Debt Obligations - Scheduled Principal Payments on Outstanding Borrowings (Parenthetical) (Details) - USD ($)		1 Months Ended	2 Months Ended	12 Months Ended
	Jan. 31, 2018	Apr. 30, 2018	Mar. 31, 2018	Jan. 31, 2018	May 31, 2017
Debt Instrument [Line Items]
Line of credit facility maximum borrowing capacity	$ 50,000,000			$ 50,000,000
Line of credit facility, outstanding borrowings	50,000,000			$ 50,000,000
Debt instrument, covenant description				Based on the Company’s assessment, it is probable that it will be unable to comply with its financial covenants through January 31, 2019, and it may fail to comply with certain financial covenants as early as May 31, 2018, and as such it has classified all outstanding debt balances as of January 31, 2018 as a current liability
Note Purchase Agreement | Convertible Promissory Notes
Debt Instrument [Line Items]
Notes issued	0
Line of credit facility maximum borrowing capacity					$ 25,000,000
Note Purchase Agreement | Convertible Promissory Notes | Subsequent Event
Debt Instrument [Line Items]
Notes issued			$ 25,000,000
Line of credit facility, maturity month and year			2019-08
TriplePoint Credit Facility | Subsequent Event
Debt Instrument [Line Items]
Line of credit facility, maturity month and year		2019-08
Line of credit facility, outstanding borrowings		$ 50,000,000
SVB Credit Facility | Revolving Line of Credit
Debt Instrument [Line Items]
Line of credit facility maximum borrowing capacity	20,000,000			$ 20,000,000
Line of credit facility, outstanding borrowings	$ 19,000,000			$ 19,000,000
Line of credit facility expiration period				2018-05
SVB Credit Facility | Subsequent Event | Revolving Line of Credit
Debt Instrument [Line Items]
Line of credit facility maximum borrowing capacity		12,500,000
Non-formula SVB Credit Facility | Subsequent Event | Revolving Line of Credit
Debt Instrument [Line Items]
Line of credit facility, outstanding borrowings		$ 5,000,000
Line of credit facility expiration period		2018-05