Lines of credit (Details Textual)	Dec. 31, 2016
Line of Credit Facility [Line Items]
Debt Covenant Percentage Of Total Net Assets	20.00%

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

Name:	us-gaap_LineOfCreditFacilityLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration