Benefit Plans - Contribution and Benefit Payment Expectations (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012
Contribution And Benefit Payment [Line Items]
2012 expected contributions	$ 150
PEC
Contribution And Benefit Payment [Line Items]
2012 expected contributions	75
PEF
Contribution And Benefit Payment [Line Items]
2012 expected contributions	$ 75

The employer's best estimate, as soon as it can be reasonably determined, of contributions expected to be paid to the plan in the current remaining fiscal period. Estimated contributions may be presented in the aggregate combining (1) contributions required by funding regulations or laws, (2) discretionary contributions, and (3) noncash contributions.

No definition available.

Name:	us-gaap_DefinedBenefitPlanEstimatedFutureEmployerContributionsInCurrentFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant