Financial Assets and Liabilities Subject to Recurring Fair Value Measurements (Detail) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	$ 59.6	$ 118.4
Derivative liabilities	82.9	49.3
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities	1,244.6	1,140.9
Derivative assets	59.6	118.4
Derivative liabilities	82.9	49.3
Fair Value, Measurements, Recurring | Cross currency swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	50.7	102.7
Derivative liabilities	65.4	37.1
Fair Value, Measurements, Recurring | Interest-rate swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	4.9	7.0
Derivative liabilities	7.3	9.3
Fair Value, Measurements, Recurring | Foreign-exchange contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	4.0	8.7
Derivative liabilities	10.2	2.9
Fair Value, Measurements, Recurring | U.S. tax-exempt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities	564.0	595.0
Fair Value, Measurements, Recurring | U.S. corporate securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities	58.8	47.8
Fair Value, Measurements, Recurring | U.S. government and agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities	15.6	16.0
Fair Value, Measurements, Recurring | Non-U.S. corporate securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities	378.5	308.0
Fair Value, Measurements, Recurring | Non-U.S. government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities	93.1	98.2
Fair Value, Measurements, Recurring | Other debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities	134.6	75.9
Level 1 | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities	15.1	15.4
Derivative assets	0.0	0.0
Derivative liabilities	0.0	0.0
Level 1 | Fair Value, Measurements, Recurring | Cross currency swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0.0	0.0
Derivative liabilities	0.0	0.0
Level 1 | Fair Value, Measurements, Recurring | Interest-rate swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0.0	0.0
Derivative liabilities	0.0	0.0
Level 1 | Fair Value, Measurements, Recurring | Foreign-exchange contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0.0	0.0
Derivative liabilities	0.0	0.0
Level 1 | Fair Value, Measurements, Recurring | U.S. tax-exempt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities	0.0	0.0
Level 1 | Fair Value, Measurements, Recurring | U.S. corporate securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities	0.0	0.0
Level 1 | Fair Value, Measurements, Recurring | U.S. government and agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities	15.1	15.4
Level 1 | Fair Value, Measurements, Recurring | Non-U.S. corporate securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities	0.0	0.0
Level 1 | Fair Value, Measurements, Recurring | Non-U.S. government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities	0.0	0.0
Level 1 | Fair Value, Measurements, Recurring | Other debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities	0.0	0.0
Level 2 | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities	1,229.5	1,125.5
Derivative assets	59.6	118.4
Derivative liabilities	82.9	49.3
Level 2 | Fair Value, Measurements, Recurring | Cross currency swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	50.7	102.7
Derivative liabilities	65.4	37.1
Level 2 | Fair Value, Measurements, Recurring | Interest-rate swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	4.9	7.0
Derivative liabilities	7.3	9.3
Level 2 | Fair Value, Measurements, Recurring | Foreign-exchange contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	4.0	8.7
Derivative liabilities	10.2	2.9
Level 2 | Fair Value, Measurements, Recurring | U.S. tax-exempt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities	564.0	595.0
Level 2 | Fair Value, Measurements, Recurring | U.S. corporate securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities	58.8	47.8
Level 2 | Fair Value, Measurements, Recurring | U.S. government and agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities	0.5	0.6
Level 2 | Fair Value, Measurements, Recurring | Non-U.S. corporate securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities	378.5	308.0
Level 2 | Fair Value, Measurements, Recurring | Non-U.S. government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities	93.1	98.2
Level 2 | Fair Value, Measurements, Recurring | Other debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities	$ 134.6	$ 75.9