Note 5 - Derivative Instruments (Details) - Derivative Instruments on the Condensed Consolidated Statements of Financial Position (USD $) In Millions, unless otherwise specified	Mar. 31, 2014		Dec. 31, 2013		Mar. 31, 2013
Designated as cash flow hedges and fair value hedges
Net amounts of assets and liabilities presented in our unaudited Condensed Consolidated Statements of Financial Position (3)	$ (82)
Current Natural Gas Contracts [Member] | Designated as Hedging Instrument [Member]
Designated as cash flow hedges and fair value hedges
Assets	2		3		3
Liabilities			(1)		(1)
Current Natural Gas Contracts [Member] | Not Designated as Hedging Instrument [Member]
Designated as cash flow hedges and fair value hedges
Assets	675	[1],[2]	691	[1],[2]	332
Liabilities	(703)	[1],[2]	(761)	[1],[2]	(327)
Current Interest Rate Swap Agreements [Member] | Designated as Hedging Instrument [Member]
Designated as cash flow hedges and fair value hedges
Assets		[1],[2]		[1],[2]	5
Liabilities		[1],[2]		[1],[2]
Long-Term Natural Gas Contracts [Member] | Designated as Hedging Instrument [Member]
Designated as cash flow hedges and fair value hedges
Assets	757	[1]	900	[1]	386	[1]
Liabilities	(801)	[1]	(982)	[1]	(376)	[1]
Gross amounts offset in our unaudited Condensed Consolidated Statements of Financial Position (2)	(619)	[2]	(781)	[2]	(275)	[2]
Gross amounts offset in our unaudited Condensed Consolidated Statements of Financial Position (2)	719	[2]	902	[2]	352	[2]
Long-Term Natural Gas Contracts [Member] | Not Designated as Hedging Instrument [Member]
Designated as cash flow hedges and fair value hedges
Assets	80	[1],[2]	206	[1],[2]	46
Liabilities	(98)	[1],[2]	(220)	[1],[2]	(48)
Designated as Hedging Instrument [Member]
Designated as cash flow hedges and fair value hedges
Assets	2	[1],[2]	3	[1],[2]	8
Liabilities		[1],[2]	(1)	[1],[2]	(1)
Net amounts of assets and liabilities presented in our unaudited Condensed Consolidated Statements of Financial Position (3)	138	[3]	119	[3]	111	[3]
Net amounts of assets and liabilities presented in our unaudited Condensed Consolidated Statements of Financial Position (3)	(82)	[3]	(80)	[3]	(24)	[3]
Not Designated as Hedging Instrument [Member]
Designated as cash flow hedges and fair value hedges
Assets	755	[1],[2]	897	[1],[2]	378
Liabilities	$ (801)	[1],[2]	$ (981)	[1],[2]	$ (375)

[1] 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.

[2] As required by the authoritative guidance related to derivatives and hedging, the gross amounts of recognized assets and liabilities above do not include cashcollateral held on deposit in broker margin accounts of $100 million as of March 31, 2014, $121 million as of December 31, 2013 and $77 million as of March 31, 2013. Cash collateral is included in the "Gross amounts offset in our unaudited Condensed Consolidated Statements of Financial Position" line of this table.

[3] At March 31, 2014, December 31, 2013 and March 31, 2013 we held letters of credit from counterparties that would offset, under master netting arrangements, aninsignificant portion of these assets.