Note 11 - Other Comprehensive Loss ("OCL") - Components of AOCL (Details) - Reclassification out of Accumulated Other Comprehensive Income [Member] - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2017
Commodity Contract [Member]
Other comprehensive income (loss), reclassification adjustment from AOCI on derivatives, net of tax	$ 905	$ 1,639
Commodity Contract [Member] | Fuel Expense [Member]
Other comprehensive income (loss), reclassification adjustment from AOCI on derivatives, before tax	1,472	2,665
Commodity Contract [Member] | Income Tax Expense [Member]
Other comprehensive income (loss), reclassification adjustment from AOCI on derivatives, before tax	(567)	(1,026)
Interest Rate Swap [Member] | Interest Expense [Member]
Other comprehensive income (loss), reclassification adjustment from AOCI on derivatives, before tax	118	249
Interest Rate Cap [Member]
Other comprehensive income (loss), reclassification adjustment from AOCI on derivatives, before tax	73	153
Interest Rate Cap [Member] | Income Tax Expense [Member]
Other comprehensive income (loss), reclassification adjustment from AOCI on derivatives, before tax	$ (45)	$ (96)