Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Net Cash Provided by (Used in) Operating Activities [Abstract]
Net income	$ 1,959	$ 1,725
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, depletion and accretion, including nuclear fuel and energy contract amortization	2,930	2,856
Impairment of long-lived assets	25	162
Gain on consolidation and acquisition of businesses	0	(268)
Gain on sales of assets	(10)	(356)
Deferred income taxes and amortization of investment tax credits	241	459
Net fair value changes related to derivatives	(363)	522
Net realized and unrealized (gains) losses on nuclear decommissioning trust fund investments	221	(141)
Other non-cash operating activities	856	698
Changes in assets and liabilities:
Accounts receivable	175	198
Inventories	65	(316)
Accounts payable, accrued expenses and other current liabilities	(147)	(322)
Option premiums received, net	27	21
Counterparty collateral received (posted), net	305	(615)
Income taxes	300	72
Pension and non-pension postretirement benefit contributions	(430)	(516)
Other assets and liabilities	(480)	(536)
Net cash flows provided by operating activities	5,674	3,643
Cash flows from investing activities
Capital expenditures	(5,443)	(4,114)
Proceeds from nuclear decommissioning trust fund sales	4,551	5,464
Investment in nuclear decommissioning trust funds	(4,737)	(5,550)
Acquisition of businesses	(28)	(67)
Proceeds from sale of long-lived assets	145	660
Proceeds from termination of direct financing lease investment	0	335
Proceeds from sales of investments	0	7
Change in restricted cash	(70)	(151)
Cash and restricted cash acquired from consolidations and acquisitions	0	129
Other investing activities	(107)	(89)
Net cash flows used in investing activities	(5,689)	(3,376)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Changes in short-term borrowings	230	236
Issuance of long-term debt	5,909	3,212
Retirement of long-term debt	(1,745)	(1,214)
Distributions to noncontrolling interest of consolidated VIE	0
Payments to Noncontrolling Interests		(415)
Dividends paid on common stock	(819)	(799)
Proceeds from employee stock plans	24	25
Other financing activities	(65)	(158)
Proceeds from Issuance of Common Stock	1,868
Net cash flows provided by financing activities	5,402	887
Increase in cash and cash equivalents	5,387	1,154
Cash and cash equivalents at beginning of period	1,878	1,609
Cash and cash equivalents at end of period	7,265	2,763
Exelon Generation Co L L C [Member]
Net Cash Provided by (Used in) Operating Activities [Abstract]
Net income	1,208	1,037
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, depletion and accretion, including nuclear fuel and energy contract amortization	1,887	1,853
Impairment of long-lived assets	1	138
Gain on consolidation and acquisition of businesses	0	(268)
Gain on sales of assets	(7)	(355)
Deferred income taxes and amortization of investment tax credits	21	154
Net fair value changes related to derivatives	(252)	509
Net realized and unrealized (gains) losses on nuclear decommissioning trust fund investments	221	(141)
Other non-cash operating activities	227	251
Changes in assets and liabilities:
Accounts receivable	252	153
Receivables from and payables to affiliates, net	16	72
Inventories	69	(286)
Accounts payable, accrued expenses and other current liabilities	(156)	(311)
Option premiums received, net	27	21
Counterparty collateral received (posted), net	376	(634)
Income taxes	(70)	172
Pension and non-pension postretirement benefit contributions	(189)	(214)
Other assets and liabilities	(425)	(367)
Net cash flows provided by operating activities	3,206	1,784
Cash flows from investing activities
Capital expenditures	(2,774)	(1,961)
Proceeds from nuclear decommissioning trust fund sales	4,551	5,464
Investment in nuclear decommissioning trust funds	(4,737)	(5,550)
Proceeds from nuclear decommissioning trust fund sales	0
Acquisition of businesses	(28)	(67)
Proceeds from sale of long-lived assets	144	660
Change in restricted cash	(84)	(116)
Cash and restricted cash acquired from consolidations and acquisitions	0	129
Other investing activities	(92)	(34)
Changes in Exelon intercompany money pool	1,205	0
Funding of Exelon intercompany money pool		44
Net cash flows used in investing activities	(3,020)	(1,431)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Changes in short-term borrowings	0	7
Issuance of long-term debt	1,307	1,112
Retirement of long-term debt	(64)	(552)
Repayments of Related Party Debt	(550)	0
Distributions to noncontrolling interest of consolidated VIE	0
Payments to Noncontrolling Interests		(415)
Other financing activities	(6)	(67)
Distribution to member	(2,368)	(440)
Changes in Exelon intercompany money pool	1,205	0
Contribution from member	55	55
Net cash flows provided by financing activities	(421)	(300)
Increase in cash and cash equivalents	(235)	53
Cash and cash equivalents at beginning of period	780	1,258
Cash and cash equivalents at end of period	545	1,311
Commonwealth Edison Co [Member]
Net Cash Provided by (Used in) Operating Activities [Abstract]
Net income	339	335
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, depletion and accretion, including nuclear fuel and energy contract amortization	528	521
Deferred income taxes and amortization of investment tax credits	107	154
Other non-cash operating activities	312	116
Changes in assets and liabilities:
Accounts receivable	(114)	(109)
Receivables from and payables to affiliates, net	(23)	(55)
Inventories	(23)	(12)
Accounts payable, accrued expenses and other current liabilities	(20)	59
Income taxes	389	15
Pension and non-pension postretirement benefit contributions	(142)	(237)
Other assets and liabilities	(7)	62
Net cash flows provided by operating activities	1,346	849
Cash flows from investing activities
Capital expenditures	(1,670)	(1,173)
Proceeds from sales of investments	0	7
Change in restricted cash	2	(2)
Other investing activities	22	20
Net cash flows used in investing activities	(1,646)	(1,148)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Changes in short-term borrowings	300	344
Issuance of long-term debt	400	650
Retirement of long-term debt	(260)	(617)
Dividends paid on common stock	(226)	(230)
Other financing activities	(4)	(8)
Contributions from parent	75	168
Net cash flows provided by financing activities	285	307
Increase in cash and cash equivalents	(15)	8
Cash and cash equivalents at beginning of period	66	36
Cash and cash equivalents at end of period	51	44
PECO Energy Co [Member]
Net Cash Provided by (Used in) Operating Activities [Abstract]
Net income	299	255
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, depletion and accretion, including nuclear fuel and energy contract amortization	198	176
Gain on sales of assets		0
Deferred income taxes and amortization of investment tax credits	11	7
Other non-cash operating activities	69	70
Changes in assets and liabilities:
Accounts receivable	(15)	63
Receivables from and payables to affiliates, net	0	(20)
Inventories	8	5
Accounts payable, accrued expenses and other current liabilities	(17)	19
Income taxes	69	16
Pension and non-pension postretirement benefit contributions	(37)	(12)
Other assets and liabilities	(18)	(75)
Net cash flows provided by operating activities	567	504
Cash flows from investing activities
Capital expenditures	(435)	(461)
Change in restricted cash	(1)	0
Other investing activities	11	9
Changes in Exelon intercompany money pool	55	0
Net cash flows used in investing activities	(425)	(452)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Issuance of long-term debt	0	300
Dividends paid on common stock	(209)	(240)
Other financing activities	(2)	(7)
Payments of Ordinary Dividends, Preferred Stock and Preference Stock	(16)	(24)
Changes in Exelon intercompany money pool	55	0
Net cash flows provided by financing activities	(140)	77
Increase in cash and cash equivalents	2	129
Cash and cash equivalents at beginning of period	30	217
Cash and cash equivalents at end of period	32	346
Baltimore Gas and Electric Company [Member]
Net Cash Provided by (Used in) Operating Activities [Abstract]
Net income	212	156
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, depletion and accretion, including nuclear fuel and energy contract amortization	271	275
Deferred income taxes and amortization of investment tax credits	79	57
Other non-cash operating activities	111	129
Changes in assets and liabilities:
Accounts receivable	62	101
Receivables from and payables to affiliates, net	(8)	(11)
Inventories	10	(21)
Accounts payable, accrued expenses and other current liabilities	49	(50)
Counterparty collateral received (posted), net	(27)	16
Income taxes	(6)	53
Pension and non-pension postretirement benefit contributions	(14)	(13)
Other assets and liabilities	(43)	(67)
Net cash flows provided by operating activities	696	625
Cash flows from investing activities
Capital expenditures	(506)	(458)
Change in restricted cash	2	(37)
Other investing activities	13	15
Net cash flows used in investing activities	(491)	(480)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Changes in short-term borrowings	(70)	(115)
Retirement of long-term debt	(37)	(35)
Dividends paid on common stock	(116)	0
Other financing activities	(15)	11
Contributions from parent	6
Payments of Ordinary Dividends, Preferred Stock and Preference Stock	(10)	(10)
Net cash flows provided by financing activities	(242)	(149)
Increase in cash and cash equivalents	(37)	(4)
Cash and cash equivalents at beginning of period	64	31
Cash and cash equivalents at end of period	$ 27	$ 27