Supplemental Financial Information - Summary of Other Income (Expense) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Supplemental Financial Information Tables [Line Items]
Gain (Loss) on Sale of Derivatives	[1]	$ (26)
Payments of Debt Restructuring Costs	[2]	(22)
Net realized income on decommissioning trust funds - Regulatory Agreement Units	[3]	232	$ 216	$ 256
Net realized income on decommissioning trust funds - Non-Regulatory Agreement Units	[3]	156	159	77
Net unrealized income (losses) on decommissioning trust funds - Regulatory Agreement Units		(282)	180	406
Net unrealized income (losses) on decommissioning trust funds - Non-Regulatory Agreement		(197)	134	146
Net unrealized income (losses) on pledged assets		7	29	7
Regulatory offset to decommissioning trust fund-related activities	[4]	21	(358)	(546)
Total decommissioning-related activities		(63)	360	346
Investment income		8	1	8
Long-term lease income		15	24	28
Interest income related to uncertain income tax positions		1	40	24
AFUDC—Equity		24	21	22
Other		17	9	32
Other, net		(46)	455	460
Exelon Generation Co L L C [Member]
Supplemental Financial Information Tables [Line Items]
Net realized income on decommissioning trust funds - Regulatory Agreement Units	[3]	232	216	256
Net realized income on decommissioning trust funds - Non-Regulatory Agreement Units	[3]	156	159	77
Net unrealized income (losses) on decommissioning trust funds - Regulatory Agreement Units		(282)	180	406
Net unrealized income (losses) on decommissioning trust funds - Non-Regulatory Agreement		(197)	134	146
Net unrealized income (losses) on pledged assets		7	29	7
Regulatory offset to decommissioning trust fund-related activities	[4]	21	(358)	(546)
Total decommissioning-related activities		(63)	360	346
Investment income		3	1	(1)
Long-term lease income		0	0	0
Interest income related to uncertain income tax positions		1	54	4
AFUDC—Equity		0	0	0
Other		(1)	(9)	6
Other, net		(60)	406	355
Commonwealth Edison Co [Member]
Supplemental Financial Information Tables [Line Items]
Net realized income on decommissioning trust funds - Regulatory Agreement Units	[3]	0	0	0
Net realized income on decommissioning trust funds - Non-Regulatory Agreement Units	[3]	0	0	0
Net unrealized income (losses) on decommissioning trust funds - Regulatory Agreement Units		0	0	0
Net unrealized income (losses) on decommissioning trust funds - Non-Regulatory Agreement		0	0	0
Net unrealized income (losses) on pledged assets		0	0	0
Regulatory offset to decommissioning trust fund-related activities	[4]	0	0	0
Total decommissioning-related activities		0	0	0
Investment income		0	0	0
Long-term lease income		0	0	0
Interest income related to uncertain income tax positions		0	0	0
AFUDC—Equity		5	3	11
Other		16	14	15
Other, net		21	17	26
Other Income		21
PECO Energy Co [Member]
Supplemental Financial Information Tables [Line Items]
Net realized income on decommissioning trust funds - Regulatory Agreement Units	[3]	0	0	0
Net realized income on decommissioning trust funds - Non-Regulatory Agreement Units	[3]	0	0	0
Net unrealized income (losses) on decommissioning trust funds - Regulatory Agreement Units		0	0	0
Net unrealized income (losses) on decommissioning trust funds - Non-Regulatory Agreement		0	0	0
Net unrealized income (losses) on pledged assets		0	$ 0	$ 0
Regulatory offset to decommissioning trust fund-related activities	[4]	0
Total decommissioning-related activities		0	$ 0	$ 0
Investment income			(1)	(1)
Long-term lease income		0	0	0
Interest income related to uncertain income tax positions		0	0	0
AFUDC—Equity		5	6	4
Other		2	2	3
Other, net		5	7	6
Baltimore Gas and Electric Company [Member]
Supplemental Financial Information Tables [Line Items]
Net realized income on decommissioning trust funds - Regulatory Agreement Units	[3]	0	0	0
Net realized income on decommissioning trust funds - Non-Regulatory Agreement Units	[3]	0	0	0
Net unrealized income (losses) on decommissioning trust funds - Regulatory Agreement Units		0	0	0
Net unrealized income (losses) on decommissioning trust funds - Non-Regulatory Agreement		0	0	0
Net unrealized income (losses) on pledged assets		0	$ 0	0
Regulatory offset to decommissioning trust fund-related activities	[4]	0		0
Total decommissioning-related activities		0	$ 0	0
Investment income	[5]	4	7	9
Long-term lease income		0	0	0
Interest income related to uncertain income tax positions		0	0	0
AFUDC—Equity		14	12	7
Other		0	(1)	1
Other, net		$ 18	$ 18	$ 17

[1] In January 2015, in connection with Generation's $750 million issuance of five-year Senior Unsecured Notes, Exelon terminated certain floating-to-fixed interest rate swaps. As the original forecasted transactions were a series of future interest payments over a ten year period, a portion of the anticipated interest payments are probable not to occur. As a result, $26 million of anticipated payments were reclassified from Accumulated OCI to Other, net in Exelon's Consolidated Statement of Operations and Comprehensive Income.

[2] (e)See Note 14—Debt and Credit Agreements and 4—Mergers, Acquisitions, and Dispositions for additional information on the PHI merger related debt exchange.

[3] Includes investment income and realized gains and losses on sales of investments within the nuclear decommissioning trust funds.

[4] Includes the elimination of NDT fund activity for the Regulatory Agreement Units, including the elimination of net income taxes related to all NDT fund activity for those units. See Note 16 — Asset Retirement Obligations for additional information regarding the accounting for nuclear decommissioning.

[5] Relates to the cash return on BGE’s rate stabilization deferral. See Note 3 — Regulatory Matters for additional information regarding the rate stabilization deferral.