Organization and Summary of Significant Accounting Policies - Additional Information (Detail)			1 Months Ended	12 Months Ended
	Jul. 31, 2016	May 25, 2016	Jul. 31, 2016	Dec. 31, 2018	Dec. 31, 2017 USD ($) Segment shares	Dec. 31, 2016 USD ($) shares	Dec. 31, 2015 USD ($) shares	Jan. 01, 2018 USD ($)	Jan. 01, 2017 USD ($)
Organization and Summary of Significant Accounting Policies [Line Items]
Reverse stock split, description					one-for-ten (1:10) reverse stock split
Reverse stock split, ratio		10
Maximum period for cash and highly liquid securities with original maturities					90 days or less
Minimum period for marketable securities classified as available-for-sale with original maturities					More than 90 days
Amount of letter of credit, description					The Company was required to maintain a letter of credit securing an amount equal to twelve months of the then current monthly installment of base rent for the original term of the lease for its facilities, which ended on August 31, 2017.
Restricted cash					$ 192,000	$ 3,311,000
Secured letter of credit for the extended lease term					$ 200,000
Renewal period for lease for lease beyond its expiration	16 months		16 months		5 years
Renewal lease agreement expiry date	Dec. 31, 2018		Dec. 31, 2018
Weighted average amortization period for capitalized patent costs					8 years
Research and development expense					$ 0	374,000	$ 230,000
Deferred contract costs					$ 10,500,000	$ 5,500,000
Common stock equivalents excluded from the calculation of diluted net income per share | shares					1,800,000	7,350	33,720
Likelihood threshold for recognition of uncertain tax position					50.00%
Unrecognized tax benefits					$ 0
U.S. federal corporate tax rate					35.00%
Number of business segment | Segment					1
Deferred revenue					$ 11,700,000	$ 3,018,000
Deferred contract costs					$ 10,502,000	$ 5,513,000
Stock Options and RSUs [Member]
Organization and Summary of Significant Accounting Policies [Line Items]
Estimated forfeiture rate of stock-based compensation						8.75%	8.75%
ASU No. 2016-09 [Member]
Organization and Summary of Significant Accounting Policies [Line Items]
Adjustment to beginning retained earnings due to adoption of new accounting standard									$ 100,000
ASU No. 2014-09 [Member] | Subsequent Event [Member]
Organization and Summary of Significant Accounting Policies [Line Items]
Adjustment to beginning retained earnings due to adoption of new accounting standard								$ 900,000
Deferred revenue								11,400,000
Deferred contract costs								$ 10,500,000
Scenario, Forecast [Member]
Organization and Summary of Significant Accounting Policies [Line Items]
U.S. federal corporate tax rate				21.00%
Patent application costs [Member]
Organization and Summary of Significant Accounting Policies [Line Items]
Estimated economic lives of the patents					20 years
Minimum [Member] | Equipment [Member]
Organization and Summary of Significant Accounting Policies [Line Items]
Estimated useful life of property and equipment					5 years
Minimum [Member] | All other property and equipment [Member]
Organization and Summary of Significant Accounting Policies [Line Items]
Estimated useful life of property and equipment					3 years
Maximum [Member] | Equipment [Member]
Organization and Summary of Significant Accounting Policies [Line Items]
Estimated useful life of property and equipment					10 years
Maximum [Member] | All other property and equipment [Member]
Organization and Summary of Significant Accounting Policies [Line Items]
Estimated useful life of property and equipment					5 years