Consolidated Statement of Changes in Shareholders Equity (Unaudited) - 6 months ended Jun. 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]	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] Retained Earnings [Member]	Baltimore Gas and Electric Company [Member] Preferred Stock [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															$ 2,753
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	$ 1,203
Beginning Balance at Dec. 31, 2014									$ 14,051	$ 3,803	$ 8,951	$ (36)	$ 1,333
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		$ 1,372			1,331		35	6	875	841		0	34	209		209		189			189		157		157	$ 0
Noncontrolling Interest, Increase from Sale of Parent Equity Interest									3	0		0	3
Long-term incentive plan activity (in shares)		1,252
Long-term incentive plan activity		$ 29	29
Employee stock purchase plan issuances (in shares)		790
Employee stock purchase plan issuances		$ 16	16
Appropriation of retained earnings for future dividends																		0			(189)	189
Tax benefit on stock compensation		1	1
Common stock dividends		(537)			(537)			(6)						(139)		(139)		(150)				(150)	(77)		(77)
Contribution from parent																		45		45
Distribution to members									(2,262)	(2,262)		0	0
Allocation of tax benefit from parent																		3		3
Consolidated VIE dividend to non-controlling interest		0							0
Minority Interest Increase From Acquisition		3					3
Reversal of CENG equity method AOCI		0							0
Preferred security dividends		(6)																					(6)		(6)	0
Other comprehensive loss, net of income taxes of $53		58				58			(11)	0		(11)	0
Other comprehensive income (loss), net of tax	[1]	58							(11)
Ending Balance at Jun. 30, 2015									$ 12,656	$ 2,382	$ 8,951	$ (47)	$ 1,370
Ending Balance at Jun. 30, 2015		$ 25,069	$ 16,755	$ (2,327)	$ 11,704	$ (2,626)	$ 1,370	$ 193															2,827
Ending Balance (in shares) at Jun. 30, 2015		896,610
Ending Balance at Jun. 30, 2015		$ 23,506												$ 3,191	$ 2,439	$ 751	$ 1	$ 7,994	$ 1,588	$ 5,516	$ (1,639)	$ 2,529	$ 2,637	$ 1,360	$ 1,277	$ 190

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