Represents the authorized rate for the allowance for funds used during construction. This financing cost is capitalized as part of the cost of construction projects.

No definition available.

Name:	ceg_AllowanceForFundsUsedDuringConstructionRate
Namespace Prefix:	ceg_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Significant Accounting Policies (Details 4)			12 Months Ended
Significant Accounting Policies (Details 4)	Nov. 06, 2011	Dec. 31, 2009	Dec. 31, 2011 Electric distribution plant	Dec. 31, 2011 Electric transmission plant	Dec. 31, 2011 Gas plant	Dec. 31, 2011 Common plant
Public utility property, plant and equipment:
Rate authorized for allowance for funds used during construction (as a percent)			8.06%	8.92%	7.90%	8.13%
Deconsolidation of Subsidiary upon Sale
Percent of membership interest in CENG sold	49.99%	49.99%