Note 6 - Derivative Instruments (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2014
Note 6 - Derivative Instruments (Details) [Line Items]
Cash Flow Hedge Derivative Instrument Assets at Fair Value	$ 1.5	$ 1.5
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	0.3	0.6
Gain (Loss) on Cash Flow Hedge Ineffectiveness, Net		0.1
Gain (Loss) from Components Excluded from Assessment of Cash Flow Hedge Effectiveness, Net		0.1
Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months		$ 0.6
Gallons of Diesel [Member] | Fuel Requirements 2014 [Member]
Note 6 - Derivative Instruments (Details) [Line Items]
Derivative, Number of Instruments Held	6,800,000	6,800,000
Percent of Projected Fuel Requirements		24.80%
Fuel Requirements 2015 [Member] | Gallons of Diesel [Member]
Note 6 - Derivative Instruments (Details) [Line Items]
Derivative, Number of Instruments Held	11,000,000	11,000,000
Percent of Projected Fuel Requirements		20.00%
Fuel Requirements 2016 [Member] | Gallons of Diesel [Member]
Note 6 - Derivative Instruments (Details) [Line Items]
Derivative, Number of Instruments Held	4,500,000	4,500,000
Percent of Projected Fuel Requirements		8.20%