Fair Value Measurements and Investments - Additional Information (Detail) - USD ($) $ in Millions			6 Months Ended
	Oct. 25, 2019	Apr. 30, 2018	Jun. 30, 2020
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Decrease in fair value of future net sales			$ 6.9
eNeura Inc [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Payments of restructured debt security	$ 4.0
Spinal Kinetics [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Milestone achievement period		5 years	12 months
Contingent consideration			$ 35.8
Spinal Kinetics [Member] | Other Current Liabilities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Contingent consideration			14.5
Spinal Kinetics [Member] | Other Long-term Liabilities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Contingent consideration			$ 21.3
Maximum [Member] | Spinal Kinetics [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Future milestone payments		$ 60.0
US Food And Drug Administration [Member] | Spinal Kinetics [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Future milestone payments		15.0
Revenue Milestone [Member] | Spinal Kinetics [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Future milestone payments		$ 45.0