Contingencies and Commitments (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Commitments And Contingencies Disclosure [Line Items]
Rental expenses	$ 2,546	$ 2,872	$ 2,823
Purchase Commitment, Remaining Minimum Amount Committed	$ 135,054	$ 147,139