Fair Value of Financial Assets and Liabilities (Detail) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands		Jun. 30, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current assets		$ 8,739	$ 16,614
Fair value of other non-current assets		21,337	11,859
Fair value of financial assets, Total		30,076	28,473
Fair value of other current liabilities		78,534	55,971
Fair value of other non-current liabilities		89,094	165,449
Fair value of financial liabilities, Total		167,628	221,420
Contingent Acquisition Consideration
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current liabilities		76,466	53,648
Fair value of other non-current liabilities		57,674	135,318
NQDC Plan Liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current liabilities		2,068	2,323
Fair value of other non-current liabilities		31,420	30,131
Restricted Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current assets	[1]	7,721	15,647
Fair value of other non-current assets	[1]	6,889
Strategic Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other non-current assets	[2]	1,616
NQDC Plan Assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current assets		1,018	967
Fair value of other non-current assets		12,832	11,859
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		1,616	0
Fair value of financial assets, Total		1,616	0
Fair value of other current liabilities		1,050	1,356
Fair value of other non-current liabilities		18,588	18,272
Fair value of financial liabilities, Total		19,638	19,628
Quoted Price In Active Markets For Identical Assets (Level 1) | Contingent Acquisition Consideration
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
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		1,050	1,356
Fair value of other non-current liabilities		18,588	18,272
Quoted Price In Active Markets For Identical Assets (Level 1) | Restricted Investments
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
Quoted Price In Active Markets For Identical Assets (Level 1) | Strategic Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other non-current assets	[2]	1,616
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
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		8,739	16,614
Fair value of other non-current assets		19,721	11,859
Fair value of financial assets, Total		28,460	28,473
Fair value of other current liabilities		1,018	967
Fair value of other non-current liabilities		12,832	11,859
Fair value of financial liabilities, Total		13,850	12,826
Significant Other Observable Inputs (Level 2) | Contingent Acquisition Consideration
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
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		1,018	967
Fair value of other non-current liabilities		12,832	11,859
Significant Other Observable Inputs (Level 2) | Restricted Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current assets	[1]	7,721	15,647
Fair value of other non-current assets	[1]	6,889
Significant Other Observable Inputs (Level 2) | Strategic Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other non-current assets	[2]	0
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		1,018	967
Fair value of other non-current assets		12,832	11,859
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 of financial assets, Total		0	0
Fair value of other current liabilities		76,466	53,648
Fair value of other non-current liabilities		57,674	135,318
Fair value of financial liabilities, Total		134,140	188,966
Significant Unobservable Inputs (Level 3) | Contingent Acquisition Consideration
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current liabilities		76,466	53,648
Fair value of other non-current liabilities		57,674	135,318
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
Significant Unobservable Inputs (Level 3) | Restricted Investments
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
Significant Unobservable Inputs (Level 3) | Strategic Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other non-current assets	[2]	0
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

[1] The restricted investments at June 30, 2018 and December 31, 2017 secure the Company’s irrevocable standby letters of credit obtained in connection with certain commercial agreements.

[2] The Company has investments in marketable equity securities measured using quoted prices in an active market that are considered strategic investments and included in other assets on the Company’s Consolidated Balance Sheets.