Mergers, Acquisitions and Dispositions - Summary of Major Classes of Assets and Liabilities Held for Sale (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2014	Dec. 31, 2015
Significant Acquisitions and Disposals [Line Items]
Total assets held for sale		$ 147	$ 4
Accrued expenses		1,539	2,376
Other current liabilities		931	842
Electricity Generation Plant, Non-Nuclear [Member]
Significant Acquisitions and Disposals [Line Items]
Property, plant and equipment, net	[1]	143
Inventory		4
Total assets held for sale		147
Accrued expenses			1
Other current liabilities			$ 4
Total liabilities held for sale	[2]	5
Asset impairment charges		$ 50

[1] The total aggregate book value of property, plant and equipment is net of a $50 million pre-tax impairment loss recorded within Operating and maintenance expense on Exelon’s and Generation’s Statements of Operations and Comprehensive Income for the year ended December 31, 2014. See Note 8 — Impairment of Long-Lived Assets for further information.

[2] Included within Other current liabilities on Exelon's and Generation's Consolidated Balance Sheets.