Commitments and Contingencies - Schedule of Commercial Commitments (Details) $ in Millions		12 Months Ended
		Dec. 31, 2016 USD ($) MW	Sep. 30, 2016 USD ($)
Guarantor Obligations [Line Items]
Contractual Obligation		$ 3,297
Contractual Obligation, Due in Next Fiscal Year		2,333
Contractual Obligation, Due after Fifth Year		648
Contractual Obligation, Due in Fifth Year		6
Contractual Obligation, Due in Fourth Year		29
Contractual Obligation, Due in Third Year		2
Contractual Obligation, Due in Second Year		279
Baltimore Gas and Electric Company [Member]
Guarantor Obligations [Line Items]
Contractual Obligation		263
Contractual Obligation, Due in Next Fiscal Year		12
Contractual Obligation, Due after Fifth Year		250
Contractual Obligation, Due in Fifth Year		0
Contractual Obligation, Due in Fourth Year		0
Contractual Obligation, Due in Third Year		0
Contractual Obligation, Due in Second Year		1
PECO Energy Co [Member]
Guarantor Obligations [Line Items]
Contractual Obligation		210
Contractual Obligation, Due in Next Fiscal Year		32
Contractual Obligation, Due after Fifth Year		178
Contractual Obligation, Due in Fifth Year		0
Contractual Obligation, Due in Fourth Year		0
Contractual Obligation, Due in Third Year		0
Contractual Obligation, Due in Second Year		0
Commonwealth Edison Co [Member]
Guarantor Obligations [Line Items]
Contractual Obligation		225
Contractual Obligation, Due in Next Fiscal Year		23
Contractual Obligation, Due after Fifth Year		200
Contractual Obligation, Due in Fifth Year		0
Contractual Obligation, Due in Fourth Year		0
Contractual Obligation, Due in Third Year		0
Contractual Obligation, Due in Second Year		2
Exelon Generation Co L L C [Member]
Guarantor Obligations [Line Items]
Contractual Obligation	[1]	2,491
Contractual Obligation, Due in Next Fiscal Year	[1]	2,205
Contractual Obligation, Due after Fifth Year	[1]	0
Contractual Obligation, Due in Fifth Year	[1]	0
Contractual Obligation, Due in Fourth Year	[1]	13
Contractual Obligation, Due in Third Year	[1]	0
Contractual Obligation, Due in Second Year	[1]	273
Pepco Holdings LLC [Member]
Guarantor Obligations [Line Items]
Contractual Obligation		37
Contractual Obligation, Due in Next Fiscal Year		15
Contractual Obligation, Due after Fifth Year		20
Contractual Obligation, Due in Fifth Year		0
Contractual Obligation, Due in Fourth Year		0
Contractual Obligation, Due in Third Year		0
Contractual Obligation, Due in Second Year		2
Potomac Electric Power Company [Member]
Guarantor Obligations [Line Items]
Contractual Obligation		15
Contractual Obligation, Due in Next Fiscal Year		9
Contractual Obligation, Due after Fifth Year		6
Contractual Obligation, Due in Fifth Year		0
Contractual Obligation, Due in Fourth Year		0
Contractual Obligation, Due in Third Year		0
Contractual Obligation, Due in Second Year		0
Delmarva Power and Light Company [Member]
Guarantor Obligations [Line Items]
Contractual Obligation		11
Contractual Obligation, Due in Next Fiscal Year		3
Contractual Obligation, Due after Fifth Year		7
Contractual Obligation, Due in Fifth Year		0
Contractual Obligation, Due in Fourth Year		0
Contractual Obligation, Due in Third Year		0
Contractual Obligation, Due in Second Year		1
Atlantic City Electric Company [Member]
Guarantor Obligations [Line Items]
Contractual Obligation		9
Contractual Obligation, Due in Next Fiscal Year		3
Contractual Obligation, Due after Fifth Year		5
Contractual Obligation, Due in Fifth Year		0
Contractual Obligation, Due in Fourth Year		0
Contractual Obligation, Due in Third Year		0
Contractual Obligation, Due in Second Year		1
Surety Bond [Member]
Guarantor Obligations [Line Items]
Contractual Obligation	[2]	1,035
Contractual Obligation, Due in Next Fiscal Year	[2]	978
Contractual Obligation, Due after Fifth Year	[2]	0
Contractual Obligation, Due in Fifth Year	[2]	6
Contractual Obligation, Due in Fourth Year	[2]	16
Contractual Obligation, Due in Third Year	[2]	2
Contractual Obligation, Due in Second Year	[2]	33
Surety Bond [Member] | Baltimore Gas and Electric Company [Member]
Guarantor Obligations [Line Items]
Contractual Obligation	[3]	11
Contractual Obligation, Due in Next Fiscal Year	[3]	10
Contractual Obligation, Due after Fifth Year	[3]	0
Contractual Obligation, Due in Fifth Year	[3]	0
Contractual Obligation, Due in Fourth Year	[3]	0
Contractual Obligation, Due in Third Year	[3]	0
Contractual Obligation, Due in Second Year	[3]	1
Surety Bond [Member] | PECO Energy Co [Member]
Guarantor Obligations [Line Items]
Contractual Obligation	[4]	9
Contractual Obligation, Due in Next Fiscal Year	[4]	9
Contractual Obligation, Due after Fifth Year	[4]	0
Contractual Obligation, Due in Fifth Year	[4]	0
Contractual Obligation, Due in Fourth Year	[4]	0
Contractual Obligation, Due in Third Year	[4]	0
Contractual Obligation, Due in Second Year	[4]	0
Surety Bond [Member] | Commonwealth Edison Co [Member]
Guarantor Obligations [Line Items]
Contractual Obligation	[5]	11
Contractual Obligation, Due in Next Fiscal Year	[5]	9
Contractual Obligation, Due after Fifth Year	[5]	0
Contractual Obligation, Due in Fifth Year	[5]	0
Contractual Obligation, Due in Fourth Year	[5]	0
Contractual Obligation, Due in Third Year	[5]
Contractual Obligation, Due in Second Year	[5]	2
Surety Bond [Member] | Exelon Generation Co L L C [Member]
Guarantor Obligations [Line Items]
Contractual Obligation	[1]	945
Contractual Obligation, Due in Next Fiscal Year	[1]	918
Contractual Obligation, Due after Fifth Year	[1]	0
Contractual Obligation, Due in Fifth Year	[1]	0
Contractual Obligation, Due in Fourth Year	[1]	0
Contractual Obligation, Due in Third Year	[1]	0
Contractual Obligation, Due in Second Year	[1]	27
Surety Bond [Member] | Pepco Holdings LLC [Member]
Guarantor Obligations [Line Items]
Contractual Obligation	[6]	16
Contractual Obligation, Due in Next Fiscal Year	[6]	14
Contractual Obligation, Due after Fifth Year	[6]	0
Contractual Obligation, Due in Fifth Year	[6]	0
Contractual Obligation, Due in Fourth Year	[6]	0
Contractual Obligation, Due in Third Year	[6]	0
Contractual Obligation, Due in Second Year	[6]	2
Surety Bond [Member] | Potomac Electric Power Company [Member]
Guarantor Obligations [Line Items]
Contractual Obligation	[7]	9
Contractual Obligation, Due in Next Fiscal Year	[7]	9
Contractual Obligation, Due after Fifth Year	[7]	0
Contractual Obligation, Due in Fifth Year	[7]	0
Contractual Obligation, Due in Fourth Year	[7]	0
Contractual Obligation, Due in Third Year	[7]	0
Contractual Obligation, Due in Second Year	[7]	0
Surety Bond [Member] | Delmarva Power and Light Company [Member]
Guarantor Obligations [Line Items]
Contractual Obligation	[8]	4
Contractual Obligation, Due in Next Fiscal Year	[8]	3
Contractual Obligation, Due after Fifth Year	[8]	0
Contractual Obligation, Due in Fifth Year	[8]	0
Contractual Obligation, Due in Fourth Year	[8]	0
Contractual Obligation, Due in Third Year	[8]	0
Contractual Obligation, Due in Second Year	[8]	1
Surety Bond [Member] | Atlantic City Electric Company [Member]
Guarantor Obligations [Line Items]
Contractual Obligation	[9]	3
Contractual Obligation, Due in Next Fiscal Year	[9]	2
Contractual Obligation, Due after Fifth Year	[9]	0
Contractual Obligation, Due in Fifth Year	[9]	0
Contractual Obligation, Due in Fourth Year	[9]	0
Contractual Obligation, Due in Third Year	[9]	0
Contractual Obligation, Due in Second Year	[9]	1
Trust Preferred Securities [Member]
Guarantor Obligations [Line Items]
Contractual Obligation	[10]	628
Contractual Obligation, Due in Next Fiscal Year	[2]	0
Contractual Obligation, Due after Fifth Year	[2]	628
Contractual Obligation, Due in Fifth Year	[2]	0
Contractual Obligation, Due in Fourth Year	[2]	0
Contractual Obligation, Due in Third Year	[2]	0
Contractual Obligation, Due in Second Year	[2]	0
Trust Preferred Securities [Member] | Baltimore Gas and Electric Company [Member]
Guarantor Obligations [Line Items]
Contractual Obligation	[11]	250
Contractual Obligation, Due in Next Fiscal Year	[11]	0
Contractual Obligation, Due after Fifth Year	[11]	250
Contractual Obligation, Due in Fifth Year	[11]	0
Contractual Obligation, Due in Fourth Year	[11]	0
Contractual Obligation, Due in Third Year	[11]	0
Contractual Obligation, Due in Second Year	[11]	0
Trust Preferred Securities [Member] | PECO Energy Co [Member]
Guarantor Obligations [Line Items]
Contractual Obligation	[12]	178
Contractual Obligation, Due in Next Fiscal Year	[12]	0
Contractual Obligation, Due after Fifth Year	[12]	178
Contractual Obligation, Due in Fifth Year	[12]	0
Contractual Obligation, Due in Fourth Year	[12]	0
Contractual Obligation, Due in Third Year	[12]	0
Contractual Obligation, Due in Second Year	[12]	0
Trust Preferred Securities [Member] | Commonwealth Edison Co [Member]
Guarantor Obligations [Line Items]
Contractual Obligation	[13]	200
Contractual Obligation, Due in Next Fiscal Year	[13]	0
Contractual Obligation, Due after Fifth Year	[13]	200
Contractual Obligation, Due in Fifth Year	[13]	0
Contractual Obligation, Due in Fourth Year	[13]	0
Contractual Obligation, Due in Third Year	[13]	0
Contractual Obligation, Due in Second Year	[13]	0
Financial Standby Letter of Credit [Member]
Guarantor Obligations [Line Items]
Contractual Obligation	[1]	1,614
Contractual Obligation, Due in Next Fiscal Year	[1]	1,355
Contractual Obligation, Due after Fifth Year	[1]	0
Contractual Obligation, Due in Fifth Year	[1]	0
Contractual Obligation, Due in Fourth Year	[1]	13
Contractual Obligation, Due in Third Year	[1]	0
Contractual Obligation, Due in Second Year	[1]	246
Financial Standby Letter of Credit [Member] | Baltimore Gas and Electric Company [Member]
Guarantor Obligations [Line Items]
Contractual Obligation	[14]	2
Contractual Obligation, Due in Next Fiscal Year	[14]	2
Contractual Obligation, Due after Fifth Year	[14]	0
Contractual Obligation, Due in Fifth Year	[14]	0
Contractual Obligation, Due in Fourth Year	[14]	0
Contractual Obligation, Due in Third Year	[14]	0
Contractual Obligation, Due in Second Year	[14]	0
Financial Standby Letter of Credit [Member] | PECO Energy Co [Member]
Guarantor Obligations [Line Items]
Contractual Obligation	[15]	23
Contractual Obligation, Due in Next Fiscal Year	[15]	23
Contractual Obligation, Due after Fifth Year	[15]	0
Contractual Obligation, Due in Fifth Year	[15]	0
Contractual Obligation, Due in Fourth Year	[15]	0
Contractual Obligation, Due in Third Year	[15]	0
Contractual Obligation, Due in Second Year	[15]	0
Financial Standby Letter of Credit [Member] | Commonwealth Edison Co [Member]
Guarantor Obligations [Line Items]
Contractual Obligation	[16]	14
Contractual Obligation, Due in Next Fiscal Year	[16]	14
Contractual Obligation, Due after Fifth Year	[16]	0
Contractual Obligation, Due in Fifth Year	[16]	0
Contractual Obligation, Due in Fourth Year	[16]	0
Contractual Obligation, Due in Third Year	[16]	0
Contractual Obligation, Due in Second Year	[16]	0
Financial Standby Letter of Credit [Member] | Exelon Generation Co L L C [Member]
Guarantor Obligations [Line Items]
Contractual Obligation	[1]	1,546
Contractual Obligation, Due in Next Fiscal Year	[1]	1,287
Contractual Obligation, Due after Fifth Year	[1]	0
Contractual Obligation, Due in Fifth Year	[1]	0
Contractual Obligation, Due in Fourth Year	[1]	13
Contractual Obligation, Due in Third Year	[1]	0
Contractual Obligation, Due in Second Year	[1]	246
Financial Standby Letter of Credit [Member] | Pepco Holdings LLC [Member]
Guarantor Obligations [Line Items]
Contractual Obligation	[17]	1
Contractual Obligation, Due in Next Fiscal Year	[17]	1
Contractual Obligation, Due after Fifth Year	[17]	0
Contractual Obligation, Due in Fifth Year	[17]	0
Contractual Obligation, Due in Fourth Year	[17]	0
Contractual Obligation, Due in Third Year	[17]	0
Contractual Obligation, Due in Second Year	[17]	0
Financial Standby Letter of Credit [Member] | Atlantic City Electric Company [Member]
Guarantor Obligations [Line Items]
Contractual Obligation	[18]	1
Contractual Obligation, Due in Next Fiscal Year	[18]	1
Contractual Obligation, Due after Fifth Year	[18]	0
Contractual Obligation, Due in Fifth Year	[18]	0
Contractual Obligation, Due in Fourth Year	[18]	0
Contractual Obligation, Due in Third Year	[18]	0
Contractual Obligation, Due in Second Year	[18]	0
GuaranteedLeaseResidualValues [Member]
Guarantor Obligations [Line Items]
Contractual Obligation			$ 20
Contractual Obligation, Due in Next Fiscal Year		0
Contractual Obligation, Due after Fifth Year			$ 20
Contractual Obligation, Due in Fifth Year		0
Contractual Obligation, Due in Fourth Year		0
Contractual Obligation, Due in Third Year		0
Contractual Obligation, Due in Second Year		0
GuaranteedLeaseResidualValues [Member] | Pepco Holdings LLC [Member]
Guarantor Obligations [Line Items]
Contractual Obligation	[19]	20
Contractual Obligation, Due in Next Fiscal Year	[19]	0
Contractual Obligation, Due after Fifth Year	[19]	20
Contractual Obligation, Due in Fifth Year	[19]	0
Contractual Obligation, Due in Fourth Year	[19]	0
Contractual Obligation, Due in Third Year	[19]	0
Contractual Obligation, Due in Second Year	[19]	0
GuaranteedLeaseResidualValues [Member] | Potomac Electric Power Company [Member]
Guarantor Obligations [Line Items]
Contractual Obligation	[20]	6
Contractual Obligation, Due in Next Fiscal Year	[20]	0
Contractual Obligation, Due after Fifth Year	[20]	6
Contractual Obligation, Due in Fifth Year	[20]	0
Contractual Obligation, Due in Fourth Year	[20]	0
Contractual Obligation, Due in Third Year	[20]	0
Contractual Obligation, Due in Second Year	[20]	0
GuaranteedLeaseResidualValues [Member] | Delmarva Power and Light Company [Member]
Guarantor Obligations [Line Items]
Contractual Obligation	[21]	7
Contractual Obligation, Due in Next Fiscal Year	[21]	0
Contractual Obligation, Due after Fifth Year	[21]	7
Contractual Obligation, Due in Fifth Year	[21]	0
Contractual Obligation, Due in Fourth Year	[21]	0
Contractual Obligation, Due in Third Year	[21]	0
Contractual Obligation, Due in Second Year	[21]	0
GuaranteedLeaseResidualValues [Member] | Atlantic City Electric Company [Member]
Guarantor Obligations [Line Items]
Contractual Obligation	[22]	5
Contractual Obligation, Due in Next Fiscal Year	[22]	0
Contractual Obligation, Due after Fifth Year	[22]	5
Contractual Obligation, Due in Fifth Year	[22]	0
Contractual Obligation, Due in Fourth Year	[22]	0
Contractual Obligation, Due in Third Year	[22]	0
Contractual Obligation, Due in Second Year	[22]	$ 0
Maximum [Member] | Exelon Generation Co L L C [Member]
Guarantor Obligations [Line Items]
Business Acquisition, Expected New Generation Mwh | MW		300

[1] Letters of credit (non-debt)—Exelon and certain of its subsidiaries maintain non-debt letters of credit to provide credit support for certain transactions as requested by third parties.

[2] Surety bonds—Guarantees issued related to contract and commercial agreements, excluding bid bonds.

[3] Surety bonds—Guarantees issued related to contract and commercial agreements, excluding bid bonds.

[4] Surety bonds—Guarantees issued related to contract and commercial agreements, excluding bid bonds.

[5] Surety bonds—Guarantees issued related to contract and commercial agreements, excluding bid bonds.

[6] {F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOjY2ZTAyZGU0MjJhODQwMGQ4YTI0ZmVhYjg5OGIyNGRifFRleHRTZWxlY3Rpb246NEU0NTM4RjY2RDg5Q0NDMzBBRDQ4MTMyN0M0QjQ3RTQM}

[7] _

[8] _

[9] {F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOjY2ZTAyZGU0MjJhODQwMGQ4YTI0ZmVhYjg5OGIyNGRifFRleHRTZWxlY3Rpb246RUU4QUM2NTgyMUMwMjIzMjBDNUE4MTNDQTYxNzQzQ0QM}

[10] Includes $200 million of Trust Preferred Securities of ComEd Financing III, $178 million of Trust Preferred Securities of PECO Trust III and IV and $250 million of Trust Preferred Securities of BGE Capital Trust II.

[11] {F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOjY2ZTAyZGU0MjJhODQwMGQ4YTI0ZmVhYjg5OGIyNGRifFRleHRTZWxlY3Rpb246N0E5NzcxMDgwMEM1RjEwQzcxMzk5RjkyNUQyNTk1QTIM}

[12] {F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOjY2ZTAyZGU0MjJhODQwMGQ4YTI0ZmVhYjg5OGIyNGRifFRleHRTZWxlY3Rpb246NDlFNDNFOEEzNDdGRkJFODIxM0Q5RjkyNUQyNTY4NUIM}

[13] {F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOjY2ZTAyZGU0MjJhODQwMGQ4YTI0ZmVhYjg5OGIyNGRifFRleHRTZWxlY3Rpb246MjkyMjMzMEMzNjIzOTc1NjY5NjA5RjkyNUQyNTczQjIM}

[14] Letters of credit (non-debt)—BGE maintains non-debt letters of credit to provide credit support for certain transactions as requested by third parties.

[15] Letters of credit (non-debt)—PECO maintains non-debt letters of credit to provide credit support for certain transactions as requested by third parties.

[16] Letters of credit (non-debt)—ComEd maintains non-debt letters of credit to provide credit support for certain transactions as requested by third parties.

[17] {F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOjY2ZTAyZGU0MjJhODQwMGQ4YTI0ZmVhYjg5OGIyNGRifFRleHRTZWxlY3Rpb246NDI3QUMyNzExNTcwRUUzMTc2QjM4MTMyMURFRkI1MjUM}

[18] {F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOjY2ZTAyZGU0MjJhODQwMGQ4YTI0ZmVhYjg5OGIyNGRifFRleHRTZWxlY3Rpb246Njc3QzlCQzdEQjY1NDZDOTYyNDM4MTNDNDY1OEVBQkUM}

[19] {F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOjY2ZTAyZGU0MjJhODQwMGQ4YTI0ZmVhYjg5OGIyNGRifFRleHRTZWxlY3Rpb246RUI3QjVENUVBNUUxMEEwQUI3ODU4MTMyRTczMjg1RDQM}

[20] _

[21] _

[22] {F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOjY2ZTAyZGU0MjJhODQwMGQ4YTI0ZmVhYjg5OGIyNGRifFRleHRTZWxlY3Rpb246QzEyOUM0NEQ3Rjc2MzAwMUNEOTM4MTNDRkEzNzExMDcM}