Note 6 - Employee Benefit Plans (Details) - Net Periodic Benefit Costs Not Yet Recognized (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Net Regulatory Assets [Member] | Pension Plan [Member]
Note 6 - Employee Benefit Plans (Details) - Net Periodic Benefit Costs Not Yet Recognized [Line Items]
Net loss	$ 76	$ 61
Total	76	61
Net Regulatory Assets [Member] | Other Postretirement Benefit Plan [Member]
Note 6 - Employee Benefit Plans (Details) - Net Periodic Benefit Costs Not Yet Recognized [Line Items]
Prior service credit	(18)	(20)
Net loss	57	60
Total	39	40
Accumulated AOCI [Member] | Pension Plan [Member]
Note 6 - Employee Benefit Plans (Details) - Net Periodic Benefit Costs Not Yet Recognized [Line Items]
Prior service credit	(6)	(9)
Net loss	307	210
Total	301	201
Accumulated AOCI [Member] | Other Postretirement Benefit Plan [Member]
Note 6 - Employee Benefit Plans (Details) - Net Periodic Benefit Costs Not Yet Recognized [Line Items]
Net loss	36	30
Total	36	30
Total Net Regulatory Assets And AOCI [Member] | Pension Plan [Member]
Note 6 - Employee Benefit Plans (Details) - Net Periodic Benefit Costs Not Yet Recognized [Line Items]
Prior service credit	(6)	(9)
Net loss	383	271
Total	377	262
Total Net Regulatory Assets And AOCI [Member] | Other Postretirement Benefit Plan [Member]
Note 6 - Employee Benefit Plans (Details) - Net Periodic Benefit Costs Not Yet Recognized [Line Items]
Prior service credit	(18)	(20)
Net loss	93	90
Total	$ 75	$ 70