Derivative Instruments And Hedging Activities (Cash Flow Hedges Included In Accumulated Other Comprehensive Loss) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012		Mar. 31, 2011
Derivative Instruments, Gain (Loss) [Line Items]
Accumulated Other Comprehensive Loss After-tax	$ 31		$ 73
Portion Expected to be Reclassified to Income during the Next 12 Months	18		39
Energy Commodity [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Accumulated Other Comprehensive Loss After-tax	21	[1]	62	[1]
Portion Expected to be Reclassified to Income during the Next 12 Months	17	[1]	38	[1]
Maximum Term	26 months	[1]	38 months	[1]
Interest Rate [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Accumulated Other Comprehensive Loss After-tax	10		11
Portion Expected to be Reclassified to Income during the Next 12 Months	$ 1		$ 1
Maximum Term	245 months		257 months

[1] The unrealized derivative losses recorded in AOCL relate to forecasted physical natural gas and electricity purchases which are used to supply retail natural gas and electricity contracts that are in gain positions and subject to accrual accounting. Under accrual accounting, no asset is recorded on PHI's consolidated balance sheet and the purchase cost is not recognized until the period of distribution.