Regulatory Matters (Regulatory Assets And Liabilities) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Regulatory Assets [Line Items]
Regulatory assets - long-term	$ 9,276	$ 9,337
Regulatory assets - current	192	164
Total Regulatory Assets	9,468	9,501
Regulatory liabilities	846	977
Regulatory liabilities - current	286	118
Total Regulatory Liabilities	1,132	1,095
Unrecognized Pension And Other Postretirement Costs [Member]
Regulatory Assets [Line Items]
Regulatory assets - long-term	5,594	5,852
Future Income Tax [Member]
Regulatory Assets [Line Items]
Regulatory assets - long-term	1,840	1,798
Environmental Remediation Costs [Member]
Regulatory Assets [Line Items]
Regulatory assets - long-term	729	681
Pension And Other Post Retirement Benefits Deferrals [Member]
Regulatory Assets [Line Items]
Regulatory assets - long-term	219	198
Revenue Taxes [Member]
Regulatory Assets [Line Items]
Regulatory assets - long-term	167	163
Surcharge For New York State Assessment [Member]
Regulatory Assets [Line Items]
Regulatory assets - long-term	143	90
Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory assets - long-term	125	128
Net Electric Deferrals [Member]
Regulatory Assets [Line Items]
Regulatory assets - long-term	116	121
Deferred Derivative Losses - Long-Term [Member]
Regulatory Assets [Line Items]
Regulatory assets - long-term	78	60
O&R Transition Bond Charges [Member]
Regulatory Assets [Line Items]
Regulatory assets - long-term	43	44
Preferred Stock Redemption [Member]
Regulatory Assets [Line Items]
Regulatory assets - long-term	30
Workers' Compensation [Member]
Regulatory Assets [Line Items]
Regulatory assets - long-term	22	23
Property Tax Reconciliation [Member]
Regulatory Assets [Line Items]
Regulatory assets - long-term	13	13
Regulatory liabilities	68	35
Recoverable Energy Costs - Long Term [Member]
Regulatory Assets [Line Items]
Regulatory assets - long-term		14
Other [Member]
Regulatory Assets [Line Items]
Regulatory assets - long-term	157	152
Deferred Derivative Losses - Current [Member]
Regulatory Assets [Line Items]
Regulatory assets - current	192	164
Allowance For Cost Of Removal Less Salvage [Member]
Regulatory Assets [Line Items]
Regulatory liabilities	457	448
World Trade Center Settlement Proceeds [Member]
Regulatory Assets [Line Items]
Regulatory liabilities	62	62
Net Unbilled Revenue Deferrals [Member]
Regulatory Assets [Line Items]
Regulatory liabilities	51	104
Long-Term Interest Rate Reconciliation [Member]
Regulatory Assets [Line Items]
Regulatory liabilities	42	30
Carrying Charges On Transmission And Distribution Net Plant [Member]
Regulatory Assets [Line Items]
Regulatory liabilities	41	38
Gas Line Losses [Member]
Regulatory Assets [Line Items]
Regulatory liabilities	17	21
Expenditure Prudence Proceeding [Member]
Regulatory Assets [Line Items]
Regulatory liabilities	8	11
Energy Efficiency Programs [Member]
Regulatory Assets [Line Items]
Regulatory liabilities	6	22
Other Liabilities [Member]
Regulatory Assets [Line Items]
Regulatory liabilities	94	206
Electric Surcharge Offset [Member]
Regulatory Assets [Line Items]
Regulatory liabilities - current	134
Refundable Energy Costs - Current [Member]
Regulatory Assets [Line Items]
Regulatory liabilities - current	99	51
Revenue Decoupling Mechanism [Member]
Regulatory Assets [Line Items]
Regulatory liabilities - current	51	66
Deferred Derivative Gains - Current [Member]
Regulatory Assets [Line Items]
Regulatory liabilities - current	$ 2	$ 1