Stock issuance and stock repurchase program (Details Textual) - shares shares in Thousands	May 23, 2016	Dec. 16, 2014
Stock Issuance and Stock Repurchase Program [Abstract]
Stock Repurchase Program, Number of Shares Authorized to be Repurchased	20,000	20,000

The number of shares authorized to be repurchased by an entity's Board of Directors under a stock repurchase plan.

No definition available.

Name:	us-gaap_StockRepurchaseProgramNumberOfSharesAuthorizedToBeRepurchased
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant