Commitments and Contingencies - Schedule of Minimum Future Operating Lease Payments (Details) - USD ($) $ in Millions		3 Months Ended	9 Months Ended	12 Months Ended
		Mar. 23, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Nov. 30, 2016
Operating Leases Future Minimum Payments Due [Line Items]
Lease and rental expense				$ 777	$ 922	$ 865
2015			$ 183	183
2016			179	179
2017			123	123
2018			140	140
2019			133	133
Remaining years			968	968
Total minimum future lease payments			1,726	1,726
Exelon Generation Co L L C [Member]
Operating Leases Future Minimum Payments Due [Line Items]
Lease and rental expense	[1]			667	851	806
2015			70	70
2016			75	75
2017			30	30
2018			48	48
2019			47	47
Remaining years			644	644
Total minimum future lease payments			914	914
Commonwealth Edison Co [Member]
Operating Leases Future Minimum Payments Due [Line Items]
Lease and rental expense				15	12	15
2015			11	11
2016			6	6
2017			6	6
2018			3	3
2019			3	3
Remaining years			0	0
Total minimum future lease payments			29	29
Commonwealth Edison Co [Member] | Real Estate Leases and Railroad Licenses [Member]
Operating Leases Future Minimum Payments Due [Line Items]
Total minimum future lease payments			2	2
PECO Energy Co [Member]
Operating Leases Future Minimum Payments Due [Line Items]
Lease and rental expense				7	9	14
2015			3	3
2016			3	3
2017			4	4
2018			4	4
2019			4	4
Remaining years			0	0
Total minimum future lease payments			18	18
PECO Energy Co [Member] | Real Estate Leases and Railroad Licenses [Member]
Operating Leases Future Minimum Payments Due [Line Items]
Total minimum future lease payments			4	4
Baltimore Gas and Electric Company [Member]
Operating Leases Future Minimum Payments Due [Line Items]
Lease and rental expense				22	32	12
2015			32	32			$ 21
2016			34	34			25
2017			34	34			26
2018			34	34			27
2019			32	32			28
Operating Leases, Future Minimum Payments, Due Thereafter							$ 14
Remaining years			33	33
Total minimum future lease payments			199	199
Baltimore Gas and Electric Company [Member] | Real Estate Leases and Railroad Licenses [Member]
Operating Leases Future Minimum Payments Due [Line Items]
Total minimum future lease payments			2	2
Pepco Holdings LLC [Member]
Operating Leases Future Minimum Payments Due [Line Items]
2015			50	50
2016			49	49
2017			36	36
2018			38	38
2019			34	34
Remaining years			211	211
Total minimum future lease payments			418	418
Pepco Holdings LLC [Member] | Predecessor [Member]
Operating Leases Future Minimum Payments Due [Line Items]
Lease and rental expense					0	0
Pepco Holdings LLC [Member] | Successor [Member]
Operating Leases Future Minimum Payments Due [Line Items]
Lease and rental expense		$ 0	49
Potomac Electric Power Company [Member]
Operating Leases Future Minimum Payments Due [Line Items]
Lease and rental expense				8	7	8
2015			7	7
2016			6	6
2017			5	5
2018			4	4
2019			3	3
Remaining years			7	7
Total minimum future lease payments			32	32
Delmarva Power and Light Company [Member]
Operating Leases Future Minimum Payments Due [Line Items]
Lease and rental expense				15	14	14
2015			13	13
2016			17	17
2017			7	7
2018			10	10
2019			9	9
Remaining years			54	54
Total minimum future lease payments			110	110
Delmarva Power and Light Company [Member] | Real Estate Leases and Railroad Licenses [Member]
Operating Leases Future Minimum Payments Due [Line Items]
Total minimum future lease payments			2	2
Atlantic City Electric Company [Member]
Operating Leases Future Minimum Payments Due [Line Items]
Lease and rental expense				13	$ 13	$ 12
2015			8	8
2016			8	8
2017			7	7
2018			6	6
2019			5	5
Remaining years			20	20
Total minimum future lease payments			$ 54	$ 54

[1] Includes contingent operating lease payments associated with contracted generation agreements that are not included in the minimum future operating lease payments table above. Payments made under Generation’s contracted generation lease agreements totaled $604 million, $798 million and $755 million during 2016, 2015 and 2014, respectively. Excludes contract amortization associated with purchase accounting and contract acquisitions.