Nuclear Decommissioning Trust Fund Investments (Fair Value And The Gross Unrealized Losses Of The Available-For-Sale Securities Held In Nuclear Decommissioning Trust Fund) (Details) $ in Millions	Dec. 31, 2015 USD ($)
Nuclear Decommissioning Trust Fund Investments [Line Items]
Less than 12 months, fair value	$ 152
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	6
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	5
12 months or greater, fair value	8
Total, fair value	160
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	11
Debt Securities
Nuclear Decommissioning Trust Fund Investments [Line Items]
Less than 12 months, fair value	136
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	3
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	1
12 months or greater, fair value	4
Total, fair value	140
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	4
Equity Securities
Nuclear Decommissioning Trust Fund Investments [Line Items]
Less than 12 months, fair value	16
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	3
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	4
12 months or greater, fair value	4
Total, fair value	20
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 7