Stock-Based Compensation (Share-Based Compensation Arrangement By Share-Based Payment Award, Options, Grants In Period, Weighted Average Grant Date Fair Value) (Details) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Restricted stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in dollars per share)	$ 45.56	$ 43.57	$ 26.49
Restricted stock | Consumers Energy Company
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in dollars per share)	45.53	43.57	26.51
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in dollars per share)	49.76	50.35	41.77
Restricted stock units | Consumers Energy Company
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in dollars per share)	$ 49.70	$ 51.15	$ 42.01