Notes Payable - Additional Information (Detail) - USD ($)		1 Months Ended	3 Months Ended	6 Months Ended
	Apr. 17, 2014	Apr. 30, 2014	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Jul. 31, 2014
Line of Credit Facility [Line Items]
Grant date fair value of warrants granted as preferred stock warrant liability					$ 326,000
Loss on extinguishment of debt					(57,000)
IPO [Member] | Tranche 1 Loan [Member]
Line of Credit Facility [Line Items]
Exercise price of warrants granted						$ 7.92
Warrants to purchase common stock converted from warrants to purchase redeemable convertible preferred stock						37,878
2011 Modification Agreement [Member]
Line of Credit Facility [Line Items]
Borrowing capacity under the agreement	$ 5,000,000
Credit facility, Monthly repayment period				33 monthly installments
Outstanding borrowings, Monthly repayment amount	$ 152,000
Outstanding borrowings, Interest rate above prime lending rate	4.75%
Outstanding borrowings, Interest rate	8.00%
Outstanding borrowings, Effective annual interest rate	11.00%
Proceeds from (repayments of) lines of credit	$ (1,898,000)
Loss on extinguishment of debt		$ 36,000
Outstanding borrowings, Principal	1,667,000
Outstanding borrowings, Interest	6,000
Additional final payment	225,000
2011 Modification Agreement [Member] | Extinguishment of Debt [Member]
Line of Credit Facility [Line Items]
Debt discount			$ 10,000		$ 10,000
Fees paid to lenders			$ 47,000
2014 Credit Facility [Member]
Line of Credit Facility [Line Items]
Borrowing capacity under the agreement	20,000,000
Outstanding borrowings, Monthly repayment amount				$ 15,000,000
Outstanding borrowings, Effective annual interest rate				11.00%
Loan and Security Agreement date				Apr. 17, 2014
Credit facility, Final payment percent of amounts drawn under the facility				3.75%
Outstanding borrowings, Interest				$ 2,501,000
Additional final payment				$ 563,000
2014 Credit Facility [Member] | Promissory Notes [Member]
Line of Credit Facility [Line Items]
Debt instrument, Maturity date				Apr. 01, 2018
2014 Credit Facility [Member] | Tranche 1 Loan [Member]
Line of Credit Facility [Line Items]
Borrowing capacity under the agreement	15,000,000
Credit facility, Monthly repayment period				30 consecutive, equal monthly installments
Outstanding borrowings, Interest rate				8.25%
Last installment payment				Mar. 01, 2018
First date of principal repayment				Oct. 01, 2015
Warrants to purchase shares of redeemable convertible preferred stock		100,000
Exercise price of warrants granted		$ 3.00
Warrants, Date from which warrants or rights exercisable		Apr. 30, 2021
Grant date fair value of warrants granted as preferred stock warrant liability		$ 326,000
Debt discount		$ 290,000
2014 Credit Facility [Member] | Tranche 1 Loan [Member] | Promissory Notes [Member]
Line of Credit Facility [Line Items]
Proceeds from (repayments of) lines of credit	15,000,000
2014 Credit Facility [Member] | Tranche 2 Loan [Member]
Line of Credit Facility [Line Items]
Borrowing capacity under the agreement	$ 5,000,000