Schedule I - Condensed Financial Information - Condensed Balance Sheet (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
CURRENT ASSETS
Cash and temporary cash investments	$ 699	$ 674	$ 394	$ 648
Special deposits	8	327
Accounts receivable - other	1,201	1,251
Income taxes receivable	224
Prepayments	163	136
Other current assets	278	235
TOTAL CURRENT ASSETS	3,854	3,891
Investments in subsidiaries and others	816	461
Goodwill	429	429
Other noncurrent assets	9,811	7,859
TOTAL ASSETS	44,308	40,647	41,209
CURRENT LIABILITIES
Long-term debt due within one year	560	485
Notes payable	800	1,451
Accrued taxes	72	476
Other current liabilities	508	478
TOTAL CURRENT LIABILITIES	3,781	4,730
LONG-TERM DEBT	11,631	10,489
Shareholders' Equity
Common Shareholders' Equity	12,576	12,245
TOTAL LIABILITIES AND SHAREHOLDER'S EQUITY	44,308	40,647
Consolidated Edison Inc [Member]
CURRENT ASSETS
Cash and temporary cash investments	3	12	4	205
Special deposits	1	315
Accounts receivable - other		185
Income taxes receivable	224
Accounts receivable from affiliated companies	381	950
Prepayments	5	2
Other current assets	4
TOTAL CURRENT ASSETS	618	1,464
Investments in subsidiaries and others	12,277	11,954
Goodwill	406	406
Deferred income tax	18	14
Other noncurrent assets	11	4
TOTAL ASSETS	13,330	13,842
CURRENT LIABILITIES
Long-term debt due within one year	2	2
Notes payable	274	173
Accounts payable to affiliated companies	147	148
Accrued taxes	13	426
Other current liabilities	10	538
TOTAL CURRENT LIABILITIES	446	1,287
Total Liabilities	446	1,287
LONG-TERM DEBT	308	310
Shareholders' Equity
Common stock, including additional paid-in capital	5,023	5,027
Retained earnings	7,553	7,218
Common Shareholders' Equity	12,576	12,245
TOTAL LIABILITIES AND SHAREHOLDER'S EQUITY	$ 13,330	$ 13,842