Financing Arrangements - Additional Information (Details)		1 Months Ended						12 Months Ended
	Mar. 28, 2017 Installment $ / shares shares	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($) shares	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($) shares	Feb. 28, 2015 USD ($)	Nov. 30, 2014 USD ($) Installment	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	May 31, 2015 USD ($)
Debt Instrument [Line Items]
Proceeds from lines of credit										$ 1,900,000
Unamortized debt issuance costs written-off									$ 321,000
Lines of credit, repaid in full										1,900,000
Notes payable									$ 12,000,000
Weighted average interest rate								11.54%	11.00%
Interest expense on debt								$ 1,100,000	$ 1,200,000
Amortization of debt issuance costs								132,000	131,000	88,000
Net proceeds from Initial public offering excluding underwriting discounts and commissions			$ 32,400,000					32,426,000
Series B-1 Convertible Preferred Stock
Debt Instrument [Line Items]
Number of shares called by warrant | shares					173,862
The March 28, 2017 Preferred stock warrant | Series B-1 Convertible Preferred Stock
Debt Instrument [Line Items]
Number of shares called by warrant | shares	76,704		61,363
Class of warrant, exercise price | $ / shares	$ 5.8667
Maximum
Debt Instrument [Line Items]
Number of shares called by warrant | shares			84,000
Minimum
Debt Instrument [Line Items]
Net proceeds from Initial public offering excluding underwriting discounts and commissions			$ 25,000,000
2014 Line of Credit
Debt Instrument [Line Items]
Line of credit, outstanding borrowed amount						$ 1,000,000					$ 900,000
Debt instrument interest rate						4.75%
Debt instrument basis spread						1.50%
Lines of credit, repaid in full					$ 1,900,000
2014 Line of Credit | Prime Rate
Debt Instrument [Line Items]
Debt instrument variable interest rate						3.25%
2015 Term Note | Other Expense, Net
Debt Instrument [Line Items]
Unamortized debt issuance costs written-off		$ 300,000
Loss consisting of prepayment fees and miscellaneous fees		$ 200,000
Notes Payable | 2014 Line of Credit
Debt Instrument [Line Items]
Maximum borrowing capacity							$ 7,000,000
Notes Payable | 2014 Term Note
Debt Instrument [Line Items]
Maximum borrowing capacity							3,000,000
Line of credit, outstanding borrowed amount							3,000,000	0	0
Proceeds from lines of credit							$ 1,800,000
Debt instrument interest rate							5.75%
Debt instrument basis spread							2.50%
Debt instrument interest payment due end period							2015-10
Debt instrument number of periodic payment of principal and interest | Installment							24
Origination fees							$ 15,000
Facilities fees							70,000
Termination fees							$ 60,000
Interest expense recognized				$ 55,000
Unamortized debt issuance costs written-off				$ 77,000						$ 77,000
Notes Payable | 2014 Term Note | Prime Rate
Debt Instrument [Line Items]
Debt instrument variable interest rate							3.25%
Notes Payable | 2015 Term Note
Debt Instrument [Line Items]
Debt instrument number of periodic payment of principal and interest | Installment	36
Notes payable								$ 0	$ 11,700,000
Debt instrument maturity date	Oct. 31, 2020
Notes Payable | 2015 Term Note | Minimum
Debt Instrument [Line Items]
Debt instrument variable rate	11.00%
Notes Payable | 2015 Term Note | Three -Month LIBOR | Maximum
Debt Instrument [Line Items]
Debt instrument basis spread	7.50%
Notes Payable | 2015 Term Note | Three -Month LIBOR | Minimum
Debt Instrument [Line Items]
Debt instrument basis spread	2.50%