Early Nuclear Plant Retirements Early Nuclear Plant Retirements (Tables)

12 Months Ended

Dec. 31, 2017

Implications of Potential Early Plant Retirements [Abstract]

Schedule of Other Operating Cost and Expense, by Component [Table Text Block]

The total annual impact of these charges by year are summarized in the table below.

Income statement expense (pre-tax)	2017(a)		2016(b)
Depreciation and Amortization
Accelerated depreciation(c)	$	250	$	712
Accelerated nuclear fuel amortization	12		60
Operating and Maintenance
One-time charges(d,e)	77		26
Change in ARO accretion, net of any contractual offset(f)	—		2
Contractual offset for ARC depreciation(f)	—		(86		)
Total	$	339	$	714

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(a) Reflects incremental charges for TMI including incremental accelerated depreciation and amortization from May 30, 2017 through December 31, 2017.

(b) Reflects incremental charges for Clinton and Quad Cities including incremental accelerated depreciation and amortization from June 2, 2016 through December 6, 2016. In December 2016, as a result of reversing its retirement decision for Clinton and Quad Cities, Exelon and Generation updated the expected economic useful life for both facilities, to 2027 for Clinton, commensurate with the end of the Illinois ZES, and to 2032 for Quad Cities, the end of its current operating license. Depreciation was therefore adjusted beginning December 7, 2016, to reflect these extended useful life estimates.

(c) Reflects incremental accelerated depreciation of plant assets, including any ARC.

(d) Primarily includes materials and supplies inventory reserve adjustments, employee related costs and CWIP impairments.

(e) In June 2016, as a result of the retirement decision for Clinton and Quad Cities, Exelon and Generation recognized one-time charges of $146 million. In December 2016, as a result of reversing its retirement decision for Clinton and Quad Cities, Exelon and Generation reversed approximately $120 million of these one-time charges initially recorded in June 2016.

(f) For Quad Cities based on the regulatory agreement with the Illinois Commerce Commission, decommissioning-related activities are offset within Exelon's and Generation's Consolidated Statements of Operations and Comprehensive Income. The offset results in an equal adjustment to the noncurrent payables to ComEd at Generation and an adjustment to the regulatory liabilities at ComEd. Likewise, ComEd has recorded an equal noncurrent affiliate receivable from Generation and corresponding regulatory liability.

ScheduleOfOtherOperatingCostAndExpenseByComponent2 [Table Text Block]

The following table provides the balance sheet amounts as of December 31, 2017 for Generation’s ownership share of the significant assets and liabilities associated with Salem.

(in millions)	12/31/2017
Asset Balances
Materials and supplies inventory	$	44
Nuclear fuel inventory, net	113
Completed plant, net	439
Construction work in progress	33
Liability Balances
Asset retirement obligation	(442		)
NRC License Renewal Term	2036 (unit 1)
	2040 (unit 2)

On February 2, 2018, Exelon announced that Generation will permanently cease generation operations at Oyster Creek at the end of its current operating cycle in October 2018. See Note 28 — Subsequent Events for additional information regarding the early retirement of Oyster Creek.