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Plant, Property, and Equipment (Public Utilities, Allowance for Funds Used During Construction, Schedule of Composite Rate Table) (Details) - Consumers Energy Company | 12 Months Ended
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Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Electric Utility |  |  |
Property, Plant and Equipment [Line Items] |  |  |
AFUDC Capitalization rate | 6.40% | 6.90% | 6.80%
Gas Utility |  |  |
Property, Plant and Equipment [Line Items] |  |  |
AFUDC Capitalization rate | 5.80% | 5.90% | 6.00%

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- Definition Effective rate, including composite rate, of cost of financing additions to qualifying regulated assets, commonly called allowance for funds used during construction. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 835 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6501662&loc=d3e56162-110433 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 835 -Section 25 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6501569&loc=d3e55921-110430 + Details
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