Financings and Capitalization (Major Long-Term Debt Transactions) (Details)
$ in Millions |
3 Months Ended |
|
Mar. 31, 2020
USD ($)
|
|---|
| Debt Instrument [Line Items] |
|
| Principal balance |
$ 1,175
|
| Consumers Energy Company |
|
| Debt Instrument [Line Items] |
|
| Principal balance |
875
|
| First Mortgage Bonds Due August 2051 | Consumers Energy Company |
|
| Debt Instrument [Line Items] |
|
| Principal balance |
$ 575
|
| Interest Rate |
3.50%
|
| CMS Energy Corporation |
|
| Debt Instrument [Line Items] |
|
| Principal balance |
$ 300
|
| Term Loan Facility Due February 2021 | CMS Energy Corporation | Term loan facility |
|
| Debt Instrument [Line Items] |
|
| Principal balance |
$ 300
|
| Effective interest rate |
1.572%
|
| Term Loan Facility Due February 2021 | London Interbank Offered Rate (LIBOR) | CMS Energy Corporation | Term loan facility |
|
| Debt Instrument [Line Items] |
|
| Basis spread on variable rate |
0.50%
|
| Term loan facility due January 2021 | Term loan facility | Consumers Energy Company |
|
| Debt Instrument [Line Items] |
|
| Principal balance |
$ 300
|
| Effective interest rate |
1.466%
|
| Term loan facility due January 2021 | London Interbank Offered Rate (LIBOR) | Term loan facility |
|
| Debt Instrument [Line Items] |
|
| Basis spread on variable rate |
0.45%
|