Fair Value of Financial Instruments (Details) - A reconciliation of all liabilities measured at fair value on a recurring basis using significant unobservable inputs (Level 3) for the three months - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance	$ 67	$ 3,414
Issuances
Revaluation loss (gains) included in (loss) gain on revaluation of financial instruments, net	3	(182)
Settlements	(70)
Balance		3,232
Total gains included in other income and (expenses) attributable to liabilities still held as of March 31		182
Convertible preferred stock warrant liability [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance	67	134
Issuances
Revaluation loss (gains) included in (loss) gain on revaluation of financial instruments, net	3	(32)
Settlements	(70)
Balance		102
Total gains included in other income and (expenses) attributable to liabilities still held as of March 31		32
Convertible promissory notes embedded derivative liability [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance		3,280
Issuances
Revaluation loss (gains) included in (loss) gain on revaluation of financial instruments, net		(150)
Settlements
Balance		3,130
Total gains included in other income and (expenses) attributable to liabilities still held as of March 31		$ 150