Note 13 - Supplemental Cash Flow Information - Summary of Supplemental Non-cash Transaction and Nonmonetary Exchange Information (Details) - USD ($) $ in Thousands	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017
Supplemental Non-cash Transactions:
Capital expenditures incurred but not paid at September 30	$ 3,350	$ 5,591
Property acquired under capital leases		1,078
Additions to ARO asset	$ 752	$ 200

Amount of asset retirement obligations incurred during the period.

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Future cash outflow to pay for purchases of fixed assets that have occurred.

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