Commitments and Contingencies (North Carolina Ash Basins) (Details) (North Carolina Ash Basins [Member], USD $) In Billions, unless otherwise specified	Mar. 31, 2014
Minimum [Member]
Commitments And Contingencies [Line Items]
Loss contingency, range of possible loss, minimum	$ 2.0
Maximum [Member]
Commitments And Contingencies [Line Items]
Loss contingency, range of possible loss, maximum	10.0
Baseline Assumptions [Member]
Commitments And Contingencies [Line Items]
Loss contingency, range of possible loss, minimum	2.0	[1]
Loss contingency, range of possible loss, maximum	2.5	[1]
Estimated Additional Costs Related To Full Excavation [Member]
Commitments And Contingencies [Line Items]
Loss contingency, range of possible loss, minimum	4.0	[2]
Loss contingency, range of possible loss, maximum	5.5	[2]
Estimated Additionall Costs Related to All-Dry Systems [Member]
Commitments And Contingencies [Line Items]
Loss contingency, range of possible loss, minimum	1.0	[3]
Loss contingency, range of possible loss, maximum	$ 2.0	[3]

[1] Assumes (i) hybrid cap in place closure for ash basins at ten coal plants, (ii) excavation and relocation of ash to lined structural fills or landfills for the retired Dan River, Riverbend and Sutton coal plants, (iii) dry fly ash conversion at the Asheville units and Cliffside Unit 5, (iv) continued structural fill disposal for the Asheville coal plant, and (v) dry bottom ash handling conversions and fly ash reliability improvements. Includes costs for actions noted in the March 12, 2014 letter to the Governor of North Carolina and existing plans to close ash basins.

[2] Represents estimated additional costs to excavate and relocate ash to lined landfills for the ten plants under hybrid cap in place closure in the baseline assumptions.

[3] Represents estimated additional costs to convert all active coal plants to all-dry pneumatic bottom ash handling systems and thermally-driven evaporation of other process water.