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, 2018	Dec. 31, 2017	Dec. 31, 2016
Restricted stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in dollars per share)	$ 26.49	$ 28.61	$ 31.74
Restricted stock | Consumers Energy Company
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in dollars per share)	26.51	28.67	31.77
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in dollars per share)	41.77	41.98	39.12
Restricted stock units | Consumers Energy Company
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in dollars per share)	$ 42.01	$ 41.97	$ 39.12