Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities
Net Income (Loss)	$ 3,849	$ 1,204	$ 2,250
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	5,427	5,576	3,987
Impairment losses of long-lived assets, intangibles and regulatory assets	573	306	36
Deconsolidation, Gain (Loss), Amount	(213)	0	0
Gain (Loss) on Disposition of Assets	(3)	48	(18)
Business Combination, Bargain Purchase, Gain Recognized, Amount	(233)	0	0
Deferred income taxes and amortization of investment tax credits	(361)	664	752
Net fair value changes related to derivatives	151	24	(367)
Net realized and unrealized (gains) losses on nuclear decommissioning trust fund investments	(616)	(229)	131
Other non-cash operating activities	721	1,333	1,109
Changes in assets and liabilities:
Accounts receivable	(426)	(432)	240
Inventories	(72)	7	4
Accounts payable and accrued expenses	(390)	771	(121)
Increase (Decrease) in Premiums Receivable	28	(66)	58
Increase (Decrease) Cash Collateral from Counterparties	(158)	931	347
Income taxes	299	576	97
Pension and non-pension postretirement benefit contributions	(405)	(397)	(502)
Increase (Decrease) in Prepaid Taxes	0	(1,250)	0
Other assets and liabilities	(691)	(621)	(387)
Net Cash Provided by (Used in) Operating Activities	7,480	8,445	7,616
Cash flows from investing activities
Capital expenditures	(7,584)	(8,553)	(7,624)
Payments to Acquire Businesses, Net of Cash Acquired		(6,962)	0
Proceeds from Sale and Collection of Lease Receivables	0	360	0
Proceeds from nuclear decommissioning trust fund sales	7,845	9,496	6,895
Investment in nuclear decommissioning trust funds	(8,113)	(9,738)	(7,147)
Acquisitions of businesses, net	(208)	(6,934)	(40)
Proceeds from sales of long-lived assets	219	61	147
Change in restricted cash	(50)	(42)	66
Other investing activities	(43)	(153)	(119)
Net cash flows used in investing activities	(7,934)	(15,503)	(7,822)
Cash flows from financing activities
Proceeds from (Repayments of) Short-term Debt	(261)	(353)	80
Proceeds from (Repayments of) Short-term Debt, Maturing in Three Months or Less	621	240	0
Repayments of Debt, Maturing in More than Three Months	(700)	(462)	0
Issuance of long-term debt	3,470	4,716	6,709
Retirement of long-term debt	(2,490)	(1,936)	(2,687)
Proceeds from Issuance of Common Stock	0	0	1,868
Redemption of preference stock	0	(190)	0
Dividends paid on common stock	(1,236)	(1,166)	(1,105)
Proceeds from employee stock plans	(150)	(55)	(32)
Proceeds from Noncontrolling Interests	396	372	32
Other financing activities	(83)	(85)	(99)
Net cash flows provided by financing activities	717	1,191	4,830
Increase (Decrease) in cash and cash equivalents	263	(5,867)	4,624
Cash and cash equivalents at beginning of period	635	6,502	1,878
Cash and cash equivalents at end of period	898	635	6,502
Parent Company [Member]
Cash flows from operating activities
Net Income (Loss)	3,770	1,134	2,269
Changes in assets and liabilities:
Net Cash Provided by (Used in) Operating Activities	1,921	1,029	3,071
Cash flows from investing activities
Payments to Acquire Businesses, Net of Cash Acquired	0
Other investing activities	(5)	5	(55)
Increase (Decrease) Due from Affiliates	(129)	1,390	(1,217)
Net cash flows used in investing activities	(1,851)	(7,324)	(934)
Cash flows from financing activities
Issuance of long-term debt	0	1,800	4,200
Retirement of long-term debt	(569)	(46)	(2,263)
Contributions from member	1,879	1,912	3,209
Proceeds from Issuance of Common Stock	0	0	1,868
Dividends paid on common stock	(1,236)	(1,166)	(1,105)
Proceeds from employee stock plans	(150)	(55)	(32)
Other financing activities	(9)	(20)	(58)
Net cash flows provided by financing activities	(14)	623	2,674
Increase (Decrease) in cash and cash equivalents	56	(5,672)	4,811
Cash and cash equivalents at beginning of period	18	5,690	879
Cash and cash equivalents at end of period	74	18	5,690
Increase (Decrease) Due from Affiliates	(129)	1,390	(1,217)
Exelon Generation Co L L C [Member]
Cash flows from operating activities
Net Income (Loss)	2,771	558	1,340
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	3,056	3,519	2,589
Impairment losses of long-lived assets, intangibles and regulatory assets	510	243	12
Deconsolidation, Gain (Loss), Amount	(213)	0	0
Gain (Loss) on Disposition of Assets	(2)	59	(12)
Business Combination, Bargain Purchase, Gain Recognized, Amount	(233)	0	0
Deferred income taxes and amortization of investment tax credits	(2,022)	(269)	49
Net fair value changes related to derivatives	167	40	(249)
Net realized and unrealized (gains) losses on nuclear decommissioning trust fund investments	(616)	(229)	131
Other non-cash operating activities	112	15	268
Changes in assets and liabilities:
Accounts receivable	(276)	(152)	194
Receivables from and payables to affiliates, net	(7)	(21)	15
Inventories	(29)	(4)	16
Accounts payable and accrued expenses	2	29	(149)
Increase (Decrease) in Premiums Receivable	28	(66)	58
Increase (Decrease) Cash Collateral from Counterparties	(129)	923	407
Income taxes	496	182	(18)
Pension and non-pension postretirement benefit contributions	(148)	(152)	(245)
Other assets and liabilities	(168)	(231)	(207)
Net Cash Provided by (Used in) Operating Activities	3,299	4,444	4,199
Cash flows from investing activities
Capital expenditures	(2,259)	(3,078)	(3,841)
Proceeds from nuclear decommissioning trust fund sales	7,845	9,496	6,895
Investment in nuclear decommissioning trust funds	(8,113)	(9,738)	(7,147)
Acquisitions of businesses, net	(208)	(293)	(40)
Proceeds from sales of long-lived assets	218	37	147
Change in restricted cash	(17)	(35)	35
Other investing activities	(58)	(240)	(118)
Net cash flows used in investing activities	(2,592)	(3,851)	(4,069)
Cash flows from financing activities
Proceeds from (Repayments of) Short-term Debt, Maturing in Three Months or Less	(620)	620	0
Repayments of Debt, Maturing in More than Three Months	(200)	(162)	0
Proceeds from Debt, Maturing in More than Three Months	121	240	0
Issuance of long-term debt	1,645	388	1,309
Retirement of long-term debt	(1,261)	(202)	(89)
Proceeds from (Repayments of) Restricted Cash, Financing Activities	(50)
Repayments of Related Party Debt	0	0	(550)
Increase (Decrease) in Due to Affiliates	(1)	(1,191)	1,252
Distributions to member	(659)	(922)	(2,474)
Contributions from member	102	142	47
Proceeds from Noncontrolling Interests	396	372	32
Other financing activities	(54)	(19)	(6)
Net cash flows provided by financing activities	(581)	(734)	(479)
Increase (Decrease) in cash and cash equivalents	126	(141)	(349)
Cash and cash equivalents at beginning of period	290	431	780
Cash and cash equivalents at end of period	416	290	431
Commonwealth Edison Co [Member]
Cash flows from operating activities
Net Income (Loss)	567	378	426
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	850	775	707
Deferred income taxes and amortization of investment tax credits	659	439	353
Other non-cash operating activities	164	215	416
Changes in assets and liabilities:
Accounts receivable	(59)	(25)	(93)
Receivables from and payables to affiliates, net	8	3	(19)
Inventories	4	1	(40)
Accounts payable and accrued expenses	(297)	339	68
Increase (Decrease) Cash Collateral from Counterparties	(26)	7	(33)
Income taxes	(308)	306	192
Pension and non-pension postretirement benefit contributions	(41)	(38)	(150)
Other assets and liabilities	6	105	69
Net Cash Provided by (Used in) Operating Activities	1,527	2,505	1,896
Cash flows from investing activities
Capital expenditures	(2,250)	(2,734)	(2,398)
Acquisitions of businesses, net		0
Change in restricted cash	(66)	0	2
Other investing activities	20	49	34
Net cash flows used in investing activities	(2,296)	(2,685)	(2,362)
Cash flows from financing activities
Proceeds from (Repayments of) Short-term Debt, Maturing in Three Months or Less	0	(294)	(10)
Issuance of long-term debt	1,000	1,200	850
Retirement of long-term debt	(425)	(665)	(260)
Dividends paid on common stock	(422)	(369)	(299)
Other financing activities	(15)	(18)	(16)
Contributions from parent	651	315	202
Net cash flows provided by financing activities	789	169	467
Increase (Decrease) in cash and cash equivalents	20	(11)	1
Cash and cash equivalents at beginning of period	56	67	66
Cash and cash equivalents at end of period	76	56	67
PECO Energy Co [Member]
Cash flows from operating activities
Net Income (Loss)	434	438	378
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	286	270	260
Deferred income taxes and amortization of investment tax credits	19	78	90
Other non-cash operating activities	54	65	70
Changes in assets and liabilities:
Accounts receivable	(44)	(71)	37
Receivables from and payables to affiliates, net	(6)	6	3
Inventories	1	6	10
Accounts payable and accrued expenses	6	67	(25)
Income taxes	34	8	(9)
Pension and non-pension postretirement benefit contributions	(24)	(30)	(40)
Other assets and liabilities	(5)	(8)	(4)
Net Cash Provided by (Used in) Operating Activities	755	829	770
Cash flows from investing activities
Capital expenditures	(732)	(686)	(601)
Acquisitions of businesses, net		0
Change in restricted cash	0	(1)	(1)
Other investing activities	4	20	14
Increase (Decrease) Due from Affiliates	131	(131)	0
Net cash flows used in investing activities	(597)	(798)	(588)
Cash flows from financing activities
Issuance of long-term debt	325	300	350
Retirement of long-term debt	0	(300)	0
Dividends paid on common stock	(288)	(277)	(279)
Other financing activities	(3)	(4)	(4)
Contributions from parent	16	18	16
Net cash flows provided by financing activities	50	(263)	83
Increase (Decrease) in cash and cash equivalents	208	(232)	265
Cash and cash equivalents at beginning of period	63	295	30
Cash and cash equivalents at end of period	271	63	295
Increase (Decrease) Due from Affiliates	131	(131)	0
Baltimore Gas and Electric Company [Member]
Cash flows from operating activities
Net Income (Loss)	307	294	288
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	473	423	366
Impairment losses of long-lived assets, intangibles and regulatory assets	7	52	0
Deferred income taxes and amortization of investment tax credits	145	118	165
Other non-cash operating activities	65	88	137
Changes in assets and liabilities:
Accounts receivable	(5)	(98)	84
Receivables from and payables to affiliates, net	(4)	3	(2)
Inventories	(9)	1	18
Accounts payable and accrued expenses	(15)	138	(3)
Increase (Decrease) Cash Collateral from Counterparties	0	0	(27)
Income taxes	60	18	(54)
Pension and non-pension postretirement benefit contributions	(53)	(49)	(17)
Other assets and liabilities	(150)	(43)	(173)
Net Cash Provided by (Used in) Operating Activities	821	945	782
Cash flows from investing activities
Capital expenditures	(882)	(934)	(719)
Acquisitions of businesses, net		0
Change in restricted cash	26	0	26
Other investing activities	7	24	18
Net cash flows used in investing activities	(849)	(910)	(675)
Cash flows from financing activities
Proceeds from (Repayments of) Short-term Debt, Maturing in Three Months or Less	32	(165)	90
Issuance of long-term debt	300	850	0
Retirement of long-term debt	(41)	(379)	(75)
Repayments of Related Party Debt	(250)	0	0
Redemption of preference stock	0	(190)	0
Dividends paid on common stock	(198)	(179)	(158)
Other financing activities	(5)	(11)	(13)
Contributions from parent	184	61	7
Dividends paid on preferred securities	0	(8)	(13)
Net cash flows provided by financing activities	22	(21)	(162)
Increase (Decrease) in cash and cash equivalents	(6)	14	(55)
Cash and cash equivalents at beginning of period	23	9	64
Cash and cash equivalents at end of period	17	23	9
Pepco Holdings LLC [Member] | Predecessor [Member]
Cash flows from operating activities
Net Income (Loss)			327
Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest			(9)
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization			624
Impairment losses of long-lived assets, intangibles and regulatory assets			0
Gain (Loss) on Disposition of Assets			(46)
Deferred income taxes and amortization of investment tax credits			134
Net fair value changes related to derivatives			0
Other non-cash operating activities			167
Changes in assets and liabilities:
Accounts receivable			(105)
Receivables from and payables to affiliates, net			0
Inventories			0
Accounts payable and accrued expenses			(41)
Income taxes			8
Pension and non-pension postretirement benefit contributions			(21)
Other assets and liabilities			(99)
Net Cash Provided by (Used in) Operating Activities			939
Cash flows from investing activities
Capital expenditures			(1,230)
Proceeds from sales of long-lived assets			54
Purchases of investments			0
Change in restricted cash			6
Other investing activities			9
Net cash flows used in investing activities			(1,161)
Cash flows from financing activities
Proceeds from (Repayments of) Short-term Debt			34
Proceeds from (Repayments of) Short-term Debt, Maturing in Three Months or Less			300
Repayments of Debt, Maturing in More than Three Months			0
Issuance of long-term debt			558
Retirement of long-term debt			(430)
Increase (Decrease) in Due to Affiliates			0
Distributions to member			0
Dividends paid on common stock			(275)
Proceeds from employee stock plans			(18)
Other financing activities			(26)
Contributions from parent			0
Proceeds from Issuance of Preferred Stock and Preference Stock			54
Net cash flows provided by financing activities			233
Increase (Decrease) in cash and cash equivalents			11
Cash and cash equivalents at beginning of period	170	26	15
Cash and cash equivalents at end of period		170	26
Proceeds from Issuance of Preferred Stock and Preference Stock			54
Pepco Holdings LLC [Member] | Successor [Member]
Cash flows from operating activities
Net Income (Loss)	362
Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	0
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	675
Impairment losses of long-lived assets, intangibles and regulatory assets	52
Gain (Loss) on Disposition of Assets	(1)
Deferred income taxes and amortization of investment tax credits	252
Net fair value changes related to derivatives	0
Other non-cash operating activities	59
Changes in assets and liabilities:
Accounts receivable	(26)
Receivables from and payables to affiliates, net	(2)
Inventories	(37)
Accounts payable and accrued expenses	(106)
Income taxes	79
Pension and non-pension postretirement benefit contributions	(99)
Other assets and liabilities	(258)
Net Cash Provided by (Used in) Operating Activities	950
Cash flows from investing activities
Capital expenditures	(1,396)
Proceeds from sales of long-lived assets	1
Purchases of investments	0
Change in restricted cash	1
Other investing activities	(2)
Net cash flows used in investing activities	(1,396)
Cash flows from financing activities
Proceeds from (Repayments of) Short-term Debt	328
Proceeds from (Repayments of) Short-term Debt, Maturing in Three Months or Less	0
Repayments of Debt, Maturing in More than Three Months	(500)
Issuance of long-term debt	202
Retirement of long-term debt	(169)
Increase (Decrease) in Due to Affiliates	0
Distributions to member	(311)
Dividends paid on common stock	0
Proceeds from employee stock plans	0
Other financing activities	(2)
Contributions from parent	758
Proceeds from Issuance of Preferred Stock and Preference Stock	0
Net cash flows provided by financing activities	306
Increase (Decrease) in cash and cash equivalents	(140)
Cash and cash equivalents at beginning of period	170
Cash and cash equivalents at end of period	30	170
Proceeds from Issuance of Preferred Stock and Preference Stock	0
Potomac Electric Power Company [Member]
Cash flows from operating activities
Net Income (Loss)	205	42	187
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	321	295	256
Impairment losses of long-lived assets, intangibles and regulatory assets	14	0	0
Gain (Loss) on Disposition of Assets	1	(8)	(46)
Deferred income taxes and amortization of investment tax credits	113	153	150
Other non-cash operating activities	(5)	183	54
Changes in assets and liabilities:
Accounts receivable	(20)	(41)	(43)
Receivables from and payables to affiliates, net	0	44	0
Inventories	(24)	1	(5)
Accounts payable and accrued expenses	(63)	32	(21)
Income taxes	81	110	(46)
Pension and non-pension postretirement benefit contributions	(72)	(32)	(14)
Other assets and liabilities	(142)	(128)	(99)
Net Cash Provided by (Used in) Operating Activities	407	651	373
Cash flows from investing activities
Capital expenditures	(628)	(586)	(544)
Acquisitions of businesses, net		0
Proceeds from sales of long-lived assets	1	12	54
Purchases of investments	0	(30)	0
Change in restricted cash	(2)	(31)	3
Other investing activities	(1)	(12)	10
Net cash flows used in investing activities	(630)	(647)	(477)
Cash flows from financing activities
Proceeds from (Repayments of) Short-term Debt	3	(41)	(40)
Issuance of long-term debt	202	4	208
Retirement of long-term debt	(13)	(11)	(22)
Dividends paid on common stock	(133)	(136)	(146)
Other financing activities	(1)	(3)	(9)
Contributions from parent	161	187	112
Net cash flows provided by financing activities	219	0	103
Increase (Decrease) in cash and cash equivalents	(4)	4	(1)
Cash and cash equivalents at beginning of period	9	5	6
Cash and cash equivalents at end of period	5	9	5
Delmarva Power and Light Company [Member]
Cash flows from operating activities
Net Income (Loss)	121	(9)	76
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	167	157	148
Impairment losses of long-lived assets, intangibles and regulatory assets	6	0	0
Deferred income taxes and amortization of investment tax credits	89	109	73
Other non-cash operating activities	9	114	33
Changes in assets and liabilities:
Accounts receivable	(22)	(5)	(24)
Receivables from and payables to affiliates, net	11	13	3
Inventories	(5)	0	6
Accounts payable and accrued expenses	(8)	(4)	(8)
Increase (Decrease) Cash Collateral from Counterparties	0	1	(1)
Income taxes	26	28	(26)
Pension and non-pension postretirement benefit contributions	(2)	(22)	0
Other assets and liabilities	(71)	(72)	(14)
Net Cash Provided by (Used in) Operating Activities	321	310	266
Cash flows from investing activities
Capital expenditures	(428)	(349)	(352)
Acquisitions of businesses, net		0
Proceeds from sales of long-lived assets	0	9	0
Change in restricted cash	0	0	5
Other investing activities	(1)	4	2
Net cash flows used in investing activities	(429)	(336)	(345)
Cash flows from financing activities
Proceeds from (Repayments of) Short-term Debt	216	(105)	(1)
Issuance of long-term debt	0	175	200
Retirement of long-term debt	(40)	(100)	(100)
Dividends paid on common stock	(112)	(54)	(92)
Other financing activities	0	(1)	(2)
Contributions from parent	0	152	75
Net cash flows provided by financing activities	64	67	80
Increase (Decrease) in cash and cash equivalents	(44)	41	1
Cash and cash equivalents at beginning of period	46	5	4
Cash and cash equivalents at end of period	2	46	5
Atlantic City Electric Company [Member]
Cash flows from operating activities
Net Income (Loss)	77	(42)	40
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	146	165	175
Impairment losses of long-lived assets, intangibles and regulatory assets	7	0	0
Deferred income taxes and amortization of investment tax credits	32	22	31
Other non-cash operating activities	17	155	37
Changes in assets and liabilities:
Accounts receivable	14	(8)	(67)
Receivables from and payables to affiliates, net	0	13	1
Inventories	(7)	(1)	(1)
Accounts payable and accrued expenses	(2)	9	9
Income taxes	(11)	174	(34)
Pension and non-pension postretirement benefit contributions	(20)	(17)	(2)
Other assets and liabilities	(47)	(85)	67
Net Cash Provided by (Used in) Operating Activities	206	385	256
Cash flows from investing activities
Capital expenditures	(312)	(311)	(300)
Acquisitions of businesses, net		0
Proceeds from sales of long-lived assets	0	2	0
Change in restricted cash	3	(2)	(6)
Other investing activities	(1)	2	0
Net cash flows used in investing activities	(310)	(309)	(306)
Cash flows from financing activities
Proceeds from (Repayments of) Short-term Debt	108	(5)	(122)
Issuance of long-term debt	0	0	150
Retirement of long-term debt	(35)	(48)	(58)
Dividends paid on common stock	(68)	(63)	(12)
Other financing activities	0	(1)	(2)
Contributions from parent	0	139	95
Net cash flows provided by financing activities	5	22	51
Increase (Decrease) in cash and cash equivalents	(99)	98	1
Cash and cash equivalents at beginning of period	101	3	2
Cash and cash equivalents at end of period	$ 2	$ 101	$ 3