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Contingencies And Commitments (Expected Remediation Cost By Year) (Details)
$ in Millions
Jun. 30, 2018
USD ($)
Bay Harbor  
Site Contingency [Line Items]  
2018 $ 2
2019 4
2020 4
2021 4
2022 4
2023 4
Gas Utility | Manufactured Gas Plant | Consumers Energy Company  
Site Contingency [Line Items]  
2018 11
2019 18
2020 10
2021 18
2022 7
2023 $ 2