Commitments and Contingencies (Guarantees, Surety Bonds and Letters of Credit) (Narrative) (Details) (USD $)	Dec. 31, 2013
Guarantor Obligations [Line Items]
Exposure under guarantees	$ 4,421,000,000
Purchased surety bonds	147,000,000
Standby Letters of Credit
Guarantor Obligations [Line Items]
Authorized standby letters of credit with financial institutions	11,000,000
Minimum
Guarantor Obligations [Line Items]
Annual future contributions	4,000,000
Maximum
Guarantor Obligations [Line Items]
Annual future contributions	19,000,000
Third Party and Equity Method Investee
Guarantor Obligations [Line Items]
Estimate of possible loss	69,000,000
Exposure under guarantees	39,000,000
Third Party and Equity Method Investee | Through 2019
Guarantor Obligations [Line Items]
Exposure under guarantees	90,000,000
Virginia Electric and Power Company
Guarantor Obligations [Line Items]
Purchased Surety Bonds	59,000,000
Authorized issuance of standby letters of credit	1,000,000
Virginia Electric and Power Company | Tax-Exempt Financings
Guarantor Obligations [Line Items]
Estimate of possible loss	$ 14,000,000