Supplemental Financial Information - Summary of Depreciation, Amortization, Accretion and Depletion (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Supplemental Financial Information Tables [Line Items]
Property, plant and equipment		$ 2,227	$ 2,080	$ 1,893
Regulatory assets		170	191	212
Amortization of intangible assets, net		54	44	48
Nuclear fuel	[1]	1,116	1,073	921
ARO accretion	[2]	398	345	275
Total depreciation, amortization, accretion and depletion		3,987	3,868	3,779
Exelon Generation Co L L C [Member]
Supplemental Financial Information Tables [Line Items]
Property, plant and equipment		1,007	922	813
Regulatory assets		0	0	0
Amortization of intangible assets, net		47	44	43
Nuclear fuel	[1]	1,116	1,073	921
ARO accretion	[2]	397	345	275
Total depreciation, amortization, accretion and depletion		2,589	2,519	2,559
Commonwealth Edison Co [Member]
Supplemental Financial Information Tables [Line Items]
Property, plant and equipment		635	588	545
Regulatory assets		72	99	119
Amortization of intangible assets, net		0	0	5
Amortization of Intangible Assets		7	7	7
Nuclear fuel	[1]	0	0	0
ARO accretion	[2]	0	0	0
Total depreciation, amortization, accretion and depletion		707	687	669
PECO Energy Co [Member]
Supplemental Financial Information Tables [Line Items]
Property, plant and equipment		240	227	219
Regulatory assets		20	9	9
Amortization of intangible assets, net		0	0	0
Nuclear fuel	[1]	0	0	0
ARO accretion	[2]	0	0	0
Total depreciation, amortization, accretion and depletion		260	236	228
Baltimore Gas and Electric Company [Member]
Supplemental Financial Information Tables [Line Items]
Property, plant and equipment		289	288	264
Regulatory assets		77	83	84
Amortization of intangible assets, net		0	0	0
Nuclear fuel	[1]	0	0	0
ARO accretion	[2]	0	0	0
Total depreciation, amortization, accretion and depletion		366	371	348
Unamortized Energy Contracts [Member]
Supplemental Financial Information Tables [Line Items]
Amortization of Intangible Assets	[3]	22	135	430
Unamortized Energy Contracts [Member] | Exelon Generation Co L L C [Member]
Supplemental Financial Information Tables [Line Items]
Amortization of Intangible Assets	[3]	22	135	507
Unamortized Energy Contracts [Member] | Commonwealth Edison Company [Member]
Supplemental Financial Information Tables [Line Items]
Amortization of Intangible Assets	[3]	0
Unamortized Energy Contracts [Member] | Commonwealth Edison Co [Member]
Supplemental Financial Information Tables [Line Items]
Amortization of Intangible Assets	[3]		0	0
Unamortized Energy Contracts [Member] | PECO Energy Co [Member]
Supplemental Financial Information Tables [Line Items]
Amortization of Intangible Assets	[3]	0	0	0
Unamortized Energy Contracts [Member] | Baltimore Gas and Electric Company [Member]
Supplemental Financial Information Tables [Line Items]
Amortization of Intangible Assets	[3]	$ 0	$ 0	$ 0

[1] Included in Purchased power and fuel expense on the Registrants’ Consolidated Statements of Operations and Comprehensive Income.

[2] Included in Operating and maintenance expense on the Registrants’ Consolidated Statements of Operations and Comprehensive Income.

[3] Included in Operating revenues or Purchased power and fuel on the Registrants’ Consolidated Statements of Operations and Comprehensive Income.