Stock-Based Compensation Plans (Details) (USD $)	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011		Jun. 30, 2013
Common Stock [Abstract]
Common Stock without par - Authorized	2,000,000,000		2,000,000,000
Common Stock without par - Outstanding	857,290,484		854,781,389
Common Stock reserved for warrants	24,570
Authorized Shares for LTIP [Abstract]
Authorized Shares for LTIP	16,000,000
Share Based Compensation Components [Abstract]
Performance Shares Expense	$ 48,000,000		$ 46,000,000		$ 26,000,000
Stock-based compensation costs	120,000,000		94,000,000		67,000,000
Stock options	3,000,000		15,000,000		8,000,000
Restricted stock units	61,000,000		50,000,000		31,000,000
Other stock-based awards	6,000,000		4,000,000		4,000,000
Total stock-based compensation included in operating and maintenance expense	118,000,000		115,000,000		69,000,000
Income Tax Benefit	(44,000,000)		(44,000,000)		(27,000,000)
Total after-tax stock based compensation expense	74,000,000		71,000,000		42,000,000
Share Based Compensation Pre Tax Expense [Line Items]
Pre-tax stock based compensation expense	118,000,000	[1],[2]	115,000,000	[1]	69,000,000	[1],[3]
Realized tax benefit when exercised/distributed:
Stock options	0		3,000,000		2,000,000
Restricted stock units	11,000,000		11,000,000		8,000,000
Performance share awards	11,000,000		7,000,000		7,000,000
Stock deferral plan	1,000,000		0		1,000,000
Excess tax benefits included in other financing activities of Exelon's Consolidated Statements of Cash Flows:
Stock options	0		2,000,000		1,000,000
Restricted stock units	0		0		0
Performance share awards	0		0		0
Stock deferral plan	0		0		0
Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Roll Forward
Shares outstanding, beginning balance - shares	21,903,781
Exercised - shares	(670,957)
Forfeited - shares	(54,743)
Expired - shares	(893,758)
Shares outstanding, ending balance - shares	21,035,445		21,903,781
Exercisable stock options - shares	20,188,327	[4]
Shares outstanding, ending balance - weighted average remaining contractual life (years)	4 years 8 months 23 days
Exercisable stock options - weighted average remaining contractual life (years)	4 years 7 months 2 days
Shares outstanding, ending balance - aggregate intrinsic value	10,000,000
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Roll Forward
Equity instruments other than options - shares, beginning balance	1,960,665	[5]
Vested - shares	(1,058,804)
Forfeited - shares	(54,743)
Equity instruments other than options - shares, ending balance	847,118	[5]	1,960,665	[5]
Equity instruments other than options - Weighted average grant date fair value (per share), beginning balance	$ 40.56	[5]
Vested - Weighted average grant date fair value (per share)	$ 40.89
Forfeited - Weighted average grant date fair value (per share)	$ 39.36
Equity instruments other than options - Weighted average grant date fair value (per share), ending balance	$ 40.22	[5]	$ 40.56	[5]
Schedule Of Share Based Compensation Arrangements By Share Based Payment Award Footnotes To Table [Abstract]
Fully vested stock based compensation issued to retirement-eligible employees			448,827
Stock based compensation issued to retirement eligible employees that vested immediately on the date of the grant.			1,348,000
Fair value of each option estimated using the Black-Scholes-Merton option-pricing model
Dividend yield			0.0528%		0.0484%
Expected volatility			0.232%		0.244%
Risk-free interest rate			0.013%		0.0265%
Weighted average grant date fair value			$ 4.18		$ 6.22
Additional Information Regarding Stock Options Exercised [Abstract]
Intrinsic value	4,000,000	[6]	19,000,000	[6]	5,000,000	[6]
Cash received for exercise price	19,000,000		47,000,000		13,000,000
Unrecognized compensation costs related to nonvested stock options	2,000,000
Weighted Average Period Non Vested Stock Options Are Expected To Be Recognized Over	2 years 5 months
Restricted Stock Units [Abstract]
Obligations related to outstanding restricted stock units not yet settled			58,000,000				77,000,000
Obligations related to outstanding restricted stock units that will be settled in cash	64,000,000
Fair value of settled restricted stock	28,000,000		25,000,000		19,000,000
Performance Share Awards [Abstract]
Weighted average grant date fair value	31.55		39.71		43.52
Performance shares settled at fair value of	26,000,000		23,000,000		22,000,000
Performance shares settled at fair value and paid with cash	12,000,000		3,000,000		10,000,000
Unrecognized compensation costs related to nonvested performance shares	34,000,000
Weighted average period	1 year 11 months
Obligation Related To Outstanding Performance Share Awards [Abstract]
Current Liabilities	13,000,000	[7]	7,000,000	[7]
Deferred credits and other liabilities	24,000,000	[8]	11,000,000	[8]
Common stock	32,000,000		35,000,000
Total	69,000,000		53,000,000
Share Repurchases [Abstract]
Number of shares of common stock purchased under 2004 share repurchase program	35,000,000
Value of shares of common stock purchased under 2004 share repurchase program	2,300,000,000
Approved number of shares of common stock for repurchased under Q3 2008 share repurchase program	1,500,000,000
Employee Stock Option [Member]
Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Roll Forward
Shares outstanding, beginning balance - weighted average exercise price (per share)	$ 45.91
Exercised - weighted average exercise price (per share)	$ 28.02
Forfeited - weighted average exercise price (per share)	$ 39.36
Expired - weighted average exercise price (per share)	$ 49.08
Shares outstanding, ending balance - weighted average exercise price (per share)	$ 46.07
Exercisable stock options - weighted average exercise price (per share)	$ 46.31	[4]
Exercisable stock options - aggregate intrinsic value	10,000,000	[4]
Restricted Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Roll Forward
Equity instruments other than options - shares, beginning balance	2,029,161	[9]
Granted - shares	2,828,187
Vested - shares	(842,439)
Forfeited - shares	(108,199)
Undistributed Vested Awards - shares	(520,013)	[10]
Equity instruments other than options - shares, ending balance	3,386,697	[9]
Granted - Weighted average grant date fair value (per share)	$ 31.06
Vested - Weighted average grant date fair value (per share)	$ 42.90
Forfeited - Weighted average grant date fair value (per share)	$ 36.37
Undistributed Vested Awards - weighted average exercise price (per share)	$ 32.62	[10]
Schedule Of Share Based Compensation Arrangements By Share Based Payment Award Footnotes To Table [Abstract]
Fully vested stock based compensation issued to retirement-eligible employees	686,121
Share Based Compensation Acquisition Arrangement [Abstract]
No Sale Restricted Stock Converted Shares	153,654
No Sale Restricted Stock Converted Value	6,000,000
Performance Share Awards [Member]
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Roll Forward
Equity instruments other than options - shares, beginning balance	1,312,734	[11]
Granted - shares	2,629,171
Vested - shares	(612,624)
Forfeited - shares	(24,451)
Undistributed Vested Awards - shares	(1,290,640)	[12]
Equity instruments other than options - shares, ending balance	2,014,190	[11]
Equity instruments other than options - Weighted average grant date fair value (per share), beginning balance	$ 40.08	[11]
Granted - Weighted average grant date fair value (per share)	$ 31.55
Vested - Weighted average grant date fair value (per share)	$ 40.13
Forfeited - Weighted average grant date fair value (per share)	$ 32.17
Undistributed Vested Awards - weighted average exercise price (per share)	$ 34.28	[12]
Equity instruments other than options - Weighted average grant date fair value (per share), ending balance	$ 32.74	[11]
Schedule Of Share Based Compensation Arrangements By Share Based Payment Award Footnotes To Table [Abstract]
Fully vested stock based compensation issued to retirement-eligible employees	204,643		455,418
Exelon Generation Co L L C [Member]
Share Based Compensation Pre Tax Expense [Line Items]
Pre-tax stock based compensation expense	48,000,000	[2]	42,000,000		31,000,000	[3]
Commonwealth Edison Co [Member]
Common Stock [Abstract]
Par value of common stock	$ 12.50
Common Stock par - Authorized	250,000,000
Common Stock par - Outstanding	127,016,896		127,016,761
Warrants Outstanding	73,709		74,182
Common Stock reserved for warrants			24,727
Share Based Compensation Pre Tax Expense [Line Items]
Pre-tax stock based compensation expense	9,000,000	[2]	11,000,000		5,000,000	[3]
PECO Energy Co [Member]
Common Stock [Abstract]
Common Stock without par - Authorized	500,000,000
Common Stock without par - Outstanding	170,478,507		170,478,507
Share Based Compensation Pre Tax Expense [Line Items]
Pre-tax stock based compensation expense	5,000,000	[2]	5,000,000		5,000,000	[3]
Baltimore Gas and Electric Company [Member]
Common Stock [Abstract]
Common Stock without par - Authorized	175,000,000
Common Stock without par - Outstanding	1,000		1,000
Share Based Compensation Pre Tax Expense [Line Items]
Pre-tax stock based compensation expense	6,000,000	[2]	5,000,000		6,000,000	[3]
Business Services Company [Member]
Share Based Compensation Pre Tax Expense [Line Items]
Pre-tax stock based compensation expense	$ 50,000,000	[13],[2]	$ 52,000,000	[13]	$ 28,000,000	[13],[3]

[1] The stock-based compensation expense (pre-tax) for December 31, 2013 reflects the impact of changes to the retirement eligibility requirements for employees participating in the LTIP. In addition, the stock-based compensation expense at ComEd does not reflect the impact of the ComEd Key Manager Long-Term Performance Program in 2013 for certain employees, which is not considered stock-based compensation expense under the applicable authoritative guidance. In 2012, these employees participated in the Exelon Restricted Stock Award Program.

[2] BGE's stock-based compensation expense (pre-tax) for December 31, 2012 excludes $2 million of cost incurred in 2012 prior to the closing of Exelon's merger with Constellation on March 12, 2012. This amount is not included in Exelon's stock-based compensation expense for the year ended December 31, 2012 shown in the tables titled Components of Stock-Based Compensation Expense and Subsidiaries above.

[3] The total stock-based compensation expense (pre-tax) for December 31, 2011 of $69 million does not include the $6 million expense for BGE as those costs were incurred prior to the closing of Exelon’s merger with Constellation on March 12, 2012.

[4] Includes stock options issued to retirement eligible employees.

[5] Excludes 1,348,913 and 2,647,536 of stock options issued to retirement-eligible employees as of December 31, 2013 and December 31, 2012, respectively, as they are fully vested.

[6] The difference between the market value on the date of exercise and the option exercise price.

[7] Represents the current liability related to performance share awards expected to be settled in cash.

[8] Represents the long-term liability related to performance share awards expected to be settled in cash.

[9] Excludes 931,628 and 686,121 of restricted stock units issued to retirement-eligible employees as of December 31, 2013 and December 31, 2012, respectively, as they are fully vested.

[10] Represents restricted stock units that vested but were not distributed to retirement-eligible employees during 2013.

[11] Excludes 1,411,824 and 204,643 of performance share awards issued to retirement-eligible employees as of December 31, 2013 and December 31, 2012, respectively, as they are fully vested.

[12] Represents performance share awards that vested but were not distributed to retirement-eligible employees during 2013.

[13] (a)         BGE's stock-based compensation expense (pre-tax) for December 31, 2012 excludes $2 million of cost incurred in 2012 prior to the closing of Exelon's merger with Constellation on March 12, 2012. This amount is not included in Exelon's stock-based compensation expense for the year ended December 31, 2012 shown in the tables titled Components of Stock-Based Compensation Expense and Subsidiaries above. (b)        These amounts primarily represent amounts billed to Exelon's subsidiaries through intercompany allocations. These amounts are not included in the Generation, ComEd, PECO and BGE amounts above. (c)        The stock-based compensation expense (pre-tax) for December 31, 2013 reflects the impact of changes to the retirement eligibility requirements for employees participating in the LTIP. In addition, the stock-based compensation expense at ComEd does not reflect the impact of the ComEd Key Manager Long-Term Performance Program in 2013 for certain employees, which is not considered stock-based compensation expense under the applicable authoritative guidance. In 2012, these employees participated in the Exelon Restricted Stock Award Program. (d)        The total stock-based compensation expense (pre-tax) for December 31, 2011 of $69 million does not include the $6 million expense for BGE as those costs were incurred prior to the closing of Exelon’s merger with Constellation on March 12, 2012.