Fair Value Measurements and Investments - Additional Information (Detail) - USD ($) $ in Millions			3 Months Ended
	Oct. 25, 2019	Apr. 30, 2018	Mar. 31, 2020
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Decrease in fair value of future net sales			$ 9.0
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
Contingent consideration			33.7
Spinal Kinetics [Member] | Other Long-term Liabilities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Contingent consideration			$ 33.7
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