Regulatory Matters (Regulatory Assets And Liabilities) (Details) (USD $) In Millions	Sep. 30, 2011	Dec. 31, 2010
Regulatory Assets [Line Items]
Regulatory assets	$ 7,206	$ 7,683
Regulatory assets - current	110	203
Total Regulatory Assets	7,316	7,886
Regulatory liabilities	821	652
Regulatory liabilities - current	257	295
Total Regulatory Liabilities	1,078	947
Unrecognized Pension And Other Postretirement Costs [Member]
Regulatory Assets [Line Items]
Regulatory assets	3,769	4,371
Future Federal Income Tax [Member]
Regulatory Assets [Line Items]
Regulatory assets	1,763	1,593
Environmental Remediation Costs [Member]
Regulatory Assets [Line Items]
Regulatory assets	681	695
Pension And Other Post Retirement Benefits Deferrals [Member]
Regulatory Assets [Line Items]
Regulatory assets	198	138
Revenue Taxes [Member]
Regulatory Assets [Line Items]
Regulatory assets	160	145
Surcharge For New York State Assessment [Member]
Regulatory Assets [Line Items]
Regulatory assets	150	121
Net Electric Deferrals [Member]
Regulatory Assets [Line Items]
Regulatory assets	126	156
Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory assets	81	57
O & R Transition Bond Charges [Member]
Regulatory Assets [Line Items]
Regulatory assets	45	48
Deferred Derivative Losses - Long-Term [Member]
Regulatory Assets [Line Items]
Regulatory assets	34	74
Workers' Compensation [Member]
Regulatory Assets [Line Items]
Regulatory assets	25	31
Accrued Unbilled Revenues [Member]
Regulatory Assets [Line Items]
Regulatory assets	22
Property Tax Reconciliation [Member]
Regulatory Assets [Line Items]
Regulatory assets	12	34
World Trade Center Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory assets	9	45
Recoverable Energy Cost [Member]
Regulatory Assets [Line Items]
Regulatory assets	2	42
Other [Member]
Regulatory Assets [Line Items]
Regulatory assets	129	133
Deferred Derivative Losses - Current [Member]
Regulatory Assets [Line Items]
Regulatory assets - current	110	190
Recoverable Energy Costs - Current [Member]
Regulatory Assets [Line Items]
Regulatory assets - current		13
Allowance For Cost Of Removal Less Salvage [Member]
Regulatory Assets [Line Items]
Regulatory liabilities	440	422
World Trade Center Settlement Proceeds [Member]
Regulatory Assets [Line Items]
Regulatory liabilities	62
Carrying Charges On Transmission And Distribution Net Plant [Member]
Regulatory Assets [Line Items]
Regulatory liabilities	39	28
Bonus Depreciation [Member]
Regulatory Assets [Line Items]
Regulatory liabilities	24	1
Energy Efficiency Programs [Member]
Regulatory Assets [Line Items]
Regulatory liabilities	23	12
Gas Line Losses [Member]
Regulatory Assets [Line Items]
Regulatory liabilities	21
New York State Tax Refund [Member]
Regulatory Assets [Line Items]
Regulatory liabilities	20	30
Gain On Sale Of Properties [Member]
Regulatory Assets [Line Items]
Regulatory liabilities	14	28
Expenditure Prudence Proceeding [Member]
Regulatory Assets [Line Items]
Regulatory liabilities	11
Other Liabilities [Member]
Regulatory Assets [Line Items]
Regulatory liabilities	167	131
Net Unbilled Revenue Deferrals - Current [Member]
Regulatory Assets [Line Items]
Regulatory liabilities - current	116	136
Revenue Decoupling Mechanism [Member]
Regulatory Assets [Line Items]
Regulatory liabilities	99	38
Refundable Energy Cost - Current [Member]
Regulatory Assets [Line Items]
Regulatory liabilities - current	38	117
Deferred Derivative Gains - Current [Member]
Regulatory Assets [Line Items]
Regulatory liabilities - current	$ 4	$ 4