Consolidated Statement of Changes in Shareholders Equity (Unaudited) (USD $) In Millions, except Share data in Thousands, unless otherwise specified		Total	Common Stock [Member]	Treasury Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Noncontrolling Interest [Member]	Preference Stock Not Subject To Mandatory Redemption [Member]	Exelon Generation Co L L C [Member]	Exelon Generation Co L L C [Member] Undistributed Earnings [Member]	Exelon Generation Co L L C [Member] Membership Interest [Member]	Exelon Generation Co L L C [Member] Accumulated Other Comprehensive Income (Loss) [Member]	Exelon Generation Co L L C [Member] Noncontrolling Interest [Member]	PECO Energy Co [Member]	PECO Energy Co [Member] Common Stock [Member]	PECO Energy Co [Member] Retained Earnings [Member]	PECO Energy Co [Member] Accumulated Other Comprehensive Income (Loss) [Member]	Commonwealth Edison Co [Member]	Commonwealth Edison Co [Member] Common Stock [Member]	Commonwealth Edison Co [Member] Other Additional Capital [Member]	Commonwealth Edison Co [Member] Retained Earnings, Unappropriated [Member]	Commonwealth Edison Co [Member] Retained Earnings, Appropriated [Member]	Baltimore Gas and Electric Company [Member]	Baltimore Gas and Electric Company [Member] Common Stock [Member]	Baltimore Gas and Electric Company [Member] Nonredeemable Preferred Stock [Member]	Baltimore Gas and Electric Company [Member] Retained Earnings [Member]
Beginning Balance at Dec. 31, 2013		$ 22,732												$ 3,065	$ 2,415	$ 649	$ 1	$ 7,528	$ 1,588	$ 5,190	$ (1,639)	$ 2,389	$ 2,365	$ 1,360	$ 190	$ 1,005
Beginning Balance at Dec. 31, 2013		22,940	16,741	(2,327)	10,358	(2,040)	15	193															2,555
Beginning Balance (in shares) at Dec. 31, 2013		892,034
Beginning Balance at Dec. 31, 2013									12,742	3,613	8,898	214	17
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		1,725			1,604		111	10	1,037	926		0	111	255		255		335			335		156		0	156
Noncontrolling Interest, Increase from Sale of Parent Equity Interest									2	0		0	2
Long-term incentive plan activity (in shares)		1,439
Long-term incentive plan activity		49	49
Employee stock purchase plan issuances (in shares)		735
Employee stock purchase plan issuances		25	25
Appropriation of retained earnings for future dividends																		0			(335)	335
Tax benefit on stock compensation		(7)	(7)
Common stock dividends		(802)			(802)			(10)						(240)		(240)		(230)				(230)
Contribution from parent																		168		168
Distribution to members									(440)	(440)		0	0
Allocation of tax benefit from members									55		55
Preferred stock redemption premium														(6)
Allocation of tax benefit from parent														24	24			4		4
Consolidated VIE dividend to non-controlling interest		415							415				(415)
Reversal of CENG equity method AOCI, net of income taxes of $77		(116)				(116)
Minority Interest Increase From Acquisition		3					3
Reversal of CENG equity method AOCI		(116)							(116)			(116)
Preferred security dividends		(10)																					(10)		0	(10)
Long-term Debt, Excluding Current Maturities		(131)	(131)
Noncontrolling interest acquired		1,548					1,548		1,548				1,548
Increase (Decrease) in Pension and Postretirement Obligations		2	2
Other comprehensive loss, net of income taxes of $53		239				239			(87)	0		(87)	0
Other comprehensive income (loss), net of tax	[1]	123							(203)
Ending Balance at Sep. 30, 2014		23,595												3,104	2,439	664	1	7,805	1,588	5,362	(1,639)	2,494	2,511	1,360	190	1,151
Ending Balance at Sep. 30, 2014		25,050	16,679	(2,327)	11,160	(1,917)	1,262	193															2,701
Ending Balance (in shares) at Sep. 30, 2014		894,208
Ending Balance at Sep. 30, 2014									14,326	4,099	8,953	11	1,263
Beginning Balance at Jun. 30, 2014
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		1,074							849					81				126					49
Reversal of CENG equity method AOCI		0							0
Other comprehensive income (loss), net of tax		(11)							(26)
Ending Balance at Sep. 30, 2014		23,595												3,104			1	7,805	1,588				2,511	1,360
Ending Balance at Sep. 30, 2014		25,050		(2,327)																			2,701
Ending Balance (in shares) at Sep. 30, 2014		894,208
Ending Balance at Sep. 30, 2014									$ 14,326

[1] All amounts are net of tax. Amounts in parenthesis represent a decrease in accumulated other comprehensive income.