Debt and Credit Agreements - Summary of Outstanding Long-term Debt (Details) - USD ($) $ in Millions		9 Months Ended	12 Months Ended
		Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jun. 30, 2014
Debt Instrument [Line Items]
Long-term Debt, Gross			$ 33,657	$ 33,311
Unamortized debt discount and premium, net			(57)	(68)
Long-term debt (including amounts due within one year)(a)			865	962
Long-term debt due within one year			(2,088)	(2,430)
Long-term debt			32,176	31,575
Long-term debt to financing trusts			389	641
Total long-term debt to financing trusts			390	648
Unamortized Debt Issuance Expense	[1]		(201)	(200)
Repayments of Long-term Debt			2,490	1,936	$ 2,687
2017			2,075
2018			959
2019			3,564
2020			1,513
2021			3,084
ComEd Financing Three Affiliate [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross			206	206
Long-term debt to financing trusts			$ 205	205
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	81
Long-term debt to financing trusts			$ 81	81
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	103
Long-term debt to financing trusts			$ 103	103
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			$ 0	258
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			$ 2,600	2,300
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			$ 0	41
Rate Stabilization Bonds [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage
Interest rate on long-term debt
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]		$ 15,197	14,123
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			$ 11,285	11,868
Senior Notes [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			2.45%
Interest rate on long-term debt			2.45%
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	435
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			$ 82	105
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]		$ 405	576
Unamortized Debt Issuance Expense	[1]		$ (1)	(7)
Notes Payable, Other Payables [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[3]		2.61%
Interest rate on long-term debt	[3]		2.61%
Notes Payable, Other Payables [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[3]		8.88%
Interest rate on long-term debt	[3]		8.88%
Junior Subordinated Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			3.497%			2.50%
Long-term Debt, Gross			$ 1,150	1,150
Interest rate on long-term debt			3.497%			2.50%
Junior Subordinated Debt [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			3.50%
Interest rate on long-term debt			3.50%
contract Payments Junior Subordinate Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross			$ 0	19
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			$ 79	103
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	112
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			$ 26	40
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			$ 90	124
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			$ 1,331	1,400
Non Recourse Fixed Rate [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			2.29%
Interest rate on long-term debt			2.29%
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%
Non Recourse Variable Rate [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross			$ 865	915
Non Recourse Variable Rate [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			3.18%
Interest rate on long-term debt			3.18%
Non Recourse Variable Rate [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			4.00%
Interest rate on long-term debt			4.00%
Capital Lease Obligations [Member]
Debt Instrument [Line Items]
Capital lease obligations, noncurrent			$ 53	69
Due in 2015			18
Due in 2016			20
Due in 2017			5
Due in 2018			1
Due in 2019			1
Due in 2020			8
Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross			8,955	9,208
Unamortized debt discount and premium, net			(8)	(17)
Long-term debt due within one year			(346)	(1,117)
Long-term debt			7,734	7,202
Long-term debt to financing trusts			910	922
Debt and Capital Lease Obligations			8,644	8,124
Unamortized Debt Issuance Expense			(60)	(65)
Capital lease obligations, noncurrent			18	22
Due in 2015			5
Due in 2016			6
Due in 2017			5
Due in 2018			1
Repayments of Long-term Debt			1,261	202	89
2017			346
2018			615
2019			2,144
2020			1
2021			1,024
Exelon Generation Co L L C [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross			$ 6,019	5,971
Exelon Generation Co L L C [Member] | Senior Notes [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			2.95%
Interest rate on long-term debt			2.95%
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	435
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			$ 82	105
Exelon Generation Co L L C [Member] | Notes Payable to Banks [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			3.15%
Interest rate on long-term debt			3.15%
Exelon Generation Co L L C [Member] | Notes Payable to Banks [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			3.35%
Interest rate on long-term debt			3.35%
Exelon Generation Co L L C [Member] | Notes Payable, Other Payables [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	[5],[6]		$ 223	382
Long-term debt			$ 198
Exelon Generation Co L L C [Member] | Notes Payable, Other Payables [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			2.61%
Interest rate on long-term debt			2.61%
Exelon Generation Co L L C [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%
Exelon Generation Co L L C [Member] | Non Recourse Fixed Rate [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross			$ 1,331	1,400
Exelon Generation Co L L C [Member] | Non Recourse Fixed Rate [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			2.29%
Interest rate on long-term debt			2.29%
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			$ 865	915
Exelon Generation Co L L C [Member] | Non Recourse Variable Rate [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			3.18%
Interest rate on long-term debt			3.18%
Exelon Generation Co L L C [Member] | Non Recourse Variable Rate [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			4.00%
Interest rate on long-term debt			4.00%
Potomac Electric Power Company [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross			$ 2,570	2,381
Unamortized debt discount and premium, net			2	(2)
Long-term debt			2,521	2,333
Long-term debt due within one year			(19)	(16)
Long-term debt			2,521	2,333
Unamortized Debt Issuance Expense	[7]		(32)	(30)
Due in 2015			13
Due in 2016			14
Repayments of Long-term Debt			13	11	22
2017			19
2018			14
2019			0
2020			2
2021			310
Potomac Electric Power Company [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross			$ 2,535	2,335
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			$ 35	46
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%
Potomac Electric Power Company [Member] | Capital Lease Obligations [Member]
Debt Instrument [Line Items]
Capital lease obligations, noncurrent			$ 27	39
Commonwealth Edison Co [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross			7,676	7,101
Unamortized debt discount and premium, net			(23)	(22)
Long-term debt due within one year			(840)	(425)
Long-term debt			6,761	6,608
Long-term debt to financing trusts			205	205
Total long-term debt to financing trusts			206	206
Debt and Capital Lease Obligations			6,761	6,608
Unamortized Debt Issuance Expense	[8]		(52)	(46)
Repayments of Long-term Debt			425	665	260
2017			840
2018			300
2019			500
2020			350
2021			0
Commonwealth Edison Co [Member] | ComEd Financing Three Affiliate [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross			206	206
Long-term debt to financing trusts			205	205
Unamortized Debt Issuance Expense	[8]		$ (1)	(1)
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]		$ 7,529	6,954
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	147
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
Due in 2020			1
PECO Energy Co [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross			2,925	2,600
Unamortized debt discount and premium, net			(5)	(5)
Long-term debt			2,403	2,580
Long-term debt to financing trusts			184	184
Long-term debt due within one year			(500)	0
Debt and Capital Lease Obligations			2,403	2,580
Unamortized Debt Issuance Expense	[7]		(17)	(15)
Repayments of Long-term Debt			0	300	0
2017			500
2018			0
2019			0
2020			300
2021			350
PECO Energy Co [Member] | PECO Trust Three Affiliate [Member]
Debt Instrument [Line Items]
Long-term debt to financing trusts			$ 81	81
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	103
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]		$ 2,925	2,600
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			$ 2,600	2,341
Unamortized debt discount and premium, net			(6)	(4)
Long-term debt			2,577	2,281
Long-term debt to financing trusts			0	252
Total long-term debt to financing trusts			0	258
Long-term debt due within one year			0	(41)
Long-term debt			2,577	2,281
Unamortized Debt Issuance Expense			(17)	(15)
Repayments of Long-term Debt			41	379	75
2017			0
2018			0
2019			0
2020			300
2021			250
Baltimore Gas and Electric Company [Member] | BGE Trust Member [Member]
Debt Instrument [Line Items]
Long-term debt to financing trusts			0	252
Total long-term debt to financing trusts			0	258
Unamortized Debt Issuance Expense			$ 0	(6)
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			$ 0	41
Baltimore Gas and Electric Company [Member] | Rate Stabilization Bonds [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage
Interest rate on long-term debt
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			$ 2,600	2,300
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			$ 5,189	5,157
Unamortized debt discount and premium, net			5	1
Long-term debt (including amounts due within one year)(a)			686
Long-term debt due within one year			(396)	(253)
Long-term debt			5,478	5,645
Unamortized Debt Issuance Expense	[7]		(6)	(2)
2017			383
2018			44
2019			20
2020			262
2021			310
Pepco Holdings LLC [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross			$ 185	266
Pepco Holdings LLC [Member] | Unsecured Debt [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage
Interest rate on long-term debt
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	[12]		$ 4,743	4,569
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	[13]		$ 33	46
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	112
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			$ 26	40
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	[14]		$ 90	124
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			$ 1,309	1,348
Unamortized debt discount and premium, net			2	2
Long-term debt due within one year			(79)	(105)
Long-term debt			1,217	1,221
Long-term debt due within one year			(83)	(119)
Long-term debt			1,217	1,221
Unamortized Debt Issuance Expense	[7]		(11)	(10)
Repayments of Long-term Debt			40	100	100
2017			83
2018			12
2019			0
2020			0
2021			0
Delmarva Power and Light Company [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross			$ 1,171	1,196
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	112
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			$ 26	40
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			$ 1,127	1,162
Unamortized debt discount and premium, net			(1)	(1)
Long-term debt			840	1,120
Long-term debt due within one year			(281)	(35)
Long-term debt			840	1,120
Unamortized Debt Issuance Expense	[7]		(5)	(6)
Repayments of Long-term Debt			35	48	$ 58
2017			281
2018			18
2019			20
2020			260
2021			0
Atlantic City Electric Company [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross			$ 1,037	1,038
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	[15]		$ 90	$ 124
2017			31
2018			18
2019			20
2020			$ 21
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%
AGEPFNotesNov2017 [Member] | AGE Biomass project [Member] | Long-term Debt [Member]
Debt Instrument [Line Items]
Repayments of Long-term Debt		$ 228

[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 $53 million and $69 million at December 31, 2017 and 2016, respectively. Lease payments of $18 million, $20 million, $5 million, $1 million, $1 million and $8 million will be made in 2018, 2019, 2020, 2021, 2022 and thereafter, respectively.

[4] Includes financing related to Albany Green Energy, LLC (AGE). During the third quarter of 2017, Generation retired $228 million of its outstanding debt balance. As of December 31, 2016, $198 million was outstanding.

[5] Includes Generation’s capital lease obligations of $18 million and $22 million at December 31, 2017 and 2016, respectively. Generation will make lease payments of $5 million, $6 million, $5 million, $1 million and $1 million in 2018, 2019, 2020, 2021 and 2022 respectively. The capital lease matures in 2022.

[6] Includes financing related to Albany Green Energy, LLC (AGE).

[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, 2017 and 2016, respectively. Lease payments of less than $1 million annually will be made from 2018 through expiration at 2053.

[11] Substantially all of PECO’s assets are subject to the lien of its mortgage indenture

[12] Substantially all of Pepco's, DPL's, and ACE's assets are subject to the lien of its respective mortgage indenture.

[13] Includes Pepco's capital lease obligations of $27 million and $39 million at December 31, 2017 and 2016, respectively.

[14] Transition bonds are recorded as part of Long-term debt within ACE's Consolidated Balance Sheets.

[15] Substantially all of ACE's assets are subject to the lien of its respective mortgage indenture.