Consolidated Statements of Cash Flows (Unaudited) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013
Cash flows from operating activities
Net income		$ 498
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion	1,925	1,972
Impairment of assets held for sale	0
Deferred income taxes and amortization of investment tax credits	133	(468)
Net fair value changes related to derivatives	751	(28)
Net realized and unrealized (gains) losses on nuclear decommissioning trust fund investments	(168)	(27)
Other non-cash operating activities	567	576
Changes in assets and liabilities:
Accounts receivable	48	131
Inventories	(150)	(18)
Accounts payable, accrued expenses and other current liabilities	(358)	(583)
Option premiums paid, net	21	(10)
Counterparty collateral (posted) received, net	(606)	(259)
Income taxes	(16)	705
Pension and non-pension postretirement benefit contributions	(499)	(284)
Other assets and liabilities	(280)	133
Net cash flows provided by operating activities	1,751	2,338
Cash flows from investing activities
Capital expenditures	(2,501)	(2,518)
Cash Proceeds from Direct Finance Lease Contract Termination	335
Proceeds from nuclear decommissioning trust fund sales	4,219	1,448
Investment in nuclear decommissioning trust funds	(4,238)	(1,565)
Net cash acquired from consolidation of CENG	0
Proceeds from sale of long-lived assets	32	4
Cash acquired from Constellation	129
Acquisitions	(66)	(3)
Proceeds from sales of investments	0
Change in restricted cash	(40)	22
Other investing activities	(57)	63
Net cash flows provided by (used in) investing activities	(2,187)	(2,549)
Cash flows from financing activities
Payment of accounts receivable agreement	0
Changes in short-term debt	293	662
Redemption of preferred securities	0	(93)
Issuance of long-term debt	2,100	509
Retirement or repayment of long-term debt	(1,191)	(616)
Dividends paid on common stock	(533)	(716)
Dividends paid to former Constellation shareholders	0
Proceeds from employee stock plans	18	32
Dividends paid to non-controlling interest of consolidated VIE	(415)	63
Other financing activities	(83)	(62)
Net cash flows used in financing activities	189	(284)
Increase (decrease) in cash and cash equivalents	(247)	(495)
Cash and cash equivalents at beginning of period	1,609	1,486
Cash and cash equivalents at end of period	1,362	991
CityPublicServiceBoardSanAntonio [Member] | EquipmentLeasedToOtherPartyMember
Cash flows from investing activities
Cash Proceeds from Direct Finance Lease Contract Termination	335	0
Exelon Generation Co L L C [Member]
Cash flows from operating activities
Net income	188	310
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion	1,242	1,358
Impairment of assets held for sale	0	0
Deferred income taxes and amortization of investment tax credits	(15)	(44)
Net fair value changes related to derivatives	760	(21)
Net realized and unrealized (gains) losses on nuclear decommissioning trust fund investments	(168)	(27)
Other non-cash operating activities	209	315
Gain on consolidation of CENG	268
Changes in assets and liabilities:
Accounts receivable	63	88
Receivables from and payables to affiliates, net	20	(29)
Inventories	(170)	(38)
Accounts payable, accrued expenses and other current liabilities	(273)	(426)
Option premiums paid, net	21	(10)
Counterparty collateral (posted) received, net	(633)	(303)
Income taxes	72	265
Pension and non-pension postretirement benefit contributions	(210)	(120)
Other assets and liabilities	(56)	(168)
Net cash flows provided by operating activities	742	1,150
Cash flows from investing activities
Capital expenditures	(1,103)	(1,277)
Changes in intercompany money pool	190	263
Proceeds from nuclear decommissioning trust fund sales	4,219	1,448
Investment in nuclear decommissioning trust funds	(4,238)	(1,565)
Net cash acquired from consolidation of CENG	129
Proceeds from sale of long-lived assets	32
Acquisitions	66
Change in restricted cash	(17)	(11)
Other investing activities	(14)	27
Net cash flows provided by (used in) investing activities	(1,014)	(1,378)
Cash flows from financing activities
Changes in short-term debt	46	288
Issuance of long-term debt	300	209
Retirement or repayment of long-term debt	(538)	(458)
Distribution to member	(235)	(474)
Contributions from member	0	0
Dividends paid to non-controlling interest of consolidated VIE	(415)	63
Other financing activities	(29)	(49)
Net cash flows used in financing activities	(681)	(221)
Increase (decrease) in cash and cash equivalents	(953)	(449)
Cash and cash equivalents at beginning of period	1,258	671
Cash and cash equivalents at end of period	305	222
Exelon Generation Co L L C [Member] | EquipmentLeasedToOtherPartyMember
Cash flows from investing activities
Changes in intercompany money pool	(44)
Commonwealth Edison Co [Member]
Cash flows from operating activities
Net income	209	14
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion	347	337
Deferred income taxes and amortization of investment tax credits	63	(226)
Other non-cash operating activities	99	39
Changes in assets and liabilities:
Accounts receivable	(83)	18
Receivables from and payables to affiliates, net	(46)	(26)
Inventories	(4)	(11)
Accounts payable, accrued expenses and other current liabilities	27	20
Income taxes	5	240
Pension and non-pension postretirement benefit contributions	(236)	(119)
Other assets and liabilities	48	217
Net cash flows provided by operating activities	429	503
Cash flows from investing activities
Capital expenditures	(747)	(711)
Proceeds from sales of investments	7	4
Purchases of investments	(3)	(3)
Change in restricted cash	(2)	(3)
Other investing activities	14	20
Net cash flows provided by (used in) investing activities	(731)	(693)
Cash flows from financing activities
Changes in short-term debt	314	374
Issuance of long-term debt	650	0
Retirement or repayment of long-term debt	(617)	(125)
Contributions from parent	112	0
Dividends paid on common stock	(153)	(110)
Other financing activities	(2)	0
Net cash flows used in financing activities	304	139
Increase (decrease) in cash and cash equivalents	2	(51)
Cash and cash equivalents at beginning of period	36	144
Cash and cash equivalents at end of period	38	93
PECO Energy Co [Member]
Cash flows from operating activities
Net income	173	200
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion	117	113
Deferred income taxes and amortization of investment tax credits	6	25
Other non-cash operating activities	50	50
Changes in assets and liabilities:
Accounts receivable	34	55
Receivables from and payables to affiliates, net	(21)	(18)
Inventories	22	27
Accounts payable, accrued expenses and other current liabilities	30	35
Income taxes	54	39
Pension and non-pension postretirement benefit contributions	(11)	(10)
Other assets and liabilities	(114)	(49)
Net cash flows provided by operating activities	340	467
Cash flows from investing activities
Capital expenditures	(308)	(254)
Change in restricted cash	0	(1)
Other investing activities	6	4
Net cash flows provided by (used in) investing activities	(302)	(514)
Cash flows from financing activities
Changes in short-term debt	0	0
Redemption of preferred securities	0	(93)
Issuance of long-term debt	0	0
Dividends paid on common stock	(160)	(166)
Dividends paid on preferred securities	0	(1)
Other financing activities	(2)	1
Net cash flows used in financing activities	(162)	(259)
Increase (decrease) in cash and cash equivalents	(124)	(306)
Cash and cash equivalents at beginning of period	217	362
Cash and cash equivalents at end of period	93	56
PECO Energy Co [Member] | EquipmentLeasedToOtherPartyMember
Cash flows from investing activities
Changes in intercompany money pool	0	(263)
Baltimore Gas and Electric Company [Member]
Cash flows from operating activities
Net income	106	106
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion	197	175
Deferred income taxes and amortization of investment tax credits	47	98
Other non-cash operating activities	89	61
Changes in assets and liabilities:
Accounts receivable	44	(58)
Receivables from and payables to affiliates, net	(12)	(11)
Inventories	0	4
Accounts payable, accrued expenses and other current liabilities	(74)	(28)
Counterparty collateral (posted) received, net	27	0
Income taxes	(14)	(33)
Pension and non-pension postretirement benefit contributions	(8)	(11)
Other assets and liabilities	8	63
Net cash flows provided by operating activities	410	366
Cash flows from investing activities
Capital expenditures	(313)	(264)
Change in restricted cash	(30)	3
Other investing activities	11	4
Net cash flows provided by (used in) investing activities	(332)	(257)
Cash flows from financing activities
Changes in short-term debt	(65)	0
Issuance of long-term debt	0	300
Retirement or repayment of long-term debt	(35)	(33)
Contributions from parent	0	0
Dividends paid on common stock	0	0
Dividends paid on preferred securities	(6)	(6)
Change in restricted cash for dividends	0	0
Other financing activities	12	(2)
Net cash flows used in financing activities	(94)	259
Increase (decrease) in cash and cash equivalents	(16)	368
Cash and cash equivalents at beginning of period	31	89
Cash and cash equivalents at end of period	$ 15	$ 457