Summary of Common Stock Reserved for Future Issuance (Detail)	Sep. 30, 2018 shares
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Common stock reserved for future issuance	9,190,500
Exercise of Outstanding Stock Options, Vesting of RSUs, and Issuance of RSUs Vested but not Released
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Common stock reserved for future issuance	2,449,034
ESPP
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Common stock reserved for future issuance	293,888
Shares of Common Stock Available for Grant Under the 2011 Plan
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Common stock reserved for future issuance	672,223
Noncontrolling Interest in Bluehill ID AG
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Common stock reserved for future issuance	10,355
Warrants to Purchase Common Stock
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Common stock reserved for future issuance	765,000
Shares of Common Stock Issuable on Conversion of Series B Preferred Stock
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Common stock reserved for future issuance	5,000,000