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Summary of Significant Accounting Policies (Detail) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Jun. 30, 2015
Revenue Recognition (Numeric) [Abstract]        
Accounts receivable $ 186     $ 241
PPL Energy Supply LLC [Member]        
Revenue Recognition (Numeric) [Abstract]        
Costs in excess of billings on uncompleted contracts or programs 20 $ 14    
Billings in excess of cost 41 75    
Accounts receivable 186 233    
Restricted cash and cash equivalents 193 85    
Interest costs, capitalized during the period $ 23 37 $ 47  
Asset Impairment (Excluding Investments) (Numeric) [Abstract]        
Percentage in excess of gains and losses equal to the plan's projected benefit obligation to use accelerated amortization 30.00%      
Minimum percentage of gains and losses under the accelerated method that are amortized on a straight line basis 10.00%      
Maximum percentage of gains and losses under the accelerated that are amortized on a straight line basis 30.00%      
Income Taxes [Abstract]        
Intercompany tax receivables (payables) $ 105 44    
Minimum percentage to be attained of likelihood of uncertain tax position being realized 50.00%      
Fuel, materials and supplies on the Balance Sheet $ 455 358    
PPL Energy Supply LLC [Member] | Margin Deposits Posted To Counterparties [Member]        
Revenue Recognition (Numeric) [Abstract]        
Restricted cash and cash equivalents 175 67    
PPL Energy Supply LLC [Member] | Ironwood Debt Service Reserves [Member]        
Revenue Recognition (Numeric) [Abstract]        
Restricted cash and cash equivalents 17 17    
PPL Energy Supply LLC [Member] | Other Restricted Cash [Member]        
Revenue Recognition (Numeric) [Abstract]        
Restricted cash and cash equivalents 1 1    
PPL Energy Supply LLC [Member] | Fuel [Member]        
Income Taxes [Abstract]        
Fuel, materials and supplies on the Balance Sheet 243 163    
PPL Energy Supply LLC [Member] | Natural Gas Stored Underground [Member]        
Income Taxes [Abstract]        
Fuel, materials and supplies on the Balance Sheet 7 2    
PPL Energy Supply LLC [Member] | Material And Supplies [Member]        
Income Taxes [Abstract]        
Fuel, materials and supplies on the Balance Sheet $ 205 $ 193    
PPL Energy Supply LLC [Member] | Nonregulated Property Plant And Equipment Generation [Member]        
Depreciation (Details) [Abstract]        
Weighted-average rates 3.28% 3.10%    
PPL Energy Supply LLC [Member] | Nonregulated Property Plant And Equipment Generation [Member] | Brunner Island And Montour Plants [Member]        
Asset Impairment (Excluding Investments) (Numeric) [Abstract]        
Carrying value of utility plants $ 2,600      
PPL Energy Supply LLC [Member] | Nonregulated Property Plant And Equipment Generation [Member] | Brunner Island Plant [Member]        
Asset Impairment (Excluding Investments) (Numeric) [Abstract]        
Carrying value of utility plants 1,400      
PPL Energy Supply LLC [Member] | Nonregulated Property Plant And Equipment Generation [Member] | Montour Plant [Member]        
Asset Impairment (Excluding Investments) (Numeric) [Abstract]        
Carrying value of utility plants 1,200      
PPL Energy Supply LLC [Member] | Allowance For Doubtful Accounts [Member]        
Revenue Recognition (Numeric) [Abstract]        
Balance at beginning of period 21 $ 23 15  
Additions charged to income 0 1 12 [1]  
Additions charged to other accounts 0 0 0  
Deductions [2] 19 [1] 3 4  
Balance at end of period 2 21 23  
PPL Energy Supply LLC [Member] | Accounts Receivable [Member]        
Revenue Recognition (Numeric) [Abstract]        
Accounts receivable 336 $ 294 $ 313  
PPL Energy Supply LLC [Member] | Energy Related Businesses Adjustment 2014 [Member]        
Revenue Recognition (Numeric) [Abstract]        
Out of period adjustment amount, pre-tax 17      
Out of period adjustment amount, after-tax $ 10      
[1] In 2011, a wholesale customer, SMGT, filed for bankruptcy protection under Chapter 11 of the U.S. Bankruptcy code. In 2012, PPL EnergyPlus recorded an additional allowance for unpaid amounts under the long-term power contract and the U.S. Bankruptcy Court for the District of Montana approved a request to terminate the contract. In 2014, PPL EnergyPlus received an insignificant amount of cash, settling the outstanding administrative claim and therefore, the related reserve balance was offset against the accounts receivable balance.
[2] Primarily related to uncollectible accounts written off.