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Revenue - Additional Information (Detail)		1 Months Ended	3 Months Ended
Revenue - Additional Information (Detail)	Aug. 31, 2016	Dec. 31, 2014 USD ($) Installment	Mar. 31, 2019 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2018 USD ($)
Revenues [Line Items]
Distribution fees			$ 20,284,000	$ 26,190,000
Long-term trade receivables			$ 400,000		$ 400,000
Long-term trade credit maintenance services term			1 year
Allowance for doubtful accounts			$ 0		$ 0
Deferred revenue, recognized			7,900,000	22,200,000
Company recognized revenue from performance obligations satisfied in the prior period			$ 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