Discontinued Operations - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				3 Months Ended		6 Months Ended	12 Months Ended	3 Months Ended		6 Months Ended			3 Months Ended
	Mar. 31, 2013	Jun. 30, 2014 Pepco Energy Services [Member]	Dec. 31, 2013 Pepco Energy Services [Member]	Dec. 31, 2013 Pepco Energy Services [Member] Maximum [Member]	Jun. 30, 2014 Discontinued Operations [Member]	Mar. 31, 2013 Discontinued Operations [Member]	Jun. 30, 2014 Discontinued Operations [Member]	Dec. 31, 2012 Discontinued Operations [Member]	Mar. 31, 2013 Discontinued Operations [Member] Interest Expense [Member]	Mar. 31, 2013 Discontinued Operations [Member] PHI [Member]	Jun. 30, 2014 Discontinued Operations [Member] PHI [Member]	Jun. 30, 2014 Discontinued Operations [Member] PHI [Member] Proceeds From Early Termination [Member]	Jun. 30, 2014 Discontinued Operations [Member] PHI [Member] Payment Paid From Early Termination [Member]	Mar. 31, 2013 Discontinued Operations [Member] Power Delivery [Member]	Mar. 31, 2013 Discontinued Operations [Member] Other Non-Regulated [Member]	Mar. 31, 2013 Discontinued Operations [Member] Corporate and Other [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Aggregate of net cash proceeds (payments) of lease investments												$ 873	$ 2,000
Net pre-tax gain / loss											(3)
Loss on early termination of finance leases held in trust, after-tax											(2)
After-tax non-cash charges	377				6	323
Non-cash pre-tax charge						373
After-tax effect of revised lease rerun	313					313
After-tax non-cash charge									16	70
Interest benefit on uncertain tax positions														12
Interest expense on uncertain tax positions															16	66
Penalties associated with re-assessment of tax positions					0		0
Maximum percentage of penalty on the amount of additional taxes due							20.00%
Derivatives		0	0
Cash collateral posted		2	3
Letters of credit posted				1
Amount of net pre-tax loss arising during the period included in Accumulated Other Comprehensive Loss								(10)
Amount of net tax loss arising during the period included in Accumulated Other Comprehensive Loss								(6)
Pre-tax loss reclassified into Income from Discontinued operations, Before Taxes						(4)
Net of tax loss reclassified into Income from Discontinued operations, Net of Income Taxes						$ (2)