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Financings and Capitalization (Summary of Long-Term Debt Outstanding) (Details) - USD ($) | 1 Months Ended | 12 Months Ended |
--- | --- | --- | ---
Oct. 31, 2022 | Dec. 31, 2018 | Dec. 31, 2017
Debt Instrument [Line Items] |  |  |
Principal amounts outstanding |  | $ 11,683,000,000 | $ 10,265,000,000
Current amounts |  | (974,000,000) | (1,081,000,000)
Net unamortized discounts |  | (21,000,000) | (14,000,000)
Unamortized issuance costs |  | (73,000,000) | (47,000,000)
Long-term debt |  | 10,615,000,000 | 9,123,000,000
Consumers Energy Company |  |  |
Debt Instrument [Line Items] |  |  |
Principal amounts outstanding |  | 6,862,000,000 | 5,940,000,000
Current amounts |  | (26,000,000) | (343,000,000)
Net unamortized discounts |  | (16,000,000) | (8,000,000)
Unamortized issuance costs |  | (41,000,000) | (28,000,000)
Long-term debt |  | $ 6,779,000,000 | 5,561,000,000
FMB's 5.650% Due 2018 | Consumers Energy Company |  |  |
Debt Instrument [Line Items] |  |  |
Interest rate |  | 5.65% |
FMB's 6.125% Due 2019 | Consumers Energy Company |  |  |
Debt Instrument [Line Items] |  |  |
Interest rate |  | 6.125% |
FMB's 6.700% Due 2019 | Consumers Energy Company |  |  |
Debt Instrument [Line Items] |  |  |
Interest rate |  | 6.70% |
Tax-exempt pollution control revenue bond | Consumers Energy Company |  |  |
Debt Instrument [Line Items] |  |  |
Maturity Date |  | 2035 |
Principal amounts outstanding |  | $ 35,000,000 | 103,000,000
Term loans and revolving credit agreements |  |  |
Debt Instrument [Line Items] |  |  |
Maturity Date |  | 2025 |
Principal amounts outstanding |  | $ 98,000,000 | 0
Three-month LIBOR plus a spread |  | 1.50% |
Interest rate at period end |  | 4.303% |
Fixed interest rate |  | 4.702% |
Certificates of deposit | EnerBank Certificates Of Deposit |  |  |
Debt Instrument [Line Items] |  |  |
Maturity Date |  | 2019-2026 |
Certificates of deposit |  | $ 1,758,000,000 | $ 1,245,000,000
Weighted-average interest rate |  | 2.44% | 1.758%
Certificate of deposit face value |  | $ 1,000 |
First Mortgage Bonds | Consumers Energy Company |  |  |
Debt Instrument [Line Items] |  |  |
Principal amounts outstanding |  | $ 6,335,000,000 | $ 5,535,000,000
First Mortgage Bonds | FMB's 5.650% Due 2018 | Consumers Energy Company |  |  |
Debt Instrument [Line Items] |  |  |
Interest rate |  | 5.65% |
Maturity Date |  | 2018 |
Principal amounts outstanding |  | $ 0 | 250,000,000
First Mortgage Bonds | FMB's 6.125% Due 2019 | Consumers Energy Company |  |  |
Debt Instrument [Line Items] |  |  |
Interest rate |  | 6.125% |
Maturity Date |  | 2019 |
Principal amounts outstanding |  | $ 0 | 350,000,000
First Mortgage Bonds | FMB's 6.700% Due 2019 | Consumers Energy Company |  |  |
Debt Instrument [Line Items] |  |  |
Interest rate |  | 6.70% |
Maturity Date |  | 2019 |
Principal amounts outstanding |  | $ 0 | 500,000,000
First Mortgage Bonds | FMB's 5.650% Due 2020 | Consumers Energy Company |  |  |
Debt Instrument [Line Items] |  |  |
Interest rate |  | 5.65% |
Maturity Date |  | 2020 |
Principal amounts outstanding |  | $ 300,000,000 | 300,000,000
First Mortgage Bonds | FMB's 3.770% Due 2020 | Consumers Energy Company |  |  |
Debt Instrument [Line Items] |  |  |
Interest rate |  | 3.77% |
Maturity Date |  | 2020 |
Principal amounts outstanding |  | $ 100,000,000 | 100,000,000
First Mortgage Bonds | FMB's 2.850% Due 2022 | Consumers Energy Company |  |  |
Debt Instrument [Line Items] |  |  |
Interest rate |  | 2.85% |
Maturity Date |  | 2022 |
Principal amounts outstanding |  | $ 375,000,000 | 375,000,000
First Mortgage Bonds | FMB's 5.300% Due 2022 | Consumers Energy Company |  |  |
Debt Instrument [Line Items] |  |  |
Interest rate |  | 5.30% |
Maturity Date |  | 2022 |
Principal amounts outstanding |  | $ 250,000,000 | 250,000,000
First Mortgage Bonds | FMB's 3.375% Due 2023 | Consumers Energy Company |  |  |
Debt Instrument [Line Items] |  |  |
Interest rate |  | 3.375% |
Maturity Date |  | 2023 |
Principal amounts outstanding |  | $ 325,000,000 | 325,000,000
First Mortgage Bonds | FMB's 3.125% Due 2024 | Consumers Energy Company |  |  |
Debt Instrument [Line Items] |  |  |
Interest rate |  | 3.125% |
Maturity Date |  | 2024 |
Principal amounts outstanding |  | $ 250,000,000 | 250,000,000
First Mortgage Bonds | FMB's 3.190% Due 2024 | Consumers Energy Company |  |  |
Debt Instrument [Line Items] |  |  |
Interest rate |  | 3.19% |
Maturity Date |  | 2024 |
Principal amounts outstanding |  | $ 52,000,000 | 52,000,000
First Mortgage Bonds | FMB's 3.680% Due 2027 | Consumers Energy Company |  |  |
Debt Instrument [Line Items] |  |  |
Interest rate |  | 3.68% |
Maturity Date |  | 2027 |
Principal amounts outstanding |  | $ 100,000,000 | 0
First Mortgage Bonds | FMB's 3.390% Due 2027 | Consumers Energy Company |  |  |
Debt Instrument [Line Items] |  |  |
Interest rate |  | 3.39% |
Maturity Date |  | 2027 |
Principal amounts outstanding |  | $ 35,000,000 | 35,000,000
First Mortgage Bonds | FMB's 3.800% Due 2028 | Consumers Energy Company |  |  |
Debt Instrument [Line Items] |  |  |
Interest rate |  | 3.80% |
Maturity Date |  | 2028 |
Principal amounts outstanding |  | $ 300,000,000 | 0
First Mortgage Bonds | FMB's 3.180% Due 2032 | Consumers Energy Company |  |  |
Debt Instrument [Line Items] |  |  |
Interest rate |  | 3.18% |
Maturity Date |  | 2032 |
Principal amounts outstanding |  | $ 100,000,000 | 100,000,000
First Mortgage Bonds | FMB's 5.800% Due 2035 | Consumers Energy Company |  |  |
Debt Instrument [Line Items] |  |  |
Interest rate |  | 5.80% |
Maturity Date |  | 2035 |
Principal amounts outstanding |  | $ 175,000,000 | 175,000,000
First Mortgage Bonds | FMB's 3.520% Due 2037 | Consumers Energy Company |  |  |
Debt Instrument [Line Items] |  |  |
Interest rate |  | 3.52% |
Maturity Date |  | 2037 |
Principal amounts outstanding |  | $ 335,000,000 | 335,000,000
First Mortgage Bonds | FMB's 4.010% Due 2038 | Consumers Energy Company |  |  |
Debt Instrument [Line Items] |  |  |
Interest rate |  | 4.01% |
Maturity Date |  | 2038 |
Principal amounts outstanding |  | $ 215,000,000 | 0
First Mortgage Bonds | FMB's 6.170% Due 2040 | Consumers Energy Company |  |  |
Debt Instrument [Line Items] |  |  |
Interest rate |  | 6.17% |
Maturity Date |  | 2040 |
Principal amounts outstanding |  | $ 50,000,000 | 50,000,000
First Mortgage Bonds | FMB's 4.970% Due 2040 | Consumers Energy Company |  |  |
Debt Instrument [Line Items] |  |  |
Interest rate |  | 4.97% |
Maturity Date |  | 2040 |
Principal amounts outstanding |  | $ 50,000,000 | 50,000,000
First Mortgage Bonds | FMB's 4.310% Due 2042 | Consumers Energy Company |  |  |
Debt Instrument [Line Items] |  |  |
Interest rate |  | 4.31% |
Maturity Date |  | 2042 |
Principal amounts outstanding |  | $ 263,000,000 | 263,000,000
First Mortgage Bonds | FMB's 3.950% Due 2043 | Consumers Energy Company |  |  |
Debt Instrument [Line Items] |  |  |
Interest rate |  | 3.95% |
Maturity Date |  | 2043 |
Principal amounts outstanding |  | $ 425,000,000 | 425,000,000
First Mortgage Bonds | FMB's 4.100% Due 2045 | Consumers Energy Company |  |  |
Debt Instrument [Line Items] |  |  |
Interest rate |  | 4.10% |
Maturity Date |  | 2045 |
Principal amounts outstanding |  | $ 250,000,000 | 250,000,000
First Mortgage Bonds | FMB's 3.250% Due 2046 | Consumers Energy Company |  |  |
Debt Instrument [Line Items] |  |  |
Interest rate |  | 3.25% |
Maturity Date |  | 2046 |
Principal amounts outstanding |  | $ 450,000,000 | 450,000,000
First Mortgage Bonds | FMB's 3.950% Due 2047 | Consumers Energy Company |  |  |
Debt Instrument [Line Items] |  |  |
Interest rate |  | 3.95% |
Maturity Date |  | 2047 |
Principal amounts outstanding |  | $ 350,000,000 | 350,000,000
First Mortgage Bonds | FMB's 4.350% Due 2049 | Consumers Energy Company |  |  |
Debt Instrument [Line Items] |  |  |
Interest rate |  | 4.35% |
Maturity Date |  | 2049 |
Principal amounts outstanding |  | $ 550,000,000 | 0
First Mortgage Bonds | FMB's 4.050% Due 2048 | Consumers Energy Company |  |  |
Debt Instrument [Line Items] |  |  |
Interest rate |  | 4.05% |
Maturity Date |  | 2048 |
Principal amounts outstanding |  | $ 550,000,000 | 0
First Mortgage Bonds | FMB's 3.860% Due 2052 | Consumers Energy Company |  |  |
Debt Instrument [Line Items] |  |  |
Interest rate |  | 3.86% |
Maturity Date |  | 2052 |
Principal amounts outstanding |  | $ 50,000,000 | 50,000,000
First Mortgage Bonds | FMB's 4.280% Due 2057 | Consumers Energy Company |  |  |
Debt Instrument [Line Items] |  |  |
Interest rate |  | 4.28% |
Maturity Date |  | 2057 |
Principal amounts outstanding |  | $ 185,000,000 | 0
First Mortgage Bonds | FMB's 4.350% Due 2064 | Consumers Energy Company |  |  |
Debt Instrument [Line Items] |  |  |
Interest rate |  | 4.35% |
Maturity Date |  | 2064 |
Principal amounts outstanding |  | $ 250,000,000 | 250,000,000
Securitization bonds | Securitization Bonds 3.057% Due 2020-2029 | Consumers Energy Company |  |  |
Debt Instrument [Line Items] |  |  |
Maturity Date |  | 2020-2029 |
Principal amounts outstanding |  | $ 277,000,000 | $ 302,000,000
Weighted average interest rate |  | 3.057% | 2.913%
Revolving credit agreements | Revolving credit agreements | Consumers Energy Company |  |  |
Debt Instrument [Line Items] |  |  |
Maturity Date |  | 2020-2023 |
Principal amounts outstanding |  | $ 215,000,000 | $ 0
Weighted average interest rate |  | 3.331% |
Amount outstanding |  |  | 0
CMS Energy |  |  |
Debt Instrument [Line Items] |  |  |
Principal amounts outstanding |  | $ 2,965,000,000 | 3,080,000,000
Long-term debt |  | $ 2,750,000,000 | 2,830,000,000
CMS Energy | Senior Notes 8.750% Due 2019 |  |  |
Debt Instrument [Line Items] |  |  |
Interest rate |  | 8.75% |
CMS Energy | Senior Notes 6.250% Due 2020 |  |  |
Debt Instrument [Line Items] |  |  |
Interest rate |  | 6.25% |
CMS Energy | Senior Notes 2.950% Due 2027 |  |  |
Debt Instrument [Line Items] |  |  |
Interest rate |  | 2.95% |
Maturity Date |  | 2027 |
Principal amounts outstanding |  | $ 275,000,000 | 275,000,000
CMS Energy | Senior notes |  |  |
Debt Instrument [Line Items] |  |  |
Principal amounts outstanding |  | $ 2,275,000,000 | 2,675,000,000
CMS Energy | Senior notes | Senior Notes 8.750% Due 2019 |  |  |
Debt Instrument [Line Items] |  |  |
Interest rate |  | 8.75% |
Maturity Date |  | 2019 |
Principal amounts outstanding |  | $ 0 | 100,000,000
CMS Energy | Senior notes | Senior Notes 6.250% Due 2020 |  |  |
Debt Instrument [Line Items] |  |  |
Interest rate |  | 6.25% |
Maturity Date |  | 2020 |
Principal amounts outstanding |  | $ 0 | 300,000,000
CMS Energy | Senior notes | Senior Notes 5.050% Due 2022 |  |  |
Debt Instrument [Line Items] |  |  |
Interest rate |  | 5.05% |
Maturity Date |  | 2022 |
Principal amounts outstanding |  | $ 300,000,000 | 300,000,000
CMS Energy | Senior notes | Senior Notes 3.875% Due 2024 |  |  |
Debt Instrument [Line Items] |  |  |
Interest rate |  | 3.875% |
Maturity Date |  | 2024 |
Principal amounts outstanding |  | $ 250,000,000 | 250,000,000
CMS Energy | Senior notes | Senior Notes 3.600% Due 2025 |  |  |
Debt Instrument [Line Items] |  |  |
Interest rate |  | 3.60% |
Maturity Date |  | 2025 |
Principal amounts outstanding |  | $ 250,000,000 | 250,000,000
CMS Energy | Senior notes | Senior Notes 3.000% Due 2026 |  |  |
Debt Instrument [Line Items] |  |  |
Interest rate |  | 3.00% |
Maturity Date |  | 2026 |
Principal amounts outstanding |  | $ 300,000,000 | 300,000,000
CMS Energy | Senior notes | Senior Notes 3.450% Due 2027 |  |  |
Debt Instrument [Line Items] |  |  |
Interest rate |  | 3.45% |
Maturity Date |  | 2027 |
Principal amounts outstanding |  | $ 350,000,000 | 350,000,000
CMS Energy | Senior notes | Senior Notes 4.700% Due 2043 |  |  |
Debt Instrument [Line Items] |  |  |
Interest rate |  | 4.70% |
Maturity Date |  | 2043 |
Principal amounts outstanding |  | $ 250,000,000 | 250,000,000
CMS Energy | Senior notes | Senior Notes 4.875% Due 2044 |  |  |
Debt Instrument [Line Items] |  |  |
Interest rate |  | 4.875% |
Maturity Date |  | 2044 |
Principal amounts outstanding |  | $ 300,000,000 | 300,000,000
CMS Energy | Term loans and revolving credit agreements |  |  |
Debt Instrument [Line Items] |  |  |
Principal amounts outstanding |  | $ 210,000,000 | 405,000,000
CMS Energy | Term loans and revolving credit agreements | Term Loan Facility Due 2019 |  |  |
Debt Instrument [Line Items] |  |  |
Maturity Date |  | 2019 |
Principal amounts outstanding |  | $ 180,000,000 | 405,000,000
Three-month LIBOR plus a spread |  | 0.80% |
Interest rate at period end |  | 3.322% |
CMS Energy | Term loans and revolving credit agreements | Term Loan Facility Due 2023 |  |  |
Debt Instrument [Line Items] |  |  |
Three-month LIBOR plus a spread |  | 0.125% |
Interest rate at period end |  | 3.669% |
CMS Energy | Junior subordinated notes |  |  |
Debt Instrument [Line Items] |  |  |
Principal amounts outstanding |  | $ 480,000,000 | 0
CMS Energy | Junior subordinated notes | Junior Notes 5.625% Due 2078 |  |  |
Debt Instrument [Line Items] |  |  |
Interest rate |  | 5.625% |
Maturity Date |  | 2078 |
Principal amounts outstanding |  | $ 200,000,000 | 0
CMS Energy | Junior subordinated notes | Junior Notes 5.875% Due 2078 |  |  |
Debt Instrument [Line Items] |  |  |
Interest rate |  | 5.875% |
Maturity Date |  | 2078 |
Principal amounts outstanding |  | $ 280,000,000 | 0
CMS Energy | Revolving credit agreements | Revolving Credit Facilities June 5, 2023 |  |  |
Debt Instrument [Line Items] |  |  |
Maturity Date |  | 2023 |
Principal amounts outstanding |  | $ 30,000,000 | $ 0
Scenario, Forecast | Term loans and revolving credit agreements |  |  |
Debt Instrument [Line Items] |  |  |
Three-month LIBOR plus a spread | 1.75% |  |
Fixed interest rate | 4.952% |  |

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