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Revenue Recognition Provision for Doubtful Accounts (Details) - Accounting Standards Update 2016-13 [Member]
$ in Millions
 6 Months Ended
Jun. 30, 2020
USD ($)
Cumulative Effect on Retained Earnings $ 5
Energy Services Disposal Group [Member]  
Cumulative Effect on Retained Earnings 2
CERC Corp [Member]  
Cumulative Effect on Retained Earnings $ 5