate (percent)									4.625%
Borrowing Outstanding								$ 65,000,000	$ 435,000,000
Fair Value				506,000,000	$ 323,800,000	$ 506,000,000
Interest Expense				$ 14,800,000
Debt redemption price percentage					102.00%
Period from tax redemption event that debt may be redeemed					120 days
Period from rating agency event that debt may be redeemed					90 days
Interest					$ 23,500,000