XML 131 R86.htm IDEA: XBRL DOCUMENT v3.8.0.1
Income Taxes - Reconciliation to Effective Tax Rate (Details)
 3 Months Ended 12 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Dec. 31, 2018
Dec. 31, 2017
Effective Income Tax Rate Reconciliation, Percent [Abstract]        
U.S. Federal statutory rate 21.00% 35.00% 21.00% 35.00%
Increase (decrease) due to:        
State income taxes, net of Federal income tax benefit 4.10% 0.90%    
Qualified nuclear decommissioning trust fund income (0.40%) 3.50%    
Amortization of investment tax credit, including deferred taxes on basis difference (1.30%) (0.40%)    
Plant basis differences (2.70%) (2.40%)    
Production tax credits and other credits (2.80%) (0.70%)    
Noncontrolling interests (0.70%) 0.00%    
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent (6.00%)      
Statute of limitations expiration [1]   (11.50%)    
EffectiveIncomeTaxRateReconciliationPenalties   (6.60%)    
Other (2.80%) (0.10%)    
Effective income tax rate 8.40% 17.70%    
Exelon Generation Co L L C [Member]        
Effective Income Tax Rate Reconciliation, Percent [Abstract]        
U.S. Federal statutory rate 21.00% 35.00%    
Increase (decrease) due to:        
State income taxes, net of Federal income tax benefit 2.40% 1.00%    
Qualified nuclear decommissioning trust fund income (1.30%) 7.80%    
Amortization of investment tax credit, including deferred taxes on basis difference (4.30%) (0.70%)    
Plant basis differences 0.00% 0.00%    
Production tax credits and other credits (9.50%) (1.50%)    
Noncontrolling interests (2.50%) 0.10%    
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent 0.00%      
Statute of limitations expiration [1]   (3.40%)    
EffectiveIncomeTaxRateReconciliationPenalties   (14.80%)    
Other (1.30%) (0.40%)    
Effective income tax rate 4.50% 23.10%    
Commonwealth Edison Co [Member]        
Effective Income Tax Rate Reconciliation, Percent [Abstract]        
U.S. Federal statutory rate 21.00% 35.00%    
Increase (decrease) due to:        
State income taxes, net of Federal income tax benefit 8.20% 4.90%    
Qualified nuclear decommissioning trust fund income (0.00%) (0.00%)    
Amortization of investment tax credit, including deferred taxes on basis difference (0.20%) (0.20%)    
Plant basis differences 0.10% (0.20%)    
Production tax credits and other credits (0.10%) 0.00%    
Noncontrolling interests 0.00% 0.00%    
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent (7.50%)      
Statute of limitations expiration [1]   0.00%    
EffectiveIncomeTaxRateReconciliationPenalties   0.00%    
Other 0.30% (0.00%)    
Effective income tax rate 21.80% 39.50%    
PECO Energy Co [Member]        
Effective Income Tax Rate Reconciliation, Percent [Abstract]        
U.S. Federal statutory rate 21.00% 35.00%    
Increase (decrease) due to:        
State income taxes, net of Federal income tax benefit (3.90%) 0.10%    
Qualified nuclear decommissioning trust fund income (0.00%) (0.00%)    
Amortization of investment tax credit, including deferred taxes on basis difference (0.10%) (0.10%)    
Plant basis differences (14.20%) (13.20%)    
Production tax credits and other credits 0.00% 0.00%    
Noncontrolling interests 0.00% 0.00%    
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent (4.80%)      
Statute of limitations expiration [1]   0.00%    
EffectiveIncomeTaxRateReconciliationPenalties   0.00%    
Other 0.20% 0.30%    
Effective income tax rate (1.80%) 22.10%    
Baltimore Gas and Electric Company [Member]        
Effective Income Tax Rate Reconciliation, Percent [Abstract]        
U.S. Federal statutory rate 21.00% 35.00%    
Increase (decrease) due to:        
State income taxes, net of Federal income tax benefit 6.30% 5.20%    
Qualified nuclear decommissioning trust fund income (0.00%) (0.00%)    
Amortization of investment tax credit, including deferred taxes on basis difference (0.10%) (0.10%)    
Plant basis differences (0.70%) (0.90%)    
Production tax credits and other credits 0.00% 0.00%    
Noncontrolling interests 0.00% 0.00%    
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent (8.60%)      
Statute of limitations expiration [1]   0.00%    
EffectiveIncomeTaxRateReconciliationPenalties   0.00%    
Other (0.00%) (0.20%)    
Effective income tax rate 17.90% 39.00%    
Potomac Electric Power Company [Member]        
Effective Income Tax Rate Reconciliation, Percent [Abstract]        
U.S. Federal statutory rate 21.00% 35.00%    
Increase (decrease) due to:        
State income taxes, net of Federal income tax benefit 1.70% 4.60%    
Qualified nuclear decommissioning trust fund income (0.00%) (0.00%)    
Amortization of investment tax credit, including deferred taxes on basis difference (0.10%) (0.10%)    
Plant basis differences (3.40%) (5.80%)    
Production tax credits and other credits 0.00% 0.00%    
Noncontrolling interests 0.00% 0.00%    
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent (12.80%)      
Statute of limitations expiration [1]   (34.20%)    
EffectiveIncomeTaxRateReconciliationPenalties   0.00%    
Other (0.30%) 0.50%    
Effective income tax rate 6.10% 0.00%    
Delmarva Power and Light Company [Member]        
Effective Income Tax Rate Reconciliation, Percent [Abstract]        
U.S. Federal statutory rate 21.00% 35.00%    
Increase (decrease) due to:        
State income taxes, net of Federal income tax benefit 6.30% 5.30%    
Qualified nuclear decommissioning trust fund income (0.00%) (0.00%)    
Amortization of investment tax credit, including deferred taxes on basis difference (0.20%) (0.30%)    
Plant basis differences (1.30%) (1.90%)    
Production tax credits and other credits 0.00% 0.00%    
Noncontrolling interests 0.00% 0.00%    
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent (7.90%)      
Statute of limitations expiration [1]   (21.90%)    
EffectiveIncomeTaxRateReconciliationPenalties   0.00%    
Other 0.50% (0.00%)    
Effective income tax rate 18.40% 16.20%    
Atlantic City Electric Company [Member]        
Effective Income Tax Rate Reconciliation, Percent [Abstract]        
U.S. Federal statutory rate 21.00% 35.00%    
Increase (decrease) due to:        
State income taxes, net of Federal income tax benefit 6.60% 5.60%    
Qualified nuclear decommissioning trust fund income (0.00%) (0.00%)    
Amortization of investment tax credit, including deferred taxes on basis difference (0.30%) (0.40%)    
Plant basis differences (2.60%) (3.40%)    
Production tax credits and other credits 0.00% 0.00%    
Noncontrolling interests 0.00% 0.00%    
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent (8.70%)      
Statute of limitations expiration [1]   (167.10%)    
EffectiveIncomeTaxRateReconciliationPenalties   0.00%    
Other (3.50%) (3.00%)    
Effective income tax rate 12.50% (133.30%)    
Pepco Holdings LLC [Member]        
Effective Income Tax Rate Reconciliation, Percent [Abstract]        
U.S. Federal statutory rate 21.00% 35.00%    
Increase (decrease) due to:        
State income taxes, net of Federal income tax benefit 4.60% 4.90%    
Qualified nuclear decommissioning trust fund income (0.00%) (0.00%)    
Amortization of investment tax credit, including deferred taxes on basis difference (0.20%) (0.20%)    
Plant basis differences (2.60%) (3.80%)    
Production tax credits and other credits 0.00% 0.00%    
Noncontrolling interests 0.00% 0.00%    
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent (10.60%)      
Statute of limitations expiration [1]   (42.40%)    
EffectiveIncomeTaxRateReconciliationPenalties   0.00%    
Other (0.00%) (0.40%)    
Effective income tax rate 12.20% (6.90%)    
[1] Includes a remeasurement of uncertain state income tax positions for Pepco and DPL.