Balance sheet components - Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Reversal of provision for bad debt, net	$ 13	$ (61)	$ (577)
Allowance for Doubtful Accounts
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning Balance	(264)	(626)	(425)
Reversal of provision for bad debt, net	15	428	(577)
Write-offs, net of recoveries	(5)	(66)	376
Ending Balance	$ (254)	$ (264)	$ (626)

Total of the deductions in a given period to allowances and reserves, the valuation and qualifying accounts that are either netted against the cost of an asset (in order to value it at its carrying value) or that reflect a liability established to represent expected future costs, representing receivables written off as uncollectible and portions of the reserves utilized, respectively. This amount is netted against total of recoveries of amounts due the Entity that had previously been written off as uncollectible using allowances (the valuation accounts that are netted against the cost of an asset to value it at its carrying value) and total of reestablishments of reserves (liabilities established to represent expected future costs) that had previously been utilized.

No definition available.

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Namespace Prefix:	nptn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration