Contingencies and Commitments (Expected Remediation Cost By Year) (Details) $ in Millions	Mar. 31, 2021 USD ($)
Bay Harbor
Site Contingency [Line Items]
2021	$ 3
2022	4
2023	4
2024	4
2025	4
2026	4
Manufactured Gas Plant \| Consumers Energy Company
Site Contingency [Line Items]
2021	3
2022	9
2023	23
2024	11
2025	2
2026	$ 1

Undiscounted amount of accrual for environmental loss contingency to be paid in fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 5.Y.Q1)
-URI http://asc.fasb.org/extlink&oid=27011672&loc=d3e149879-122751

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- Definition

Undiscounted amount of accrual for environmental loss contingency to be paid in fourth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

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- Definition

Undiscounted amount of accrual for environmental loss contingency to be paid in remainder of current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

No definition available.

+ Details

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- Definition

Undiscounted amount of accrual for environmental loss contingency to be paid in second fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

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- Definition

Undiscounted amount of accrual for environmental loss contingency to be paid in third fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

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- Definition

Undiscounted amount of accrual for environmental loss contingency to be paid in next fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Details

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