ASSET RETIREMENT OBLIGATIONS - Estimated Payments (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Estimated payments of asset retirement obligations:
2021	$ 6,411
2022	2,723
2023	2,570
2024	3,317
2025	4,601
Thereafter	210,330
Aggregate undiscounted asset retirement obligations	229,952
Effect of discounting	(102,054)	$ (102,900)
Total asset retirement obligations	127,898	137,514	$ 137,114
Less: current portion	(6,411)
Non-current asset retirement obligations	121,487	133,018
Surety bonds outstanding to performance of reclamation obligations	$ 171,100	$ 181,600

Undiscounted amount of estimated future payments of asset retirement obligations.

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- Definition

Amount necessary to reduce estimated payments of asset retirement obligations to present value.

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No definition available.

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- Definition

Amount of surety bonds that are available for the future payment of reclamation obligations.

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No definition available.

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- Definition

Amount of estimated payments of asset retirement obligations in the fifth fiscal year following the latest fiscal year.

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No definition available.

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Amount of estimated payments of asset retirement obligations in the fourth fiscal year following the latest fiscal year.

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No definition available.

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- Definition

Amount of estimated payments of asset retirement obligations in the next fiscal year following the latest fiscal year.

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No definition available.

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Amount of estimated payments of asset retirement obligations after the fifth fiscal year following the latest fiscal year.

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No definition available.

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- Definition

Amount of estimated payments of asset retirement obligations in the third fiscal year following the latest fiscal year.

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No definition available.

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Amount of estimated payments of asset retirement obligations in the second fiscal year following the latest fiscal year.

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- Definition

The carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849

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- Definition

Current portion of the carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees.

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Noncurrent portion of the carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees.

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