Financings and Capitalization (Revolving Credit Facilities) (Details)	Mar. 31, 2020 USD ($)
Revolving Credit Facilities September 20, 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
$850m 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	7,000,000
Amount Available	843,000,000
Revolving Credit Facilities November 19, 2021 | Consumers Energy Company
Line of Credit Facility [Line Items]
Amount of Facility	250,000,000
Amount Borrowed	0
Letters of Credit Outstanding	8,000,000
Amount Available	242,000,000
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 Corporation | $550m Revolving Credit Facilities June 5, 2023
Line of Credit Facility [Line Items]
Amount of Facility	550,000,000
Amount Borrowed	25,000,000
Letters of Credit Outstanding	4,000,000
Amount Available	$ 521,000,000
Letter of Credit | $550m Revolving Credit Facilities June 5, 2023
Line of Credit Facility [Line Items]
Weighted average interest rate	1.887%
Letter of Credit | Revolving Credit Facilities September 20, 2025
Line of Credit Facility [Line Items]
Amount of Facility	$ 8,000,000