Fair Value Measurements and Investments - Schedule of Valuation Methodology and Unobservable Inputs for Level 3 Assets and Liabilities Measured at Fair Value (Detail) $ in Thousands	9 Months Ended
	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)
Spinal Kinetics [Member] | Revenue Discount Rate
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Consideration transferred	$ 18,400
Spinal Kinetics [Member] | Revenue Discount Rate | Minimum [Member]
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Business combination contingent consideration liability measurement input	6.5
Spinal Kinetics [Member] | Revenue Discount Rate | Maximum [Member]
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Business combination contingent consideration liability measurement input	6.7
Spinal Kinetics [Member] | Payment Discount Rate | Minimum [Member]
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Business combination contingent consideration liability measurement input	3.9
Spinal Kinetics [Member] | Payment Discount Rate | Maximum [Member]
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Business combination contingent consideration liability measurement input	4.0
Spinal Kinetics [Member] | Projected Year of Achievement
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Business combination contingent consideration liability measurement period	2022
Spinal Kinetics [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Spinal Kinetics contingent consideration estimated fair value at January 1	$ 35,400	$ 42,700
Decrease in fair value recognized in acquisition-related amortization and remeasurement	(2,000)	(7,600)
Payment made	(15,000)
Spinal Kinetics contingent consideration estimated fair value at September 30	18,400	$ 35,100
Neo Medical [Member]
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Neo Medical Convertible Loan	$ 7,080
Fair value implied volatility	21.60%
Fair value discount rate	90.40%