Note 5 - Derivative Instruments (Detail) - Derivative Instruments on the Consolidated Statements of Income (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012		Mar. 31, 2011
Natural gas contracts – loss reclassified from OCI into cost of goods sold for settlement of hedged item	$ 14		$ 3
Total gains on derivative instruments	2		10
Designated as Hedging Instrument [Member] | Natural Gas Contracts [Member]
Natural gas contracts – loss reclassified from OCI into cost of goods sold for settlement of hedged item	(1)		0
Designated as Hedging Instrument [Member] | Interest Rate Swap [Member]
Interest rate swaps – ineffectiveness recorded as an offset to interest expense	2		0
Not Designated as Hedging Instrument [Member] | Natural Gas Contracts [Member]
Natural gas contracts – fair value adjustments recorded in operating revenues (1)	4	[1]	11	[1]
Natural gas contracts – net gain fair value adjustments recorded in cost of goods sold (2)	(2)	[2]	(1)	[2]
Natural gas contracts – net loss fair value adjustments recorded in operation and maintenance expense	$ (1)		$ 0

[1] Associated with the fair value of existing derivative instruments at March 31, 2012 and 2011.

[2] Excludes losses recorded in cost of goods sold associated with weather derivatives of $14 million for the three months ended March 31, 2012 and gains of $3 million for the three months ended March 31, 2011.