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Asset Retirement Obligations (Tables)
12 Months Ended
Dec. 31, 2020
Asset Retirement Obligation Disclosure [Abstract]  
Schedule of ARO Obligations and Related Additions, Reductions and Accretion
The following table represents the balance of ARO obligations as of December 31, 2020 and 2019, along with the additions, reductions and accretion related to the Company's ARO obligations for the year ended December 31, 2020:
(In millions)Nuclear Decommission
Other(a)
Total
Balance as of December 31, 2019$298 $430 $728 
Revisions in estimates for current obligations(12)38 26 
Additions— 
Spending for current obligations— (43)(43)
Accretion17 29 46 
Balance as of December 31, 2020$303 $457 $760 
(a)Total accretion expense related to asset retirement obligations included in the consolidated statement of cash flows includes accretion and revisions in estimates for asset retirement liabilities on non-operating plants