Note 4 - Derivative Instruments (Details) - Derivative Instruments on the Consolidated Statements of Income (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2013		Jun. 30, 2012		Jun. 30, 2013		Jun. 30, 2012
Not designated as hedges
Total (losses) gains on derivative instruments	$ 22		$ 16		$ (5)		$ 18
Other Comprehensive Income (Loss) [Member] | Cash Flow Hedging [Member]
Designated as cash flow hedges
Natural gas contracts – loss recognized in OCI (effective portion)			(1)
Cash Flow Hedging [Member] | Cost of Sales [Member]
Designated as cash flow hedges
Natural gas contracts - gain reclassified from OCI	1		3		1		4
Cash Flow Hedging [Member] | Operating Expense [Member]
Designated as cash flow hedges
Natural gas contracts - gain reclassified from OCI			1				1
Cash Flow Hedging [Member] | Interest Expense [Member]
Designated as cash flow hedges
Interest rate swaps - ineffectiveness recorded as an offset to interest expense			(1)		(3)		(3)
Fair Value Hedging [Member] | Cost of Sales [Member]
Not designated as hedges
Natural gas contracts - net value adjustments	(1)	[1]	(1)	[1]	(1)	[1]	(3)	[1]
Fair Value Hedging [Member] | Sales [Member]
Not designated as hedges
Natural gas contracts - net value adjustments	$ 22	[2]	$ 15	[2]	$ (2)	[2]	$ 19	[2]

[1] Excludes losses recorded in operating revenues or cost of goods sold associated with weather derivatives of $3 million for the six months ended June 30, 2013 and gains of $14 million for the six months ended June 30, 2012.

[2] Associated with the fair value of existing derivative instruments at June 30, 2013 and 2012.