Fair Value Measurements - Fair Value of Financial Assets and Liabilities (Detail) - USD ($)	Sep. 30, 2019	Dec. 31, 2018
Quoted Price in Active Markets For Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets remeasured	$ 0
Liabilities remeasured	0
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current assets		$ 9,951,000
Fair value of other non-current assets	18,196,000	16,220,000
Fair value of financial assets, Total	19,331,000	26,171,000
Fair value of other current liabilities	11,135,000	86,376,000
Fair value of other non-current liabilities	63,969,000	77,309,000
Fair value of financial liabilities, Total	75,104,000	163,685,000
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	1,135,000	425,000
Fair value of other non-current liabilities	15,039,000	30,426,000
Fair Value, Measurements, Recurring | Contingent consideration
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current liabilities	10,000,000	85,951,000
Fair value of other non-current liabilities	48,930,000	46,883,000
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 other current assets		0
Fair value of other non-current assets		942,000
Fair value of financial assets, Total		942,000
Fair value of other current liabilities		55,000
Fair value of other non-current liabilities		17,598,000
Fair value of financial liabilities, Total		17,653,000
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		55,000
Fair value of other non-current liabilities		17,598,000
Fair Value, Measurements, Recurring | Quoted Price in Active Markets For Identical Assets (Level 1) | Contingent consideration
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current liabilities		0
Fair value of other non-current liabilities		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 other current assets		9,951,000
Fair value of other non-current assets	18,196,000	15,278,000
Fair value of financial assets, Total	19,331,000	25,229,000
Fair value of other current liabilities	1,135,000	370,000
Fair value of other non-current liabilities	15,039,000	12,828,000
Fair value of financial liabilities, Total	16,174,000	13,198,000
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	1,135,000	370,000
Fair value of other non-current liabilities	15,039,000	12,828,000
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Contingent 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
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		0
Fair value of other non-current assets	0	0
Fair value of financial assets, Total	0	0
Fair value of other current liabilities	10,000,000	85,951,000
Fair value of other non-current liabilities	48,930,000	46,883,000
Fair value of financial liabilities, Total	58,930,000	132,834,000
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) | Contingent consideration
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current liabilities	10,000,000	85,951,000
Fair value of other non-current liabilities	48,930,000	46,883,000
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	1,135,000	370,000
Fair value of other non-current assets	15,039,000	12,828,000
Fair Value, Measurements, Recurring | NQDC 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
Fair value of other non-current assets		0
Fair Value, Measurements, Recurring | NQDC 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	1,135,000	370,000
Fair value of other non-current assets	15,039,000	12,828,000
Fair Value, Measurements, Recurring | NQDC 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 | Restricted Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other current assets		9,581,000
Fair value of other non-current assets	3,157,000	2,450,000
Fair Value, Measurements, Recurring | Restricted 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		0
Fair value of other non-current assets		0
Fair Value, Measurements, Recurring | Restricted 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		9,581,000
Fair value of other non-current assets	3,157,000	2,450,000
Fair Value, Measurements, Recurring | Restricted 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		0
Fair value of other non-current assets	$ 0	0
Fair Value, Measurements, Recurring | Strategic Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other non-current assets		942,000
Fair Value, Measurements, Recurring | Strategic 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 non-current assets		942,000
Fair Value, Measurements, Recurring | Strategic Investments | 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		0
Fair Value, Measurements, Recurring | Strategic Investments | 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		$ 0