Fair Value Measurements - Schedule of Fair Value of Assets and Liabilities Measured on Recurring Basis (Detail) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	$ 222.4	$ 109.4
Short-term investments	222.4	109.4
Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments		61.2
Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	69.8	65.2
Total assets	317.5	201.5
Total liabilities	16.2	6.8
Short-term investments	222.4	109.4
Other current assets	0.1	1.9
Total current assets	292.3	176.5
Long-term investments	6.3	5.8
Other assets	18.9	19.2
Total long-term assets	25.2	25.0
Fair Value Measurements, Recurring [Member] | Foreign Exchange Contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives – currency forward contracts	0.1	1.1
Derivatives – currency forward contracts	2.2	0.3
Fair Value Measurements, Recurring [Member] | Interest Rate Hedge [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives – interest rate hedge – non-current	14.0	6.5
Derivatives –interest rate hedge - current		0.8
Fair Value Measurements, Recurring [Member] | Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents		42.6
Available-for-sale investments		61.2
Fair Value Measurements, Recurring [Member] | Group Insurance Contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	6.3	5.8
Fair Value Measurements, Recurring [Member] | Israeli Pension Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Pension assets	17.3	16.7
Fair Value Measurements, Recurring [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0.4	0.6
Deferred compensation plan assets	0.1	0.5
Fair Value Measurements, Recurring [Member] | U.S. Treasury Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	69.4	2.7
Available-for-sale investments	219.0	5.0
Fair Value Measurements, Recurring [Member] | Time Deposits and Certificates of Deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents		2.2
Available-for-sale investments	0.3	13.1
Fair Value Measurements, Recurring [Member] | Bankers' Acceptance Drafts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	3.1	4.0
Fair Value Measurements, Recurring [Member] | Mutual Funds and Exchange Traded Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deferred compensation plan assets	1.5	2.0
Fair Value Measurements, Recurring [Member] | U.S. Agency Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents		17.1
Available-for-sale investments		26.1
Fair Value Measurements, Recurring [Member] | Other Current Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total liabilities	2.2	0.3
Fair Value Measurements, Recurring [Member] | Other Noncurrent Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total liabilities	14.0	6.5
Fair Value Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0.4	0.6
Total assets	0.4	0.6
Total current assets	0.4	0.6
Fair Value Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0.4	0.6
Fair Value Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	69.4	64.6
Total assets	317.1	200.9
Total liabilities	16.2	6.8
Short-term investments	222.4	109.4
Other current assets	0.1	1.9
Total current assets	291.9	175.9
Long-term investments	6.3	5.8
Other assets	18.9	19.2
Total long-term assets	25.2	25.0
Fair Value Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Foreign Exchange Contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives – currency forward contracts	0.1	1.1
Derivatives – currency forward contracts	2.2	0.3
Fair Value Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Interest Rate Hedge [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives – interest rate hedge – non-current	14.0	6.5
Derivatives –interest rate hedge - current		0.8
Fair Value Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents		42.6
Available-for-sale investments		61.2
Fair Value Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Group Insurance Contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	6.3	5.8
Fair Value Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Israeli Pension Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Pension assets	17.3	16.7
Fair Value Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deferred compensation plan assets	0.1	0.5
Fair Value Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | U.S. Treasury Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	69.4	2.7
Available-for-sale investments	219.0	5.0
Fair Value Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Time Deposits and Certificates of Deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents		2.2
Available-for-sale investments	0.3	13.1
Fair Value Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Bankers' Acceptance Drafts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	3.1	4.0
Fair Value Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Mutual Funds and Exchange Traded Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deferred compensation plan assets	1.5	2.0
Fair Value Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | U.S. Agency Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents		17.1
Available-for-sale investments		26.1
Fair Value Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Current Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total liabilities	2.2	0.3
Fair Value Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Noncurrent Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total liabilities	$ 14.0	$ 6.5