Financial Assets and Liabilities Subject to Recurring Fair Value Measurements (Detail) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	$ 97.7	$ 137.3
Derivative liabilities	65.7	48.2
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities	1,078.9	1,448.1
Derivative assets	97.7	137.3
Derivative liabilities	65.7	48.2
Fair Value, Measurements, Recurring | Cross currency swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	77.6	130.5
Derivative liabilities	51.6	37.2
Fair Value, Measurements, Recurring | Interest-rate swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	5.1	1.7
Derivative liabilities	12.7	9.5
Fair Value, Measurements, Recurring | Foreign-exchange contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	15.0	5.1
Derivative liabilities	1.4	1.5
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	499.9	505.4
Fair Value, Measurements, Recurring | U.S. corporate securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities	52.8	76.7
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	16.3	15.7
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	328.6	587.0
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	99.8	193.7
Fair Value, Measurements, Recurring | Other debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities	81.5	69.6
Level 1 | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities	15.4	15.1
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	15.4	15.1
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	1,063.5	1,433.0
Derivative assets	97.7	137.3
Derivative liabilities	65.7	48.2
Level 2 | Fair Value, Measurements, Recurring | Cross currency swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	77.6	130.5
Derivative liabilities	51.6	37.2
Level 2 | Fair Value, Measurements, Recurring | Interest-rate swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	5.1	1.7
Derivative liabilities	12.7	9.5
Level 2 | Fair Value, Measurements, Recurring | Foreign-exchange contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	15.0	5.1
Derivative liabilities	1.4	1.5
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	499.9	505.4
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	52.8	76.7
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	0.9	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	328.6	587.0
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	99.8	193.7
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	$ 81.5	$ 69.6