Stock-Based Compensation (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option awards	10,000,000
Income tax benefit	$ 600,000,000		$ 548,000,000		$ 440,000,000
Stock option awards, LTIP	10,000,000
Stock option vesting period	three
Stock option vesting term	ten
Options granted	0		0
Intrinsic value for outstanding options	18,000,000		18,000,000
Intrinsic value for exercised options	21,000,000		15,000,000
Cash received for payment of the exercise price	88,000,000		100,000,000
Remaining contractual life, years	3
Total expense recognized in future periods	2,000,000
Number of units issued annually to each individual	1,687
Number of units issued annually to each individual price	$ 54.06
Number of units issued	28,497
Maximum employer contribution match	1
Amount employee contribution for employer match	9
Maximum employee investment per year	25,000
Maximum percentage allowed to invest	20.00%
Shares purchased on the open market	721,520		738,951		868,622
Weighted average share price per share, on shares purchased on open market	$ 52.50		$ 45.52		$ 38.15
TSR Portion [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding units	474,517		494,188
Weighted average fair value as of the grant date	$ 42.511	[1]	$ 37.844	[1]
Adjustment percentage used for performance awards	50.00%
Factor used for adjustment of performance awards, low end	0.00%
Factor used for adjustment of performance awards, high end	150.00%
EIP Portion [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding units	474,517		494,188
Weighted average fair value as of the grant date	$ 46.660	[2]	$ 42.591	[2]
Adjustment percentage used for performance awards	50.00%
Factor used for adjustment of performance awards, low end	0.00%
Factor used for adjustment of performance awards, high end	200.00%
Performance-Based Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unvested compensation expense	37,000,000
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Income tax benefit	$ 2,000,000		$ 6,000,000

[1] * Fair value is determined using the Monte Carlo simulation described above. Weighted average grant date fair value does not reflect any accrual or payment of dividends prior to vesting.

[2] * Fair value is determined using the market price of one share of Con Edison common stock on the grant date. The market price has not been discounted to reflect that dividends do not accrue and are not payable on Performance RSUs until vesting.