Fair Value Measurements (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended		3 Months Ended		1 Months Ended		3 Months Ended					12 Months Ended		1 Months Ended
	Dec. 31, 2013	Dec. 31, 2013 Kewaunee Utility	Jun. 30, 2012 Salem Harbor	Dec. 31, 2013 Elwood	Sep. 30, 2012 Fair Value, Measurements, Nonrecurring Kewaunee	Mar. 31, 2011 Fair Value, Measurements, Nonrecurring State Line Operating Expense	Sep. 30, 2011 Fair Value, Measurements, Nonrecurring Emissions allowances	Sep. 30, 2011 Fair Value, Measurements, Nonrecurring Emissions allowances Operating Expense	Sep. 30, 2011 Fair Value, Measurements, Nonrecurring Emissions allowances Loss from Discontinued Operations	Sep. 30, 2011 Fair Value, Measurements, Nonrecurring Emissions allowances Virginia Electric and Power Company Operating Expense	Mar. 31, 2011 Fair Value, Measurements, Nonrecurring Maximum State Line	Dec. 31, 2012 Fair Value, Measurements, Nonrecurring Brayton Point	Dec. 31, 2012 Fair Value, Measurements, Nonrecurring Brayton Point Level 2	Jun. 30, 2013 Gas, Transmission and Distribution Equipment	Dec. 31, 2013 Gas, Transmission and Distribution Equipment Fair Value, Measurements, Nonrecurring Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment charge														$ 49
Impairment charge after tax														29
Estimated fair value											1				1
Ownership percentage				50.00%
Impairment charge	1,600				378							1,600
Impairment and other charges, net of tax					281							1,000
Long lived assets estimated fair value													216
Number of utilities		2
Impairment and other charges					435
Long-lived assets impairment charges, net of tax					244
Inventory write-down					33
Inventory write down, net of tax					21
Severance costs					24
Severance costs net of tax					16
Impairment charge						55
Impairment charge, net of tax						39
After tax charge on disposal of assets			27
Pretax charge on disposal of assets			16
So2 emissions allowances obtained for arp cnd cair compliance								57		43
Salem Harbor, impairment charge							14	57	43	43
Impairment of intangible assets after tax							$ 8	$ 34	$ 26	$ 26