Note 4 - Fair Value Measurements (Detail) - Amortized Cost and Fair Value of Long-Term Debt (USD $) In Millions, unless otherwise specified	Jun. 30, 2012		Dec. 31, 2011		Jun. 30, 2011
Long-term debt amortized cost (1)	$ 3,564	[1]	$ 3,576	[1]	$ 2,174	[1]
Long-term debt fair value (1) (2)	$ 4,043	[1],[2]	$ 3,938	[1],[2]	$ 2,339	[1],[2]

[1] June 30, 2012 includes current portion of long-term debt of $230 million while December 31, 2011 includes current portion of long-term debt of $15 million as well as the debt assumed in the Nicor merger with a stepped-up carrying value of $594 million.

[2] Valued using Level 2 inputs.