Debt and Credit Facilities - Debt and Credit Facilities (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Dec. 31, 2011
Long-term debt [Line Items]
Current portion of long-term debt	$ (1,375)	$ (950)
Long-term debt, net	11,742	11,718
Long-term debt, affiliate	273	273
RCAs and available capacity [Line Items]
RCA expiration date	May 3, 2013
RCA total	1,978
Short Term Debt [Line Items]
Short-term debt	1,056	671
Parent
RCAs and available capacity [Line Items]
RCA amendment date	February 15, 2012
RCA total	478
Parent | Senior Notes Due April 15, 2012
Long-term debt [Line Items]
Maturity date	Apr. 15, 2012
Maturities of debt	450
Debt instrument, interest rate stated percentage	6.85%
Parent | Senior Notes Due April 1, 2022
Long-term debt [Line Items]
Debt instrument, face amount	450
Maturity date	Apr. 01, 2022
Debt instrument issuance date	March 8, 2012
Debt instrument, interest rate stated percentage	3.15%
PEC
Long-term debt [Line Items]
Current portion of long-term debt	(500)	(500)
Long-term debt, net	3,693	3,693
Short Term Debt [Line Items]
Short-term debt	441	188
PEF
Long-term debt [Line Items]
Current portion of long-term debt	(425)	0
Long-term debt, net	4,057	4,482
Short Term Debt [Line Items]
Short-term debt	$ 360	$ 233