Schedule I - Condensed Financial Information Of Parent Company (Investment In Consolidated Companies) (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Investments in Consolidated Companies	$ 3,897	$ 3,654
Conectiv [Member]
Investments in Consolidated Companies	1,473	1,300
Potomac Electric Power Co [Member]
Investments in Consolidated Companies	1,643	1,502
Potomac Capital Investment Corporation [Member]
Investments in Consolidated Companies	539	499
Pepco Energy Services [Member]
Investments in Consolidated Companies	238	350
PHI Service Company [Member]
Investments in Consolidated Companies	$ 4	$ 3