Asset Retirement Obligation - Asset Retirement Obligation Rollforward (Details) - Asset retirement obligation [member] $ in Thousands	12 Months Ended
Dec. 31, 2018 USD ($)
Asset Retirement Obligation, Roll Forward Analysis1 [Roll Forward]
Balance at beginning of period	$ 12,332
Changes in estimates for asset retirement obligations	843
Obligations settled	(300)
Asset retirement obligation accretion	270
Effect of movements in foreign exchange rates	(1,032)
Balance at end of period	$ 12,113

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]

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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The increase in other provisions through adjustments arising from the passage of time. [Refer: Other provisions]

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The amount recognised for new other provisions. [Refer: Other provisions]

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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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