Note 10 - Commitments and Contingencies Other Contingencies (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Loss Contingencies
Balance at December 31,	$ 16,000,000	$ 22,000,000
Additions	6,000,000	20,000,000
Expenditures	(16,000,000)	(26,000,000)
Balance at December 31,	6,000,000	16,000,000	$ 22,000,000
Fuel Spill Remediation Site Two
Loss Contingencies
Balance at December 31,	10,000,000	16,000,000
Additions	1,000,000	19,000,000
Expenditures	(11,000,000)	(25,000,000)
Balance at December 31,	0	10,000,000	16,000,000
Environmental Liability Insurance Deductible	1,000,000
Environmental Liabilities Insurance Coverage Limit	25,000,000
Insurance Settlements Receivable	0	0
Environmental Remediation Expense	93,000,000
Accrual for Environmental Loss Contingencies, Period Increase (Decrease)	68,000,000
Insurance proceeds from environmental expenditures	0	0	0
Other Liabilities
Loss Contingencies
Balance at December 31,	6,000,000	6,000,000
Additions	5,000,000	1,000,000
Expenditures	(5,000,000)	(1,000,000)
Balance at December 31,	$ 6,000,000	$ 6,000,000	$ 6,000,000