Note 5 - Derivative Instruments (Detail) - Derivative Instruments on the Condensed Consolidated Statements of Financial Position (USD $) In Millions, unless otherwise specified	Mar. 31, 2012		Dec. 31, 2011		Mar. 31, 2011
Liability Instruments
Total	$ (46)	[1],[2]	$ 31	[1],[2]	$ 24	[1],[2]
Total	(46)	[1],[2]	31	[1],[2]	24	[1],[2]
Total derivative instruments	(46)	[1],[2]	31	[1],[2]	24	[1],[2]
Designated as Hedging Instrument [Member] | Current Natural Gas Contracts [Member]
Asset Instruments
Derivative Fair Value Of Derivative Asset	5	[1],[2]	9	[1],[2]	1	[1],[2]
Designated as Hedging Instrument [Member] | Noncurrent Interest Rate Swap [Member]
Asset Instruments
Derivative Fair Value Of Derivative Asset	9	[1],[2]	13	[1],[2]	0	[1],[2]
Designated as Hedging Instrument [Member] | Current Natural Gas Contracts [Member]
Liability Instruments
Derivative Fair Value Of Derivative Liability	(11)	[1],[2]	(12)	[1],[2]	(2)	[1],[2]
Designated as Hedging Instrument [Member] | Noncurrent Interest Rate Swap [Member]
Liability Instruments
Derivative Fair Value Of Derivative Liability	(11)	[1],[2]	(13)	[1],[2]	0	[1],[2]
Designated as Hedging Instrument [Member]
Liability Instruments
Total	(8)	[1],[2]	(3)	[1],[2]	(1)	[1],[2]
Total	(8)	[1],[2]	(3)	[1],[2]	(1)	[1],[2]
Total derivative instruments	(8)	[1],[2]	(3)	[1],[2]	(1)	[1],[2]
Not Designated as Hedging Instrument [Member] | Current Natural Gas Contracts [Member]
Asset Instruments
Derivative Fair Value Of Derivative Asset	683	[1],[2]	706	[1],[2]	333	[1],[2]
Not Designated as Hedging Instrument [Member] | Noncurrent Natural Gas Contracts [Member]
Asset Instruments
Derivative Fair Value Of Derivative Asset	82	[1],[2]	133	[1],[2]	77	[1],[2]
Not Designated as Hedging Instrument [Member] | Current Natural Gas Contracts [Member]
Liability Instruments
Derivative Fair Value Of Derivative Liability	(718)	[1],[2]	(689)	[1],[2]	(323)	[1],[2]
Not Designated as Hedging Instrument [Member] | Noncurrent Natural Gas Contracts [Member]
Liability Instruments
Derivative Fair Value Of Derivative Liability	(85)	[1],[2]	(116)	[1],[2]	(62)	[1],[2]
Not Designated as Hedging Instrument [Member]
Liability Instruments
Total	(38)	[1],[2]	34	[1],[2]	25	[1],[2]
Total	(38)	[1],[2]	34	[1],[2]	25	[1],[2]
Total derivative instruments	$ (38)	[1],[2]	$ 34	[1],[2]	$ 25	[1],[2]

[1] These amounts are netted within our unaudited Condensed Consolidated Statements of Financial Position for amounts which we have netting arrangements with the counterparties.

[2] As required by the authoritative guidance related to derivatives and hedging, the fair value amounts are presented on a gross basis. As a result, the amounts do not include cash collateral held on deposit in broker margin accounts of $209 million as of March 31, 2012, $147 million as of December 31, 2011 and $88 million as of March 31, 2011. Accordingly, these amounts will differ from the amounts presented on our unaudited Condensed Consolidated Statements of Financial Position and the fair value information presented for our derivative instruments in the recurring fair values table of Note 4.