Fair Value of Financial Assets and Liabilities (Detail) - USD ($) $ in Thousands		Dec. 31, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Available-for-sale securities		$ 621,231	$ 167,562
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Cash and cash equivalents		397,040	875,486
Fair value of Available-for-sale securities		621,231	167,562
Fair value of other current assets		18,266	15,767
Fair value of other non-current assets		27,951	41,310
Fair value of financial assets, Total		1,064,488	1,100,125
Fair value of other current liabilities		56,545	6,211
Fair value of other non-current liabilities		66,423	62,332
Fair value of financial liabilities, Total		122,968	68,543
Fair Value, Measurements, Recurring | Overnight Deposits
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Cash and cash equivalents		290,731	225,159
Fair Value, Measurements, Recurring | Money Market Instruments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Cash and cash equivalents		106,309	650,327
Fair Value, Measurements, Recurring | Nonqualified Deferred Compensation Plan Liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current liabilities		1,591	2,304
Fair value of other non-current liabilities		30,703	23,565
Fair Value, Measurements, Recurring | Forward Foreign Currency Exchange Contract, Liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current liabilities	[1]	2,008	12
Fair value of other non-current liabilities	[1]	3,057
Fair Value, Measurements, Recurring | Contingent Acquisition Consideration Payable
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current liabilities		52,946	3,895
Fair value of other non-current liabilities		32,663	38,767
Fair Value, Measurements, Recurring | Quoted Price In Active Markets For Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Cash and cash equivalents		290,731	225,159
Fair value of other non-current assets		18,056	30,811
Fair value of financial assets, Total		308,787	255,970
Fair value of other current liabilities		1,151	1,790
Fair value of other non-current liabilities		24,341	18,453
Fair value of financial liabilities, Total		25,492	20,243
Fair Value, Measurements, Recurring | Quoted Price In Active Markets For Identical Assets (Level 1) | Overnight Deposits
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Cash and cash equivalents		290,731	225,159
Fair Value, Measurements, Recurring | Quoted Price In Active Markets For Identical Assets (Level 1) | Nonqualified Deferred Compensation Plan Liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current liabilities		1,151	1,790
Fair value of other non-current liabilities		24,341	18,453
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Cash and cash equivalents		106,309	650,327
Fair value of Available-for-sale securities		621,231	167,562
Fair value of other current assets		18,266	13,381
Fair value of other non-current assets		9,895	10,499
Fair value of financial assets, Total		755,701	841,769
Fair value of other current liabilities		2,448	526
Fair value of other non-current liabilities		9,419	5,112
Fair value of financial liabilities, Total		11,867	5,638
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Money Market Instruments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Cash and cash equivalents		106,309	650,327
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Nonqualified Deferred Compensation Plan Liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current liabilities		440	514
Fair value of other non-current liabilities		6,362	5,112
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Forward Foreign Currency Exchange Contract, Liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current liabilities	[1]	2,008	12
Fair value of other non-current liabilities	[1]	3,057
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current assets			2,386
Fair value of financial assets, Total			2,386
Fair value of other current liabilities		52,946	3,895
Fair value of other non-current liabilities		32,663	38,767
Fair value of financial liabilities, Total		85,609	42,662
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Contingent Acquisition Consideration Payable
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current liabilities		52,946	3,895
Fair value of other non-current liabilities		32,663	38,767
Fair Value, Measurements, Recurring | Certificates of Deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Available-for-sale securities, current		56,951	54,174
Fair value of Available-for-sale securities, non-current		6,969	18,129
Fair Value, Measurements, Recurring | Certificates of Deposit | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Available-for-sale securities, current		56,951	54,174
Fair value of Available-for-sale securities, non-current		6,969	18,129
Fair Value, Measurements, Recurring | Corporate Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Available-for-sale securities, current		42,673	15,532
Fair value of Available-for-sale securities, non-current		315,240	79,604
Fair Value, Measurements, Recurring | Corporate Debt Securities | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Available-for-sale securities, current		42,673	15,532
Fair value of Available-for-sale securities, non-current		315,240	79,604
Fair Value, Measurements, Recurring | Commercial Paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Available-for-sale securities, current		12,733
Fair Value, Measurements, Recurring | Commercial Paper | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Available-for-sale securities, current		12,733
Fair Value, Measurements, Recurring | U.S. Government Agency Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Available-for-sale securities, current		83,222
Fair value of Available-for-sale securities, non-current		103,316
Fair Value, Measurements, Recurring | U.S. Government Agency Securities | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Available-for-sale securities, current		83,222
Fair value of Available-for-sale securities, non-current		103,316
Fair Value, Measurements, Recurring | Greek Government-Issued Bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Available-for-sale securities, non-current		127	123
Fair Value, Measurements, Recurring | Greek Government-Issued Bonds | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Available-for-sale securities, non-current		127	123
Fair Value, Measurements, Recurring | Nonqualified Deferred Compensation Plan Assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current assets		440	514
Fair value of other non-current assets		6,362	5,112
Fair Value, Measurements, Recurring | Nonqualified Deferred Compensation Plan Assets | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current assets		440	514
Fair value of other non-current assets		6,362	5,112
Fair Value, Measurements, Recurring | Forward Foreign Current Exchange Contract Assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current assets	[1]	10,478	10,513
Fair value of other non-current assets	[1]	3,533
Fair Value, Measurements, Recurring | Forward Foreign Current Exchange Contract Assets | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current assets	[1]	10,478	10,513
Fair value of other non-current assets	[1]	3,533
Fair Value, Measurements, Recurring | Restrictive Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current assets	[2]	7,348	2,354
Fair value of other non-current assets	[2]		5,387
Fair Value, Measurements, Recurring | Restrictive Investments | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current assets	[2]	7,348	2,354
Fair value of other non-current assets	[2]		5,387
Fair Value, Measurements, Recurring | Strategic Investment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other non-current assets	[3]	18,056	30,811
Fair Value, Measurements, Recurring | Strategic Investment | Quoted Price In Active Markets For Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other non-current assets	[3]	$ 18,056	30,811
Fair Value, Measurements, Recurring | Embedded Derivative
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current assets	[4]		2,386
Fair Value, Measurements, Recurring | Embedded Derivative | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current assets	[4]		$ 2,386

[1] See Note 12 to these Consolidated Financial Statements for further information regarding the derivative instruments.

[2] The restricted investments at December 31, 2015 and 2014 secure the Company’s irrevocable standby letter of credit obtained in connection with certain commercial agreements.

[3] The Company has investments in marketable equity securities measured using quoted prices in an active market that are considered strategic investments. See Note 7 to these Consolidated Financial Statements for additional discussion regarding the Company’s strategic investments.

[4] The embedded derivative represents the fair value of the conversion feature of a promissory note which may be settled in the issuer’s underlying shares.