Derivative Financial Instruments - Summary of Interest Rate and Foreign Currency Hedges (Details) - USD ($) $ in Millions		Dec. 31, 2015		Dec. 31, 2014
Interest Rate Swap [Member] | Derivative [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)		$ 15		$ 15
Mark-to-market derivative assets (noncurrent assets)		39		8
Total mark-to-market derivative assets		54		23
Mark-to-market derivative liabilities (current liabilities)		(8)		1
Mark-to-market derivative liabilities (noncurrent liabilities)		(8)		(114)
Total mark-to-market derivative liabilities		(16)		(113)
Interest Rate Derivative Fair Value Of Derivative Net		38		(90)
Interest Rate Swap [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)		15		12
Mark-to-market derivative assets (noncurrent assets)		14		6
Total mark-to-market derivative assets		29		18
Mark-to-market derivative liabilities (current liabilities)		(8)		1
Mark-to-market derivative liabilities (noncurrent liabilities)		(8)		(3)
Total mark-to-market derivative liabilities		(16)		(2)
Interest Rate Derivative Fair Value Of Derivative Net		13		16
Interest Rate Swap [Member] | Exelon Generation Co L L C [Member] | Derivative [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)		10		7
Mark-to-market derivative assets (noncurrent assets)		10		5
Total mark-to-market derivative assets		20		12
Mark-to-market derivative liabilities (current liabilities)		(2)		(2)
Mark-to-market derivative liabilities (noncurrent liabilities)		(1)		0
Total mark-to-market derivative liabilities		(3)		(2)
Interest Rate Derivative Fair Value Of Derivative Net		17		10
Interest Rate Swap [Member] | Exelon Generation Co L L C [Member] | Proprietary Trading [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)		10	[1]	20	[2]
Mark-to-market derivative assets (noncurrent assets)		5	[1]	7	[2]
Total mark-to-market derivative assets		15	[1]	27	[2]
Mark-to-market derivative liabilities (current liabilities)		(9)	[1]	(14)	[2]
Mark-to-market derivative liabilities (noncurrent liabilities)		(3)	[1]	(9)	[2]
Total mark-to-market derivative liabilities		(12)	[1]	(23)	[2]
Interest Rate Derivative Fair Value Of Derivative Net		3	[1]	4	[2]
Interest Rate Swap [Member] | Exelon Generation Co L L C [Member] | Collateral And Netting [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)		(5)	[3]	(22)	[4]
Mark-to-market derivative assets (noncurrent assets)		(1)	[3]	(7)	[4]
Total mark-to-market derivative assets		(6)	[3]	(29)	[4]
Mark-to-market derivative liabilities (current liabilities)		11	[3]	25	[4]
Mark-to-market derivative liabilities (noncurrent liabilities)		4	[3]	10	[4]
Total mark-to-market derivative liabilities		15	[3]	35	[4]
Interest Rate Derivative Fair Value Of Derivative Net		9	[3]	6	[4]
Other Segments [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)		0		3
Mark-to-market derivative assets (noncurrent assets)		25		2
Total mark-to-market derivative assets		25		5
Mark-to-market derivative liabilities (current liabilities)		0		0
Mark-to-market derivative liabilities (noncurrent liabilities)		0		(111)
Total mark-to-market derivative liabilities		0		(111)
Interest Rate Derivative Fair Value Of Derivative Net		25		(106)
Other Segments [Member] | Interest Rate Swap [Member] | Derivative [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)		0		0
Mark-to-market derivative assets (noncurrent assets)		0		1
Total mark-to-market derivative assets		0		1
Mark-to-market derivative liabilities (current liabilities)		0		0
Mark-to-market derivative liabilities (noncurrent liabilities)		0		(101)
Total mark-to-market derivative liabilities		0		(101)
Interest Rate Derivative Fair Value Of Derivative Net		0		(100)
Other Segments [Member] | Interest Rate Swap [Member] | Collateral And Netting [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)		0	[3]	0
Mark-to-market derivative assets (noncurrent assets)		0	[3]	(19)
Total mark-to-market derivative assets	[3]	0		(19)
Mark-to-market derivative liabilities (current liabilities)		0	[3]	0
Mark-to-market derivative liabilities (noncurrent liabilities)		0	[3]	19
Total mark-to-market derivative liabilities	[3]	0		19
Interest Rate Derivative Fair Value Of Derivative Net	[3]	0		0
Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)		0		7
Mark-to-market derivative assets (noncurrent assets)		0		1
Total mark-to-market derivative assets		0		8
Mark-to-market derivative liabilities (current liabilities)		(8)		(8)
Mark-to-market derivative liabilities (noncurrent liabilities)		(8)		(4)
Total mark-to-market derivative liabilities		(16)		(12)
Interest Rate Derivative Fair Value Of Derivative Net		(16)		(4)
Designated as Hedging Instrument [Member] | Other Segments [Member]
Derivative [Line Items]
Mark-to-market derivative liabilities (current liabilities)		0
Designated as Hedging Instrument [Member] | Other Segments [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)		0		3
Mark-to-market derivative assets (noncurrent assets)		25		20
Total mark-to-market derivative assets		25		23
Mark-to-market derivative liabilities (current liabilities)				0
Mark-to-market derivative liabilities (noncurrent liabilities)		0		(29)
Total mark-to-market derivative liabilities		0		(29)
Interest Rate Derivative Fair Value Of Derivative Net		$ 25		$ (6)

[1] Generation enters into interest rate derivative contracts to economically hedge risk associated with the interest rate component of commodity positions. The characterization of the interest rate derivative contracts between the proprietary trading activity in the above table is driven by the corresponding characterization of the underlying commodity position that gives rise to the interest rate exposure. Generation does not utilize proprietary trading interest rate derivatives with the objective of benefiting from shifts or changes in market interest rates.

[2] Generation enters into interest rate derivative contracts to economically hedge risk associated with the interest rate component of commodity positions. The characterization of the interest rate derivative contracts between the proprietary trading activity in the above table is driven by the corresponding characterization of the underlying commodity position that gives rise to the interest rate exposure. Generation does not utilize proprietary trading interest rate derivatives with the objective of benefiting from shifts or changes in market interest rates.

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[4] {F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOmJiZTkxZGVlYTU0NDQzYzU5MmI5ODA2YTIzODFjMGRkfFRleHRTZWxlY3Rpb246NENEMjJCRjRDMzEyNTE4NUUyNjIxMjI1RThCMzBFMjEM}