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Fair Value Measurements (Level 3 Measurements And Sensitivity Analysis) (Detail) (USD $)
In Millions, unless otherwise specified
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Congestion Revenue Rights [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Assets, Fair Value $ 232us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByMeasurementFrequencyAxis
= pcg_CongestionRevenueRightsMember		 $ 107us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByMeasurementFrequencyAxis
= pcg_CongestionRevenueRightsMember
Liabilities, Fair Value 63us-gaap_LiabilitiesFairValueDisclosure
/ us-gaap_FairValueByMeasurementFrequencyAxis
= pcg_CongestionRevenueRightsMember		 32us-gaap_LiabilitiesFairValueDisclosure
/ us-gaap_FairValueByMeasurementFrequencyAxis
= pcg_CongestionRevenueRightsMember
Fair value measurement Valuation technique Market approach Market approach
Fair value measurement Unobservable Input CRR auction prices CRR auction prices
Power Purchase Agreements [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Assets, Fair Value 0us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByMeasurementFrequencyAxis
= pcg_PowerPurchaseAgreementsMember		 0us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByMeasurementFrequencyAxis
= pcg_PowerPurchaseAgreementsMember
Liabilities, Fair Value $ 100us-gaap_LiabilitiesFairValueDisclosure
/ us-gaap_FairValueByMeasurementFrequencyAxis
= pcg_PowerPurchaseAgreementsMember		 $ 105us-gaap_LiabilitiesFairValueDisclosure
/ us-gaap_FairValueByMeasurementFrequencyAxis
= pcg_PowerPurchaseAgreementsMember
Fair value measurement Valuation technique Discounted cash flow Discounted cash flow
Fair value measurement Unobservable Input Forward prices Forward prices
Minimum [Member] | CRR Auction Prices [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Range 15.97pcg_FairValueMeasurementUnobservableInputRange
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= pcg_CongestionRevenueRightsAuctionPricesMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember		 [1] (6.47)pcg_FairValueMeasurementUnobservableInputRange
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= pcg_CongestionRevenueRightsAuctionPricesMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember		 [1]
Minimum [Member] | Forward Prices [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Range 16.04pcg_FairValueMeasurementUnobservableInputRange
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= pcg_ForwardPricesMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember		 [1] 23.43pcg_FairValueMeasurementUnobservableInputRange
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= pcg_ForwardPricesMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember		 [1]
Maximum [Member] | CRR Auction Prices [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Range 8.17pcg_FairValueMeasurementUnobservableInputRange
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= pcg_CongestionRevenueRightsAuctionPricesMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember		 [1] 12.04pcg_FairValueMeasurementUnobservableInputRange
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= pcg_CongestionRevenueRightsAuctionPricesMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember		 [1]
Maximum [Member] | Forward Prices [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Range 56.21pcg_FairValueMeasurementUnobservableInputRange
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= pcg_ForwardPricesMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember		 [1] 51.75pcg_FairValueMeasurementUnobservableInputRange
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= pcg_ForwardPricesMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember		 [1]
[1] Represents price per megawatt-hour