Fair Value Measurements - Schedule of Fair Value of Assets and Liabilities Measured on Recurring Basis (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	$ 219,776	$ 209,434
Short-term investments	219,776	209,434
Other assets	42,390	37,883
Foreign Exchange Contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives - contracts	3,434	168
Derivatives - liabilities	343	6,198
Interest Rate Hedge [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives - contracts	8,539	6,179
Derivatives – interest rate hedge – non-current	8,539	6,179
Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	6,004	6,255
Derivatives - contracts	3,434	168
Total assets	291,166	274,765
Derivatives - liabilities	343	6,198
Cash and cash equivalents, including restricted cash	37,598	37,681
Short-term investments	219,776	209,434
Total current assets	260,808	247,283
Other assets	24,354	21,227
Total long-term assets	30,358	27,482
Fair Value Measurements, Recurring [Member] \| Foreign Exchange Contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives - contracts	3,434	168
Derivatives - liabilities	343	6,198
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	8,539	6,179
Money Market Funds [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	17,584	4,987
Restricted cash	114	119
Time Deposits and Certificates of Deposit [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	14,552	2,100
Available-for-sale investments		9,757
U.S. Agency Obligations [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	2,244
Available-for-sale investments	30,646	35,738
Bankers Acceptance Drafts [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	2,107	5,330
Asset-Backed Securities [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	38,947	36,990
U.S. Treasury Obligations [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	28,208	28,078
Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	32,057	13,750
Commercial Paper [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	13,283	30,475
Available-for-sale investments	32,057	13,750
Corporate Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	71,971	77,821
Corporate Obligations [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	4,373
Available-for-sale investments	71,971	77,821
Municipal Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	1,288	1,970
Municipal Bonds [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	1,288	1,970
Group Insurance Contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	6,004	6,255
Group Insurance Contracts [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	6,004	6,255
Israeli Pension Assets [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Pension assets	15,815	15,048
Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	17,698	5,106
Cash and cash equivalents, including restricted cash	17,698	5,106
Total current assets	17,698	5,106
Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) [Member] \| Money Market Funds [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	17,584	4,987
Restricted cash	114	119
Significant Other Observable Inputs (Level 2) [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	6,004	6,255
Derivatives - contracts	3,434	168
Total assets	273,468	269,659
Derivatives - liabilities	343	6,198
Cash and cash equivalents, including restricted cash	19,900	32,575
Short-term investments	219,776	209,434
Total current assets	243,110	242,177
Other assets	24,354	21,227
Total long-term assets	30,358	27,482
Significant Other Observable Inputs (Level 2) [Member] \| Fair Value Measurements, Recurring [Member] \| Foreign Exchange Contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives - contracts	3,434	168
Derivatives - liabilities	343	6,198
Significant Other Observable Inputs (Level 2) [Member] \| 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	8,539	6,179
Significant Other Observable Inputs (Level 2) [Member] \| Time Deposits and Certificates of Deposit [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	14,552	2,100
Available-for-sale investments		9,757
Significant Other Observable Inputs (Level 2) [Member] \| U.S. Agency Obligations [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	2,244
Available-for-sale investments	30,646	35,738
Significant Other Observable Inputs (Level 2) [Member] \| Bankers Acceptance Drafts [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	2,107	5,330
Significant Other Observable Inputs (Level 2) [Member] \| Asset-Backed Securities [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	38,947	36,990
Significant Other Observable Inputs (Level 2) [Member] \| U.S. Treasury Obligations [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	28,208	28,078
Significant Other Observable Inputs (Level 2) [Member] \| Commercial Paper [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	13,283	30,475
Available-for-sale investments	32,057	13,750
Significant Other Observable Inputs (Level 2) [Member] \| Corporate Obligations [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	4,373
Available-for-sale investments	71,971	77,821
Significant Other Observable Inputs (Level 2) [Member] \| Municipal Bonds [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	1,288	1,970
Significant Other Observable Inputs (Level 2) [Member] \| Group Insurance Contracts [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	6,004	6,255
Significant Other Observable Inputs (Level 2) [Member] \| Israeli Pension Assets [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Pension assets	$ 15,815	$ 15,048

Cash and cash equivalents including restricted cash fair value disclosure.

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Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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