Note 3 - Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2013

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

In millions	March 31, 2013		December 31, 2012		March 31, 2012
Long-term debt amortized cost	$	3,550	$	3,553	$	3,575
Long-term debt fair value (1)	$	4,006	$	4,057	$	3,922

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, 2013					December 31, 2012					March 31, 2012
In millions	Assets (1)		Liabilities			Assets (1)		Liabilities			Assets (1)		Liabilities
Natural gas derivatives
Quoted prices in active markets (Level 1)	$	14	$	(38	)	$	8	$	(45	)	$	7	$	(187	)
Significant other observable inputs (Level 2)		49		(23	)		96		(30	)		203		(68	)
Netting of cash collateral		40		37			33		36			47		162
Total carrying value (2) (3)	$	103	$	(24	)	$	137	$	(39	)	$	257	$	(93	)
Interest rate derivatives
Significant other observable inputs (Level 2)	$	6	$	-		$	3	$	-		$	9	$	(10	)

Money Market Funds [Member]

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

In millions	At March 31, 2013		At December 31, 2012		At March 31, 2012
Money market funds (1)	$	48	$	66	$	68