Revenue - Additional Information (Detail)		1 Months Ended	3 Months Ended		6 Months Ended
	Aug. 31, 2016	Dec. 31, 2014 USD ($) Installment	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)
Revenues [Line Items]
Distribution fees			$ 30,167,000	$ 16,443,000	$ 50,451,000	$ 42,633,000
Long-term trade receivables			400,000		$ 400,000		$ 400,000
Long-term trade credit maintenance services term					1 year
Allowances for doubtful accounts			0		$ 0		$ 0
Deferred revenue, recognized			3,900,000	6,800,000	17,400,000	17,900,000
Company recognized revenue from performance obligations satisfied in the prior period			0		$ 900,000
Minimum
Revenues [Line Items]
Expected long-term trade receivables collection period					3 years
Maximum
Revenues [Line Items]
Expected long-term trade receivables collection period					4 years
Itochu Corporation Agreement
Revenues [Line Items]
Number of installments | Installment		3
Remaining term of distribution agreement	8 years 6 months
Itochu Corporation Agreement | Distribution Rights
Revenues [Line Items]
Distribution fees		$ 4,000,000	$ 100,000	$ 100,000	$ 200,000	$ 200,000