Investments (Fair Value of our Marketable Debt Securities by Contractual Maturity) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013
Schedule of Held-to-maturity Securities [Line Items]
Due in one year or less	$ 122
Due after one year through five years	357
Due after five years through ten years	365
Due after ten years	394
Total	1,238
Virginia Electric and Power Company
Schedule of Held-to-maturity Securities [Line Items]
Due in one year or less	21
Due after one year through five years	176
Due after five years through ten years	202
Due after ten years	164
Total	$ 563