Note 4 - Derivative Instruments (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2013		Jun. 30, 2012		Dec. 31, 2012		Dec. 31, 2011
Note 4 - Derivative Instruments (Details) [Line Items]
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	$ 39	[1],[2]	$ 66	[1],[2]	$ 39	[1],[2]	$ 110	[1],[2]
Increase (Decrease) in Risk Management Assets and Liabilities	(14)		(18)
Collateral Already Posted, Aggregate Fair Value	94		137		69		147
Price Risk Cash Flow Hedge Unrealized Gain (Loss) to be Reclassified During Next 12 Months	1
Less Than Two Years [Member] | Natural Gas [Member]
Note 4 - Derivative Instruments (Details) [Line Items]
Percent Of Derivative Contracts	98.00%
ExpiringIn Two To Six Years [Member] | Natural Gas [Member]
Note 4 - Derivative Instruments (Details) [Line Items]
Percent Of Derivative Contracts	2.00%
Weather Derivatives [Member]
Note 4 - Derivative Instruments (Details) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	$ (3)		$ 14
Minimum [Member]
Note 4 - Derivative Instruments (Details) [Line Items]
Natural Gas Derivative Term	2
Maximum [Member]
Note 4 - Derivative Instruments (Details) [Line Items]
Natural Gas Derivative Term	6

[1] As required by the authoritative guidance related to derivatives and hedging, the gross amounts of recognized assets and liabilities above do not include cash collateral held on deposit in broker margin accounts of $94 million as of June 30, 2013, $69 million as of December 31, 2012, $137 million as of June 30, 2012 and $147 million as of December 31, 2011. Cash collateral is included in the "Gross amounts offset in our unaudited Condensed Consolidated Statements of Financial Position" line of this table.

[2] The gross amounts of recognized assets and liabilities are netted within our unaudited Condensed Consolidated Statements of Financial Position to the extent that we have netting arrangements with the counterparties.