Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Reconciliations of effective income tax rate to the statutory federal income tax rate
Effective income tax rate	32.80%	37.80%	34.70%	36.90%
Excise Taxes [Abstract]
Excise taxes	$ 95	$ 96	$ 241	$ 245
PEC [Member]
Reconciliations of effective income tax rate to the statutory federal income tax rate
Effective income tax rate	31.90%	33.40%	31.60%	34.20%
Excise Taxes [Abstract]
Excise taxes	33	33	85	86
PEF [Member]
Reconciliations of effective income tax rate to the statutory federal income tax rate
Effective income tax rate	35.90%	37.00%	36.90%	37.00%
Excise Taxes [Abstract]
Excise taxes	$ 62	$ 63	$ 156	$ 159