Borrowings - Western Alliance Bank Term Loan (Details) $ in Thousands			12 Months Ended
	Sep. 29, 2017 USD ($) installment	Jul. 07, 2016 USD ($) installment	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Sep. 30, 2017	Feb. 28, 2017
Debt Instrument [Line Items]
Amortization of debt discount			$ 82	$ 646	$ 504
Unamortized debt discount			200
Western Alliance Bank Term Loan [Member]
Debt Instrument [Line Items]
Facility fee		$ 150
Debt instrument diligence fee		25
Debt Instrument additional fee liability	$ 125	$ 10
Debt instrument, interest rate spread above otherwise applicable interest rate (as a percent)		5.00%
Debt instrument, covenant, maximum quarterly revenue negative deviation from projection (as a percent)	25.00%
Amortization of debt discount			82
Unamortized debt discount			$ 200
Secured Debt [Member] | Western Alliance Bank Term Loan [Member]
Debt Instrument [Line Items]
Debt instrument, face amount		$ 18,000
Debt instrument, interest rate (as a percent)			4.50%			5.00%
Borrowings mature date		Jun. 30, 2019
Debt instrument, description of payment terms	Under the Agreement, we will make interest-only payments on the Term Loan from October 10, 2017 and on the 10th calendar day of each month thereafter, and will make principal and interest payments in 36 equal installments beginning on October 10, 2018, and on the 10th calendar day of each month thereafter, until the maturity date of the Term Loan.	Prior to the Amendment, we made interest-only payments on the Term Loan from July 2016 through September 2016 and began making interest payments and principal payments in 33 equal monthly installments starting October 2016.
Number of monthly installments | installment	36	33
Unrestricted cash deposit to indebtedness ratio	1.25	1.50					1.00
Debt instrument, covenant, maximum cash held at a financial institution as percentage of term loan outstanding (as a percent)		100.00%
Revolving Credit Facility [Member] | Western Alliance Bank Term Loan [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 5,000	$ 2,000
Line of credit facility, maximum borrowing capacity as a percentage of eligible accounts receivable		80.00%
Debt instrument, interest rate (as a percent)			4.75%			4.75%
Borrowings mature date		Jul. 31, 2018
Prime Rate [Member] | Secured Debt [Member] | Western Alliance Bank Term Loan [Member]
Debt Instrument [Line Items]
Debt instrument, description of variable rate basis	The Term Loan bears interest at a rate per annum equal to the greater of the prime rate or 3.5%	Prior to the Amendment (as defined below), the Term Loan bore interest at a rate per annum equal to the greater of the prime rate or 3.5%
Debt instrument, prime rate, minimum (as a percent)	3.50%	3.50%
Debt instrument, basis spread on variable rate (as a percent)		0.75%
Prime Rate [Member] | Revolving Credit Facility [Member] | Western Alliance Bank Term Loan [Member]
Debt Instrument [Line Items]
Debt instrument, description of variable rate basis	The Line of Credit bears interest at a rate per annum equal to the greater of the prime rate or 3.5%	Prior to the Amendment, the Line of Credit bore interest at a rate per annum equal to the greater of the prime rate or 3.5%
Debt instrument, prime rate, minimum (as a percent)	3.50%	3.50%
Debt instrument, basis spread on variable rate (as a percent)	0.25%	0.50%