Long-Term Debt - Long-Term Debt (Detail) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Total debt	$ 5,100.9	$ 2,625.8
Less: current maturities	(0.1)
Long-term debt	5,100.8	2,625.8
0.650% Senior Notes, Due 2023
Debt Instrument [Line Items]
Total debt	697.4
4.25% Senior Notes, Due 2024
Debt Instrument [Line Items]
Total debt	398.3	397.6
7% Debentures, Due 2025
Debt Instrument [Line Items]
Total debt	124.6	124.5
3.450% Senior Notes, Due 2027
Debt Instrument [Line Items]
Total debt	297.9	297.6
3.500% Senior Notes, Due 2027
Debt Instrument [Line Items]
Total debt	496.4	495.8
2.500% Senior Notes, Due 2030
Debt Instrument [Line Items]
Total debt	491.1	490.1
2.400% Senior Notes, Due 2031
Debt Instrument [Line Items]
Total debt	891.8
6.25% Senior Notes, Due 2037
Debt Instrument [Line Items]
Total debt	228.3	228.2
4.250% Senior Notes, Due 2047
Debt Instrument [Line Items]
Total debt	592.1	591.9
3.200% Senior Notes, Due 2051
Debt Instrument [Line Items]
Total debt	882.9
Other Notes
Debt Instrument [Line Items]
Total debt	$ 0.1	$ 0.1