Financings And Capitalization (Narrative) (Details) - USD ($)	1 Months Ended	12 Months Ended
	Aug. 31, 2018	Dec. 31, 2019	Jan. 31, 2020	Dec. 31, 2018
Financing And Capitalization [Line Items]
Debt instrument face amount		$ 2,096,000,000
Limitation on payment of stock dividends		5,000,000,000.0
Dividends paid		$ 592,000,000
Common stock authorized (in shares)		350,000,000		350,000,000
Par value of common stock (in dollars per share)		$ 0.01
Preferred stock authorized (in shares)		10,000,000
Par value of preferred stock (in dollars per share)		$ 0.01
Stock offering program maximum value	$ 250,000,000
Number of shares required to settle forward contracts (in shares)		992,596
Consumers Energy Company
Financing And Capitalization [Line Items]
Interest rate coverage ratio multiplier minimum to issue FMBs		200.00%
Unrestricted retained earnings		$ 1,400,000,000
Common stock authorized (in shares)		125,000,000		125,000,000
Par value of preferred stock (in dollars per share)		$ 4.50		$ 4.50
Consumers Energy Company | Commercial Paper
Financing And Capitalization [Line Items]
Short-term debt authorized borrowings		$ 500,000,000
Weighted average annual interest rate		2.05%
Short-term borrowings outstanding		$ 90,000,000
Forward Contracts
Financing And Capitalization [Line Items]
Forward contract indexed to issuer's equity		$ 250,000,000
Subsequent Event | Term loan facility due January 2021
Financing And Capitalization [Line Items]
Debt instrument face amount			$ 300,000,000