Investments (Fair Value of our Marketable Debt Securities by Contractual Maturity) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014
Schedule of Held-to-maturity Securities [Line Items]
Due in one year or less	$ 133
Due after one year through five years	407
Due after five years through ten years	384
Due after ten years	445
Total	1,369
Virginia Electric and Power Company
Schedule of Held-to-maturity Securities [Line Items]
Due in one year or less	39
Due after one year through five years	199
Due after five years through ten years	206
Due after ten years	190
Total	$ 634