Financial Assets and Liabilities Subject to Recurring Fair Value Measurements (Detail) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative assets	$ 70.5	$ 56.3
Derivative liabilities	74.1	44.3
Fair Value, Measurements, Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable debt securities	1,194.3	1,162.1
Derivative assets	70.5	56.3
Derivative liabilities	74.1	44.3
Fair Value, Measurements, Recurring | Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable debt securities	99.2	128.4
Fair Value, Measurements, Recurring | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable debt securities	1,095.1	1,033.7
Derivative assets	70.5	56.3
Derivative liabilities	74.1	44.3
Fair Value, Measurements, Recurring | Cross currency swaps
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative assets	38.3	43.8
Derivative liabilities	19.2	13.5
Fair Value, Measurements, Recurring | Cross currency swaps | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative assets	38.3	43.8
Derivative liabilities	19.2	13.5
Fair Value, Measurements, Recurring | Interest-rate swaps
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative assets	1.6	2.0
Derivative liabilities	42.9	17.5
Fair Value, Measurements, Recurring | Interest-rate swaps | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative assets	1.6	2.0
Derivative liabilities	42.9	17.5
Fair Value, Measurements, Recurring | Foreign-exchange contracts
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative assets	30.6	10.5
Derivative liabilities	12.0	13.3
Fair Value, Measurements, Recurring | Foreign-exchange contracts | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative assets	30.6	10.5
Derivative liabilities	12.0	13.3
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	299.0	320.2
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	299.0	320.2
U.S. corporate securities | Fair Value, Measurements, Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable debt securities	184.4	165.7
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	184.4	165.7
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	105.7	129.3
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	99.2	128.4
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	6.5	0.9
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	353.6	349.8
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	353.6	349.8
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	79.3	72.4
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	79.3	72.4
Other debt securities | Fair Value, Measurements, Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable debt securities	172.3	124.7
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	$ 172.3	$ 124.7