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Debt and Credit Agreements - Summary of Outstanding Long-term Debt (Details) - USD ($)
Dec. 31, 2016
Dec. 31, 2015
Jun. 30, 2015
Debt Instrument [Line Items]      
Long-term Debt, Gross $ 33,311,000,000 $ 25,113,000,000  
Unamortized debt discount and premium, net (68,000,000) (63,000,000)  
Long-term debt (including amounts due within one year) (a) 962,000,000 275,000,000  
Long-term debt due within one year (2,430,000,000) (1,500,000,000)  
Long-term debt 31,575,000,000 23,645,000,000  
Long-term debt to financing trusts 641,000,000 641,000,000  
Total long-term debt to financing trusts 648,000,000 648,000,000  
Unamortized Debt Issuance Expense [1] (200,000,000) (180,000,000)  
ComEd Financing Three Affiliate [Member]      
Debt Instrument [Line Items]      
Long-term Debt, Gross 206,000,000 206,000,000  
Long-term debt to financing trusts $ 205,000,000 205,000,000  
ComEd Financing Three Affiliate [Member] | Maximum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 6.35%    
Interest rate on long-term debt 6.35%    
PECO Trust Three Affiliate [Member]      
Debt Instrument [Line Items]      
Long-term Debt, Gross $ 81,000,000 81,000,000  
Long-term debt to financing trusts $ 81,000,000 81,000,000  
PECO Trust Three Affiliate [Member] | Maximum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 7.38%    
Interest rate on long-term debt 7.38%    
PECO Trust Four Affiliate [Member]      
Debt Instrument [Line Items]      
Long-term Debt, Gross $ 103,000,000 103,000,000  
Long-term debt to financing trusts $ 103,000,000 103,000,000  
PECO Trust Four Affiliate [Member] | Maximum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 5.75%    
Interest rate on long-term debt 5.75%    
BGE Trust Member [Member]      
Debt Instrument [Line Items]      
Long-term Debt, Gross $ 258,000,000 258,000,000  
BGE Trust Member [Member] | Maximum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 6.20%    
Interest rate on long-term debt 6.20%    
Unsecured Debt [Member]      
Debt Instrument [Line Items]      
Long-term Debt, Gross $ 2,300,000,000 1,750,000,000  
Unsecured Debt [Member] | Minimum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 2.40%    
Interest rate on long-term debt 2.40%    
Unsecured Debt [Member] | Maximum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 6.35%    
Interest rate on long-term debt 6.35%    
Rate Stabilization Bonds [Member]      
Debt Instrument [Line Items]      
Long-term Debt, Gross $ 41,000,000 120,000,000  
Rate Stabilization Bonds [Member] | Minimum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 5.82%    
Interest rate on long-term debt 5.82%    
Rate Stabilization Bonds [Member] | Maximum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 5.82%    
Interest rate on long-term debt 5.82%    
Secured Debt [Member]      
Debt Instrument [Line Items]      
Long-term Debt, Gross [2] $ 14,123,000,000 9,019,000,000  
Secured Debt [Member] | Minimum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage [2] 1.70%    
Interest rate on long-term debt [2] 1.70%    
Secured Debt [Member] | Maximum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage [2] 7.90%    
Interest rate on long-term debt [2] 7.90%    
Senior Notes [Member]      
Debt Instrument [Line Items]      
Long-term Debt, Gross $ 11,868,000,000 9,803,000,000  
Senior Notes [Member] | Minimum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 1.55%    
Interest rate on long-term debt 1.55%    
Senior Notes [Member] | Maximum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 7.60%    
Interest rate on long-term debt 7.60%    
Pollution Control Notes [Member]      
Debt Instrument [Line Items]      
Long-term Debt, Gross $ 435,000,000 435,000,000  
Pollution Control Notes [Member] | Maximum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 2.70%    
Interest rate on long-term debt 2.70%    
Notes Payable to Banks [Member]      
Debt Instrument [Line Items]      
Long-term Debt, Gross $ 105,000,000 127,000,000  
Notes Payable to Banks [Member] | Minimum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 3.15%    
Interest rate on long-term debt 3.15%    
Notes Payable to Banks [Member] | Maximum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 3.35%    
Interest rate on long-term debt 3.35%    
Notes Payable, Other Payables [Member]      
Debt Instrument [Line Items]      
Long-term Debt, Gross [3],[4] $ 576,000,000 314,000,000  
Unamortized Debt Issuance Expense [1] $ (7,000,000) (7,000,000)  
Notes Payable, Other Payables [Member] | Minimum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage [3] 1.43%    
Interest rate on long-term debt [3] 1.43%    
Notes Payable, Other Payables [Member] | Maximum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage [3] 7.83%    
Interest rate on long-term debt [3] 7.83%    
Junior Subordinated Debt [Member]      
Debt Instrument [Line Items]      
Long-term Debt, Gross $ 1,150,000,000 1,150,000,000 $ 1,150,000,000.00
Junior Subordinated Debt [Member] | Maximum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 6.50%    
Interest rate on long-term debt 6.50%    
contract Payments Junior Subordinate Debt [Member]      
Debt Instrument [Line Items]      
Long-term Debt, Gross $ 19,000,000 64,000,000  
contract Payments Junior Subordinate Debt [Member] | Maximum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 2.50%    
Interest rate on long-term debt 2.50%    
Software License Arrangement [Member]      
Debt Instrument [Line Items]      
Long-term Debt, Gross $ 103,000,000 111,000,000  
Software License Arrangement [Member] | Maximum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 3.95%    
Interest rate on long-term debt 3.95%    
Tax-exempt Money Market Funds [Member]      
Debt Instrument [Line Items]      
Long-term Debt, Gross $ 112,000,000 0  
Tax-exempt Money Market Funds [Member] | Maximum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 5.40%    
Interest rate on long-term debt 5.40%    
Medium-term Notes [Member]      
Debt Instrument [Line Items]      
Long-term Debt, Gross $ 40,000,000 0  
Medium-term Notes [Member] | Minimum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 6.81%    
Interest rate on long-term debt 6.81%    
Medium-term Notes [Member] | Maximum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 7.72%    
Interest rate on long-term debt 7.72%    
Transition Bonds [Member]      
Debt Instrument [Line Items]      
Long-term Debt, Gross $ 124,000,000 0  
Transition Bonds [Member] | Minimum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 5.05%    
Interest rate on long-term debt 5.05%    
Transition Bonds [Member] | Maximum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 5.55%    
Interest rate on long-term debt 5.55%    
Non Recourse Fixed Rate [Member]      
Debt Instrument [Line Items]      
Long-term Debt, Gross $ 1,400,000,000 1,162,000,000  
Non Recourse Variable Rate [Member]      
Debt Instrument [Line Items]      
Long-term Debt, Gross 915,000,000 1,058,000,000  
Capital Lease Obligations [Member]      
Debt Instrument [Line Items]      
Capital lease obligations, noncurrent 69,000,000 29,000,000  
Due in 2015 17,000,000    
Due in 2016 18,000,000    
Due in 2017 20,000,000    
Due in 2018 5,000,000    
Due in 2019 1,000,000    
Due in 2020 8,000,000    
Exelon Generation Co L L C [Member]      
Debt Instrument [Line Items]      
Long-term Debt, Gross 9,208,000,000 8,919,000,000  
Unamortized debt discount and premium, net (17,000,000) (17,000,000)  
Long-term debt (including amounts due within one year) (a) 115,000,000 127,000,000  
Long-term debt due within one year (1,117,000,000) (90,000,000)  
Long-term debt 7,202,000,000 7,936,000,000  
Long-term debt to financing trusts 922,000,000 933,000,000  
Debt and Capital Lease Obligations 8,124,000,000 8,869,000,000  
Unamortized Debt Issuance Expense (65,000,000) (70,000,000)  
Capital lease obligations, noncurrent 22,000,000 21,000,000  
Due in 2016 5,000,000    
Due in 2017 6,000,000    
Due in 2018 5,000,000    
Exelon Generation Co L L C [Member] | Senior Notes [Member]      
Debt Instrument [Line Items]      
Long-term Debt, Gross $ 5,971,000,000 5,971,000,000  
Exelon Generation Co L L C [Member] | Senior Notes [Member] | Minimum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 2.00%    
Interest rate on long-term debt 2.00%    
Exelon Generation Co L L C [Member] | Senior Notes [Member] | Maximum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 7.60%    
Interest rate on long-term debt 7.60%    
Exelon Generation Co L L C [Member] | Pollution Control Notes [Member]      
Debt Instrument [Line Items]      
Long-term Debt, Gross $ 435,000,000 435,000,000  
Exelon Generation Co L L C [Member] | Pollution Control Notes [Member] | Minimum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 2.50%    
Interest rate on long-term debt 2.50%    
Exelon Generation Co L L C [Member] | Pollution Control Notes [Member] | Maximum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 2.70%    
Interest rate on long-term debt 2.70%    
Exelon Generation Co L L C [Member] | Notes Payable to Banks [Member]      
Debt Instrument [Line Items]      
Long-term Debt, Gross $ 105,000,000 127,000,000  
Exelon Generation Co L L C [Member] | Notes Payable to Banks [Member] | Minimum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 3.20%    
Interest rate on long-term debt 3.20%    
Exelon Generation Co L L C [Member] | Notes Payable to Banks [Member] | Maximum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 3.40%    
Interest rate on long-term debt 3.40%    
Exelon Generation Co L L C [Member] | Notes Payable, Other Payables [Member]      
Debt Instrument [Line Items]      
Long-term Debt, Gross [5],[6] $ 382,000,000 166,000,000  
Long-term debt $ 198,000,000    
Exelon Generation Co L L C [Member] | Notes Payable, Other Payables [Member] | Minimum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 1.40%    
Interest rate on long-term debt 1.40%    
Exelon Generation Co L L C [Member] | Notes Payable, Other Payables [Member] | Maximum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 7.80%    
Interest rate on long-term debt 7.80%    
Exelon Generation Co L L C [Member] | Non Recourse Fixed Rate [Member]      
Debt Instrument [Line Items]      
Long-term Debt, Gross $ 1,400,000,000 1,162,000,000  
Exelon Generation Co L L C [Member] | Non Recourse Fixed Rate [Member] | Minimum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 2.30%    
Interest rate on long-term debt 2.30%    
Exelon Generation Co L L C [Member] | Non Recourse Fixed Rate [Member] | Maximum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 6.00%    
Interest rate on long-term debt 6.00%    
Exelon Generation Co L L C [Member] | Non Recourse Variable Rate [Member]      
Debt Instrument [Line Items]      
Long-term Debt, Gross $ 915,000,000 1,058,000,000  
Exelon Generation Co L L C [Member] | Non Recourse Variable Rate [Member] | Minimum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 3.20%    
Interest rate on long-term debt 3.20%    
Exelon Generation Co L L C [Member] | Non Recourse Variable Rate [Member] | Maximum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 5.00%    
Interest rate on long-term debt 5.00%    
Potomac Electric Power Company [Member]      
Debt Instrument [Line Items]      
Long-term Debt, Gross $ 2,381,000,000 2,385,000,000  
Unamortized debt discount and premium, net (2,000,000) (3,000,000)  
Long-term debt 2,333,000,000 2,340,000,000  
Long-term debt due within one year (16,000,000) (11,000,000)  
Long-term debt 2,333,000,000 2,340,000,000  
Unamortized Debt Issuance Expense [7] (30,000,000) (31,000,000)  
Potomac Electric Power Company [Member] | Secured Debt [Member]      
Debt Instrument [Line Items]      
Long-term Debt, Gross $ 2,335,000,000 2,335,000,000  
Potomac Electric Power Company [Member] | Secured Debt [Member] | Minimum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 3.05%    
Interest rate on long-term debt 3.05%    
Potomac Electric Power Company [Member] | Secured Debt [Member] | Maximum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 7.90%    
Interest rate on long-term debt 7.90%    
Potomac Electric Power Company [Member] | Notes Payable, Other Payables [Member]      
Debt Instrument [Line Items]      
Long-term Debt, Gross $ 46,000,000 50,000,000  
Potomac Electric Power Company [Member] | Notes Payable, Other Payables [Member] | Minimum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 6.20%    
Interest rate on long-term debt 6.20%    
Potomac Electric Power Company [Member] | Notes Payable, Other Payables [Member] | Maximum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 8.88%    
Interest rate on long-term debt 8.88%    
Commonwealth Edison Co [Member]      
Debt Instrument [Line Items]      
Long-term Debt, Gross $ 7,101,000,000 6,567,000,000  
Unamortized debt discount and premium, net (22,000,000) (20,000,000)  
Long-term debt due within one year (425,000,000) (665,000,000)  
Long-term debt 6,608,000,000 5,844,000,000  
Long-term debt to financing trusts 205,000,000 205,000,000  
Total long-term debt to financing trusts 206,000,000 206,000,000  
Debt and Capital Lease Obligations 6,608,000,000 5,844,000,000  
Unamortized Debt Issuance Expense [8] (46,000,000) (38,000,000)  
Commonwealth Edison Co [Member] | ComEd Financing Three Affiliate [Member]      
Debt Instrument [Line Items]      
Long-term Debt, Gross 206,000,000 206,000,000  
Long-term debt to financing trusts 205,000,000 205,000,000  
Unamortized Debt Issuance Expense [8] $ (1,000,000) (1,000,000)  
Commonwealth Edison Co [Member] | ComEd Financing Three Affiliate [Member] | Maximum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 6.35%    
Interest rate on long-term debt 6.35%    
Commonwealth Edison Co [Member] | Secured Debt [Member]      
Debt Instrument [Line Items]      
Long-term Debt, Gross [9] $ 6,954,000,000 6,419,000,000  
Commonwealth Edison Co [Member] | Secured Debt [Member] | Minimum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage [9] 2.15%    
Interest rate on long-term debt [9] 2.15%    
Commonwealth Edison Co [Member] | Secured Debt [Member] | Maximum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage [9] 6.45%    
Interest rate on long-term debt [9] 6.45%    
Commonwealth Edison Co [Member] | Notes Payable, Other Payables [Member]      
Debt Instrument [Line Items]      
Long-term Debt, Gross [10] $ 147,000,000 148,000,000  
Commonwealth Edison Co [Member] | Notes Payable, Other Payables [Member] | Minimum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage [10] 6.95%    
Interest rate on long-term debt [10] 6.95%    
Commonwealth Edison Co [Member] | Notes Payable, Other Payables [Member] | Maximum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage [10] 7.49%    
Interest rate on long-term debt [10] 7.49%    
Commonwealth Edison Co [Member] | Capital Lease Obligations [Member]      
Debt Instrument [Line Items]      
Capital lease obligations, noncurrent $ 8,000,000    
Due in 2020 1,000,000    
PECO Energy Co [Member]      
Debt Instrument [Line Items]      
Long-term Debt, Gross 2,600,000,000 2,600,000,000  
Unamortized debt discount and premium, net (5,000,000) (5,000,000)  
Long-term debt 2,580,000,000 2,280,000,000  
Long-term debt to financing trusts 184,000,000 184,000,000  
Long-term debt due within one year 0 (300,000,000)  
Debt and Capital Lease Obligations 2,580,000,000 2,280,000,000  
Unamortized Debt Issuance Expense [7] (15,000,000) (15,000,000)  
PECO Energy Co [Member] | PECO Trust Three Affiliate [Member]      
Debt Instrument [Line Items]      
Long-term debt to financing trusts $ 81,000,000 81,000,000  
PECO Energy Co [Member] | PECO Trust Three Affiliate [Member] | Maximum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 7.38%    
Interest rate on long-term debt 7.38%    
PECO Energy Co [Member] | PECO Trust Four Affiliate [Member]      
Debt Instrument [Line Items]      
Long-term debt to financing trusts $ 103,000,000 103,000,000  
PECO Energy Co [Member] | PECO Trust Four Affiliate [Member] | Maximum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 5.75%    
Interest rate on long-term debt 5.75%    
PECO Energy Co [Member] | Secured Debt [Member]      
Debt Instrument [Line Items]      
Long-term Debt, Gross [11] $ 2,600,000,000 2,600,000,000  
PECO Energy Co [Member] | Secured Debt [Member] | Minimum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage [11] 1.70%    
Interest rate on long-term debt [11] 1.70%    
PECO Energy Co [Member] | Secured Debt [Member] | Maximum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage [11] 5.95%    
Interest rate on long-term debt [11] 5.95%    
Baltimore Gas and Electric Company [Member]      
Debt Instrument [Line Items]      
Long-term Debt, Gross $ 2,341,000,000 1,870,000,000  
Unamortized debt discount and premium, net (4,000,000) (3,000,000)  
Long-term debt 2,281,000,000 1,480,000,000  
Long-term debt to financing trusts 252,000,000 252,000,000  
Total long-term debt to financing trusts 258,000,000 258,000,000  
Long-term debt due within one year (41,000,000) (378,000,000)  
Long-term debt 2,281,000,000 1,480,000,000  
Unamortized Debt Issuance Expense [12] (15,000,000) (9,000,000)  
Baltimore Gas and Electric Company [Member] | BGE Trust Member [Member]      
Debt Instrument [Line Items]      
Long-term debt to financing trusts   252,000,000  
Total long-term debt to financing trusts 258,000,000 258,000,000  
Unamortized Debt Issuance Expense [12] $ (6,000,000) (6,000,000)  
Baltimore Gas and Electric Company [Member] | BGE Trust Member [Member] | Maximum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 6.20%    
Interest rate on long-term debt 6.20%    
Baltimore Gas and Electric Company [Member] | Rate Stabilization Bonds [Member]      
Debt Instrument [Line Items]      
Long-term Debt, Gross $ 41,000,000 120,000,000  
Baltimore Gas and Electric Company [Member] | Rate Stabilization Bonds [Member] | Minimum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 5.82%    
Interest rate on long-term debt 5.82%    
Baltimore Gas and Electric Company [Member] | Rate Stabilization Bonds [Member] | Maximum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 5.82%    
Interest rate on long-term debt 5.82%    
Baltimore Gas and Electric Company [Member] | Senior Notes [Member]      
Debt Instrument [Line Items]      
Long-term Debt, Gross $ 2,300,000,000 1,750,000,000  
Baltimore Gas and Electric Company [Member] | Senior Notes [Member] | Minimum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 2.40%    
Interest rate on long-term debt 2.40%    
Baltimore Gas and Electric Company [Member] | Senior Notes [Member] | Maximum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 6.35%    
Interest rate on long-term debt 6.35%    
Pepco Holdings LLC [Member]      
Debt Instrument [Line Items]      
Long-term Debt, Gross $ 5,157,000,000 5,331,000,000  
Unamortized debt discount and premium, net 1,000,000 (2,000,000)  
Long-term debt (including amounts due within one year) (a) 742,000,000 0  
Long-term debt due within one year (253,000,000) (456,000,000)  
Long-term debt 5,645,000,000 4,823,000,000  
Unamortized Debt Issuance Expense [7] (2,000,000) (50,000,000)  
Pepco Holdings LLC [Member] | Unsecured Debt [Member]      
Debt Instrument [Line Items]      
Long-term Debt, Gross $ 266,000,000 456,000,000  
Pepco Holdings LLC [Member] | Unsecured Debt [Member] | Minimum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 6.13%    
Interest rate on long-term debt 6.13%    
Pepco Holdings LLC [Member] | Unsecured Debt [Member] | Maximum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 7.45%    
Interest rate on long-term debt 7.45%    
Pepco Holdings LLC [Member] | Secured Debt [Member]      
Debt Instrument [Line Items]      
Long-term Debt, Gross $ 4,569,000,000 4,495,000,000  
Pepco Holdings LLC [Member] | Secured Debt [Member] | Minimum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 3.05%    
Interest rate on long-term debt 3.05%    
Pepco Holdings LLC [Member] | Secured Debt [Member] | Maximum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 7.90%    
Interest rate on long-term debt 7.90%    
Pepco Holdings LLC [Member] | Notes Payable, Other Payables [Member]      
Debt Instrument [Line Items]      
Long-term Debt, Gross $ 46,000,000 57,000,000  
Pepco Holdings LLC [Member] | Notes Payable, Other Payables [Member] | Minimum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 6.20%    
Interest rate on long-term debt 6.20%    
Pepco Holdings LLC [Member] | Notes Payable, Other Payables [Member] | Maximum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 8.88%    
Interest rate on long-term debt 8.88%    
Pepco Holdings LLC [Member] | Tax-exempt Money Market Funds [Member]      
Debt Instrument [Line Items]      
Long-term Debt, Gross $ 112,000,000 112,000,000  
Pepco Holdings LLC [Member] | Tax-exempt Money Market Funds [Member] | Maximum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 5.40%    
Interest rate on long-term debt 5.40%    
Pepco Holdings LLC [Member] | Medium-term Notes [Member]      
Debt Instrument [Line Items]      
Long-term Debt, Gross $ 40,000,000 40,000,000  
Pepco Holdings LLC [Member] | Medium-term Notes [Member] | Minimum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 6.81%    
Interest rate on long-term debt 6.81%    
Pepco Holdings LLC [Member] | Medium-term Notes [Member] | Maximum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 7.72%    
Interest rate on long-term debt 7.72%    
Pepco Holdings LLC [Member] | Transition Bonds [Member]      
Debt Instrument [Line Items]      
Long-term Debt, Gross [13] $ 124,000,000 171,000,000  
Pepco Holdings LLC [Member] | Transition Bonds [Member] | Minimum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 5.05%    
Interest rate on long-term debt 5.05%    
Pepco Holdings LLC [Member] | Transition Bonds [Member] | Maximum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 5.55%    
Interest rate on long-term debt 5.55%    
Delmarva Power and Light Company [Member]      
Debt Instrument [Line Items]      
Long-term Debt, Gross $ 1,348,000,000 1,273,000,000  
Unamortized debt discount and premium, net 2,000,000 2,000,000  
Long-term debt due within one year (105,000,000)    
Long-term debt 1,221,000,000 1,061,000,000  
Long-term debt due within one year (119,000,000) (204,000,000)  
Long-term debt 1,221,000,000 1,061,000,000  
Unamortized Debt Issuance Expense [7] (10,000,000) (10,000,000)  
Delmarva Power and Light Company [Member] | Secured Debt [Member]      
Debt Instrument [Line Items]      
Long-term Debt, Gross $ 1,196,000,000 1,121,000,000  
Delmarva Power and Light Company [Member] | Secured Debt [Member] | Minimum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 3.50%    
Interest rate on long-term debt 3.50%    
Delmarva Power and Light Company [Member] | Secured Debt [Member] | Maximum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 4.15%    
Interest rate on long-term debt 4.15%    
Delmarva Power and Light Company [Member] | Tax-exempt Money Market Funds [Member]      
Debt Instrument [Line Items]      
Long-term Debt, Gross $ 112,000,000 112,000,000  
Delmarva Power and Light Company [Member] | Tax-exempt Money Market Funds [Member] | Maximum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 5.40%    
Interest rate on long-term debt 5.40%    
Delmarva Power and Light Company [Member] | Medium-term Notes [Member]      
Debt Instrument [Line Items]      
Long-term Debt, Gross $ 40,000,000 40,000,000  
Delmarva Power and Light Company [Member] | Medium-term Notes [Member] | Minimum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 6.81%    
Interest rate on long-term debt 6.81%    
Delmarva Power and Light Company [Member] | Medium-term Notes [Member] | Maximum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 7.72%    
Interest rate on long-term debt 7.72%    
Atlantic City Electric Company [Member]      
Debt Instrument [Line Items]      
Long-term Debt, Gross $ 1,162,000,000 1,210,000,000  
Unamortized debt discount and premium, net (1,000,000) (1,000,000)  
Long-term debt 1,120,000,000 1,153,000,000  
Long-term debt due within one year (35,000,000) (48,000,000)  
Long-term debt 1,120,000,000 1,153,000,000  
Unamortized Debt Issuance Expense [7] (6,000,000) (8,000,000)  
Atlantic City Electric Company [Member] | Secured Debt [Member]      
Debt Instrument [Line Items]      
Long-term Debt, Gross $ 1,038,000,000 1,039,000,000  
Atlantic City Electric Company [Member] | Secured Debt [Member] | Minimum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 3.38%    
Interest rate on long-term debt 3.38%    
Atlantic City Electric Company [Member] | Secured Debt [Member] | Maximum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 7.75%    
Interest rate on long-term debt 7.75%    
Atlantic City Electric Company [Member] | Transition Bonds [Member]      
Debt Instrument [Line Items]      
Long-term Debt, Gross [14] $ 124,000,000 $ 171,000,000  
Atlantic City Electric Company [Member] | Transition Bonds [Member] | Minimum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 5.05%    
Interest rate on long-term debt 5.05%    
Atlantic City Electric Company [Member] | Transition Bonds [Member] | Maximum [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 5.55%    
Interest rate on long-term debt 5.55%    
[1] Amounts owed to these financing trusts are recorded as Long-term debt to financing trusts within Exelon’s Consolidated Balance Sheets.
[2] Substantially all of ComEd’s assets other than expressly excepted property and substantially all of PECO’s, Pepco's, DPL's and ACE's assets are subject to the liens of their respective mortgage indentures.
[3] Includes capital lease obligations of $69 million and $29 million at December 31, 2016 and 2015, respectively. Lease payments of $17 million, $18 million, $20 million, $5 million, $1 million, and $8 million will be made in 2017, 2018, 2019, 2020, 2021 and thereafter, respectively.
[4] Includes financing related to Albany Green Energy, LLC (AGE), which is a consolidated variable interest entity (see Note 2 - Variable Interest Entities for additional information). The agreement is scheduled to expire on November 17, 2017, at a variable rate equal to LIBOR plus 1.25%. As of December 31, 2016, $198 million was outstanding.
[5] Includes Generation’s capital lease obligations of $22 million and $21 million at December 31, 2016 and 2015, respectively. Generation will make lease payments of $5 million, $5 million, $6 million and $5 million and $1 million in 2017, 2018, 2019, 2020 and 2021 respectively. The capital lease matures in 2020.
[6] Includes financing related to Albany Green Energy, LLC (AGE), which is a consolidated variable interest entity (see Note 2 - Variable Interest Entities for additional information). The agreement is scheduled to expire on November 17, 2017, at a variable rate equal to LIBOR plus 1.25%. As of December 31, 2016, $198 million was outstanding.
[7] Amounts owed to this financing trust are recorded as Long-term debt to financing trusts within PECO’s Consolidated Balance Sheets.
[8] Amount owed to this financing trust is recorded as Long-term debt to financing trust within ComEd’s Consolidated Balance Sheets.
[9] Substantially all of ComEd’s assets other than expressly excepted property are subject to the lien of its mortgage indenture.
[10] Includes ComEd’s capital lease obligations of $8 million at both December 31, 2016 and 2015, respectively. Lease payments of less than $1 million will be made from 2017 through expiration at 2053.
[11] Substantially all of PECO’s assets are subject to the lien of its mortgage indenture
[12] Amount owed to this financing trust is recorded as Long-term debt to financing trust within BGE’s Consolidated Balance Sheets.
[13] Transition bonds are recorded as part of Long-term debt within ACE's Consolidated Balance Sheets.
[14] Substantially all of ACE's assets are subject to the lien of its respective mortgage indenture.