Financial Assets and Liabilities Subject to Recurring Fair Value Measurements (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative assets	$ 56.3	$ 94.7
Derivative liabilities	44.3	24.6
Fair Value, Measurements, Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable debt securities	1,162.1	1,020.4
Derivative assets	56.3	94.7
Derivative liabilities	44.3	24.6
Fair Value, Measurements, Recurring | Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable debt securities	128.4	97.1
Fair Value, Measurements, Recurring | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable debt securities	1,033.7	923.3
Derivative assets	56.3	94.7
Derivative liabilities	44.3	24.6
Fair Value, Measurements, Recurring | Cross currency swaps
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative assets	43.8	75.4
Derivative liabilities	13.5	11.2
Fair Value, Measurements, Recurring | Cross currency swaps | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative assets	43.8	75.4
Derivative liabilities	13.5	11.2
Fair Value, Measurements, Recurring | Interest-rate swaps
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative assets	2.0	9.1
Derivative liabilities	17.5	7.3
Fair Value, Measurements, Recurring | Interest-rate swaps | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative assets	2.0	9.1
Derivative liabilities	17.5	7.3
Fair Value, Measurements, Recurring | Foreign-exchange contracts
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative assets	10.5	10.2
Derivative liabilities	13.3	6.1
Fair Value, Measurements, Recurring | Foreign-exchange contracts | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative assets	10.5	10.2
Derivative liabilities	13.3	6.1
U.S. tax-exempt securities | Fair Value, Measurements, Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable debt securities	320.2	325.1
U.S. tax-exempt securities | Fair Value, Measurements, Recurring | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable debt securities	320.2	325.1
U.S. corporate securities | Fair Value, Measurements, Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable debt securities	165.7	147.4
U.S. corporate securities | Fair Value, Measurements, Recurring | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable debt securities	165.7	147.4
U.S. government and agency securities | Fair Value, Measurements, Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable debt securities	129.3	98.7
U.S. government and agency securities | Fair Value, Measurements, Recurring | Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable debt securities	128.4	97.1
U.S. government and agency securities | Fair Value, Measurements, Recurring | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable debt securities	0.9	1.6
Non-U.S. corporate securities | Fair Value, Measurements, Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable debt securities	349.8	271.3
Non-U.S. corporate securities | Fair Value, Measurements, Recurring | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable debt securities	349.8	271.3
Non-U.S. government securities | Fair Value, Measurements, Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable debt securities	72.4	55.9
Non-U.S. government securities | Fair Value, Measurements, Recurring | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable debt securities	72.4	55.9
Other debt securities | Fair Value, Measurements, Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable debt securities	124.7	122.0
Other debt securities | Fair Value, Measurements, Recurring | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable debt securities	$ 124.7	$ 122.0