Note 5 - Derivative Instruments (Details) - Derivative Instruments on the Condensed Consolidated Statements of Financial Position (USD $) In Millions, unless otherwise specified	Jun. 30, 2014		Dec. 31, 2013		Jun. 30, 2013
Designated as cash flow or fair value hedges
Net amounts of assets and liabilities presented in our unaudited Condensed Consolidated Statements of Financial Position (3)	$ (62)
Current Natural Gas Contracts [Member] | Designated as Hedging Instrument [Member]
Designated as cash flow or fair value hedges
Assets	2		3		2
Liabilities	(1)		(1)		(1)
Current Natural Gas Contracts [Member] | Not Designated as Hedging Instrument [Member]
Designated as cash flow or fair value hedges
Assets	702		691		456
Liabilities	(721)		(761)		(445)
Long-Term Natural Gas Contracts [Member] | Not Designated as Hedging Instrument [Member]
Designated as cash flow or fair value hedges
Assets	77		206		124
Liabilities	(89)		(220)		(139)
Long-Term Natural Gas Contracts [Member]
Designated as cash flow or fair value hedges
Assets	781	[1],[2]	900	[1],[2]	582	[1],[2]
Liabilities	(811)	[1],[2]	(982)	[1],[2]	(585)	[1],[2]
Gross amounts offset in our unaudited Condensed Consolidated Statements of Financial Position (2)	(667)	[2]	(781)	[2]	(452)	[2]
Gross amounts offset in our unaudited Condensed Consolidated Statements of Financial Position (2)	749	[2]	902	[2]	546	[2]
Designated as Hedging Instrument [Member]
Designated as cash flow or fair value hedges
Net amounts of assets and liabilities presented in our unaudited Condensed Consolidated Statements of Financial Position (3)	114	[3]	119	[3]	130	[3]
Net amounts of assets and liabilities presented in our unaudited Condensed Consolidated Statements of Financial Position (3)	(62)	[3]	(80)	[3]	(39)	[3]
Not Designated as Hedging Instrument [Member]
Designated as cash flow or fair value hedges
Assets	779		897		580
Liabilities	$ (810)		$ (981)		$ (584)

[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 cash collateral held on deposit in broker margin accounts of $82 million as of June 30, 2014, $121 million as of December 31, 2013 and $94 million as of June 30, 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 June 30, 2014, December 31, 2013 and June 30, 2013 we held letters of credit from counterparties that would offset, under master netting arrangements, an insignificant portion of these assets.