Legal settlements (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Legal Settlements [Abstract]
Legal settlements, including amounts awarded in a dispute and charges/amounts paid out in a separate dispute.	$ 0	$ 1,798	$ 0
Legal settlement charge		6,500
LegalSettlementChargeForLegalFees		700
Payments for Legal Settlements		7,500
Gross legal settlement award		8,800
Legal settlements		$ 5,300