Supplemental Financial Information - Supplemental Cash Flow Information (Details) - USD ($)		3 Months Ended		9 Months Ended			12 Months Ended
		Mar. 23, 2016		Dec. 31, 2016		Sep. 30, 2016	Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015
Supplemental Cash Flow Information [Line Items]
Interest (net of amount capitalized)							$ 2,430,000,000		$ 1,340,000,000		$ 930,000,000
Income taxes (net of refunds)							540,000,000		(441,000,000)		342,000,000
Pension and non-pension postretirement benefit costs							643,000,000		619,000,000		637,000,000
Income (Loss) from Equity Method Investments							32,000,000		24,000,000		7,000,000
Provision for uncollectible accounts							125,000,000		155,000,000		120,000,000
Provision for excess and obsolete inventory							56,000,000		12,000,000		10,000,000
Stock-based compensation costs							88,000,000		111,000,000		97,000,000
Other decommissioning related-activity							(313,000,000)	[1]	(384,000,000)	[2]	(82,000,000)	[3]
Energy-related options							7,000,000	[4]	(11,000,000)	[5]	21,000,000	[6]
Amortization of regulatory asset related to debt costs							9,000,000		9,000,000		7,000,000
Amortization of rate stabilization deferral							(10,000,000)		76,000,000		73,000,000
Amortization of debt fair value adjustment							(18,000,000)		(11,000,000)		(17,000,000)
Merger-related commitments (c)							0	[7]	558,000,000	[8],[9]
Restructuring Costs							35,000,000		99,000,000
Amortization of Debt Issuance Costs							64,000,000		8,000,000	[10]	58,000,000
Discrete impacts from EIMA							(52,000,000)	[11]	35,000,000		144,000,000	[12]
Lower of cost or market inventory adjustment									37,000,000		23,000,000
Environmental Expense and Liabilities							44,000,000
Litigation Settlement, Amount Awarded from Other Party									(28,000,000)
Proceeds from Collection of Other Receivables									13,000,000
Increase (Decrease) in Accrued Liabilities							109,000,000		70,000,000		24,000,000
Other							(30,000,000)		(35,000,000)		(13,000,000)
Adjustments, Noncash Items, to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities							721,000,000		1,333,000,000		1,109,000,000
Fair value of net assets contributed to Generation in connection with the PHI Merger, net of cash							(42,000,000)		(128,000,000)		(96,000,000)
NonCashFairValueAdjustment	[9],[13]								0
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability	[9],[13]								0
Business Combination, Contingent Consideration, Liability, Noncurrent							0
Payments to Acquire Businesses, Gross							208,000,000		6,934,000,000		40,000,000
Change in PPE related to ARO update				$ 191,000,000			29,000,000		191,000,000		885,000,000
Noncash or Part Noncash Acquisition, Fixed Assets Acquired							16,000,000		$ 54,000,000	[14]
Contribution of Property	[15]										0
Noncash or Part Noncash Divestiture, Description	[9]								37
Non Cash Dissolution of Financing Trust Due to Long-term Debt Retirement							(8,000,000)
Other Noncash Expense							(68,000,000)	[16]	$ 95,000,000		77,000,000
License Costs	[17]										95,000,000
noncash member [Member]
Supplemental Cash Flow Information [Line Items]
Merger-related commitments (c)									0
Asset Retirement Obligation, Revision of Estimate									2,000,000
NonCashFairValueAdjustment									0
Payments to Acquire Businesses, Gross									0
Predecessor [Member]
Supplemental Cash Flow Information [Line Items]
Income (Loss) from Equity Method Investments											0
Other decommissioning related-activity	[3]										0
Energy-related options	[6],[18]										0
Amortization of debt fair value adjustment											0
Discrete impacts from EIMA	[12]										0
Change in PPE related to ARO update											0
Contribution of Property	[15]										0
Other Noncash Expense											0
License Costs	[17]										0
Indemnification Agreement [Member]
Supplemental Cash Flow Information [Line Items]
Energy-related options	[18]										57,000,000
Contribution of Property							0	[19]	0	[20]
Non Cash Licensing Agreement							(5,000,000)
Exelon Generation Co L L C [Member]
Supplemental Cash Flow Information [Line Items]
Interest (net of amount capitalized)							391,000,000		339,000,000		348,000,000
Income taxes (net of refunds)							337,000,000		435,000,000		476,000,000
Pension and non-pension postretirement benefit costs							227,000,000		218,000,000		269,000,000
Income (Loss) from Equity Method Investments											8,000,000
Income (Loss) from Equity Method Investments, Net of Dividends or Distributions							33,000,000		25,000,000		8,000,000
Provision for uncollectible accounts							38,000,000		19,000,000		22,000,000
Provision for excess and obsolete inventory							51,000,000		6,000,000		9,000,000
Stock-based compensation costs							0		0		0
Other decommissioning related-activity							(313,000,000)	[1]	(384,000,000)	[2]	(82,000,000)	[3]
Energy-related options							7,000,000	[4]	(11,000,000)	[5]	21,000,000	[6]
Amortization of regulatory asset related to debt costs							0		0		0
Amortization of rate stabilization deferral							0		0		0
Amortization of debt fair value adjustment							(12,000,000)		(11,000,000)		(17,000,000)
Merger-related commitments (c)							0	[7]	53,000,000	[8],[9]
Restructuring Costs							31,000,000		22,000,000
Asset Retirement Obligation, Revision of Estimate						$ 61,000,000	1,000,000		1,000,000
Amortization of Debt Issuance Costs							37,000,000		17,000,000		15,000,000
Discrete impacts from EIMA							0	[11]	0	[10]	0	[12]
Lower of cost or market inventory adjustment									36,000,000		23,000,000
Environmental Expense and Liabilities							44,000,000
Litigation Settlement, Amount Awarded from Other Party									0
Proceeds from Collection of Other Receivables									0
Increase (Decrease) in Accrued Liabilities							0		0		0
Other							4,000,000		25,000,000		0
Adjustments, Noncash Items, to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities							112,000,000		15,000,000		268,000,000
Fair value of net assets contributed to Generation in connection with the PHI Merger, net of cash							(73,000,000)		50,000,000		(82,000,000)
NonCashFairValueAdjustment	[9],[13]								0
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability	[9],[13]								0
Business Combination, Contingent Consideration, Liability, Noncurrent							33,000,000
Payments to Acquire Businesses, Gross							208,000,000		293,000,000		40,000,000
Change in PPE related to ARO update				191,000,000			29,000,000		191,000,000		885,000,000
Noncash or Part Noncash Acquisition, Fixed Assets Acquired							16,000,000		$ 54,000,000	[14]
Dividends, Stock							0
Contribution of Property	[15]										0
Noncash or Part Noncash Divestiture, Description	[9]								37
Non Cash Dissolution of Financing Trust Due to Long-term Debt Retirement							0
Other Noncash Expense							(35,000,000)	[16]	$ 95,000,000		77,000,000
License Costs	[17]										0
Exelon Generation Co L L C [Member] | noncash member [Member]
Supplemental Cash Flow Information [Line Items]
Merger-related commitments (c)									0
Asset Retirement Obligation, Revision of Estimate									0
NonCashFairValueAdjustment									119,000,000
Payments to Acquire Businesses, Gross									0
Exelon Generation Co L L C [Member] | Indemnification Agreement [Member]
Supplemental Cash Flow Information [Line Items]
Energy-related options	[18]										57,000,000
Contribution of Property							0	[19]	0	[20]
Non Cash Licensing Agreement							0
Commonwealth Edison Co [Member]
Supplemental Cash Flow Information [Line Items]
Interest (net of amount capitalized)							307,000,000		298,000,000		308,000,000
Income taxes (net of refunds)							83,000,000		(444,000,000)		(265,000,000)
Pension and non-pension postretirement benefit costs							176,000,000		166,000,000		206,000,000
Income (Loss) from Equity Method Investments							0		0		0
Provision for uncollectible accounts							34,000,000		41,000,000		53,000,000
Provision for excess and obsolete inventory							3,000,000		4,000,000		1,000,000
Stock-based compensation costs							0		0		0
Other decommissioning related-activity							0	[1]	0	[2]	0	[3]
Energy-related options							0	[4]	0	[5]	0	[6]
Amortization of regulatory asset related to debt costs							4,000,000		4,000,000		5,000,000
Amortization of rate stabilization deferral							0		0		0
Amortization of debt fair value adjustment							0		0		0
Merger-related commitments (c)							0	[7]	0	[8],[9]
Restructuring Costs							0		0
Amortization of Debt Issuance Costs							5,000,000		4,000,000		4,000,000
Discrete impacts from EIMA							(52,000,000)	[11]	8,000,000	[10]	144,000,000	[12]
Lower of cost or market inventory adjustment									0		0
Environmental Expense and Liabilities							0
Litigation Settlement, Amount Awarded from Other Party									0
Proceeds from Collection of Other Receivables									0
Increase (Decrease) in Accrued Liabilities							0		0		0
Other							6,000,000		(12,000,000)		3,000,000
Adjustments, Noncash Items, to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities							164,000,000		215,000,000		416,000,000
Fair value of net assets contributed to Generation in connection with the PHI Merger, net of cash							61,000,000		(91,000,000)		(34,000,000)
NonCashFairValueAdjustment	[9],[13]								0
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability	[9],[13]								0
Business Combination, Contingent Consideration, Liability, Noncurrent							0
Payments to Acquire Businesses, Gross									0
Change in PPE related to ARO update				0			0		0		0
Noncash or Part Noncash Acquisition, Fixed Assets Acquired							0		$ 0	[14]
Dividends, Stock							0
Contribution of Property	[15]										7,000,000
Noncash or Part Noncash Divestiture, Description	[9]								0
Non Cash Dissolution of Financing Trust Due to Long-term Debt Retirement							0
Other Noncash Expense							(12,000,000)	[16]	$ 0		0
License Costs	[17]										0
Commonwealth Edison Co [Member] | noncash member [Member]
Supplemental Cash Flow Information [Line Items]
Merger-related commitments (c)									0
Commonwealth Edison Co [Member] | noncash member [Member]
Supplemental Cash Flow Information [Line Items]
Asset Retirement Obligation, Revision of Estimate									0
NonCashFairValueAdjustment									0
Commonwealth Edison Co [Member] | Indemnification Agreement [Member]
Supplemental Cash Flow Information [Line Items]
Energy-related options	[18]										0
Contribution of Property		$ 0	[20]				21,000,000	[19]	158,000,000	[20]
Non Cash Licensing Agreement							0
PECO Energy Co [Member]
Supplemental Cash Flow Information [Line Items]
Interest (net of amount capitalized)							103,000,000		104,000,000		94,000,000
Income taxes (net of refunds)							47,000,000		64,000,000		64,000,000
Pension and non-pension postretirement benefit costs							29,000,000		33,000,000		39,000,000
Income (Loss) from Equity Method Investments							0		0		0
Provision for uncollectible accounts							26,000,000		30,000,000		30,000,000
Provision for excess and obsolete inventory							0		0		0
Stock-based compensation costs							0		0		0
Other decommissioning related-activity							0	[1]	0	[2]	0	[3]
Energy-related options							0	[4]	0	[5]	0	[6]
Amortization of regulatory asset related to debt costs							1,000,000		1,000,000		2,000,000
Amortization of rate stabilization deferral							0		0		0
Amortization of debt fair value adjustment							0		0		0
Merger-related commitments (c)							0	[7]	0	[8],[9]
Restructuring Costs							0		0
Amortization of Debt Issuance Costs							2,000,000		3,000,000		2,000,000
Discrete impacts from EIMA							0	[11]	0	[10]	0	[12]
Lower of cost or market inventory adjustment									1,000,000		0
Environmental Expense and Liabilities							0
Litigation Settlement, Amount Awarded from Other Party									0
Proceeds from Collection of Other Receivables									0
Increase (Decrease) in Accrued Liabilities							0		0		0
Other							(4,000,000)		(3,000,000)		(3,000,000)
Adjustments, Noncash Items, to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities							54,000,000		65,000,000		70,000,000
Fair value of net assets contributed to Generation in connection with the PHI Merger, net of cash							(22,000,000)		(11,000,000)		13,000,000
NonCashFairValueAdjustment	[9],[13]								0
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability	[9],[13]								0
Business Combination, Contingent Consideration, Liability, Noncurrent							0
Payments to Acquire Businesses, Gross									0
Change in PPE related to ARO update				0			0		0		0
Noncash or Part Noncash Acquisition, Fixed Assets Acquired							0		$ 0	[14]
Dividends, Stock							0
Contribution of Property	[15]										0
Noncash or Part Noncash Divestiture, Description	[9]								0
Non Cash Dissolution of Financing Trust Due to Long-term Debt Retirement							0
Other Noncash Expense							0	[16]	$ 0		0
License Costs	[17]										0
PECO Energy Co [Member] | noncash member [Member]
Supplemental Cash Flow Information [Line Items]
Merger-related commitments (c)									0
Asset Retirement Obligation, Revision of Estimate									0
NonCashFairValueAdjustment									0
PECO Energy Co [Member] | Indemnification Agreement [Member]
Supplemental Cash Flow Information [Line Items]
Energy-related options	[18]										0
Contribution of Property							0	[19]	0	[20]
Non Cash Licensing Agreement							0
Baltimore Gas and Electric Company [Member]
Supplemental Cash Flow Information [Line Items]
Interest (net of amount capitalized)							96,000,000		92,000,000		120,000,000
Income taxes (net of refunds)							(2,000,000)		31,000,000		73,000,000
Pension and non-pension postretirement benefit costs							62,000,000		67,000,000		65,000,000
Income (Loss) from Equity Method Investments							0		0		0
Provision for uncollectible accounts							8,000,000		1,000,000		15,000,000
Provision for excess and obsolete inventory							0		0		0
Stock-based compensation costs							0		0		0
Other decommissioning related-activity							0	[1]	0	[2]	0	[3]
Energy-related options							0	[4]	0	[5]	0	[6]
Amortization of regulatory asset related to debt costs							0		0		0
Amortization of rate stabilization deferral							7,000,000		81,000,000		73,000,000
Amortization of debt fair value adjustment							0		0		0
Merger-related commitments (c)							0	[7]	0	[8],[9]
Restructuring Costs							0		0
Amortization of Debt Issuance Costs							2,000,000		1,000,000		2,000,000
Discrete impacts from EIMA							0	[11]	0	[10]	0	[12]
Lower of cost or market inventory adjustment									0		0
Environmental Expense and Liabilities							0
Litigation Settlement, Amount Awarded from Other Party									(28,000,000)
Proceeds from Collection of Other Receivables									13,000,000
Increase (Decrease) in Accrued Liabilities							0		0		0
Other							(14,000,000)		(21,000,000)		(18,000,000)
Adjustments, Noncash Items, to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities							65,000,000		88,000,000		137,000,000
Fair value of net assets contributed to Generation in connection with the PHI Merger, net of cash							(23,000,000)		(86,000,000)		9,000,000
NonCashFairValueAdjustment	[9],[13]								0
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability	[9],[13]								0
Business Combination, Contingent Consideration, Liability, Noncurrent							0
Payments to Acquire Businesses, Gross									0
Change in PPE related to ARO update				0			0		0		0
Noncash or Part Noncash Acquisition, Fixed Assets Acquired							0		$ 0	[14]
Dividends, Stock							0
Contribution of Property	[15]										0
Noncash or Part Noncash Divestiture, Description	[9]								0
Non Cash Licensing Agreement							0
Non Cash Dissolution of Financing Trust Due to Long-term Debt Retirement							8,000,000
Other Noncash Expense							0	[16]	$ 0		0
License Costs	[17]										0
Baltimore Gas and Electric Company [Member] | noncash member [Member]
Supplemental Cash Flow Information [Line Items]
Merger-related commitments (c)									0
Asset Retirement Obligation, Revision of Estimate									0
NonCashFairValueAdjustment									0
Baltimore Gas and Electric Company [Member] | Indemnification Agreement [Member]
Supplemental Cash Flow Information [Line Items]
Energy-related options	[18]										0
Contribution of Property							0	[19]	0	[20]
Pepco Holdings LLC [Member] | Successor [Member]
Supplemental Cash Flow Information [Line Items]
Interest (net of amount capitalized)				209,000,000			236,000,000
Income taxes (net of refunds)				258,000,000			(144,000,000)
Pension and non-pension postretirement benefit costs				86,000,000			94,000,000
Income (Loss) from Equity Method Investments				0			1,000,000
Income (Loss) from Equity Method Investments, Net of Dividends or Distributions				0			(1,000,000)
Provision for uncollectible accounts				65,000,000			19,000,000
Provision for excess and obsolete inventory				1,000,000			2,000,000
Stock-based compensation costs				0			0
Other decommissioning related-activity				0	[2]		0	[1]
Energy-related options				0	[5]		0	[4]
Amortization of regulatory asset related to debt costs				3,000,000			4,000,000
Amortization of rate stabilization deferral				(5,000,000)			(17,000,000)
Amortization of debt fair value adjustment				0			(6,000,000)
Merger-related commitments (c)				317,000,000	[8],[9]		(8,000,000)	[7]
Restructuring Costs				56,000,000			3,000,000
Amortization of Debt Issuance Costs				1,000,000			4,000,000
Discrete impacts from EIMA	[11]						0
Lower of cost or market inventory adjustment				0
Environmental Expense and Liabilities							0
Litigation Settlement, Amount Awarded from Other Party									0
Proceeds from Collection of Other Receivables									0
Increase (Decrease) in Accrued Liabilities							0		0
Other				(12,000,000)			(27,000,000)
Adjustments, Noncash Items, to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities				514,000,000			59,000,000
Fair value of net assets contributed to Generation in connection with the PHI Merger, net of cash				21,000,000			(12,000,000)
NonCashFairValueAdjustment	[9],[13]			127,000,000
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability	[9],[13]			53,000,000
Business Combination, Contingent Consideration, Liability, Noncurrent							0
Payments to Acquire Businesses, Gross				29,000,000
Change in PPE related to ARO update							0
Noncash or Part Noncash Acquisition, Fixed Assets Acquired				$ 0	[14]		0
Dividends, Stock							0
Contribution of Property	[19]						0
Noncash or Part Noncash Divestiture, Description	[9]			0
Non Cash Licensing Agreement							0
Non Cash Dissolution of Financing Trust Due to Long-term Debt Retirement							0
Other Noncash Expense				$ 0			(8,000,000)	[16]
Pepco Holdings LLC [Member] | Successor [Member] | noncash member [Member]
Supplemental Cash Flow Information [Line Items]
Merger-related commitments (c)				33,000,000
Asset Retirement Obligation, Revision of Estimate				2,000,000
NonCashFairValueAdjustment				0
Pepco Holdings LLC [Member] | Predecessor [Member]
Supplemental Cash Flow Information [Line Items]
Interest (net of amount capitalized)		43,000,000									268,000,000
Income taxes (net of refunds)		11,000,000									(13,000,000)
Pension and non-pension postretirement benefit costs		23,000,000									97,000,000
Income (Loss) from Equity Method Investments		0
Income (Loss) from Equity Method Investments, Net of Dividends or Distributions		0									0
Provision for uncollectible accounts		16,000,000									61,000,000
Provision for excess and obsolete inventory		1,000,000									1,000,000
Stock-based compensation costs		3,000,000									13,000,000
Other decommissioning related-activity	[2]	0
Energy-related options	[5]	0
Amortization of regulatory asset related to debt costs		1,000,000									5,000,000
Amortization of rate stabilization deferral		5,000,000									(2,000,000)
Amortization of debt fair value adjustment		0
Merger-related commitments (c)	[8],[9]	0
Restructuring Costs		0
Amortization of Debt Issuance Costs		0									2,000,000
Discrete impacts from EIMA	[10]	0
Lower of cost or market inventory adjustment		0									0
Litigation Settlement, Amount Awarded from Other Party		0
Proceeds from Collection of Other Receivables		0
Increase (Decrease) in Accrued Liabilities									0		0
Other		(3,000,000)									(10,000,000)
Adjustments, Noncash Items, to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities		46,000,000									167,000,000
Fair value of net assets contributed to Generation in connection with the PHI Merger, net of cash		11,000,000									(6,000,000)
NonCashFairValueAdjustment	[9],[13]	0
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability	[9],[13]	0
Payments to Acquire Businesses, Gross		0
Change in PPE related to ARO update				0					0
Noncash or Part Noncash Acquisition, Fixed Assets Acquired	[14]	$ 0
Noncash or Part Noncash Divestiture, Description	[9]	0
Other Noncash Expense		$ 0
Pepco Holdings LLC [Member] | Predecessor [Member] | noncash member [Member]
Supplemental Cash Flow Information [Line Items]
Merger-related commitments (c)		0
Asset Retirement Obligation, Revision of Estimate		0
NonCashFairValueAdjustment		$ 0
Pepco Holdings LLC [Member] | Indemnification Agreement [Member] | Successor [Member]
Supplemental Cash Flow Information [Line Items]
Noncash or Part Noncash Acquisition, Fixed Assets Acquired	[20]			0
Potomac Electric Power Company [Member]
Supplemental Cash Flow Information [Line Items]
Interest (net of amount capitalized)							114,000,000		118,000,000		116,000,000
Income taxes (net of refunds)							(104,000,000)		216,000,000		(6,000,000)
Pension and non-pension postretirement benefit costs							25,000,000		31,000,000		30,000,000
Income (Loss) from Equity Method Investments							0		0		0
Provision for uncollectible accounts							8,000,000		29,000,000		21,000,000
Provision for excess and obsolete inventory							1,000,000		3,000,000		0
Stock-based compensation costs							0		0		0
Other decommissioning related-activity							0	[1]	0	[2]	0	[3]
Energy-related options							0	[4]	0	[5]	0	[6]
Amortization of regulatory asset related to debt costs							2,000,000		2,000,000		2,000,000
Amortization of rate stabilization deferral							(17,000,000)		(12,000,000)		1,000,000
Amortization of debt fair value adjustment							0		0		0
Merger-related commitments (c)							(6,000,000)	[7]	125,000,000	[8],[9]
Restructuring Costs							0		0
Amortization of Debt Issuance Costs							2,000,000		0		0
Discrete impacts from EIMA							0	[11]	0	[10]	0	[12]
Lower of cost or market inventory adjustment									0		0
Environmental Expense and Liabilities							0
Litigation Settlement, Amount Awarded from Other Party									0
Proceeds from Collection of Other Receivables									0
Increase (Decrease) in Accrued Liabilities							0		0		0
Other							(12,000,000)		5,000,000		0
Adjustments, Noncash Items, to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities							(5,000,000)		183,000,000		54,000,000
Fair value of net assets contributed to Generation in connection with the PHI Merger, net of cash							(5,000,000)		27,000,000		(1,000,000)
NonCashFairValueAdjustment	[9],[13]								0
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability	[9],[13]								0
Business Combination, Contingent Consideration, Liability, Noncurrent							0
Payments to Acquire Businesses, Gross									0
Change in PPE related to ARO update				0			0		0		0
Noncash or Part Noncash Acquisition, Fixed Assets Acquired							0		$ 0	[14]
Dividends, Stock							0
Contribution of Property	[15]										0
Noncash or Part Noncash Divestiture, Description	[9]								0
Non Cash Dissolution of Financing Trust Due to Long-term Debt Retirement							0
Other Noncash Expense							(8,000,000)	[16]	$ 0		0
License Costs	[17]										0
Potomac Electric Power Company [Member] | noncash member [Member]
Supplemental Cash Flow Information [Line Items]
Merger-related commitments (c)									33,000,000
Asset Retirement Obligation, Revision of Estimate									0
NonCashFairValueAdjustment									0
Potomac Electric Power Company [Member] | Indemnification Agreement [Member]
Supplemental Cash Flow Information [Line Items]
Energy-related options	[18]										0
Contribution of Property							0	[19]	0	[20]
Non Cash Licensing Agreement							0
Delmarva Power and Light Company [Member]
Supplemental Cash Flow Information [Line Items]
Interest (net of amount capitalized)							49,000,000		47,000,000		47,000,000
Income taxes (net of refunds)							(49,000,000)		115,000,000		(5,000,000)
Pension and non-pension postretirement benefit costs							13,000,000		18,000,000		15,000,000
Income (Loss) from Equity Method Investments							0		0		0
Provision for uncollectible accounts							3,000,000		23,000,000		20,000,000
Provision for excess and obsolete inventory							1,000,000		1,000,000		0
Stock-based compensation costs							0		0		0
Other decommissioning related-activity							0	[1]	0	[2]	0	[3]
Energy-related options							0	[4]	0	[5]	0	[6]
Amortization of regulatory asset related to debt costs							1,000,000		1,000,000		1,000,000
Amortization of rate stabilization deferral							0		2,000,000		(3,000,000)
Amortization of debt fair value adjustment							0		0		0
Merger-related commitments (c)							(2,000,000)	[7]	82,000,000	[8],[9]
Restructuring Costs							0		0
Amortization of Debt Issuance Costs							0		0		0
Discrete impacts from EIMA							0	[11]	0	[10]	0	[12]
Lower of cost or market inventory adjustment									0		0
Environmental Expense and Liabilities							0
Litigation Settlement, Amount Awarded from Other Party									0
Proceeds from Collection of Other Receivables									0
Increase (Decrease) in Accrued Liabilities							0		0		0
Other							(7,000,000)		(14,000,000)		0
Adjustments, Noncash Items, to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities							9,000,000		114,000,000		33,000,000
Fair value of net assets contributed to Generation in connection with the PHI Merger, net of cash							(4,000,000)		(12,000,000)		3,000,000
NonCashFairValueAdjustment	[9],[13]								0
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability	[9],[13]								0
Business Combination, Contingent Consideration, Liability, Noncurrent							0
Payments to Acquire Businesses, Gross									0
Change in PPE related to ARO update				0			0		0		0
Noncash or Part Noncash Acquisition, Fixed Assets Acquired							0		$ 0	[14]
Dividends, Stock							0
Contribution of Property	[15]										0
Noncash or Part Noncash Divestiture, Description	[9]								0
Non Cash Dissolution of Financing Trust Due to Long-term Debt Retirement							0
Other Noncash Expense							0	[16]	$ 0		0
License Costs	[17]										0
Delmarva Power and Light Company [Member] | noncash member [Member]
Supplemental Cash Flow Information [Line Items]
Merger-related commitments (c)									0
Asset Retirement Obligation, Revision of Estimate									1,000,000
NonCashFairValueAdjustment									0
Delmarva Power and Light Company [Member] | Indemnification Agreement [Member]
Supplemental Cash Flow Information [Line Items]
Energy-related options	[18]										0
Contribution of Property							0	[19]	0	[20]
Non Cash Licensing Agreement							0
Atlantic City Electric Company [Member]
Supplemental Cash Flow Information [Line Items]
Interest (net of amount capitalized)							59,000,000		62,000,000		63,000,000
Income taxes (net of refunds)							(2,000,000)		200,000,000		0
Pension and non-pension postretirement benefit costs							13,000,000		15,000,000		15,000,000
Income (Loss) from Equity Method Investments							0		0		0
Provision for uncollectible accounts							8,000,000		32,000,000		20,000,000
Provision for excess and obsolete inventory							0		1,000,000		0
Stock-based compensation costs							0		0		0
Other decommissioning related-activity							0	[1]	0	[2]	0	[3]
Energy-related options							0	[4]	0	[5]	0	[6]
Amortization of regulatory asset related to debt costs							1,000,000		1,000,000		1,000,000
Amortization of rate stabilization deferral							0		0		0
Amortization of debt fair value adjustment							0		0		0
Merger-related commitments (c)							0	[7]	110,000,000	[8],[9]
Restructuring Costs							0		0
Amortization of Debt Issuance Costs							1,000,000		0		0
Discrete impacts from EIMA							0	[11]	0	[10]	0	[12]
Lower of cost or market inventory adjustment									0		0
Environmental Expense and Liabilities							0
Litigation Settlement, Amount Awarded from Other Party									0
Proceeds from Collection of Other Receivables									0
Increase (Decrease) in Accrued Liabilities							0		0		0
Other							(6,000,000)		(6,000,000)		1,000,000
Adjustments, Noncash Items, to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities							17,000,000		155,000,000		37,000,000
Fair value of net assets contributed to Generation in connection with the PHI Merger, net of cash							13,000,000		11,000,000		3,000,000
NonCashFairValueAdjustment	[9],[13]								0
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability	[9],[13]								0
Business Combination, Contingent Consideration, Liability, Noncurrent							0
Payments to Acquire Businesses, Gross									0
Change in PPE related to ARO update				0			0		0		0
Noncash or Part Noncash Acquisition, Fixed Assets Acquired							0		$ 0	[14]
Dividends, Stock							0
Contribution of Property	[15]										0
Noncash or Part Noncash Divestiture, Description	[9]								0
Non Cash Dissolution of Financing Trust Due to Long-term Debt Retirement							0
Other Noncash Expense							0	[16]	$ 0		0
License Costs	[17]										0
Atlantic City Electric Company [Member] | noncash member [Member]
Supplemental Cash Flow Information [Line Items]
Merger-related commitments (c)									0
Asset Retirement Obligation, Revision of Estimate									2,000,000
NonCashFairValueAdjustment									0
Atlantic City Electric Company [Member] | Indemnification Agreement [Member]
Supplemental Cash Flow Information [Line Items]
Energy-related options	[18]										$ 0
Contribution of Property							0	[19]	$ 0	[20]
Non Cash Licensing Agreement							$ 0
Severance [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Supplemental Cash Flow Information [Line Items]
Discrete impacts from EIMA	[10]			$ 0

[1] Includes the elimination of NDT fund activity for the Regulatory Agreement Units, including the elimination of operating revenues, ARO accretion, ARC amortization, investment income and income taxes related to all NDT fund activity for these units. See Note 15 — Asset Retirement Obligations for additional information regarding the accounting for nuclear decommissioning.

[2] Includes the elimination of NDT fund activity for the Regulatory Agreement Units, including the elimination of operating revenues, ARO accretion, ARC amortization, investment income and income taxes related to all NDT fund activity for these units. See Note 15 — Asset Retirement Obligations for additional information regarding the accounting for nuclear decommissioning.

[3] Includes the elimination of NDT fund activity for the Regulatory Agreement Units, including the elimination of operating revenues, ARO accretion, ARC amortization, investment income and income taxes related to all NDT fund activity for these units. See Note 15 — Asset Retirement Obligations for additional information regarding the accounting for nuclear decommissioning.

[4] Includes option premiums reclassified to realized at the settlement of the underlying contracts and recorded to results of operations.

[5] Includes option premiums reclassified to realized at the settlement of the underlying contracts and recorded to results of operations.

[6] Includes option premiums reclassified to realized at the settlement of the underlying contracts and recorded to results of operations.

[7] See Note 4 - Mergers, Acquisitions and Dispositions for more information.

[8] Excludes $5 million of forgiveness of Accounts receivable related to merger commitments recorded in connection with the PHI Merger, the balance is included within Provision for uncollectible accounts.

[9] See Note 4 - Mergers, Acquisitions and Dispositions for more information.

[10] Reflects the change in distribution rates pursuant to EIMA, which allows for the recovery of costs by a utility through a pre-established performance-based formula rate. See Note 3 — Regulatory Matters for more information.

[11] Reflects the change in ComEd's distribution and energy efficiency formula rates . See Note 3 — Regulatory Matters for more information.

[12] Reflects the change in distribution rates pursuant to EIMA, which allows for the recovery of costs by a utility through a pre-established performance-based formula rate. See Note 3 — Regulatory Matters for more information.

[13] Immediately following closing of the PHI Merger, the net assets associated with PHI’s unregulated business interests were distributed by PHI to Exelon. Exelon contributed a portion of such net assets to Generation.

[14] Reflects the transfer of nuclear fuel to Entergy under the cost reimbursement provisions of the FitzPatrick acquisition agreements. See Note 4 - Mergers, Acquisitions and Dispositions for more information.

[15] See Note 14 — Income Taxes for discussion of the like-kind exchange tax position.

[16] On December 1, 2017, Exelon adopted a single, standard vacation accrual policy for all non-represented, non-craft (represented and craft policies remained unchanged) employees effective January 1, 2018. To reflect the new policy, Exelon recorded a one-time, $68 million pre-tax credit to expense to reverse 2018 vacation cost originally accrued throughout 2017 that will now be accrued ratably over the year in 2018.

[17] Relates to a long-term software license agreement entered into on May 30, 2015. Exelon is required to make payments starting August of 2015 through May of 2024. See Note 13 - Debt and Credit Agreements.

[18] Relates to the nuclear fuel procurement contracts for the purchase of fixed quantities of uranium, which was delivered to Generation in 2015. Generation is required to make payments starting September 30, 2018, with the final payment being due no later than September 30, 2020.

[19] See Note 14 — Income Taxes for discussion of the like-kind exchange tax position.

[20] See Note 14 — Income Taxes for discussion of the like-kind exchange tax position.