Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash flows from operating activities
Net income	$ 2,250	$ 1,820	$ 1,729
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	3,987	3,868	3,779
Impairment of long-lived assets	36	687	171
Gain on consolidation and acquisition of businesses	0	(296)	0
Gain on sales of assets	(18)	(437)	(13)
Gain on sales of assets	(18)	(437)	(13)
Deferred income taxes and amortization of investment tax credits	752	502	119
Net fair value changes related to derivatives	(367)	716	(445)
Net realized and unrealized losses (gains) on nuclear decommissioning trust fund investments	131	(210)	(170)
Other non-cash operating activities	1,109	1,054	718
Changes in assets and liabilities:
Accounts receivable	240	(318)	(97)
Inventories	4	(380)	(100)
Accounts payable and accrued expenses	(121)	49	(116)
Option premiums received (paid), net	58	38	(36)
Collateral received (posted), net	347	(1,719)	215
Income taxes	97	(143)	883
Pension and non-pension postretirement benefit contributions	(502)	(617)	(422)
Other assets and liabilities	(387)	(157)	128
Net cash flows provided by operating activities	7,616	4,457	6,343
Cash flows from investing activities
Capital expenditures	(7,624)	(6,077)	(5,395)
Proceeds from termination of direct financing lease investment	0	335	0
Proceeds from nuclear decommissioning trust fund sales	6,895	7,396	4,217
Investment in nuclear decommissioning trust funds	(7,147)	(7,551)	(4,450)
Acquisitions of businesses	(40)	(386)	0
Proceeds from sales of long-lived assets	147	1,719	32
Proceeds from sales of investments	0	7	22
Cash and restricted cash acquired from consolidations and acquisitions	0	140	0
Purchases of investments	0	(3)	(4)
Change in restricted cash	66	(104)	(43)
Distribution from CENG	0	13	115
Other investing activities	(119)	(88)	112
Net cash flows used in investing activities	(7,822)	(4,599)	(5,394)
Cash flows from financing activities
Payment of accounts receivable agreement	0	0	(210)
Issuance of long-term debt	6,709	3,463	2,055
Retirement of long-term debt	(2,687)	(1,545)	(1,589)
Redemption of preferred securities	0	0	(93)
Distribution to noncontrolling interest of consolidated VIE	0	(421)	0
Dividends paid on common stock	(1,105)	(1,065)	(1,249)
Proceeds from employee stock plans	32	35	47
Other financing activities	67	178	119
Contributions from parent			0
Net cash flows provided by (used in) financing activities	4,830	411	(826)
Proceeds from Issuance of Common Stock	1,868	0	0
Proceeds from (Repayments of) Short-term Debt, Maturing in Three Months or Less	80	122	332
Increase in cash and cash equivalents	4,624	269	123
Cash and cash equivalents at beginning of period	1,878	1,609	1,486
Cash and cash equivalents at end of period	6,502	1,878	1,609
Parent Company [Member]
Cash flows from operating activities
Net income	2,269	1,623	1,719
Changes in assets and liabilities:
Net cash flows provided by operating activities	3,071	806	1,053
Cash flows from investing activities
Capital expenditures	0	1	0
Proceeds from termination of direct financing lease investment	0	335	0
Change in restricted cash	0	0	38
Other investing activities	(55)	(126)	15
Changes in Exelon intercompany money pool	(1,217)	(83)	(60)
Net cash flows used in investing activities	(934)	57	439
Cash flows from financing activities
Issuance of long-term debt	4,200	1,150	0
Retirement of long-term debt	(2,263)	(23)	(450)
Dividends paid on common stock	(1,105)	(1,065)	(1,249)
Proceeds from employee stock plans	32	35	47
Other financing activities	58	84	6
Contribution from member	3,209	1,370	1,175
Net cash flows provided by (used in) financing activities	2,674	13	(1,648)
Proceeds from Issuance of Common Stock	1,868	0	0
Proceeds from (Repayments of) Short-term Debt, Maturing in Three Months or Less	0	0	10
Increase in cash and cash equivalents	4,811	876	(156)
Cash and cash equivalents at beginning of period	879	3	159
Cash and cash equivalents at end of period	5,690	879	3
Exelon Generation Co L L C [Member]
Cash flows from operating activities
Net income	1,340	1,019	1,060
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	2,589	2,519	2,559
Impairment of long-lived assets	12	663	157
Gain on consolidation and acquisition of businesses	0	(296)	0
Gain on sales of assets	(12)	(437)	(13)
Gain on sales of assets	(12)	(437)	(13)
Deferred income taxes and amortization of investment tax credits	49	(198)	315
Net fair value changes related to derivatives	(249)	635	(448)
Net realized and unrealized losses (gains) on nuclear decommissioning trust fund investments	131	(210)	(170)
Other non-cash operating activities	268	346	270
Changes in assets and liabilities:
Accounts receivable	194	(215)	109
Receivables from and payables to affiliates, net	15	15	2
Inventories	16	(359)	(88)
Accounts payable and accrued expenses	(149)	29	(160)
Option premiums received (paid), net	58	38	(36)
Collateral received (posted), net	407	(1,748)	162
Income taxes	(18)	265	402
Pension and non-pension postretirement benefit contributions	(245)	(297)	(149)
Other assets and liabilities	(207)	57	(85)
Net cash flows provided by operating activities	4,199	1,826	3,887
Cash flows from investing activities
Capital expenditures	(3,841)	(3,012)	(2,752)
Proceeds from nuclear decommissioning trust fund sales	6,895	7,396	4,217
Investment in nuclear decommissioning trust funds	(7,147)	(7,551)	(4,450)
Acquisitions of businesses	(40)	(386)	0
Proceeds from sales of long-lived assets	147	1,719	32
Cash and restricted cash acquired from consolidations and acquisitions	0	140	0
Change in restricted cash	35	(87)	(64)
Distribution from CENG	0	13	115
Other investing activities	(118)	(43)	30
Changes in Exelon intercompany money pool	0	44	(44)
Net cash flows used in investing activities	(4,069)	(1,767)	(2,916)
Cash flows from financing activities
Issuance of long-term debt	1,309	1,112	854
Retirement of long-term debt	(89)	(586)	(570)
Repayments of Related Party Debt	(550)
Changes in Exelon intercompany money pool	1,252	0	0
Distribution to noncontrolling interest of consolidated VIE	0	(421)	0
Other financing activities	(26)	67	82
Distribution to member	(2,474)	(645)	(625)
Contribution from member	47	53	26
Contributions from parent			0
Net cash flows provided by (used in) financing activities	(479)	(537)	(384)
Proceeds from (Repayments of) Short-term Debt, Maturing in Three Months or Less	0	17	13
Increase in cash and cash equivalents	(349)	(478)	587
Cash and cash equivalents at beginning of period	780	1,258	671
Cash and cash equivalents at end of period	431	780	1,258
Commonwealth Edison Co [Member]
Cash flows from operating activities
Net income	426	408	249
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	707	687	669
Gain on sales of assets	(1)	(2)	0
Deferred income taxes and amortization of investment tax credits	353	433	(57)
Other non-cash operating activities	416	255	28
Changes in assets and liabilities:
Accounts receivable	(93)	(121)	(12)
Receivables from and payables to affiliates, net	(19)	(11)	(12)
Inventories	(40)	(16)	(18)
Accounts payable and accrued expenses	68	95	91
Collateral received (posted), net	(33)	2	53
Income taxes	192	(159)	178
Pension and non-pension postretirement benefit contributions	(150)	(248)	(122)
Other assets and liabilities	69	1	171
Net cash flows provided by operating activities	1,896	1,326	1,218
Cash flows from investing activities
Capital expenditures	(2,398)	(1,689)	(1,433)
Proceeds from sales of investments	0	7	7
Purchases of investments	0	(3)	(4)
Change in restricted cash	2	(2)	(2)
Other investing activities	34	32	45
Net cash flows used in investing activities	(2,362)	(1,655)	(1,387)
Cash flows from financing activities
Issuance of long-term debt	850	900	350
Retirement of long-term debt	(260)	(617)	(252)
Dividends paid on common stock	(299)	(307)	(220)
Other financing activities	16	10	1
Contributions from parent	202	273	176
Net cash flows provided by (used in) financing activities	467	359	61
Proceeds from (Repayments of) Short-term Debt, Maturing in Three Months or Less	(10)	120	184
Increase in cash and cash equivalents	1	30	(108)
Cash and cash equivalents at beginning of period	66	36	144
Cash and cash equivalents at end of period	67	66	36
PECO Energy Co [Member]
Cash flows from operating activities
Net income	378	352	395
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	260	236	228
Deferred income taxes and amortization of investment tax credits	90	88	20
Net realized and unrealized losses (gains) on nuclear decommissioning trust fund investments	2
Other non-cash operating activities	70	92	108
Changes in assets and liabilities:
Accounts receivable	37	(16)	(79)
Receivables from and payables to affiliates, net	3	(6)	(18)
Inventories	10	2	2
Accounts payable and accrued expenses	(25)	58	31
Income taxes	(9)	(57)	87
Pension and non-pension postretirement benefit contributions	(40)	(16)	(31)
Other assets and liabilities	(4)	(21)	4
Net cash flows provided by operating activities	770	712	747
Cash flows from investing activities
Capital expenditures	(601)	(661)	(537)
Change in restricted cash	(1)	0	(2)
Other investing activities	14	12	8
Net cash flows used in investing activities	(588)	(649)	(531)
Cash flows from financing activities
Payment of accounts receivable agreement	0	0	(210)
Issuance of long-term debt	350	300	550
Retirement of long-term debt	0	(250)	(300)
Redemption of preferred securities	0	0	(93)
Dividends paid on common stock	(279)	(320)	(332)
Other financing activities	4	4	2
Contributions from parent	16	24	27
Dividends paid on preferred securities	0	0	(1)
Net cash flows provided by (used in) financing activities	83	(250)	(361)
Increase in cash and cash equivalents	265	(187)	(145)
Cash and cash equivalents at beginning of period	30	217	362
Cash and cash equivalents at end of period	295	30	217
Baltimore Gas and Electric Company [Member]
Cash flows from operating activities
Net income	288	211	210
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	366	371	348
Deferred income taxes and amortization of investment tax credits	165	116	125
Other non-cash operating activities	137	180	153
Changes in assets and liabilities:
Accounts receivable	84	46	(127)
Receivables from and payables to affiliates, net	(2)	(1)	(14)
Inventories	18	(6)	1
Accounts payable and accrued expenses	(3)	(75)	(6)
Collateral received (posted), net	(27)	27	0
Income taxes	(54)	45	(33)
Pension and non-pension postretirement benefit contributions	(17)	(16)	(24)
Other assets and liabilities	(173)	(158)	(72)
Net cash flows provided by operating activities	782	740	561
Cash flows from investing activities
Capital expenditures	(719)	(620)	(587)
Change in restricted cash	26	(22)	2
Other investing activities	18	20	14
Net cash flows used in investing activities	(675)	(622)	(571)
Cash flows from financing activities
Issuance of long-term debt	0	0	300
Retirement of long-term debt	(75)	(70)	(467)
Dividends paid on common stock	(158)	0	0
Other financing activities	13	(13)	3
Contributions from parent	7	0	0
Dividends paid on preferred securities	(13)	(13)	(13)
Net cash flows provided by (used in) financing activities	(162)	(85)	(48)
Proceeds from (Repayments of) Short-term Debt, Maturing in Three Months or Less	90	(15)	135
Increase in cash and cash equivalents	(55)	33	(58)
Cash and cash equivalents at beginning of period	64	31	89
Cash and cash equivalents at end of period	$ 9	$ 64	$ 31