XML 37 R23.htm IDEA: XBRL DOCUMENT
v3.21.2

Note 4 - Other Long-term Assets (Tables) | 9 Months Ended
--- | ---
Sep. 30, 2021
Notes Tables |
Schedule of Other Assets, Noncurrent [Table Text Block] |
|  | September 30, |  |  | December 31, |
|  | 2021 |  |  | 2020 |
Advanced coal royalties |  | $ | 6,705 |  |  | $ | 6,449 |
Other |  |  | 1,723 |  |  |  | 1,809 |
Total other assets |  | $ | 8,428 |  |  | $ | 8,258 |

X
- Definition Tabular disclosure of noncurrent assets. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.17) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
Name: | us-gaap_ScheduleOfOtherAssetsNoncurrentTextBlock
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_TableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration