Fair Value of Financial Assets and Liabilities (Detail) - USD ($) $ in Thousands		Jun. 30, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Available-for-sale securities		$ 856,657	$ 968,651
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Cash and cash equivalents		46,275	250,164
Fair value of Available-for-sale securities		854,948	954,058
Fair value of other current assets		12,238	17,929
Fair value of other non-current assets		13,905	21,379
Fair value of financial assets, Total		927,366	1,243,530
Fair value of other current liabilities		67,572	53,764
Fair value of other non-current liabilities		158,596	144,076
Fair value of financial liabilities, Total		226,168	197,840
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		44,566	235,571
Fair Value, Measurements, Recurring | NQDC Plan Liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current liabilities		2,987	2,236
Fair value of other non-current liabilities		29,191	26,424
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]	9,492	5,201
Fair value of other non-current liabilities	[1]	6,506	2,342
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		55,093	46,327
Fair value of other non-current liabilities		122,899	115,310
Fair Value, Measurements, Recurring | Corporate Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Cash and cash equivalents		1,709	8,593
Fair value of Available-for-sale securities, current		252,696	193,974
Fair value of Available-for-sale securities, non-current		360,045	437,150
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		8,976	16,075
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 Cash and cash equivalents			6,000
Fair value of Available-for-sale securities, current		111,240	168,498
Fair value of Available-for-sale securities, non-current		121,822	135,427
Fair Value, Measurements, Recurring | NQDC Plan Assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current assets		661	163
Fair value of other non-current assets		11,347	9,121
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]	2,250	14,012
Fair value of other non-current assets	[1]	2,558	8,194
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]	9,327	3,754
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
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		169	134
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
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		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	4,064
Fair value of financial assets, Total		0	4,064
Fair value of other current liabilities		2,326	2,073
Fair value of other non-current liabilities		17,844	17,303
Fair value of financial liabilities, Total		20,170	19,376
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) | NQDC Plan Liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current liabilities		2,326	2,073
Fair value of other non-current liabilities		17,844	17,303
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 | Quoted Price In Active Markets For Identical Assets (Level 1) | Corporate Debt Securities
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, current		0	0
Fair value of Available-for-sale securities, non-current		0	0
Fair Value, Measurements, Recurring | Quoted Price In Active Markets For Identical Assets (Level 1) | Commercial Paper
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 | Quoted Price In Active Markets For Identical Assets (Level 1) | U.S. Government Agency Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Cash and cash equivalents			0
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 | Quoted Price In Active Markets For Identical Assets (Level 1) | NQDC Plan Assets
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 | Quoted Price In Active Markets For Identical Assets (Level 1) | 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]	0	0
Fair value of other non-current assets	[1]	0	0
Fair Value, Measurements, Recurring | Quoted Price In Active Markets For Identical Assets (Level 1) | Restrictive Investments
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 | Quoted Price In Active Markets For Identical Assets (Level 1) | Certificates of Deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Available-for-sale securities, current			0
Fair Value, Measurements, Recurring | Quoted Price In Active Markets For Identical Assets (Level 1) | 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		0	0
Fair Value, Measurements, Recurring | Quoted Price In Active Markets For Identical Assets (Level 1) | 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
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		46,275	250,164
Fair value of Available-for-sale securities		854,948	954,058
Fair value of other current assets		12,238	17,929
Fair value of other non-current assets		13,905	17,315
Fair value of financial assets, Total		927,366	1,239,466
Fair value of other current liabilities		10,153	5,364
Fair value of other non-current liabilities		17,853	11,463
Fair value of financial liabilities, Total		28,006	16,827
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		44,566	235,571
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | NQDC Plan Liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current liabilities		661	163
Fair value of other non-current liabilities		11,347	9,121
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]	9,492	5,201
Fair value of other non-current liabilities	[1]	6,506	2,342
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 Other Observable Inputs (Level 2) | Corporate Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Cash and cash equivalents		1,709	8,593
Fair value of Available-for-sale securities, current		252,696	193,974
Fair value of Available-for-sale securities, non-current		360,045	437,150
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Commercial Paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Available-for-sale securities, current		8,976	16,075
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | U.S. Government Agency Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Cash and cash equivalents			6,000
Fair value of Available-for-sale securities, current		111,240	168,498
Fair value of Available-for-sale securities, non-current		121,822	135,427
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | NQDC Plan Assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current assets		661	163
Fair value of other non-current assets		11,347	9,121
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | 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]	2,250	14,012
Fair value of other non-current assets	[1]	2,558	8,194
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Restrictive Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current assets	[2]	9,327	3,754
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | 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
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | 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		169	134
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Strategic Investment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other non-current assets	[3]		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		55,093	46,327
Fair value of other non-current liabilities		122,899	115,310
Fair value of financial liabilities, Total		177,992	161,637
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) | NQDC 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		55,093	46,327
Fair value of other non-current liabilities		122,899	115,310
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Corporate Debt Securities
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, current		0	0
Fair value of Available-for-sale securities, non-current		0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Commercial Paper
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 | Significant Unobservable Inputs (Level 3) | U.S. Government Agency Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Cash and cash equivalents			0
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 | Significant Unobservable Inputs (Level 3) | NQDC Plan Assets
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 | Significant Unobservable Inputs (Level 3) | 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]	0	0
Fair value of other non-current assets	[1]	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Restrictive Investments
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 | Significant Unobservable Inputs (Level 3) | Certificates of Deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Available-for-sale securities, current			0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | 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		$ 0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Strategic Investment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other non-current assets	[3]		$ 0

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

[2] The restricted investments at June 30, 2017 and December 31, 2016 secure the Company’s irrevocable standby letter of credit obtained in connection with certain commercial agreements.

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