Fair Value Measurements (Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Millions		Jun. 30, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments		$ 70	$ 64
Total assets		3,509	3,428
Electricity		149	170
Natural Gas		1	1
Total liabilities		150	171
Amount primarily related to deferred taxes on appreciation of investment value		343	314
Nuclear Decommissioning Trusts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments		11	36
Total assets	[1]	2,889	2,784	[2]
Fixed-income securities		1,221	1,215
Global equity securities		1,644	1,520
Financial Instruments Measured At NAV		13	13
Price Risk Management Instrument [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets		270	288
Electricity		258	286
Natural Gas		12	2
Rabbi Trusts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets		133	127
Fixed-income securities		59	57
Life insurance contracts		74	70
Long-Term Disability Trust [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments		4	7
Total assets		147	165
Financial Instruments Measured At NAV		143	158
Fair Value Measurements, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments		70	64
Total assets		2,449	2,321
Total liabilities		31	69
Fair Value Measurements, Level 1 [Member] | Nuclear Decommissioning Trusts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments		11	36
Total assets	[1]	2,353	2,250	[2]
Fixed-income securities		698	694
Global equity securities		1,644	1,520
Financial Instruments Measured At NAV		0	0
Fair Value Measurements, Level 1 [Member] | Price Risk Management Instrument [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets		22	0
Electricity		21	0
Natural Gas		1	0
Electricity		26	69
Natural Gas		5	0
Fair Value Measurements, Level 1 [Member] | Rabbi Trusts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets		0	0
Fixed-income securities		0	0
Life insurance contracts		0	0
Fair Value Measurements, Level 1 [Member] | Long-Term Disability Trust [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments		4	7
Total assets		4	7
Financial Instruments Measured At NAV		0	0
Fair Value Measurements, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments		0	0
Total assets		690	658
Total liabilities		5	3
Fair Value Measurements, Level 2 [Member] | Nuclear Decommissioning Trusts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments		0	0
Total assets	[1]	523	521	[2]
Fixed-income securities		523	521
Global equity securities		0	0
Financial Instruments Measured At NAV		0	0
Fair Value Measurements, Level 2 [Member] | Price Risk Management Instrument [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets		34	10
Electricity		23	9
Natural Gas		11	1
Electricity		2	1
Natural Gas		3	2
Fair Value Measurements, Level 2 [Member] | Rabbi Trusts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets		133	127
Fixed-income securities		59	57
Life insurance contracts		74	70
Fair Value Measurements, Level 2 [Member] | Long-Term Disability Trust [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments		0	0
Total assets		0	0
Financial Instruments Measured At NAV		0	0
Fair Value Measurements, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments		0	0
Total assets		215	259
Total liabilities		149	170
Fair Value Measurements, Level 3 [Member] | Nuclear Decommissioning Trusts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments		0	0
Total assets	[1]	0	0	[2]
Fixed-income securities		0	0
Global equity securities		0	0
Financial Instruments Measured At NAV		0	0
Fair Value Measurements, Level 3 [Member] | Price Risk Management Instrument [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets		215	259
Electricity		215	259
Natural Gas		0	0
Electricity		149	170
Natural Gas		0	0
Fair Value Measurements, Level 3 [Member] | Rabbi Trusts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets		0	0
Fixed-income securities		0	0
Life insurance contracts		0	0
Fair Value Measurements, Level 3 [Member] | Long-Term Disability Trust [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments		0	0
Total assets		0	0
Financial Instruments Measured At NAV		0	0
Netting [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	[3]	0	0
Total assets	[3]	(1)	19
Total liabilities	[3]	(35)	(71)
Netting [Member] | Nuclear Decommissioning Trusts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	[3]	0	0
Total assets	[1],[3]	0	0	[2]
Fixed-income securities	[3]	0	0
Global equity securities	[3]	0	0
Financial Instruments Measured At NAV	[3]	0	0
Netting [Member] | Price Risk Management Instrument [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	[3]	(1)	19
Electricity	[3]	(1)	18
Natural Gas	[3]	0	1
Electricity	[3]	(28)	(70)
Natural Gas	[3]	(7)	(1)
Netting [Member] | Rabbi Trusts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	[3]	0	0
Fixed-income securities	[3]	0	0
Life insurance contracts	[3]	0	0
Netting [Member] | Long-Term Disability Trust [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	[3]	0	0
Total assets	[3]	0	0
Financial Instruments Measured At NAV	[3]	$ 0	$ 0

[1] Represents amount before deducting $343 million, primarily related to deferred taxes on appreciation of investment value.

[2] Represents amount before deducting $314 million, primarily related to deferred taxes on appreciation of investment value.

[3] Includes the effect of the contractual ability to settle contracts under master netting agreements and margin cash collateral.