Debt - Long Term Debt (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2023	Dec. 31, 2022	Mar. 10, 2022	Feb. 15, 2022	Sep. 22, 2020
Debt Instrument [Line Items]
Long-term Debt	$ 1,388.6	$ 1,386.9
Derivative, Gain (Loss) on Derivative, Net	0.5
Gain (Loss) on Derivative Instruments, Net, Pretax	0.4
Senior Notes, 2.400 Percent Due September 30, 2030
Debt Instrument [Line Items]
Long-term Debt					$ 395.8
Senior Notes, 3.800 Percent Due February 23, 2033
Debt Instrument [Line Items]
Long-term Debt				$ 395.1
5.875% Fixed-Rate Reset Junior Subordinated Debentures due 2062
Debt Instrument [Line Items]
Long-term Debt			$ 144.7
Senior Notes | Senior Notes, 4.35 Percent Due February 15, 2025
Debt Instrument [Line Items]
Long-term Debt	$ 449.6	449.3
Stated interest rate	4.35%
Senior Notes | Senior Notes, 2.400 Percent Due September 30, 2030
Debt Instrument [Line Items]
Long-term Debt	$ 396.9	396.6
Stated interest rate					2.40%
Senior Notes | Senior Notes, 3.800 Percent Due February 23, 2033
Debt Instrument [Line Items]
Long-term Debt	395.8	395.5
Stated interest rate				3.80%
Senior Notes | Senior Notes, 5.875 Percent Due March 15, 2062
Debt Instrument [Line Items]
Long-term Debt	$ 146.3	$ 145.5
Junior Debt | Senior Notes, 5.875 Percent Due March 15, 2062
Debt Instrument [Line Items]
Stated interest rate			5.875%