Income Taxes - Schedule of Carryforwards and Corresponding Valuation Allowances (Details) $ in Millions	Dec. 31, 2016 USD ($)
Internal Revenue Service (IRS) [Member]
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards	$ 99
State net operating losses and credit carryforwards	282	[1]
Internal Revenue Service (IRS) [Member] | Exelon Generation Co L L C [Member]
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards	4
State net operating losses and credit carryforwards	11
Internal Revenue Service (IRS) [Member] | Commonwealth Edison Co [Member]
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards	29
State net operating losses and credit carryforwards	82
Internal Revenue Service (IRS) [Member] | PECO Energy Co [Member]
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards	0
State net operating losses and credit carryforwards	0
Internal Revenue Service (IRS) [Member] | Baltimore Gas and Electric Company [Member]
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards	0
State net operating losses and credit carryforwards	0
Internal Revenue Service (IRS) [Member] | Potomac Electric Power Company [Member]
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards	15
State net operating losses and credit carryforwards	44
Internal Revenue Service (IRS) [Member] | Delmarva Power and Light Company [Member]
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards	13
State net operating losses and credit carryforwards	38
Internal Revenue Service (IRS) [Member] | Atlantic City Electric Company [Member]
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards	6
State net operating losses and credit carryforwards	18
Internal Revenue Service (IRS) [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards	42
State net operating losses and credit carryforwards	121
Internal Revenue Service (IRS) [Member] | General Business Tax Credit Carryforward [Member]
Operating Loss Carryforwards [Line Items]
Federal general business credits carryforwards	511	[2]
Internal Revenue Service (IRS) [Member] | General Business Tax Credit Carryforward [Member] | Exelon Generation Co L L C [Member]
Operating Loss Carryforwards [Line Items]
Federal general business credits carryforwards	509
Internal Revenue Service (IRS) [Member] | General Business Tax Credit Carryforward [Member] | Commonwealth Edison Co [Member]
Operating Loss Carryforwards [Line Items]
Federal general business credits carryforwards	1
Internal Revenue Service (IRS) [Member] | General Business Tax Credit Carryforward [Member] | PECO Energy Co [Member]
Operating Loss Carryforwards [Line Items]
Federal general business credits carryforwards	0
Internal Revenue Service (IRS) [Member] | General Business Tax Credit Carryforward [Member] | Baltimore Gas and Electric Company [Member]
Operating Loss Carryforwards [Line Items]
Federal general business credits carryforwards	1
Internal Revenue Service (IRS) [Member] | General Business Tax Credit Carryforward [Member] | Potomac Electric Power Company [Member]
Operating Loss Carryforwards [Line Items]
Federal general business credits carryforwards	0
Internal Revenue Service (IRS) [Member] | General Business Tax Credit Carryforward [Member] | Delmarva Power and Light Company [Member]
Operating Loss Carryforwards [Line Items]
Federal general business credits carryforwards	0
Internal Revenue Service (IRS) [Member] | General Business Tax Credit Carryforward [Member] | Atlantic City Electric Company [Member]
Operating Loss Carryforwards [Line Items]
Federal general business credits carryforwards	0
Internal Revenue Service (IRS) [Member] | General Business Tax Credit Carryforward [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Operating Loss Carryforwards [Line Items]
Federal general business credits carryforwards	0
State and Local Jurisdiction [Member]
Operating Loss Carryforwards [Line Items]
State net operating losses and credit carryforwards	3,501	[3]
Deferred taxes on state tax attributes (net)	186
Valuation allowance on state tax attributes	20
State and Local Jurisdiction [Member] | Exelon Generation Co L L C [Member]
Operating Loss Carryforwards [Line Items]
State net operating losses and credit carryforwards	1,245	[3]
Deferred taxes on state tax attributes (net)	65
Valuation allowance on state tax attributes	9
State and Local Jurisdiction [Member] | Commonwealth Edison Co [Member]
Operating Loss Carryforwards [Line Items]
State net operating losses and credit carryforwards	0
Deferred taxes on state tax attributes (net)	0
Valuation allowance on state tax attributes	0
State and Local Jurisdiction [Member] | PECO Energy Co [Member]
Operating Loss Carryforwards [Line Items]
State net operating losses and credit carryforwards	0
Deferred taxes on state tax attributes (net)	0
Valuation allowance on state tax attributes	0
State and Local Jurisdiction [Member] | Baltimore Gas and Electric Company [Member]
Operating Loss Carryforwards [Line Items]
State net operating losses and credit carryforwards	425	[4]
Deferred taxes on state tax attributes (net)	23
Valuation allowance on state tax attributes	1
State and Local Jurisdiction [Member] | Potomac Electric Power Company [Member]
Operating Loss Carryforwards [Line Items]
State net operating losses and credit carryforwards	360	[5]
Deferred taxes on state tax attributes (net)	20
Valuation allowance on state tax attributes	0
State and Local Jurisdiction [Member] | Delmarva Power and Light Company [Member]
Operating Loss Carryforwards [Line Items]
State net operating losses and credit carryforwards	639	[6]
Deferred taxes on state tax attributes (net)	36
Valuation allowance on state tax attributes	0
State and Local Jurisdiction [Member] | Atlantic City Electric Company [Member]
Operating Loss Carryforwards [Line Items]
State net operating losses and credit carryforwards	272	[7]
Deferred taxes on state tax attributes (net)	16
Valuation allowance on state tax attributes	0
State and Local Jurisdiction [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Operating Loss Carryforwards [Line Items]
State net operating losses and credit carryforwards	1,522	[8]
Deferred taxes on state tax attributes (net)	86
Valuation allowance on state tax attributes	$ 10

[1] Exelon's federal net operating loss will begin expiring in 2032.

[2] Exelon’s federal general business credit carryforwards will begin expiring in 2033.

[3] Exelon’s and Generation's state net operating losses and credit carryforwards, which are presented on a post-apportioned basis, will begin expiring in 2017.

[4] BGE's state net operating loss carryforwards, which are presented on a post-apportioned basis, will begin expiring in 2026

[5] Pepco's state net operating loss carryforwards, which are presented on a post-apportioned basis, will begin expiring in 2028

[6] DPL's state net operating loss carryforwards, which are presented on a post-apportioned basis, will begin expiring in 2023.

[7] ACE's state net operating loss carryforwards, which are presented on a post-apportioned basis, will begin expiring in 2032.

[8] PHI's state net operating loss carryforwards, which are presented on a post-apportioned basis, will begin expiring in 2023.