Note 17 - Supplemental Cash Flow Information - Summary of Supplemental Non-cash Transaction and Nonmonetary Exchange Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Supplemental Non-cash Transactions:
Capital expenditures incurred but not paid at December 31	$ 5,092	$ 3,508	$ 11,600
Property acquired under capital leases	1,078		20
Additions to ARO asset	228	159	254
Note receivable on sale of asset			2,650
Property, Plant and Equipment [Member]
Nonmonetary Exchanges:
Property, plant and equipment			710
Deferred Revenue [Member]
Nonmonetary Exchanges:
Property, plant and equipment			(2,310)
Prepaid Expenses [Member]
Nonmonetary Exchanges:
Property, plant and equipment			1,600
IRUs Received [Member]
Nonmonetary Exchanges:
Property, plant and equipment			2,765
IRUs Relinquished [Member]
Nonmonetary Exchanges:
Property, plant and equipment			(2,765)
Noncontrolling Interest [Member]
Supplemental Non-cash Transactions:
Assets contributed to joint venture by noncontrolling interest			$ 922