Revenue from Contracts with Customers - Contract Assets and Liabilities (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Jan. 01, 2018
Change in Contract with Customer, Asset and Liability [Abstract]
Contract with Customer, Asset, Net, Current	$ 174	$ 187	$ 283
Contract with Customer, Asset, Reclassified to Receivable	(143)	(146)
Contract with Customer, Asset, Cumulative Catch-up Adjustment to Revenue, Change in Measure of Progress	130	50
Contract with Customer, Liability, Current	33	27	35
Contract with Customer, Liability, Cumulative Catch-up Adjustment to Revenue, Modification of Contract	94	179
Contract with Customer, Liability, Revenue Recognized	(88)	(187)
Exelon Generation Co L L C [Member]
Change in Contract with Customer, Asset and Liability [Abstract]
Contract with Customer, Asset, Net, Current	174	187	283
Contract with Customer, Asset, Reclassified to Receivable	(143)	(146)
Contract with Customer, Asset, Cumulative Catch-up Adjustment to Revenue, Change in Measure of Progress	130	50
Contract with Customer, Liability, Current	71	42	$ 35
Contract with Customer, Liability, Cumulative Catch-up Adjustment to Revenue, Modification of Contract	287	465
Contract with Customer, Liability, Revenue Recognized	$ (258)	$ (458)

No definition available.

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Amount of increase (decrease) in revenue recognized for cumulative catch-up adjustment from change in measure of progress which increases (decreases) right to consideration in exchange for good or service transferred to customer when right is conditioned on something other than passage of time.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
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Amount, after allowance for credit loss, of right to consideration in exchange for good or service transferred to customer when right is conditioned on something other than passage of time, classified as current.

+ References

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Amount of decrease in right to consideration in exchange for good or service transferred to customer when right is conditioned on something other than passage of time from transfer to receivable due to right to consideration becoming unconditional.

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Amount of increase (decrease) in revenue recognized for cumulative catch-up adjustment from contract modification which (increases) decreases obligation to transfer good or service to customer for which consideration from customer has been received or is due.

+ References

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Amount of obligation to transfer good or service to customer for which consideration has been received or is receivable, classified as current.

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Amount of revenue recognized that was previously included in balance of obligation to transfer good or service to customer for which consideration from customer has been received or is due.

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