Other Non-current Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Other Non-current Liabilities [Abstract]
Tax payable	$ 21,604	$ 25,958
Finance lease obligation	8,738	7,875
Share unit liabilities		2,865
Other non-current liabilities	9,094	10,075
Other non-current liabilities, Total	$ 39,436	$ 46,773