Consolidated Statement of Changes in Shareholders Equity (Unaudited) - 9 months ended Sep. 30, 2015 - USD ($) shares in Thousands, $ in Millions		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]	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]	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]	Baltimore Gas and Electric Company [Member]	Baltimore Gas and Electric Company [Member] Common Stock [Member]	Baltimore Gas and Electric Company [Member] Membership Interest [Member]	Baltimore Gas and Electric Company [Member] Retained Earnings [Member]	Baltimore Gas and Electric Company [Member] Preference Stock Not Subject To Mandatory Redemption [Member]
Beginning Balance (in shares) at Dec. 31, 2014		894,568
Beginning Balance at Dec. 31, 2014		$ 24,133	$ 16,709	$ (2,327)	$ 10,910	$ (2,684)	$ 1,332	$ 193	$ 7,907	$ 1,588	$ 5,468	$ (1,639)	$ 2,490	$ 14,051	$ 3,803	$ 8,951	$ (36)	$ 1,333	$ 3,121	$ 2,439	$ 681	$ 1	$ 2,753	$ 1,360	$ 2,563	$ 1,203	$ 190
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		1,959			1,959		(10)	10	339			339		1,208	1,218		0	(10)	299	0			212		212	212
Net income attributable to common shareholders		$ 1,959																	299		299	0	202
Noncontrolling Interest, Increase from Sale of Parent Equity Interest														2	0		0	2
Long-term incentive plan activity (in shares)		1,394
Long-term incentive plan activity		$ 47	47
Employee stock purchase plan issuances (in shares)		1,083
Employee stock purchase plan issuances		$ 24	24
Appropriation of retained earnings for future dividends									0			(339)	339
Tax benefit on stock compensation		(1)	(1)
Common stock dividends		(823)			(823)			(10)	(226)				(226)							0	(209)	0	(116)		(116)	(116)
Contribution from parent									75		75
Distribution to members														(2,368)	(2,368)		0	0
Allocation of tax benefit from members																			16	16	0	0	6	6	6
Allocation of tax benefit from parent									5		5
Consolidated VIE dividend to non-controlling interest		0												0
Minority Interest Increase From Acquisition		4					4
Reversal of CENG equity method AOCI		0												0
Preferred security dividends		$ (10)																					(10)		(10)	(10)
Stock Issued During Period, Shares, New Issues		57,500
Stock Issued During Period, Value, New Issues		$ 1,868	1,868
Other comprehensive loss, net of income taxes of $53		88				88								(24)	0		(24)	0
Other comprehensive income (loss), net of tax	[1]	88												(24)
Ending Balance at Sep. 30, 2015		$ 27,289	$ 18,647	$ (2,327)	$ 12,046	$ (2,596)	$ 1,326	$ 193	$ 8,100	$ 1,588	$ 5,548	$ (1,639)	$ 2,603	$ 12,924	$ 2,653	$ 9,006	$ (60)	$ 1,325	$ 3,227	$ 2,455	$ 771	$ 1	$ 2,845	$ 1,366	$ 2,655	$ 1,289	$ 190
Ending Balance (in shares) at Sep. 30, 2015		954,545

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