Schedule I - Condensed Financial Information of Parent Company - Investment in Consolidated Companies (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Investments in Consolidated Companies	$ 3,935	$ 2,633
Conectiv LLC [Member]
Investments in Consolidated Companies	1,730	1,473
Potomac Electric Power Co [Member]
Investments in Consolidated Companies	1,922	1,643
Potomac Capital Investment Corporation (PCI) [Member]
Investments in Consolidated Companies	29	(729)
Pepco Energy Services [Member]
Investments in Consolidated Companies	250	242
PHI Service Company [Member]
Investments in Consolidated Companies	$ 4	$ 4