Fair Value of Financial Assets and Liabilities - Fair Value Assets Liabilities Measured On Recurring Basis Unobservable Input Reconciliation (Details) - USD ($)	3 Months Ended				6 Months Ended
	Jun. 30, 2016	Jun. 30, 2016	Mar. 23, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Mar. 31, 2016	Mar. 24, 2016	Dec. 31, 2015	Mar. 31, 2015	Dec. 31, 2014
Fair Value, Inputs, Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	$ 1,185,000,000	$ 1,185,000,000		$ 1,536,000,000	$ 1,185,000,000	$ 1,536,000,000	$ 1,547,000,000		$ 1,529,000,000	$ 1,484,000,000	$ 1,501,000,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	423,000,000			(5,000,000)	(427,000,000)	35,000,000
Total realized / unrealized gains (losses)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates	0			0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Nuclear Decommissioning Payable	0			(2,000,000)	2,000,000	(1,000,000)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Regulatory assets	52,000,000			25,000,000	38,000,000	1,000,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	109,000,000			123,000,000	206,000,000	192,000,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	2,000,000			(7,000,000)	4,000,000	24,000,000
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	(260,000,000)			177,000,000	(40,000,000)	358,000,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	65,000,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements				33,000,000	91,000,000	62,000,000
Purchases, sales, issuances and settlements
Purchases	109,000,000			123,000,000	206,000,000	192,000,000
Ending balance
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Change In Collateral	32,000,000			(30,000,000)	(82,000,000)	18,000,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	0			11,000,000	2,000,000	15,000,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3	0			30,000,000	7,000,000	35,000,000
Fair Value, Inputs, Level 3 [Member] | Consolidation, Eliminations [Member]
Total realized / unrealized gains (losses)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates	8,000,000			(7,000,000)	(12,000,000)	17,000,000
Included in noncurrent payables to affiliates						17,000,000
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Regulatory assets	8,000,000			7,000,000	12,000,000
Exelon Generation Co L L C [Member]
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract]
Fair Value, Assets and Liabilities Measured on Recurring Basis, Gain (Loss) Included in Earnings	164,000,000			(389,000,000)
Exelon Generation Co L L C [Member] | Interest Rate Swap [Member]
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract]
Realized Investment Gains (Losses)	4,000,000				11,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	1,386,000,000	1,386,000,000		1,759,000,000	1,386,000,000	1,759,000,000	1,792,000,000		1,776,000,000	1,725,000,000	1,708,000,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	424,000,000			(5,000,000)	(428,000,000)	35,000,000
Total realized / unrealized gains (losses)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates	(8,000,000)			7,000,000	12,000,000	(17,000,000)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Nuclear Decommissioning Payable	0			(2,000,000)	2,000,000	(1,000,000)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Regulatory assets	0			0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	109,000,000			123,000,000	206,000,000	192,000,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	2,000,000			(7,000,000)	4,000,000	24,000,000
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	(261,000,000)			177,000,000	(41,000,000)	358,000,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	65,000,000			0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements				33,000,000	91,000,000	62,000,000
Purchases, sales, issuances and settlements
Purchases	109,000,000			123,000,000	206,000,000	192,000,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers Into Level 3				0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers out of Level 3				0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Period Increase (Decrease)	40,000,000				15,000,000
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Change In Collateral	32,000,000			(30,000,000)	(82,000,000)	18,000,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	0			11,000,000	2,000,000	15,000,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3	0			30,000,000	7,000,000	35,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	715,000,000	715,000,000		667,000,000	715,000,000	667,000,000	684,000,000		670,000,000	612,000,000	605,000,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	(4,000,000)			2,000,000	6,000,000	(4,000,000)
Total realized / unrealized gains (losses)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates	(8,000,000)			7,000,000	12,000,000	(17,000,000)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Nuclear Decommissioning Payable	0			0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Regulatory assets				0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	85,000,000			79,000,000	119,000,000	107,000,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	(1,000,000)			0	(1,000,000)	8,000,000
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	3,000,000				4,000,000	3,000,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	(65,000,000)			(33,000,000)	(91,000,000)	(62,000,000)
Purchases, sales, issuances and settlements
Purchases	85,000,000			79,000,000	119,000,000	107,000,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers out of Level 3				0		0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Change In Collateral	0			0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	0			0	0	(4,000,000)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3	0				0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Pledged Assets For Zion Station Decommissioning [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	25,000,000	25,000,000		41,000,000	25,000,000	41,000,000	25,000,000		22,000,000	44,000,000	50,000,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	0			0	0	0
Total realized / unrealized gains (losses)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates	0			0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Nuclear Decommissioning Payable	0			(2,000,000)	2,000,000	(1,000,000)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Regulatory assets				0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	0			1,000,000	1,000,000	1,000,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	0			(2,000,000)	0	11,000,000
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	0				0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	0			0	0	0
Purchases, sales, issuances and settlements
Purchases	0			1,000,000	1,000,000	1,000,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers Into Level 3				0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers out of Level 3				0		0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Change In Collateral	0			0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	0				0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3	0				0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Derivative [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	609,000,000	609,000,000		1,021,000,000	609,000,000	1,021,000,000	1,047,000,000		1,051,000,000	1,066,000,000	1,050,000,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	428,000,000			(7,000,000)	(434,000,000)	39,000,000
Total realized / unrealized gains (losses)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates	0			0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Nuclear Decommissioning Payable	0			0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Regulatory assets				0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	23,000,000			16,000,000	82,000,000	57,000,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	(1,000,000)			(5,000,000)	(3,000,000)	5,000,000
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	(264,000,000)				(45,000,000)	355,000,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	0			0	0	0
Purchases, sales, issuances and settlements
Purchases	23,000,000			16,000,000	82,000,000	57,000,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers Into Level 3				30,000,000
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Change In Collateral	32,000,000			(30,000,000)	(82,000,000)	18,000,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	0			11,000,000	2,000,000	11,000,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3	0				(7,000,000)	35,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Other Investments [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	37,000,000	37,000,000		30,000,000	37,000,000	30,000,000	36,000,000		33,000,000	3,000,000	3,000,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	0			0	0	0
Total realized / unrealized gains (losses)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates	0			0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Nuclear Decommissioning Payable	0			0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Regulatory assets				0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	1,000,000			27,000,000	4,000,000	27,000,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	0			0	0	0
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	0				0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	0			0	0	0
Purchases, sales, issuances and settlements
Purchases	1,000,000			27,000,000	4,000,000	27,000,000
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Change In Collateral	0			0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	0			0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3				0	0	0
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings				0
Total realized / unrealized gains (losses)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates				0		0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Nuclear Decommissioning Payable				0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Regulatory assets				18,000,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases				0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales				0
Purchases, sales, issuances and settlements
Purchases				0
Ending balance				(223,000,000)		(223,000,000)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Change In Collateral				0
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 3 [Member] | Derivative [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	(221,000,000)	(221,000,000)		(223,000,000)	(221,000,000)	(223,000,000)	(265,000,000)		(247,000,000)	(241,000,000)	(207,000,000)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	0				0	0
Total realized / unrealized gains (losses)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates	0				0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Nuclear Decommissioning Payable	0				0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Regulatory assets	44,000,000				26,000,000	(16,000,000)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	0				0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	0				0	0
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)					0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	0				0	0
Purchases, sales, issuances and settlements
Purchases	0				0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers Into Level 3						0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers out of Level 3						0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Change In Collateral	0				0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	0				0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3	0				0
Pepco Holdings LLC [Member] | 6311 Life Insurance [Member] | Predecessor [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings			$ 0
Pepco Holdings LLC [Member] | 6311 Life Insurance [Member] | Successor [Member]
Total realized / unrealized gains (losses)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		(1,000,000)
Purchases, sales, issuances and settlements
Purchases		(1,000,000)
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 3 [Member] | Successor [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value								$ 20,000,000
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 3 [Member] | 6311 Life Insurance [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value								0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		1,000,000
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 3 [Member] | 6311 Life Insurance [Member] | Predecessor [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value			20,000,000	20,000,000		20,000,000			19,000,000	19,000,000	19,000,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings			(1,000,000)	(2,000,000)		(3,000,000)
Total realized / unrealized gains (losses)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases			0	(1,000,000)		(1,000,000)
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)			1,000,000	1,000,000		2,000,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements						(1,000,000)
Purchases, sales, issuances and settlements
Purchases			0	(1,000,000)		(1,000,000)
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 3 [Member] | 6311 Life Insurance [Member] | Successor [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	20,000,000	20,000,000			20,000,000		20,000,000	$ 20,000,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	(1,000,000)
Total realized / unrealized gains (losses)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Nuclear Decommissioning Payable	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Regulatory assets	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	(1,000,000)	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	0	0
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	1,000,000	1,000,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	0	0		0
Purchases, sales, issuances and settlements
Purchases	(1,000,000)	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers Into Level 3	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers out of Level 3	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Change In Collateral	0	0
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 3 [Member] | Preferred Stock [Member] | Predecessor [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value			0	3,000,000		3,000,000			18,000,000	3,000,000	3,000,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings			18,000,000	0		0
Total realized / unrealized gains (losses)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases			0	0		0
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)			0			0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements			0	0		0
Purchases, sales, issuances and settlements
Purchases			$ 0	0		0
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 3 [Member] | Preferred Stock [Member] | Successor [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value				3,000,000		3,000,000
Total realized / unrealized gains (losses)
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)				0
Delmarva Power and Light Company [Member] | 6311 Life Insurance [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings						0
Total realized / unrealized gains (losses)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases						0
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)						0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements						1,000,000
Purchases, sales, issuances and settlements
Purchases						0
Ending balance				0		0
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 3 [Member] | 6311 Life Insurance [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value											1,000,000
Potomac Electric Power Company [Member] | 6311 Life Insurance [Member]
Total realized / unrealized gains (losses)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	(1,000,000)			(1,000,000)	(1,000,000)	(1,000,000)
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)					2,000,000	2,000,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	0			0	0	0
Purchases, sales, issuances and settlements
Purchases	(1,000,000)			(1,000,000)	(1,000,000)	(1,000,000)
Ending balance				20,000,000		20,000,000
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 3 [Member] | 6311 Life Insurance [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	20,000,000	$ 20,000,000		20,000,000	20,000,000	20,000,000	$ 20,000,000		$ 19,000,000	$ 19,000,000	$ 18,000,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	(1,000,000)			(2,000,000)
Total realized / unrealized gains (losses)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases					2,000,000	3,000,000
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	$ 1,000,000			$ 1,000,000
Purchases, sales, issuances and settlements
Purchases					$ 2,000,000	$ 3,000,000