Pledged cash deposits (Details Textual)	6 Months Ended
Jun. 30, 2015
Minimum [Member]
Cash and Cash Equivalents [Line Items]
Percentage Of Cash And Cash Equivalent Reserve Deposit Required	30.00%
Maximum [Member]
Cash and Cash Equivalents [Line Items]
Percentage Of Cash And Cash Equivalent Reserve Deposit Required	100.00%

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