Commitments And Contingent Liabilities (Minimum Fuel Purchase Requirements) (Detail) - Jun. 30, 2015 - Power [Member] - USD ($) $ in Millions	Total
Long-term Purchase Commitment [Line Items]
Coverage percentage of nuclear fuel commitments of uranium, enrichment, and fabrication requirements	100.00%
Commitments Through 2019 [Member] | Nuclear Fuel Uranium [Member]
Long-term Purchase Commitment [Line Items]
Total minimum purchase requirements	$ 443
Commitments Through 2019 [Member] | Nuclear Fuel Enrichment [Member]
Long-term Purchase Commitment [Line Items]
Total minimum purchase requirements	342
Commitments Through 2019 [Member] | Nuclear Fuel Fabrication [Member]
Long-term Purchase Commitment [Line Items]
Total minimum purchase requirements	185
Commitments Through 2019 [Member] | Natural Gas [Member]
Long-term Purchase Commitment [Line Items]
Total minimum purchase requirements	1,072
Commitments Through 2019 [Member] | Coal [Member]
Long-term Purchase Commitment [Line Items]
Total minimum purchase requirements	$ 360