Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Net Cash Provided by (Used in) Operating Activities [Abstract]
Net income	$ 1,372	$ 651
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	1,957	1,925
Impairment of long-lived assets	24	112
Gain on consolidation and acquisition of businesses	0	(268)
Gain on sales of assets	(8)	(18)
Deferred income taxes and amortization of investment tax credits	211	133
Net fair value changes related to derivatives	(507)	751
Net realized and unrealized gains on nuclear decommissioning trust fund investments	(2)	(168)
Other non-cash operating activities	579	473
Changes in assets and liabilities:
Accounts receivable	253	48
Inventories	159	(150)
Accounts payable, accrued expenses and other current liabilities	(668)	(358)
Option premiums received, net	22	21
Counterparty collateral received (posted), net	417	(606)
Income taxes	247	(16)
Pension and non-pension postretirement benefit contributions	(301)	(499)
Other assets and liabilities	214	(280)
Net cash flows provided by operating activities	3,969	1,751
Cash flows from investing activities
Capital expenditures	(3,460)	(2,501)
Proceeds from nuclear decommissioning trust fund sales	3,314	4,219
Investment in nuclear decommissioning trust funds	(3,437)	(4,238)
Acquisition of businesses	(28)	(66)
Proceeds from sale of long-lived assets	145	32
Proceeds from termination of direct financing lease investment	0	335
Change in restricted cash	(3)	(40)
Cash and restricted cash acquired from consolidations and acquisitions	0	129
Other investing activities	(77)	(57)
Net cash flows used in investing activities	(3,546)	(2,187)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Changes in short-term borrowings	94	293
Issuance of long-term debt	5,907	2,100
Retirement of long-term debt	(1,708)	(1,191)
Distributions to noncontrolling interest of consolidated VIE	0	(415)
Dividends paid on common stock	(537)	(533)
Proceeds from employee stock plans	16	18
Other financing activities	(59)	(83)
Net cash flows provided by financing activities	3,713	189
Increase (decrease) in cash and cash equivalents	4,136	(247)
Cash and cash equivalents at beginning of period	1,878	1,609
Cash and cash equivalents at end of period	6,014	1,362
Exelon Generation Co L L C [Member]
Net Cash Provided by (Used in) Operating Activities [Abstract]
Net income	875	188
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	1,255	1,242
Impairment of long-lived assets	(1)	88
Gain on consolidation and acquisition of businesses	0	(268)
Gain on sales of assets	(6)	(18)
Deferred income taxes and amortization of investment tax credits	65	(15)
Net fair value changes related to derivatives	(396)	760
Net realized and unrealized gains on nuclear decommissioning trust fund investments	(2)	(168)
Other non-cash operating activities	134	139
Changes in assets and liabilities:
Accounts receivable	291	63
Receivables from and payables to affiliates, net	(11)	(20)
Inventories	134	(170)
Accounts payable, accrued expenses and other current liabilities	(485)	(273)
Option premiums received, net	22	21
Counterparty collateral received (posted), net	440	(633)
Income taxes	27	72
Pension and non-pension postretirement benefit contributions	(122)	(210)
Other assets and liabilities	203	(56)
Net cash flows provided by operating activities	2,423	742
Cash flows from investing activities
Capital expenditures	(1,764)	(1,103)
Proceeds from nuclear decommissioning trust fund sales	3,314	4,219
Investment in nuclear decommissioning trust funds	(3,437)	(4,238)
Proceeds from nuclear decommissioning trust fund sales	0
Acquisition of businesses	(28)	(66)
Proceeds from sale of long-lived assets	144	32
Change in restricted cash	(16)	(17)
Cash and restricted cash acquired from consolidations and acquisitions	0	129
Other investing activities	(63)	(14)
Changes in Exelon intercompany money pool	638	190
Funding of Exelon intercompany money pool		44
Net cash flows used in investing activities	(1,850)	(1,014)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Changes in short-term borrowings	15	46
Issuance of long-term debt	1,307	300
Retirement of long-term debt	(39)	(538)
Repayments of Related Party Debt	(550)	0
Distributions to noncontrolling interest of consolidated VIE	0	(415)
Other financing activities	(6)	(29)
Distribution to member	(2,262)	(235)
Changes in Exelon intercompany money pool	638	190
Net cash flows provided by financing activities	(897)	(681)
Increase (decrease) in cash and cash equivalents	(324)	(953)
Cash and cash equivalents at beginning of period	780	1,258
Cash and cash equivalents at end of period	456	305
Commonwealth Edison Co [Member]
Net Cash Provided by (Used in) Operating Activities [Abstract]
Net income	189	209
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	352	347
Deferred income taxes and amortization of investment tax credits	36	63
Other non-cash operating activities	222	99
Changes in assets and liabilities:
Accounts receivable	(57)	(83)
Receivables from and payables to affiliates, net	(10)	(46)
Inventories	(19)	(4)
Accounts payable, accrued expenses and other current liabilities	(52)	27
Income taxes	239	5
Pension and non-pension postretirement benefit contributions	(125)	(236)
Other assets and liabilities	25	48
Net cash flows provided by operating activities	800	429
Cash flows from investing activities
Capital expenditures	(1,061)	(747)
Proceeds from sales of investments	0	7
Purchases of investments	0	(3)
Change in restricted cash	0	(2)
Other investing activities	17	14
Net cash flows used in investing activities	(1,044)	(731)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Changes in short-term borrowings	199	314
Issuance of long-term debt	400	650
Retirement of long-term debt	(260)	(617)
Dividends paid on common stock	(150)	(153)
Other financing activities	(5)	(2)
Contributions from parent	45	112
Net cash flows provided by financing activities	229	304
Increase (decrease) in cash and cash equivalents	(15)	2
Cash and cash equivalents at beginning of period	66	36
Cash and cash equivalents at end of period	51	38
PECO Energy Co [Member]
Net Cash Provided by (Used in) Operating Activities [Abstract]
Net income	209	173
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	131	117
Gain on sales of assets		0
Deferred income taxes and amortization of investment tax credits	4	6
Other non-cash operating activities	45	50
Changes in assets and liabilities:
Accounts receivable	(18)	34
Receivables from and payables to affiliates, net	(2)	(21)
Inventories	21	22
Accounts payable, accrued expenses and other current liabilities	3	30
Income taxes	57	54
Pension and non-pension postretirement benefit contributions	(15)	(11)
Other assets and liabilities	(60)	(114)
Net cash flows provided by operating activities	375	340
Cash flows from investing activities
Capital expenditures	(289)	(308)
Change in restricted cash	(1)	0
Other investing activities	9	6
Changes in Exelon intercompany money pool	41	0
Net cash flows used in investing activities	(281)	(302)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Dividends paid on common stock	(139)	(160)
Other financing activities	0	(2)
Changes in Exelon intercompany money pool	41	0
Net cash flows provided by financing activities	(98)	(162)
Increase (decrease) in cash and cash equivalents	(4)	(124)
Cash and cash equivalents at beginning of period	30	217
Cash and cash equivalents at end of period	26	93
Baltimore Gas and Electric Company [Member]
Net Cash Provided by (Used in) Operating Activities [Abstract]
Net income	157	106
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	192	197
Deferred income taxes and amortization of investment tax credits	54	47
Other non-cash operating activities	76	89
Changes in assets and liabilities:
Accounts receivable	25	44
Receivables from and payables to affiliates, net	(2)	(12)
Inventories	23	0
Accounts payable, accrued expenses and other current liabilities	(49)	(74)
Counterparty collateral received (posted), net	(23)	27
Income taxes	(6)	(14)
Pension and non-pension postretirement benefit contributions	(9)	(8)
Other assets and liabilities	51	8
Net cash flows provided by operating activities	489	410
Cash flows from investing activities
Capital expenditures	(304)	(313)
Change in restricted cash	21	(30)
Other investing activities	8	11
Net cash flows used in investing activities	(275)	(332)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Changes in short-term borrowings	(120)	(65)
Retirement of long-term debt	(37)	(35)
Dividends paid on common stock	(77)	0
Other financing activities	(14)	12
Contributions from parent	0
Proceeds from employee stock plans	(6)	(6)
Net cash flows provided by financing activities	(254)	(94)
Increase (decrease) in cash and cash equivalents	(40)	(16)
Cash and cash equivalents at beginning of period	64	31
Cash and cash equivalents at end of period	$ 24	$ 15