Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Aug. 31, 2016	Oct. 31, 2015
Significant Accounting Policies [Line Items]
Restricted cash	$ 1,143,000	$ 943,000
Allowances for doubtful accounts	0	0
Inventory lower of cost and market adjustment	1,939,000	2,578,000	$ 598,000
Impairment loss recognized	0	0	$ 0
Deferred offering costs	0	0
Wrote off deferred offering costs		2,900,000
Distribution fee reclassified to deferred revenue	10,433,000	5,961,000
Reserve for deferred costs of revenue	$ 0	0
Excise tax on medical devices	2.30%
Deferred commission	$ 2,600,000	799,000
Penalties and interest related to income taxes	0
Operating leases future minimum payments due	$ 2,892,000
Itochu Corporation Agreement
Significant Accounting Policies [Line Items]
Remaining term of distribution agreement	8 years 6 months
Asset Retirement Obligation
Significant Accounting Policies [Line Items]
Asset retirement obligation	$ 294,000				$ 250,000
Accretion expenses	$ 36,000	8,000
Software
Significant Accounting Policies [Line Items]
Property and equipment, useful life	3 years
License Cost
Significant Accounting Policies [Line Items]
Estimated useful life	3 years
Distribution Rights
Significant Accounting Policies [Line Items]
Distribution fee reclassified to deferred revenue	$ 3,822,000
Distribution Rights | Itochu Corporation Agreement
Significant Accounting Policies [Line Items]
Distribution fee reclassified to deferred revenue	$ 4,000,000			$ 4,000,000
Minimum
Significant Accounting Policies [Line Items]
Property and equipment, useful life	2 years
Minimum | Patents
Significant Accounting Policies [Line Items]
Estimated useful life	5 years
Maximum
Significant Accounting Policies [Line Items]
Property and equipment, useful life	15 years
Maximum | Patents
Significant Accounting Policies [Line Items]
Estimated useful life	7 years
Irrevocable Standby Letters of Credit
Significant Accounting Policies [Line Items]
Letters of credit drawn, amount	$ 0	0
Collateral for Letters of Credit
Significant Accounting Policies [Line Items]
Restricted cash	900,000	$ 900,000
Collateral For Credit Card
Significant Accounting Policies [Line Items]
Restricted cash	$ 200,000