Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Subsequent events (Details) - USD ($) $ in Thousands	Jun. 01, 2020	May 31, 2020	Aug. 08, 2019
Hercules Loan Agreement
Subsequent Event [Line Items]
Maximum borrowing capacity			$ 30,000
Hercules Loan Agreement \| Subsequent events
Subsequent Event [Line Items]
Maximum borrowing capacity	$ 40,000	$ 30,000
Hercules Loan Agreement, fourth advance \| Subsequent events
Subsequent Event [Line Items]
Maximum borrowing capacity	$ 10,000