Commitments And Contingent Liabilities (Minimum Fuel Purchase Requirements) (Detail) (Power [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014
Long-term Purchase Commitment [Line Items]
Coverage percentage of nuclear fuel commitments of uranium, enrichment, and fabrication requirements	100.00%
Commitments Through 2017 [Member] | Nuclear Fuel Uranium [Member]
Long-term Purchase Commitment [Line Items]
Total minimum purchase requirements	$ 439
Commitments Through 2017 [Member] | Nuclear Fuel Enrichment [Member]
Long-term Purchase Commitment [Line Items]
Total minimum purchase requirements	431
Commitments Through 2017 [Member] | Nuclear Fuel Fabrication [Member]
Long-term Purchase Commitment [Line Items]
Total minimum purchase requirements	208
Commitments Through 2017 [Member] | Natural Gas [Member]
Long-term Purchase Commitment [Line Items]
Total minimum purchase requirements	1,186
Commitments Through 2017 [Member] | Coal [Member]
Long-term Purchase Commitment [Line Items]
Total minimum purchase requirements	$ 306