Fair Value of Financial Assets and Liabilities (Detail) - USD ($) $ in Thousands		Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Available-for-sale securities		$ 954,058	$ 621,231
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Cash and cash equivalents		408,330	397,040
Fair value of Available-for-sale securities		954,058	621,231
Fair value of other current assets		17,929	18,266
Fair value of other non-current assets		21,379	27,951
Fair value of financial assets, Total		1,401,696	1,064,488
Fair value of other current liabilities		53,764	56,545
Fair value of other non-current liabilities		144,076	66,423
Fair value of financial liabilities, Total		197,840	122,968
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		235,571	290,731
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		172,759	106,309
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		2,236	1,591
Fair value of other non-current liabilities		26,424	30,703
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]	5,201	2,008
Fair value of other non-current liabilities	[1]	2,342	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		46,327	52,946
Fair value of other non-current liabilities		115,310	32,663
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		235,571	290,731
Fair value of Available-for-sale securities		0	0
Fair value of other current assets		0	0
Fair value of other non-current assets		4,064	18,056
Fair value of financial assets, Total		239,635	308,787
Fair value of other current liabilities		2,073	1,151
Fair value of other non-current liabilities		17,303	24,341
Fair value of financial liabilities, Total		19,376	25,492
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		235,571	290,731
Fair Value, Measurements, Recurring | Quoted Price In Active Markets For Identical Assets (Level 1) | Money Market Instruments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Cash and cash equivalents		0	0
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		2,073	1,151
Fair value of other non-current liabilities		17,303	24,341
Fair Value, Measurements, Recurring | Quoted Price In Active Markets For Identical Assets (Level 1) | 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]	0	0
Fair value of other non-current liabilities	[1]	0	0
Fair Value, Measurements, Recurring | Quoted Price In Active Markets For Identical Assets (Level 1) | Contingent Acquisition Consideration Payable
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current liabilities		0	0
Fair value of other non-current liabilities		0	0
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		172,759	106,309
Fair value of Available-for-sale securities		954,058	621,231
Fair value of other current assets		17,929	18,266
Fair value of other non-current assets		17,315	9,895
Fair value of financial assets, Total		1,162,061	755,701
Fair value of other current liabilities		5,364	2,448
Fair value of other non-current liabilities		11,463	9,419
Fair value of financial liabilities, Total		16,827	11,867
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Overnight Deposits
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Cash and cash equivalents		0	0
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		172,759	106,309
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		163	440
Fair value of other non-current liabilities		9,121	6,362
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]	5,201	2,008
Fair value of other non-current liabilities	[1]	2,342	3,057
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Contingent Acquisition Consideration Payable
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current liabilities		0	0
Fair value of other non-current liabilities		0	0
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 Cash and cash equivalents		0	0
Fair value of Available-for-sale securities		0	0
Fair value of other current assets		0	0
Fair value of other non-current assets		0	0
Fair value of financial assets, Total		0	0
Fair value of other current liabilities		46,327	52,946
Fair value of other non-current liabilities		115,310	32,663
Fair value of financial liabilities, Total		161,637	85,609
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Overnight Deposits
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Cash and cash equivalents		0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Money Market Instruments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Cash and cash equivalents		0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Nonqualified Deferred Compensation Plan Liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current liabilities		0	0
Fair value of other non-current liabilities		0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | 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]	0	0
Fair value of other non-current liabilities	[1]	0	0
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		46,327	52,946
Fair value of other non-current liabilities		115,310	32,663
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		2,800	56,951
Fair value of Available-for-sale securities, non-current			6,969
Fair Value, Measurements, Recurring | Certificates of Deposit | 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 Available-for-sale securities, current		0	0
Fair value of Available-for-sale securities, non-current			0
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		2,800	56,951
Fair value of Available-for-sale securities, non-current			6,969
Fair Value, Measurements, Recurring | Certificates of Deposit | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Available-for-sale securities, current		0	0
Fair value of Available-for-sale securities, non-current			0
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		193,974	42,673
Fair value of Available-for-sale securities, non-current		437,150	315,240
Fair Value, Measurements, Recurring | Corporate Debt Securities | 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 Available-for-sale securities, current		0	0
Fair value of Available-for-sale securities, non-current		0	0
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		193,974	42,673
Fair value of Available-for-sale securities, non-current		437,150	315,240
Fair Value, Measurements, Recurring | Corporate Debt Securities | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Available-for-sale securities, current		0	0
Fair value of Available-for-sale securities, non-current		0	0
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		16,075	12,733
Fair Value, Measurements, Recurring | Commercial Paper | 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 Available-for-sale securities, current		0	0
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		16,075	12,733
Fair Value, Measurements, Recurring | Commercial Paper | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Available-for-sale securities, current		0	0
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		168,499	83,222
Fair value of Available-for-sale securities, non-current		135,426	103,316
Fair Value, Measurements, Recurring | U.S. Government Agency Securities | 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 Available-for-sale securities, current		0	0
Fair value of Available-for-sale securities, non-current		0	0
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		168,499	83,222
Fair value of Available-for-sale securities, non-current		135,426	103,316
Fair Value, Measurements, Recurring | U.S. Government Agency Securities | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Available-for-sale securities, current		0	0
Fair value of Available-for-sale securities, non-current		0	0
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		134	127
Fair Value, Measurements, Recurring | Greek Government-Issued Bonds | 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 Available-for-sale securities, non-current		0	0
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		134	127
Fair Value, Measurements, Recurring | Greek Government-Issued Bonds | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Available-for-sale securities, non-current		0	0
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		163	440
Fair value of other non-current assets		9,121	6,362
Fair Value, Measurements, Recurring | Nonqualified Deferred Compensation Plan Assets | 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 current assets		0	0
Fair value of other non-current assets		0	0
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		163	440
Fair value of other non-current assets		9,121	6,362
Fair Value, Measurements, Recurring | Nonqualified Deferred Compensation Plan Assets | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current assets		0	0
Fair value of other non-current assets		0	0
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]	14,012	10,478
Fair value of other non-current assets	[1]	8,194	3,533
Fair Value, Measurements, Recurring | Forward Foreign Current Exchange Contract Assets | 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 current assets	[1]	0	0
Fair value of other non-current assets	[1]	0	0
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]	14,012	10,478
Fair value of other non-current assets	[1]	8,194	3,533
Fair Value, Measurements, Recurring | Forward Foreign Current Exchange Contract Assets | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current assets	[1]	0	0
Fair value of other non-current assets	[1]	0	0
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]	3,754	7,348
Fair Value, Measurements, Recurring | Restrictive Investments | 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 current assets	[2]	0	0
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]	3,754	7,348
Fair Value, Measurements, Recurring | Restrictive Investments | 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]	0	0
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]	4,064	18,056
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]	4,064	18,056
Fair Value, Measurements, Recurring | Strategic Investment | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other non-current assets	[3]	0	0
Fair Value, Measurements, Recurring | Strategic Investment | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other non-current assets	[3]	$ 0	$ 0

[1] See Note 11 to these Consolidated Financial Statements for further information regarding the derivative instruments.

[2] The restricted investments at December 31, 2016 and 2015 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 6 to these Consolidated Financial Statements for additional discussion regarding the Company’s strategic investments.