Debt (Details)	1 Months Ended		3 Months Ended		9 Months Ended
	Dec. 31, 2014 USD ($) tranche installment	Jun. 30, 2013 USD ($) installment	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Dec. 01, 2014 USD ($)	Nov. 30, 2014 USD ($)	Mar. 31, 2014 USD ($)
Interest expense on debt
End-of-term payment					$ 59,000	$ 60,000
Term Loans
Debt
Maximum borrowing capacity	$ 15,000,000	$ 10,000,000
Amount not drawn									$ 5,000,000
Number of installments | installment	24
Period after which debt is repayable	24 months
Prepayment penalties for prepayment within one year of the loan origination (as a percent)	2.00%
Prepayment penalties for prepayment within two years of the loan origination (as a percent)	1.00%
Prepayment penalties for prepayment after two years of the loan origination (as a percent)	0.00%
Number of tranches | tranche	3
Cash paid for interest on debt	$ 14,000
End-of term payment	110,000
Amount of prepayment premium waived								$ 75,000
Amount of end of term payment			$ 237,500		237,500		$ 110,000	$ 225,000
Third-party fees paid	45,000
Debt and unpaid accrued end-of-term payment	5,003,000		5,062,000		5,062,000
Unamortized note discount	(80,000)		(60,000)		(60,000)
Net debt obligation	4,923,000		5,002,000		5,002,000
Future principal payments
2017			2,437,000		2,437,000
2018			2,563,000		2,563,000
Total			5,000,000		$ 5,000,000
End of term payment as a percentage of total outstanding principal balance					4.75%
Interest expense on debt
Nominal interest			64,000	$ 78,000	$ 189,000	230,000
Amortization of debt discount			7,000	16,000	20,000	48,000
End-of-term payment			21,000	20,000	60,000	60,000
Total			$ 92,000	$ 114,000	$ 269,000	$ 338,000
Term Loans | Term Loan Due 2017
Debt
Amount drawn down		$ 5,000,000
Number of installments | installment		30
Period after which debt is repayable		18 months
Interest rate (as a percent)		6.06%
Prepayment penalties for prepayment within one year of the loan origination (as a percent)		2.25%
Prepayment penalties for prepayment within two years of the loan origination (as a percent)		1.50%
Prepayment penalties for prepayment after two years of the loan origination (as a percent)		0.75%
Repayment of debt	5,000,000
Term Loans | Term Loan Tranche One
Debt
Maximum borrowing capacity	5,000,000
Amount drawn down	$ 5,000,000
Interest rate (as a percent)	5.00%
Term Loans | Term Loan Tranche Two
Debt
Maximum borrowing capacity	$ 5,000,000
Term Loans | Term Loan Tranche Three
Debt
Maximum borrowing capacity	$ 5,000,000