Fair Value Measurements and Investments - Schedule of Reconciliation For Contingent Consideration Measured At Fair Value Using Significant Unobservable Inputs (Level 3) (Detail) - Fair Value, Inputs, Level 3 [Member] - Spinal Kinetics [Member] - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Spinal Kinetics contingent consideration estimated fair value at January 1	$ 42,700	$ 28,560
Increase (decrease) in fair value recognized in acquisition-related amortization and remeasurement	(7,600)	28,140
Payment made		(15,000)
Spinal Kinetics contingent consideration estimated fair value at September 30	$ 35,100	$ 41,700