Notes Payable - Additional Information (Detail)	1 Months Ended	3 Months Ended	12 Months Ended
	Apr. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2017 USD ($) Amendment $ / shares shares
Debt Instrument [Line Items]
Outstanding principal balance of loan		$ 6,094,000
Subsequent Event [Member] | SVB [Member] | Loan Agreement [Member]
Debt Instrument [Line Items]
Borrowing amount	$ 5,500,000
Repayment of remaining obligations	5,900,000
Amended Loan Agreement [Member]
Debt Instrument [Line Items]
Number of loan amendments | Amendment			2
Debt instrument, Effective interest rate description		interest on the borrowings under the Loan Agreement at a per annum rate equal to 8.54% plus the then effective one-month U.S. LIBOR rate.
Line of credit facility final payment, additional amount due			$ 312,500
Maturity date			Apr. 01, 2020
Outstanding principal balance of loan		$ 6,094,000
Warrants expiration term			5 years
Number of warrants issued | shares			208,002
Warrants exercise price for shares | $ / shares			$ 3.2454
Estimated fair value of warrants issued			$ 500,000
Loan, Covenant description		Pursuant to the Loan Agreement and the Amendments, the Company is bound during the term of the Loan Agreement and the Amendments by a variety of affirmative covenants, including, without limitation, certain information delivery requirements and notice requirements, and negative covenants, including, without limitation, restrictions on incurring certain additional indebtedness, making certain asset dispositions, entering into certain mergers, acquisitions or other business combination transactions or incurring any non-permitted lien or other encumbrance on the Company’s assets. Upon the occurrence of an event of default under the Loan Agreement and the Amendments (subject to cure periods for certain events of default), all amounts owed by the Company thereunder would begin to bear interest at a rate that is 5.0% higher than the rate that would otherwise be applicable and may be declared immediately due and payable by the Collateral Agent. In the event of default by the Company, the Lenders would be entitled to exercise their remedies thereunder, including the right to accelerate the debt, upon which the Company may be required to repay all amounts then outstanding under the Loan Agreement and the Amendments, which could harm the Company's financial condition. The Company was in compliance with all applicable covenants set forth in the Loan Agreement and the Amendments as of March 31, 2019 and December 31, 2018. The principal payments due under the Loan Agreement and the Amendments have been classified as a current liability at December 31, 2018 due to the considerations discussed in Note 1 and the assessment that the material adverse change clause under the Loan Agreement and the Amendments is not within the Company's control. The Company has not been notified of an event of default by the Lenders as of the date of the filing of this Form 10-Q.
Amended Loan Agreement [Member] | Subsequent Event [Member]
Debt Instrument [Line Items]
Repayment of remaining obligations	$ 5,900,000
Amended Loan Agreement [Member] | Extension of Maturity Date [Member]
Debt Instrument [Line Items]
Percentage of penalty for prepaying loan before maturity			0.50%
Amended Loan Agreement [Member] | Other Accrued Liabilities [Member]
Debt Instrument [Line Items]
Line of credit facility final payment accrued			$ 321,000
Amended Loan Agreement [Member] | LIBOR Rate [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Effective Percentage			8.54%