Debt Schedule (Detail) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Debt Instrument
Long-term Debt, Excluding Current Maturities	$ 3,427.8	$ 3,442.2
Debt Instrument, Unamortized Premium (Discount), Net	2.5	2.3
Debt Issuance Costs, Noncurrent, Net	(33.2)	(34.6)
Long-term Debt	3,429.8	3,442.2
Five-Year Term Loan Facility
Debt Instrument
Line of Credit Facility, Fair Value of Amount Outstanding	350.0	0.0
Notes Issued in 1998 with 2028 Maturity Date \| Senior Notes
Debt Instrument
Long-term Debt, Excluding Current Maturities	335.8	335.8
Notes Issued in 2002 \| Senior Notes
Debt Instrument
Long-term Debt, Excluding Current Maturities	39.5	39.5
Notes Payable due 2042 \| Senior Notes
Debt Instrument
Long-term Debt, Excluding Current Maturities	500.0	500.0
Notes Issued in 2014 \| Senior Notes
Debt Instrument
Long-term Debt, Excluding Current Maturities	0.0	350.0
Notes Issued in 2015 \| Senior Notes
Debt Instrument
Long-term Debt, Excluding Current Maturities	275.0	275.0
Notes Issued in 2019 \| Senior Notes
Debt Instrument
Long-term Debt, Excluding Current Maturities	400.0	400.0
Notes Issued in 2019 due 2049 \| Senior Notes
Debt Instrument
Long-term Debt, Excluding Current Maturities	450.0	450.0
Notes Issued in 2021 due 2051 \| Senior Notes
Debt Instrument
Long-term Debt, Excluding Current Maturities	600.0	600.0
Notes Issued 1990 to 1996 \| Medium-term Notes
Debt Instrument
Short-term Debt, outstanding principal	2.0	0.0
Notes Issued 1990 to 1996 \| Medium-term Notes
Debt Instrument
Long-term Debt, Excluding Current Maturities	18.5	20.5
Notes Issued in 1998 with 2038 Maturity Date \| Junior Subordinated Debt
Debt Instrument
Long-term Debt, Excluding Current Maturities	189.7	203.7
Notes Issued in 2018 with a 2058 Maturity Date \| Junior Subordinated Debt
Debt Instrument
Long-term Debt, Excluding Current Maturities	$ 300.0	$ 300.0

Amount of debt and lease obligation, classified as current.

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