Note 13 - Subsequent Events (Details) T in Thousands, $ / T in Thousands, $ in Millions	Oct. 26, 2021 USD ($) T $ / T
2022 Domestic Sales Contracts
Subsequent Events
Average per ton \| $ / T	196
Amount of coal contracted to sell	1,670
Percentage of projected coal sales	54.00%
Projected production of coal (in tons)	3,100
Coronado Asset Purchase Agreement
Subsequent Events
Amount of aggregate cash purchase price \| $	$ 30

The cash outflow for purchases of and capital improvements on property, plant and equipment (capital expenditures), software, and other intangible assets.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3213-108585

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 50
-Section 30
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=123362884&loc=d3e9212-128498

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 50
-Section 30
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=123362884&loc=d3e9215-128498

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 50
-Section 25
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=123385561&loc=d3e9135-128495

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