Note 4 - Fair Value Measurements (Details) - Derivative Assets and Liabilities (Natural Gas Derivatives [Member], USD $) In Millions, unless otherwise specified	Jun. 30, 2014		Dec. 31, 2013		Jun. 30, 2013
Natural gas derivatives
Derivative Assets	$ 111	[1],[2],[3]	$ 116	[1],[2],[3]	$ 129	[1],[2],[3]
Derivative Liabilities	(62)	[2],[3]	(80)	[2],[3]	(39)	[2],[3]
Netting of cash collateral	46	[1]	43	[1]	47	[1]
Netting of cash collateral	36		78		47
Fair Value, Inputs, Level 1 [Member]
Natural gas derivatives
Derivative Assets	8	[1]	6	[1]	4	[1]
Derivative Liabilities	(38)		(79)		(51)
Fair Value, Inputs, Level 2 [Member]
Natural gas derivatives
Derivative Assets	57	[1]	67	[1]	78	[1]
Derivative Liabilities	$ (60)		$ (79)		$ (35)

[1] Balances of $3 million at June 30, 2014, $3 million at December 31, 2013 and $1 million at June 30, 2013 associated with certain weather derivatives have been excluded, as they are accounted for based on intrinsic value rather than fair value.

[2] There were no significant unobservable inputs (Level 3) for any of the dates presented.

[3] There were no significant transfers between Level 1, Level 2 or Level 3 for any of the dates presented.