New Accounting Standards (Details) - USD ($) $ in Millions |
9 Months Ended | |
|---|---|---|
Sep. 30, 2016 |
Dec. 31, 2015 |
|
| Unamortized debt issuance costs | $ 44 | $ 41 |
| New Accounting Pronouncement, Early Adoption, Effect [Member] | ||
| Excess tax benefit related to stock | 7 | |
| Retained Earnings (Accumulated Deficit) [Member] | ||
| Cumulative effect of change in accounting principle | 33 | |
| Consumers Energy Company [Member] | ||
| Unamortized debt issuance costs | 25 | $ 23 |
| Consumers Energy Company [Member] | New Accounting Pronouncement, Early Adoption, Effect [Member] | ||
| Excess tax benefit related to stock | $ 7 |