Supplemental Financial Information - Balance Sheet (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2013		Dec. 31, 2012
Investments In Affiliates Subsidiaries Associates And Joint Ventures [Abstract]
Equity Method Investments		$ 1,925,000,000		$ 1,849,000,000
Total Equity Method Investments		2,324,000,000		2,270,000,000
Other Investments [Abstract]
Total investments		3,112,000,000		3,055,000,000
Supplemental Financial Information Textuals [Abstract]
Payment to IRS	302,000,000
Capital Leases, Net Investment in Direct Financing Leases [Abstract]
Estimated residual value of leased assets		1,465,000,000		1,492,000,000
Less: unearned income		(767,000,000)		(807,000,000)
Net investment in long-term leases		698,000,000		685,000,000
Accrued Liabilities Current [Abstract]
Compensation-related accruals		683,000,000	[1]	708,000,000	[1]
Taxes accrued		315,000,000		353,000,000
Interest accrued		234,000,000		232,000,000
Severance accrued		66,000,000		91,000,000
Other accrued expenses		335,000,000	[2]	412,000,000	[2]
Total accrued expenses		1,633,000,000		1,796,000,000
Financing Receivable Recorded Investment [Line Items]
Installment plan receivables		19,000,000		18,000,000
Property, Plant And Equipment [Abstract]
Accumulated depreciation		13,713,000,000	[3]	12,184,000,000	[3]
Accumulated amortization of nuclear fuel		2,371,000,000
Accounts receivable, net
Allowance for uncollectible accounts		(272,000,000)		(293,000,000)
Accumulated Other Comprehensive Income (Loss) [Abstract]
Accumulated other comprehensive income (loss), net		(2,040,000,000)		(2,767,000,000)
Capital Leases Net Investment In Direct Financing Leases [Member]
Other Investments [Abstract]
Other Investments		698,000,000		685,000,000
Trust For Benefit Of Employees [Member]
Other Investments [Abstract]
Other Investments		90,000,000	[4]	100,000,000	[4]
Financing Trusts [Member]
Investments In Affiliates Subsidiaries Associates And Joint Ventures [Abstract]
Equity Method Investments		22,000,000	[5]	22,000,000	[5]
Keystone Fuels [Member]
Investments In Affiliates Subsidiaries Associates And Joint Ventures [Abstract]
Equity Method Investments		32,000,000		38,000,000
Conemaugh Fuels [Member]
Investments In Affiliates Subsidiaries Associates And Joint Ventures [Abstract]
Equity Method Investments		21,000,000		26,000,000
CENG [Member]
Investments In Affiliates Subsidiaries Associates And Joint Ventures [Abstract]
Equity Method Investments		1,925,000,000		1,849,000,000
Safe Harbor [Member]
Investments In Affiliates Subsidiaries Associates And Joint Ventures [Abstract]
Equity Method Investments		285,000,000		293,000,000
Malacha [Member]
Investments In Affiliates Subsidiaries Associates And Joint Ventures [Abstract]
Equity Method Investments		8,000,000		8,000,000
Sacramento Solar [Member]
Investments In Affiliates Subsidiaries Associates And Joint Ventures [Abstract]
Equity Method Investments		31,000,000		34,000,000
Exelon Generation Co L L C [Member]
Investments In Affiliates Subsidiaries Associates And Joint Ventures [Abstract]
Equity Method Investments		1,925,000,000		1,849,000,000
Total Equity Method Investments		2,302,000,000		2,247,000,000
Other Investments [Abstract]
Total investments		2,325,000,000		2,269,000,000
Capital Leases, Net Investment in Direct Financing Leases [Abstract]
Net investment in long-term leases		693,000,000
Accrued Liabilities Current [Abstract]
Compensation-related accruals		337,000,000	[1]	371,000,000	[1]
Taxes accrued		212,000,000		247,000,000
Interest accrued		72,000,000		60,000,000
Severance accrued		31,000,000		42,000,000
Other accrued expenses		324,000,000	[2]	396,000,000	[2]
Total accrued expenses		976,000,000		1,116,000,000
Property, Plant And Equipment [Abstract]
Accumulated depreciation		7,034,000,000	[6]	6,014,000,000	[6]
Accumulated amortization of nuclear fuel				2,078,000,000
Accounts receivable, net
Allowance for uncollectible accounts		(57,000,000)		(84,000,000)
Accumulated Other Comprehensive Income (Loss) [Abstract]
Accumulated other comprehensive income (loss), net		214,000,000		513,000,000
Exelon Generation Co L L C [Member] | Trust For Benefit Of Employees [Member]
Other Investments [Abstract]
Other Investments		23,000,000	[4]	22,000,000	[4]
Exelon Generation Co L L C [Member] | Financing Trusts [Member]
Investments In Affiliates Subsidiaries Associates And Joint Ventures [Abstract]
Equity Method Investments				0	[5]
Exelon Generation Co L L C [Member] | Keystone Fuels [Member]
Investments In Affiliates Subsidiaries Associates And Joint Ventures [Abstract]
Equity Method Investments		32,000,000		38,000,000
Exelon Generation Co L L C [Member] | Conemaugh Fuels [Member]
Investments In Affiliates Subsidiaries Associates And Joint Ventures [Abstract]
Equity Method Investments		21,000,000		26,000,000
Exelon Generation Co L L C [Member] | CENG [Member]
Investments In Affiliates Subsidiaries Associates And Joint Ventures [Abstract]
Equity Method Investments		1,925,000,000		1,849,000,000
Exelon Generation Co L L C [Member] | Safe Harbor [Member]
Investments In Affiliates Subsidiaries Associates And Joint Ventures [Abstract]
Equity Method Investments		285,000,000		293,000,000
Exelon Generation Co L L C [Member] | Malacha [Member]
Investments In Affiliates Subsidiaries Associates And Joint Ventures [Abstract]
Equity Method Investments		8,000,000		8,000,000
Exelon Generation Co L L C [Member] | Sacramento Solar [Member]
Investments In Affiliates Subsidiaries Associates And Joint Ventures [Abstract]
Equity Method Investments		31,000,000		33,000,000
Commonwealth Edison Co [Member]
Investments In Affiliates Subsidiaries Associates And Joint Ventures [Abstract]
Total Equity Method Investments		6,000,000		6,000,000
Other Investments [Abstract]
Total investments		11,000,000		14,000,000
Accrued Liabilities Current [Abstract]
Compensation-related accruals		135,000,000	[1]	125,000,000	[1]
Taxes accrued		62,000,000		61,000,000
Interest accrued		95,000,000		96,000,000
Severance accrued		3,000,000		4,000,000
Other accrued expenses		12,000,000		9,000,000
Total accrued expenses		307,000,000		295,000,000
Property, Plant And Equipment [Abstract]
Accumulated depreciation		3,184,000,000		2,998,000,000
Accounts receivable, net
Allowance for uncollectible accounts		(62,000,000)		(70,000,000)
Commonwealth Edison Co [Member] | Trust For Benefit Of Employees [Member]
Other Investments [Abstract]
Other Investments		5,000,000	[4]	8,000,000	[4]
Commonwealth Edison Co [Member] | Financing Trusts [Member]
Investments In Affiliates Subsidiaries Associates And Joint Ventures [Abstract]
Equity Method Investments		6,000,000	[5]	6,000,000	[5]
Commonwealth Edison Co [Member] | Keystone Fuels [Member]
Investments In Affiliates Subsidiaries Associates And Joint Ventures [Abstract]
Equity Method Investments				0
Commonwealth Edison Co [Member] | Conemaugh Fuels [Member]
Investments In Affiliates Subsidiaries Associates And Joint Ventures [Abstract]
Equity Method Investments				0
PECO Energy Co [Member]
Investments In Affiliates Subsidiaries Associates And Joint Ventures [Abstract]
Total Equity Method Investments		8,000,000		8,000,000
Other Investments [Abstract]
Total investments		31,000,000		30,000,000
Accrued Liabilities Current [Abstract]
Compensation-related accruals		47,000,000	[1]	45,000,000	[1]
Taxes accrued		24,000,000		3,000,000
Interest accrued		32,000,000		32,000,000
Severance accrued		1,000,000		1,000,000
Other accrued expenses		2,000,000		1,000,000
Total accrued expenses		106,000,000		82,000,000
Financing Receivable Recorded Investment [Line Items]
Installment plan receivables uncollectible accounts reserve		(18,000,000)		(15,000,000)
Property, Plant And Equipment [Abstract]
Accumulated depreciation		2,935,000,000		2,797,000,000
Accounts receivable, net
Allowance for uncollectible accounts		(107,000,000)		(99,000,000)
Accumulated Other Comprehensive Income (Loss) [Abstract]
Accumulated other comprehensive income (loss), net		1,000,000		1,000,000
PECO Energy Co [Member] | Low Risk [Member]
Financing Receivable Recorded Investment [Line Items]
Installment plan receivables uncollectible accounts reserve		(1,000,000)		(1,000,000)
PECO Energy Co [Member] | Medium Risk [Member]
Financing Receivable Recorded Investment [Line Items]
Installment plan receivables		4,000,000		3,000,000
PECO Energy Co [Member] | High Risk [Member]
Financing Receivable Recorded Investment [Line Items]
Installment plan receivables		13,000,000		11,000,000
PECO Energy Co [Member] | Trust For Benefit Of Employees [Member]
Other Investments [Abstract]
Other Investments		23,000,000	[4]	22,000,000	[4]
PECO Energy Co [Member] | Financing Trusts [Member]
Investments In Affiliates Subsidiaries Associates And Joint Ventures [Abstract]
Equity Method Investments		8,000,000	[5]	8,000,000	[5]
PECO Energy Co [Member] | Keystone Fuels [Member]
Investments In Affiliates Subsidiaries Associates And Joint Ventures [Abstract]
Equity Method Investments				0
PECO Energy Co [Member] | Conemaugh Fuels [Member]
Investments In Affiliates Subsidiaries Associates And Joint Ventures [Abstract]
Equity Method Investments				0
Baltimore Gas and Electric Company [Member]
Investments In Affiliates Subsidiaries Associates And Joint Ventures [Abstract]
Total Equity Method Investments		8,000,000		8,000,000
Other Investments [Abstract]
Total investments		13,000,000		13,000,000
Accrued Liabilities Current [Abstract]
Compensation-related accruals		55,000,000	[1]	38,000,000	[1]
Taxes accrued		16,000,000		22,000,000
Interest accrued		29,000,000		37,000,000
Severance accrued		4,000,000		5,000,000
Other accrued expenses				0
Total accrued expenses		111,000,000		102,000,000
Property, Plant And Equipment [Abstract]
Accumulated depreciation		2,702,000,000		2,595,000,000
Accounts receivable, net
Allowance for uncollectible accounts		(46,000,000)		(40,000,000)
Baltimore Gas and Electric Company [Member] | Trust For Benefit Of Employees [Member]
Other Investments [Abstract]
Other Investments		5,000,000		5,000,000	[4]
Baltimore Gas and Electric Company [Member] | Financing Trusts [Member]
Investments In Affiliates Subsidiaries Associates And Joint Ventures [Abstract]
Equity Method Investments		$ 8,000,000	[5]	$ 8,000,000	[5]

[1] Primarily includes accrued payroll, bonuses and other incentives, vacation and benefits.

[2] Includes $228 million and $327 million for amounts accrued related to Antelope Valley as of December 31, 2013 and December 31, 2012, respectively.

[3] Includes accumulated amortization of nuclear fuel in the reactor core at Generation of $2,371 million and $2,078 million as of December 31, 2013 and 2012, respectively.

[4] The Registrants' investments in these marketable securities are recorded at fair market value.

[5] Includes investments in financing trusts, which were not consolidated within the financial statements of Exelon and are shown as investments in affiliates on the Consolidated Balance Sheets. See Note 1 - Significant Accounting Policies for additional information.

[6] Includes accumulated amortization of nuclear fuel in the reactor core of $2,371 million and $2,078 million as of December 31, 2013 and 2012, respectively.