Fair Value of Financial Instruments - Additional Information (Detail)	Sep. 30, 2019	Sep. 24, 2019	Jun. 30, 2019	Sep. 30, 2018
0.25% Convertible Notes
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt instrument, interest rate	0.25%		0.25%	0.25%
0.50% Finisar Convertible Notes
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt instrument, interest rate	0.50%	0.50%