Earnings per share (Details Textual) - shares	3 Months Ended
Sep. 30, 2017	Sep. 30, 2016
Earnings Per Share [Line Items]
Weighted Average Number of Shares Outstanding, Basic and Diluted	4,013,537	4,013,537

Average number of shares or units issued and outstanding that are used in calculating basic and diluted earnings per share (EPS).

No definition available.

Name:	us-gaap_WeightedAverageNumberOfShareOutstandingBasicAndDiluted
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration