Quarterly Consolidated Financial Data (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended	3 Months Ended	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 Utility [Member]	Sep. 30, 2012 Utility [Member]	Jun. 30, 2012 Utility [Member]	Mar. 31, 2012 Utility [Member]	Dec. 31, 2011 Utility [Member]
Loss accrued						$ 80
Insurance recoveries for cost incurred related to third-party claims	185			50	99	25	11	99
Disallowed capital expenditures	$ 353	$ 0	$ 36	$ 353

- Definition

The amount of indirect disallowance of costs of a recently completed plant. When it becomes probable that part of the cost of a recently completed plant will be disallowed for rate-making purposes and a reasonable estimate of the amount of the disallowance can be made, the estimated amount of the probable disallowance is deducted from the reported cost of the plant and recognized as a loss. If part of the cost is explicitly, but indirectly, disallowed (for example, by an explicit disallowance of return on investment on a portion of the plant), an equivalent amount of cost is deducted from the reported cost of the plant and recognized as a loss.

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