Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Millions		3 Months Ended
	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016	Mar. 23, 2016
Cash flows from operating activities
Net income		$ 981	$ 123
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization		1,274	1,063
Impairment of long-lived assets		10	119
Gain on sales of assets		(4)	(9)
Business Combination, Bargain Purchase, Gain Recognized, Amount		(226)	0
Deferred income taxes and amortization of investment tax credits		189	127
Net fair value changes related to derivatives		47	(107)
Gain (Loss) on Investments		175	55
Other non-cash operating activities		118	804
Changes in assets and liabilities:
Accounts receivable		313	117
Inventories		109	142
Accounts payable and accrued expenses		(623)	(571)
Option premiums (paid) received, net		(6)	17
Increase (Decrease) Cash Collateral from Counterparties		(110)	206
Income taxes		50	47
Pension and non-pension postretirement benefit contributions		(307)	(239)
Other assets and liabilities		(439)	(311)
Net cash flows provided by (used in) operating activities		1,201	1,473
Cash flows from investing activities
Capital expenditures		(2,114)	(2,202)
Proceeds from nuclear decommissioning trust fund sales		1,767	2,240
Investment in nuclear decommissioning trust funds		(1,833)	(2,297)
Acquisition of businesses, net		(212)	(6,645)
Proceeds from termination of direct financing lease investment		0	360
Change in restricted cash		(1)	(2)
Other investing activities		(18)	(2)
Net cash flows provided by (used in) investing activities		(2,411)	(8,548)
Cash flows from financing activities
Changes in short-term borrowings		721	1,647
Proceeds from short-term borrowings with maturities greater than 90 days		560	123
Repayments of Short-term Debt, Maturing in More than Three Months		(500)	0
Issuance of long-term debt		763	151
Retirement of long-term debt		(65)	(116)
Dividends paid on common stock		(303)	(287)
Proceeds from employee stock plans		12	9
Other financing activities		(4)	6
Net cash flows provided by (used in) financing activities		1,184	1,533
Increase (Decrease) in cash and cash equivalents		(26)	(5,542)
Cash and cash equivalents at beginning of period		635	6,502	$ 6,502
Cash and cash equivalents at end of period	$ 960	609	960
Exelon Generation Co L L C [Member]
Cash flows from operating activities
Net income		409	257
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization		678	667
Impairment of long-lived assets		10	119
Gain on sales of assets		(4)	0
Business Combination, Bargain Purchase, Gain Recognized, Amount		(226)	0
Deferred income taxes and amortization of investment tax credits		112	68
Net fair value changes related to derivatives		51	(106)
Gain (Loss) on Investments		175	55
Other non-cash operating activities		(10)	51
Changes in assets and liabilities:
Accounts receivable		195	173
Change Receivables Payables From Affiliates		23	(17)
Inventories		81	93
Accounts payable and accrued expenses		62	(363)
Option premiums (paid) received, net		(6)	17
Increase (Decrease) Cash Collateral from Counterparties		(102)	198
Income taxes		(81)	(60)
Pension and non-pension postretirement benefit contributions		(110)	(112)
Other assets and liabilities		(167)	(148)
Net cash flows provided by (used in) operating activities		740	782
Cash flows from investing activities
Capital expenditures		(923)	(1,125)
Proceeds from nuclear decommissioning trust fund sales		1,767	2,240
Investment in nuclear decommissioning trust funds		(1,833)	(2,297)
Acquisition of businesses, net		(212)	(1)
Change in restricted cash		18	4
Other investing activities		(29)	(25)
Net cash flows provided by (used in) investing activities		(1,212)	(1,204)
Cash flows from financing activities
Changes in short-term borrowings		(42)	1,377
Proceeds from Debt, Maturing in More than Three Months		60	123
Issuance of long-term debt		762	151
Retirement of long-term debt		(30)	(94)
Distribution to member		(164)	(55)
Proceeds from Contributions from Affiliates		0	44
Change in Exelon intercompany money pool borrowings		(1)	(1,183)
Other financing activities		(3)	5
Net cash flows provided by (used in) financing activities		582	368
Increase (Decrease) in cash and cash equivalents		110	(54)
Cash and cash equivalents at beginning of period		290	431	431
Cash and cash equivalents at end of period	377	400	377
Commonwealth Edison Co [Member]
Cash flows from operating activities
Net income		141	115
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization		208	189
Deferred income taxes and amortization of investment tax credits		137	70
Other non-cash operating activities		31	32
Changes in assets and liabilities:
Accounts receivable		92	69
Change Receivables Payables From Affiliates		(16)	0
Inventories		4	7
Accounts payable and accrued expenses		(327)	(207)
Increase (Decrease) Cash Collateral from Counterparties		(7)	7
Income taxes		(34)	20
Pension and non-pension postretirement benefit contributions		(35)	(32)
Other assets and liabilities		(49)	14
Net cash flows provided by (used in) operating activities		145	284
Cash flows from investing activities
Capital expenditures		(535)	(639)
Change in restricted cash		(1)	0
Other investing activities		7	13
Net cash flows provided by (used in) investing activities		(529)	(626)
Cash flows from financing activities
Changes in short-term borrowings		365	349
Dividends paid on common stock		(105)	(91)
Contributions from parent		100	39
Other financing activities		(1)	(1)
Net cash flows provided by (used in) financing activities		359	296
Increase (Decrease) in cash and cash equivalents		(25)	(46)
Cash and cash equivalents at beginning of period		56	67	67
Cash and cash equivalents at end of period	21	31	21
PECO Energy Co [Member]
Cash flows from operating activities
Net income		127	124
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization		71	67
Deferred income taxes and amortization of investment tax credits		24	23
Other non-cash operating activities		23	24
Changes in assets and liabilities:
Accounts receivable		(25)	(51)
Change Receivables Payables From Affiliates		(10)	4
Inventories		19	24
Accounts payable and accrued expenses		(82)	18
Income taxes		25	29
Pension and non-pension postretirement benefit contributions		(23)	(29)
Other assets and liabilities		(85)	(95)
Net cash flows provided by (used in) operating activities		64	138
Cash flows from investing activities
Capital expenditures		(159)	(195)
Changes in Exelon intercompany money pool		131	(160)
Other investing activities		1	4
Net cash flows provided by (used in) investing activities		(27)	(351)
Cash flows from financing activities
Dividends paid on common stock		(72)	(69)
Net cash flows provided by (used in) financing activities		(72)	(69)
Increase (Decrease) in cash and cash equivalents		(35)	(282)
Cash and cash equivalents at beginning of period		63	295	295
Cash and cash equivalents at end of period	13	28	13
Baltimore Gas and Electric Company [Member]
Cash flows from operating activities
Net income		125	101
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization		128	109
Deferred income taxes and amortization of investment tax credits		72	26
Other non-cash operating activities		24	44
Changes in assets and liabilities:
Accounts receivable		(7)	(44)
Change Receivables Payables From Affiliates		(7)	7
Inventories		17	17
Accounts payable and accrued expenses		(121)	3
Income taxes		33	78
Pension and non-pension postretirement benefit contributions		(44)	(38)
Other assets and liabilities		(52)	(30)
Net cash flows provided by (used in) operating activities		168	273
Cash flows from investing activities
Capital expenditures		(166)	(176)
Change in restricted cash		(19)	(20)
Other investing activities		4	5
Net cash flows provided by (used in) investing activities		(181)	(191)
Cash flows from financing activities
Changes in short-term borrowings		50	(60)
Dividends paid on common stock		(49)	(45)
Dividends paid on preference stock		0	(3)
Contributions from parent		0	21
Other financing activities		0	1
Net cash flows provided by (used in) financing activities		1	(86)
Increase (Decrease) in cash and cash equivalents		(12)	(4)
Cash and cash equivalents at beginning of period		23	9	9
Cash and cash equivalents at end of period	5	11	5
Pepco Holdings LLC [Member] | Successor [Member]
Cash flows from operating activities
Net income	(309)	140
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	14	167
Deferred income taxes and amortization of investment tax credits	(112)	13
Net fair value changes related to derivatives	0	0
Other non-cash operating activities	410	(8)
Changes in assets and liabilities:
Accounts receivable	16	68
Change Receivables Payables From Affiliates	0	(8)
Inventories	0	(11)
Accounts payable and accrued expenses	(4)	(81)
Income taxes	7	55
Pension and non-pension postretirement benefit contributions	0	(66)
Other assets and liabilities	(25)	(75)
Net cash flows provided by (used in) operating activities	(3)	194
Cash flows from investing activities
Capital expenditures	(29)	(320)
Purchases of investments	(2)	0
Change in restricted cash	(1)	2
Other investing activities	2	(3)
Net cash flows provided by (used in) investing activities	(30)	(321)
Cash flows from financing activities
Changes in short-term borrowings	(20)	145
Proceeds from short-term borrowings with maturities greater than 90 days	0	0
Repayments of Debt, Maturing in More than Three Months	0	(500)
Issuance of long-term debt	0	1
Retirement of long-term debt	0	(24)
Common stock issued for the Direct Stock Purchase and Dividend Reinvestment Plan and employee-related compensation	0	0
Distribution to member	(108)	(69)
Contributions from parent	0	500
Change in Exelon intercompany money pool borrowings	(7)	13
Other financing activities	0	0
Net cash flows provided by (used in) financing activities	(135)	66
Increase (Decrease) in cash and cash equivalents	(168)	(61)
Cash and cash equivalents at beginning of period	319	170
Cash and cash equivalents at end of period	151	109	151	319
Pepco Holdings LLC [Member] | Predecessor [Member]
Cash flows from operating activities
Net income				19
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization				152
Deferred income taxes and amortization of investment tax credits				19
Net fair value changes related to derivatives				18
Other non-cash operating activities				46
Changes in assets and liabilities:
Accounts receivable				(28)
Change Receivables Payables From Affiliates				0
Inventories				(4)
Accounts payable and accrued expenses				42
Income taxes				12
Pension and non-pension postretirement benefit contributions				(4)
Other assets and liabilities				(8)
Net cash flows provided by (used in) operating activities				264
Cash flows from investing activities
Capital expenditures				(273)
Purchases of investments				(68)
Change in restricted cash				3
Other investing activities				(5)
Net cash flows provided by (used in) investing activities				(343)
Cash flows from financing activities
Changes in short-term borrowings				(121)
Proceeds from short-term borrowings with maturities greater than 90 days				500
Repayments of Debt, Maturing in More than Three Months				0
Issuance of long-term debt				0
Retirement of long-term debt				(11)
Common stock issued for the Direct Stock Purchase and Dividend Reinvestment Plan and employee-related compensation				2
Distribution to member				0
Contributions from parent				0
Change in Exelon intercompany money pool borrowings				0
Other financing activities				2
Net cash flows provided by (used in) financing activities				372
Increase (Decrease) in cash and cash equivalents				293
Cash and cash equivalents at beginning of period	319		26	26
Cash and cash equivalents at end of period				319
Potomac Electric Power Company [Member]
Cash flows from operating activities
Net income		58	(108)
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization		82	75
Deferred income taxes and amortization of investment tax credits		5	(31)
Other non-cash operating activities		(15)	153
Changes in assets and liabilities:
Accounts receivable		45	(24)
Change Receivables Payables From Affiliates		(6)	55
Inventories		(10)	1
Accounts payable and accrued expenses		(49)	(4)
Income taxes		20	151
Pension and non-pension postretirement benefit contributions		(64)	(1)
Other assets and liabilities		(37)	(9)
Net cash flows provided by (used in) operating activities		29	258
Cash flows from investing activities
Capital expenditures		(139)	(109)
Purchases of investments		0	(31)
Change in restricted cash		0	2
Other investing activities		(5)	2
Net cash flows provided by (used in) investing activities		(144)	(136)
Cash flows from financing activities
Changes in short-term borrowings		144	(64)
Issuance of long-term debt		1	0
Dividends paid on common stock		(30)	(39)
Other financing activities		(1)	0
Net cash flows provided by (used in) financing activities		114	(103)
Increase (Decrease) in cash and cash equivalents		(1)	19
Cash and cash equivalents at beginning of period		9	5	5
Cash and cash equivalents at end of period	24	8	24
Delmarva Power and Light Company [Member]
Cash flows from operating activities
Net income		57	(72)
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization		39	39
Deferred income taxes and amortization of investment tax credits		13	(4)
Other non-cash operating activities		(7)	118
Changes in assets and liabilities:
Accounts receivable		6	4
Change Receivables Payables From Affiliates		1	20
Inventories		1	1
Accounts payable and accrued expenses		14	(3)
Income taxes		21	52
Other assets and liabilities		(23)	(8)
Net cash flows provided by (used in) operating activities		122	147
Cash flows from investing activities
Capital expenditures		(82)	(81)
Other investing activities		2	0
Net cash flows provided by (used in) investing activities		(80)	(81)
Cash flows from financing activities
Changes in short-term borrowings		0	(30)
Retirement of long-term debt		(14)	0
Dividends paid on common stock		(30)	(38)
Net cash flows provided by (used in) financing activities		(44)	(68)
Increase (Decrease) in cash and cash equivalents		(2)	(2)
Cash and cash equivalents at beginning of period		46	5	5
Cash and cash equivalents at end of period	3	44	3
Atlantic City Electric Company [Member]
Cash flows from operating activities
Net income		28	(100)
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization		35	40
Deferred income taxes and amortization of investment tax credits		(7)	(33)
Other non-cash operating activities		2	132
Changes in assets and liabilities:
Accounts receivable		14	5
Change Receivables Payables From Affiliates		(5)	20
Inventories		(1)	(2)
Accounts payable and accrued expenses		(5)	19
Income taxes		3	168
Other assets and liabilities		(6)	(3)
Net cash flows provided by (used in) operating activities		58	246
Cash flows from investing activities
Capital expenditures		(88)	(101)
Change in restricted cash		2	1
Other investing activities		1	0
Net cash flows provided by (used in) investing activities		(85)	(100)
Cash flows from financing activities
Changes in short-term borrowings		0	(5)
Retirement of long-term debt		(10)	(11)
Dividends paid on common stock		(10)	(11)
Net cash flows provided by (used in) financing activities		(20)	(27)
Increase (Decrease) in cash and cash equivalents		(47)	119
Cash and cash equivalents at beginning of period		101	3	$ 3
Cash and cash equivalents at end of period	$ 122	$ 54	$ 122