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Asset Retirement Obligation (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Asset retirement obligation    
Balance at beginning of period $ 54,907 $ 54,727
Additional obligations 11,727 8,720
Estimated obligations assumed in acquisitions 9,343  
Accretion expense 1,856 1,803
Change in estimates (108) (1,638)
Payments (9,788) (4,351)
Foreign currency translation adjustments 1,820 (4,354)
Balance at end of period, net 69,757 54,907
Less: current portion of asset retirement obligations 9,837 9,821
Balance at end of period, excluding current portion $ 59,920 $ 45,086
Other Capitalized Property Plant and Equipment    
Asset Retirement Obligation [Line Items]    
Property and equipment useful life 5 years