Quarterly report pursuant to Section 13 or 15(d)

Note 12 - Contingencies (Details Textual)

v3.19.2
Note 12 - Contingencies (Details Textual)
$ in Thousands
 3 Months Ended 6 Months Ended 12 Months Ended
Mar. 31, 2019
USD ($)
yr
Mar. 31, 2018
USD ($)
Jun. 30, 2019
USD ($)
Jun. 30, 2018
USD ($)
Dec. 31, 2018
USD ($)
Jun. 30, 2017
USD ($)
May 31, 2017
USD ($)
Jan. 27, 2017
USD ($)
Dec. 31, 2010
USD ($)
Escrow Deposit     $ 49,500   $ 49,500        
Loss Contingency Accrual, Ending Balance     49,500   49,500        
Additional Royalty Due to Disallowed Deductions               $ 4,700 $ 4,700
Bonds Posted to Appeal IBLA Decision               7,200  
Collateral for Bonds Posted Related to Appeal with IBLA               $ 6,900  
Royalties in Kind, Liability Reserve $ 2,200       2,100        
Royalties in Kind, Liability Reserve, Interest Asserted as Waived     700            
Incremental Payments for Royalties Related to Unbundling     $ 200 $ 300          
BSEE [Member]                  
Loss Contingency Accrual, Ending Balance 3,500       3,400        
Payment for Civil Penalty $ 0 $ 0              
Loss Contingency, Number of Claims Filed | yr 9                
Proposed Civil Penalties $ 7,700                
Apache Corporation [Member] | Judicial Ruling [Member]                  
Loss Contingency, Damages Payable to Other Party Except Prejudgment Interest, Attorney Fees, and Judgment Costs             $ 43,200    
Prejudgment Interest, Attorney Fees, and Judgment Costs Payable             $ 6,300    
Escrow Deposit           $ 49,500      
Loss Contingency Accrual, Ending Balance           $ 49,500      
Apache Corporation [Member] | Judicial Ruling [Member] | Other Noncurrent Assets [Member]                  
Escrow Deposit 49,500       49,500        
Apache Corporation [Member] | Judicial Ruling [Member] | Other Noncurrent Liabilities [Member]                  
Loss Contingency Accrual, Ending Balance $ 49,500       $ 49,500