Other Non-current Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Other Non-current Liabilities [Abstract]
Tax payable	$ 26,698	$ 25,958
Finance lease obligation - non-current	7,130	7,875
Share unit liabilities		2,865
Other non-current liabilities	11,029	10,075
Other non-current liabilities, Total	$ 44,857	$ 46,773