Accounts Receivable Schedule of Estimated Unbilled Revenues (Details) - USD ($)		12 Months Ended
		Dec. 31, 2016		Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenues		$ 1,673,000,000		$ 1,203,000,000
Allowance for uncollectible accounts	[1]	(334,000,000)		(284,000,000)
Regulatory Assets		11,388,000,000		6,824,000,000
Exelon Generation Co L L C [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenues	[2]	910,000,000		732,000,000
Allowance for uncollectible accounts	[1]	(91,000,000)		(77,000,000)
Commonwealth Edison Co [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenues		219,000,000		218,000,000
Allowance for uncollectible accounts	[1]	(70,000,000)		(75,000,000)
Regulatory Assets		1,167,000,000		1,113,000,000
PECO Energy Co [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenues		140,000,000		105,000,000
Allowance for uncollectible accounts	[1],[3]	(61,000,000)		(83,000,000)
Allowance for Doubtful Accounts Receivable, Noncurrent		23,000,000		8,000,000
Regulatory Assets		1,710,000,000		1,617,000,000
Baltimore Gas and Electric Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenues		182,000,000		148,000,000
Allowance for uncollectible accounts	[1]	(32,000,000)		(49,000,000)
Regulatory Assets		712,000,000		781,000,000
Pepco Holdings LLC [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Charged to Costs and Expenses		10,000,000
Pepco Holdings LLC [Member] | Successor [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenues		222,000,000
Allowance for uncollectible accounts	[1],[4]	(80,000,000)
Regulatory Assets		3,504,000,000
Pepco Holdings LLC [Member] | Predecessor [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenues				177,000,000
Allowance for uncollectible accounts	[1]			(56,000,000)
Regulatory Assets				2,582,000,000
Potomac Electric Power Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenues		123,000,000		93,000,000
Allowance for uncollectible accounts	[1]	(29,000,000)	[4]	(17,000,000)
Regulatory Assets		852,000,000		801,000,000
Charged to Costs and Expenses		6,000,000
Delmarva Power and Light Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenues		58,000,000		45,000,000
Allowance for uncollectible accounts	[1]	(24,000,000)	[4]	(17,000,000)
Regulatory Assets		348,000,000		371,000,000
Charged to Costs and Expenses		4,000,000
Atlantic City Electric Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenues		41,000,000		39,000,000
Allowance for uncollectible accounts	[1]	(27,000,000)	[4]	(17,000,000)
Regulatory Assets		501,000,000		$ 512,000,000
PHI Merger [Member] | Pepco Holdings LLC [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for uncollectible accounts		(30,000,000)
Regulatory Assets		20,000,000
PHI Merger [Member] | Potomac Electric Power Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for uncollectible accounts		(14,000,000)
Regulatory Assets		8,000,000
PHI Merger [Member] | Delmarva Power and Light Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for uncollectible accounts		(8,000,000)
Regulatory Assets		4,000,000
PHI Merger [Member] | Atlantic City Electric Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for uncollectible accounts		(8,000,000)
Regulatory Assets		$ 8,000,000

[1] Includes the allowance for uncollectible accounts on customer and other accounts receivable.

[2] Represents unbilled portion of retail receivables estimated under Exelon’s unbilled critical accounting policy.

[3] Excludes the non-current allowance for uncollectible accounts of $23 million and $8 million at December 31, 2016 and 2015, respectively, related to PECO’s current installment plan receivables described below.

[4] At December 31, 2016, as explained in Note 1—Significant Accounting Policies, PHI, Pepco, DPL and ACE estimated the allowance for uncollectible accounts on customer receivables by applying loss rates to the outstanding receivable balance by risk segment. The change in estimate resulted in an overall increase of $30 million, $14 million, $8 million, and $8 million in the allowance for uncollectible accounts with $20 million, $8 million, $4 million, and $8 million deferred as a regulatory asset on PHI's, Pepco's, DPL's and ACE's Consolidated Balance Sheets at December 31, 2016, respectively. This also resulted in a $10 million, $6 million, and $4 million pre-tax charge to provision for uncollectible accounts expense for the year ended December 31, 2016, which is included in Operating and maintenance expense on PHI's, Pepco's, and DPL's Consolidated Statements of Operations and Comprehensive Income, respectively.