Note 8 - Equity (Details) - Reclassifications Out of Accumulated Other Comprehensive Loss - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Operation and maintenance expense		$ (209)	$ (211)	$ (458)	$ (500)
Interest expense (interest rate contracts)		(42)	(45)	(86)	(91)
Total before income tax		69	96	392	645
Income tax benefit		(25)	(37)	(143)	(240)
Cash flow hedges, net of income tax		44	60	249	356
Less noncontrolling Interest		(2)	(2)	(14)	(14)
Net of tax		42	58	235	342
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net of tax	[1]	(7)	(2)	(10)	1
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Cash Flow Hedges Including Portion Attributable to Noncontrolling Interest [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before income tax	[1]	$ (4)	2	$ (4)	6
Income tax benefit	[1]		(1)		(1)
Cash flow hedges, net of income tax	[1]	$ (4)	1	$ (4)	5
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net of tax	[1]	(3)	$ 1	(3)	$ 5
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Noncontrolling Interest [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Less noncontrolling Interest	[1]	(1)		(1)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Operation and maintenance expense	[1],[2]	$ (6)	$ (6)	$ (11)	$ (8)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment, Net Prior Service Attributable to Parent [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Operation and maintenance expense	[1],[2]		1		1
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before income tax	[1]	$ (6)	(5)	$ (11)	(7)
Income tax benefit	[1]	2	2	4	3
Net of tax	[1]	(4)	(3)	(7)	(4)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Natural Gas Derivatives [Member] | Accumulated Net Gain (Loss) from Cash Flow Hedges Including Portion Attributable to Noncontrolling Interest [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Cost of goods sold (natural gas contracts)	[1]	(3)	$ 2	(4)	5
Operation and maintenance expense	[1]	$ (1)		(1)	$ 1
Reclassification out of Accumulated Other Comprehensive Income [Member] | Interest Rate Contract [Member] | Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest expense (interest rate contracts)	[1]			$ 1

[1] Amounts in parentheses indicate debits, or reductions, to our net income and credits to accumulated other comprehensive loss. Except for retirement benefit plan amounts, the net income impacts are immediate.

[2] Amortization of these accumulated other comprehensive loss components is included in the computation of net periodic benefit cost. See Note 6 for additional details about net periodic benefit cost.