Regulatory Matters (Regulatory Assets And Liabilities) (Details) (USD $) In Millions	Jun. 30, 2011	Dec. 31, 2010
Regulatory assets	$ 7,261	$ 7,683
Regulatory assets - current	130	203
Total Regulatory Assets	7,391	7,886
Regulatory liabilities	866	690
Regulatory liabilities - current	198	257
Total Regulatory Liabilities	1,064	947
Unrecognized Pension and Other Postretirement Costs [Member]
Regulatory assets	3,921	4,371
Future Federal Income Tax [Member]
Regulatory assets	1,730	1,593
Environmental Remediation Costs [Member]
Regulatory assets	684	695
Pension and Other Post Retirement Benefits Deferrals [Member]
Regulatory assets	183	138
Revenue Taxes [Member]
Regulatory assets	155	145
Net Electric Deferrals [Member]
Regulatory assets	130	156
Surcharge for New York State Assessment [Member]
Regulatory assets	98	121
Deferred Storm Costs [Member]
Regulatory assets	53	57
O & R Transition Bond Charges [Member]
Regulatory assets	47	48
Deferred Derivative Losses - Long-Term [Member]
Regulatory assets	44	74
Property Tax Reconciliation [Member]
Regulatory assets	31	34
Workers' Compensation [Member]
Regulatory assets	28	31
World Trade Center Restoration Costs [Member]
Regulatory assets	13	45
Recoverable Energy [Member]
Regulatory assets		42
Other [Member]
Regulatory assets	144	133
Deferred Derivative Losses - Current [Member]
Regulatory assets - current	121	190
Recoverable Energy Costs - Current [Member]
Regulatory assets - current	9	13
Allowance for Cost of Removal Less Salvage [Member]
Regulatory liabilities	430	422
Revenue Decoupling Mechanism [Member]
Regulatory liabilities	81	38
World Trade Center Settlement Proceeds [Member]
Regulatory liabilities	62
Carrying Changes On T&D Net Plant [Member]
Regulatory liabilities	40	28
Energy Efficiency Programs [Member]
Regulatory liabilities	28	19
New York State Tax Refund [Member]
Regulatory liabilities	20	30
Gain on Sale of Properties [Member]
Regulatory liabilities	15	31
Bonus Depreciation [Member]
Regulatory liabilities	13	1
Expenditure Prudence Proceeding [Member]
Regulatory liabilities	11
Other Liabilities [Member]
Regulatory liabilities	166	121
Net Unbilled Revenue Deferrals - Current [Member]
Regulatory liabilities - current	117	136
Refundable Energy Cost - Current [Member]
Regulatory liabilities - current	75	117
Deferred Derivative Gains - Current [Member]
Regulatory liabilities - current	$ 6	$ 4