Fair Value Measurements - Fair Value of Financial Assets and Liabilities (Detail) - USD ($)	Jun. 30, 2020	Dec. 31, 2019
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 non-current assets	21,785,000	$ 19,456,000
Fair value of financial assets, Total	22,780,000	20,633,000
Fair value of other non-current liabilities	67,453,000	67,081,000
Fair value of financial liabilities, Total	68,448,000	68,258,000
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	995,000	1,177,000
Fair value of other non-current liabilities	17,237,000	16,288,000
Fair Value, Measurements, Recurring | Contingent consideration
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of other non-current liabilities	50,216,000	50,793,000
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 non-current assets	21,785,000	19,456,000
Fair value of financial assets, Total	22,780,000	20,633,000
Fair value of other non-current liabilities	17,237,000	16,288,000
Fair value of financial liabilities, Total	18,232,000	17,465,000
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	995,000	1,177,000
Fair value of other non-current liabilities	17,237,000	16,288,000
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 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 non-current assets	0	0
Fair value of financial assets, Total	0	0
Fair value of other non-current liabilities	50,216,000	50,793,000
Fair value of financial liabilities, Total	50,216,000	50,793,000
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 non-current liabilities	50,216,000	50,793,000
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	995,000	1,177,000
Fair value of other non-current assets	17,237,000	16,288,000
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	995,000	1,177,000
Fair value of other non-current assets	17,237,000	16,288,000
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 non-current assets	4,548,000	3,168,000
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 non-current assets	4,548,000	3,168,000
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 non-current assets	$ 0	$ 0