Financings And Capitalization (Revolving Credit Facilities) (Details)	Mar. 31, 2021 USD ($)
Revolving Credit Facilities June 5, 2023 | Consumers Energy Company
Line of Credit Facility [Line Items]
Amount of Facility	$ 850,000,000
Amount Borrowed	0
Letters of Credit Outstanding	12,000,000
Amount Available	838,000,000
Revolving Credit Facilities November 19, 2020 | Consumers Energy Company
Line of Credit Facility [Line Items]
Amount of Facility	250,000,000
Amount Borrowed	0
Letters of Credit Outstanding	1,000,000
Amount Available	249,000,000
Revolving Credit Facilities April 18, 2022 | Consumers Energy Company
Line of Credit Facility [Line Items]
Amount of Facility	30,000,000
Amount Borrowed	0
Letters of Credit Outstanding	30,000,000
Amount Available	0
CMS Energy | Revolving Credit Facilities June 5, 2023
Line of Credit Facility [Line Items]
Amount of Facility	550,000,000
Amount Borrowed	0
Letters of Credit Outstanding	18,000,000
Amount Available	532,000,000
CMS Enterprises Including Subsidiaries | Revolving Credit Facilities September 25, 2025
Line of Credit Facility [Line Items]
Amount of Facility	39,000,000
Amount Borrowed	0
Letters of Credit Outstanding	39,000,000
Amount Available	0
CMS Enterprises Including Subsidiaries | Revolving Credit Facilities September 30, 2025
Line of Credit Facility [Line Items]
Amount of Facility	18,000,000
Amount Borrowed	0
Letters of Credit Outstanding	8,000,000
Amount Available	10,000,000
Letter of Credit | CMS Enterprises Including Subsidiaries | Revolving Credit Facilities September 30, 2025
Line of Credit Facility [Line Items]
Amount Available	$ 8,000,000