Note 10 - Commitments, Guarantees and Contingencies (Details) (USD $) In Millions, unless otherwise specified	0 Months Ended		3 Months Ended		12 Months Ended
	Jun. 07, 2013	Nov. 05, 2012	Mar. 31, 2014	Dec. 31, 2012	Dec. 31, 2013	Dec. 31, 2009	Feb. 01, 2012
Note 10 - Commitments, Guarantees and Contingencies (Details) [Line Items]
Gas Balancing Volume Amount (in Cubic Feet)				4,800,000,000
Illinois Commission [Member]
Note 10 - Commitments, Guarantees and Contingencies (Details) [Line Items]
Loss Contingency, Damages Sought, Value						$ 85
Loss Contingency, Estimate of Possible Loss							64
Loss Contingency, Damages Awarded, Value	72	72
Loss Contingency Accrual, Period Increase (Decrease)				8
Loss Contingency Accrual				72
Loss Contingency, Damages Paid, Value			35		29
IAG [Member]
Note 10 - Commitments, Guarantees and Contingencies (Details) [Line Items]
Loss Contingency, Damages Sought, Value						255
CUB [Member]
Note 10 - Commitments, Guarantees and Contingencies (Details) [Line Items]
Loss Contingency, Damages Sought, Value						$ 305