Asset Retirement Obligation - Asset Retirement Obligation Rollforward (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Asset Retirement Obligation, Roll Forward Analysis1 [Roll Forward]
Obligations settled	$ (695)	$ 0
Asset retirement obligation [member]
Asset Retirement Obligation, Roll Forward Analysis1 [Roll Forward]
Balance at beginning of period	12,099	0
Acquisitions through business combination		12,089
Changes in estimates for asset retirement obligations	(236)
Obligations settled	(695)
Accretion expense	256
Effect of movements in foreign exchange rates	908	10
Balance at end of period	$ 12,332	$ 12,099

The increase in other provisions resulting from acquisitions through business combinations. [Refer: Business combinations [member]; Other provisions]

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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The increase (decrease) in other provisions resulting from foreign currency exchange rate changes on provisions measured in a currency different from the entity's presentation currency. [Refer: Other provisions]

+ References

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The increase in other provisions through adjustments arising from the passage of time. [Refer: Other provisions]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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The amount recognised for new other provisions. [Refer: Other provisions]

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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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The amount used (ie incurrent and charged against the provision) for other provisions. [Refer: Other provisions]

+ References

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+ References

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