Note 4 - Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2012

Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block]

In millions	March 31, 2012		December 31, 2011		March 31, 2011
Long-term debt amortized cost (1)	$	3,573	$	3,576	$	2,173
Long-term debt fair value (1) (2)	$	3,922	$	3,938	$	2,304

Natural Gas Derivatives [Member]

Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block]

	Recurring fair values Derivative instruments
	March 31, 2012					December 31, 2011					March 31, 2011
In millions	Assets		Liabilities			Assets (1)		Liabilities			Assets (1)		Liabilities
Natural gas derivatives
Quoted prices in active markets (Level 1)	$	7	$	(187	)	$	11	$	(145	)	$	1	$	(63	)
Significant other observable inputs (Level 2)		203		(68	)		229		(68	)		101		(15	)
Netting of cash collateral		47		162			32		115			38		50
Total carrying value (2) (3)	$	257	$	(93	)	$	272	$	(98	)	$	140	$	(28	)
Interest rate derivatives
Significant other observable inputs (Level 2)	$	9	$	(10	)	$	13	$	(13	)	$	0	$	0

Money Market Funds [Member]

Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block]

In millions	March 31, 2012		December 31, 2011		March 31, 2011
Money market funds (1)	$	68	$	59	$	0