Consolidated Statements of Cash Flows (Unaudited) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Cash flows from operating activities
Net income	$ 498	$ 490
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion	1,972	1,895
Impairment of assets held for sale	0	0
Deferred income taxes and amortization of investment tax credits	(468)	227
Net fair value changes related to derivatives	(28)	(323)
Net realized and unrealized (gains) losses on nuclear decommissioning trust fund investments	(27)	(70)
Other non-cash operating activities	576	959
Changes in assets and liabilities:
Accounts receivable	131	414
Inventories	(18)	45
Accounts payable, accrued expenses and other current liabilities	(583)	(1,063)
Option premiums paid, net	(10)	(108)
Counterparty collateral (posted) received, net	(259)	451
Income taxes	705	259
Pension and non-pension postretirement benefit contributions	(284)	(90)
Other assets and liabilities	133	(373)
Net cash flows provided by operating activities	2,338	2,713
Cash flows from investing activities
Capital expenditures	(2,518)	(2,800)
Proceeds from nuclear decommissioning trust fund sales	1,448	5,371
Investment in nuclear decommissioning trust funds	(1,565)	(5,483)
Cash acquired from Constellation	0	964
Acquisitions		0
Proceeds from sales of investments	4	12
Purchases of investments	(3)	(5)
Change in restricted cash	22	(15)
Other investing activities	63	(12)
Net cash flows provided by (used in) investing activities	(2,549)	(1,968)
Cash flows from financing activities
Changes in short-term debt	662	179
Issuance of long-term debt	509	850
Retirement or repayment of long-term debt	(616)	(649)
Redemption of preferred securities	(93)
Dividends paid on common stock	(716)	(773)
Dividends paid to former Constellation shareholders	0	(51)
Proceeds from employee stock plans	32	42
Other financing activities	(62)	(10)
Net cash flows used in financing activities	(284)	(412)
Increase (decrease) in cash and cash equivalents	(495)	333
Cash and cash equivalents at beginning of period	1,486	1,016
Cash and cash equivalents at end of period	991	1,349
Exelon Generation Co L L C [Member]
Cash flows from operating activities
Net income	310	332
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion	1,358	1,423
Impairment of assets held for sale	0
Deferred income taxes and amortization of investment tax credits	(44)	168
Net fair value changes related to derivatives	(21)	(307)
Net realized and unrealized (gains) losses on nuclear decommissioning trust fund investments	(27)	(70)
Other non-cash operating activities	315	318
Changes in assets and liabilities:
Accounts receivable	88	306
Receivables from and payables to affiliates, net	(29)	(42)
Inventories	(38)	30
Accounts payable, accrued expenses and other current liabilities	(426)	(732)
Option premiums paid, net	(10)	(108)
Counterparty collateral (posted) received, net	(303)	443
Income taxes	265	314
Pension and non-pension postretirement benefit contributions	(120)	(35)
Other assets and liabilities	(168)	(174)
Net cash flows provided by operating activities	1,150	1,866
Cash flows from investing activities
Capital expenditures	(1,277)	(1,820)
Proceeds from nuclear decommissioning trust fund sales	1,448	5,371
Investment in nuclear decommissioning trust funds	(1,565)	(5,483)
Cash acquired from Constellation	0	708
Acquisitions		0
Change in restricted cash	(11)	6
Other investing activities	27	(66)
Net cash flows provided by (used in) investing activities	(1,378)	(1,284)
Cash flows from financing activities
Changes in short-term debt	288	(42)
Change in Exelon intercompany money pool borrowings	263
Issuance of long-term debt	209	850
Retirement or repayment of long-term debt	(458)	(56)
Distribution to member	(474)	(891)
Contributions from member	0	0
Other financing activities	(49)	(9)
Net cash flows used in financing activities	(221)	(148)
Increase (decrease) in cash and cash equivalents	(449)	434
Cash and cash equivalents at beginning of period	671	496
Cash and cash equivalents at end of period	222	930
Commonwealth Edison Co [Member]
Cash flows from operating activities
Net income	14	129
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion	337	300
Deferred income taxes and amortization of investment tax credits	(226)	116
Other non-cash operating activities	39	241
Changes in assets and liabilities:
Accounts receivable	18	(26)
Receivables from and payables to affiliates, net	(26)	(18)
Inventories	(11)	(7)
Accounts payable, accrued expenses and other current liabilities	20	(54)
Counterparty collateral (posted) received, net	45	8
Income taxes	240	149
Pension and non-pension postretirement benefit contributions	(119)	(12)
Other assets and liabilities	172	(104)
Net cash flows provided by operating activities	503	722
Cash flows from investing activities
Capital expenditures	(711)	(585)
Proceeds from sales of investments	4	12
Purchases of investments	(3)	(5)
Change in restricted cash	(3)	0
Other investing activities	20	11
Net cash flows provided by (used in) investing activities	(693)	(567)
Cash flows from financing activities
Changes in short-term debt	374	178
Issuance of long-term debt	0	0
Retirement or repayment of long-term debt	(125)	(450)
Contributions from parent	0	0
Dividends paid on common stock	(110)	(85)
Other financing activities	0	(3)
Net cash flows used in financing activities	139	(360)
Increase (decrease) in cash and cash equivalents	(51)	(205)
Cash and cash equivalents at beginning of period	144	234
Cash and cash equivalents at end of period	93	29
PECO Energy Co [Member]
Cash flows from operating activities
Net income	200	177
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion	113	107
Deferred income taxes and amortization of investment tax credits	25	19
Other non-cash operating activities	50	66
Changes in assets and liabilities:
Accounts receivable	55	62
Receivables from and payables to affiliates, net	(18)	9
Inventories	27	26
Accounts payable, accrued expenses and other current liabilities	35	(83)
Income taxes	39	121
Pension and non-pension postretirement benefit contributions	(10)	(8)
Other assets and liabilities	(49)	(87)
Net cash flows provided by operating activities	467	409
Cash flows from investing activities
Capital expenditures	(254)	(179)
Changes in intercompany money pool	(263)	18
Change in restricted cash	(1)	(3)
Other investing activities	4	7
Net cash flows provided by (used in) investing activities	(514)	(157)
Cash flows from financing activities
Redemption of preferred securities	(93)
Dividends paid on common stock	(166)	(172)
Dividends paid on preferred securities	(1)	(2)
Other financing activities	1
Net cash flows used in financing activities	(259)	(174)
Increase (decrease) in cash and cash equivalents	(306)	78
Cash and cash equivalents at beginning of period	362	194
Cash and cash equivalents at end of period	56	272
Baltimore Gas and Electric Company [Member]
Cash flows from operating activities
Net income	106	(14)
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion	175	150
Deferred income taxes and amortization of investment tax credits	98	91
Other non-cash operating activities	61	100
Changes in assets and liabilities:
Accounts receivable	(58)	76
Receivables from and payables to affiliates, net	(11)	(3)
Inventories	4	37
Accounts payable, accrued expenses and other current liabilities	(28)	(71)
Income taxes	(33)	(48)
Pension and non-pension postretirement benefit contributions	(11)	(8)
Other assets and liabilities	63	43
Net cash flows provided by operating activities	366	353
Cash flows from investing activities
Capital expenditures	(264)	(266)
Change in restricted cash	3	8
Other investing activities	4	(10)
Net cash flows provided by (used in) investing activities	(257)	(268)
Cash flows from financing activities
Changes in short-term debt		0
Issuance of long-term debt	300
Retirement or repayment of long-term debt	(33)	(141)
Contributions from parent	0	66
Dividends paid on common stock	0	0
Dividends paid on preferred securities	(6)	(6)
Change in restricted cash for dividends	0
Other financing activities	(2)	0
Net cash flows used in financing activities	259	(81)
Increase (decrease) in cash and cash equivalents	368	4
Cash and cash equivalents at beginning of period	89	49
Cash and cash equivalents at end of period	$ 457	$ 53