Note 13 - Supplemental Cash Flow Information - Summary of Supplemental Non-cash Transaction and Nonmonetary Exchange Information (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Supplemental Non-cash Transactions:
Capital expenditures incurred but not paid at June 30	$ 3,520	$ 1,506
Property acquired under capital leases		1,078
Additions to ARO asset	$ 708	$ 186