Investments in Nuclear Decommissioning Trusts and Other Special Use Funds - Narrative (Details) - USD ($) $ in Millions		12 Months Ended
Jan. 04, 2021	Dec. 31, 2020
Schedule of Equity Method Investments [Line Items]
Transfer to active union medical account	$ 106
APS
Schedule of Equity Method Investments [Line Items]
Employee medical claims amount		$ 14

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