Variable Interest Entities - Carrying Amounts and Classification of Consolidated VIE Assets and Liabilities (Details) - USD ($) $ in Millions		Mar. 31, 2017	Dec. 31, 2016
Variable Interest Entity [Line Items]
Consolidated VIE Assets		$ 9,909	$ 9,517
Consolidated VIE Liabilities		3,616	3,598
Assets		117,068	114,904
Liabilities	[1]	88,777	87,292
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Assets		9,148	8,893
Liabilities		3,345	3,356
Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Assets		9,820	9,441
Consolidated VIE Liabilities		3,445	3,414
Assets		48,609	46,974
Liabilities	[2]	35,045	33,718
Exelon Generation Co L L C [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Assets		9,059	8,817
Liabilities		3,174	3,170
Baltimore Gas and Electric Company [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Assets		45	26
Consolidated VIE Liabilities		42	42
Assets	[3]	8,821	8,704
Liabilities	[3]	5,897	5,856
Baltimore Gas and Electric Company [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Assets		45	26
Liabilities		42	42
Pepco Holdings LLC [Member] | Predecessor [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Assets			49
Consolidated VIE Liabilities			143
Pepco Holdings LLC [Member] | Successor [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Assets		44
Consolidated VIE Liabilities		129
Assets		21,018	21,025
Liabilities		12,431	13,009
Pepco Holdings LLC [Member] | Variable Interest Entity, Primary Beneficiary [Member] | Predecessor [Member]
Variable Interest Entity [Line Items]
Assets			49
Liabilities			143
Pepco Holdings LLC [Member] | Variable Interest Entity, Primary Beneficiary [Member] | Successor [Member]
Variable Interest Entity [Line Items]
Assets		44
Liabilities		129
Atlantic City Electric Company [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Assets		30	32
Consolidated VIE Liabilities		115	126
Assets		3,451	3,457
Liabilities		2,399	2,423
Atlantic City Electric Company [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Assets		30	32
Liabilities		115	126
CurrentAssetsMember [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Assets		1,018	954
CurrentAssetsMember [Member] | Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Assets		965	916
CurrentAssetsMember [Member] | Baltimore Gas and Electric Company [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Assets		42	23
CurrentAssetsMember [Member] | Pepco Holdings LLC [Member] | Predecessor [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Assets			14
CurrentAssetsMember [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Assets		11
CurrentAssetsMember [Member] | Atlantic City Electric Company [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Assets		7	9
NoncurrentAssetMember [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Assets		8,891	8,563
NoncurrentAssetMember [Member] | Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Assets		8,855	8,525
NoncurrentAssetMember [Member] | Baltimore Gas and Electric Company [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Assets		3	3
NoncurrentAssetMember [Member] | Pepco Holdings LLC [Member] | Predecessor [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Assets			35
NoncurrentAssetMember [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Assets		33
NoncurrentAssetMember [Member] | Atlantic City Electric Company [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Assets		23	23
CurrentLiabilityMember [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Liabilities		871	885
CurrentLiabilityMember [Member] | Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Liabilities		791	802
CurrentLiabilityMember [Member] | Baltimore Gas and Electric Company [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Liabilities		42	42
CurrentLiabilityMember [Member] | Pepco Holdings LLC [Member] | Predecessor [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Liabilities			42
CurrentLiabilityMember [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Liabilities		38
CurrentLiabilityMember [Member] | Atlantic City Electric Company [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Liabilities		34	37
NoncurrentLiabilityMember [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Liabilities		2,745	2,713
NoncurrentLiabilityMember [Member] | Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Liabilities		2,654	2,612
NoncurrentLiabilityMember [Member] | Baltimore Gas and Electric Company [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Liabilities		0	0
NoncurrentLiabilityMember [Member] | Pepco Holdings LLC [Member] | Predecessor [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Liabilities			101
NoncurrentLiabilityMember [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Liabilities		91
NoncurrentLiabilityMember [Member] | Atlantic City Electric Company [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Liabilities		$ 81	$ 89

[1] Exelon’s consolidated assets include $9,148 million and $8,893 million at March 31, 2017 and December 31, 2016, respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Exelon’s consolidated liabilities include $3,345 million and $3,356 million at March 31, 2017 and December 31, 2016, respectively, of certain VIEs for which the VIE creditors do not have recourse to Exelon. See Note 3 - Variable Interest Entities.

[2] Generation’s consolidated assets include $9,059 million and $8,817 million at March 31, 2017 and December 31, 2016, respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Generation’s consolidated liabilities include $3,174 million and $3,170 million at March 31, 2017 and December 31, 2016, respectively, of certain VIEs for which the VIE creditors do not have recourse to Generation. See Note 3 - Variable Interest Entities.

[3] BGE’s consolidated assets include $45 million and $26 million at March 31, 2017 and December 31, 2016, respectively, of BGE’s consolidated VIE that can only be used to settle the liabilities of the VIE. BGE’s consolidated liabilities include $42 million and $42 million at March 31, 2017 and December 31, 2016, respectively, of BGE’s consolidated VIE for which the VIE creditors do not have recourse to BGE. See Note 3 - Variable Interest Entities.