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, 2014		$ 22,608												$ 3,121	$ 2,439	$ 681	$ 1	$ 7,907	$ 1,588	$ 5,468	$ (1,639)	$ 2,490	$ 2,563	$ 1,360	$ 190	$ 1,203
Beginning Balance at Dec. 31, 2014		24,133	16,709	(2,327)	10,910	(2,684)	1,332	193															2,753
Beginning Balance (in shares) at Dec. 31, 2014		894,568
Beginning Balance at Dec. 31, 2014									14,051	3,803	8,951	(36)	1,333
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		738			693		42	3	485	443		0	42	139		139		90			90		109		0	109
Noncontrolling Interest, Increase from Sale of Parent Equity Interest									5	0		0	5
Long-term incentive plan activity (in shares)		1,156
Long-term incentive plan activity		12	12
Employee stock purchase plan issuances (in shares)		255
Employee stock purchase plan issuances		8	8
Appropriation of retained earnings for future dividends																		0			(90)	90
Tax benefit on stock compensation		2	2
Common stock dividends		(269)			(269)			(3)						(70)		(70)		(75)				(75)
Contribution from parent																		14		14
Distribution to members									(1,356)	(1,356)		0	0
Allocation of tax benefit from parent																		2		2
Minority Interest Increase From Acquisition		6					6
Preferred security dividends		(3)																					(3)		0	(3)
Other comprehensive loss, net of income taxes of $53		11				11			(17)	0		(17)	0
Other comprehensive income (loss), net of tax	[1]	11							(17)
Ending Balance at Mar. 31, 2015		23,065												3,190	2,439	750	1	7,938	1,588	5,484	(1,639)	2,505	2,633	1,360	190	1,273
Ending Balance at Mar. 31, 2015		24,638	16,731	(2,327)	11,334	(2,673)	1,380	193															2,823
Ending Balance (in shares) at Mar. 31, 2015		895,979
Ending Balance at Mar. 31, 2015									$ 13,168	$ 2,890	$ 8,951	$ (53)	$ 1,380

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