Stock-Based Compensation (Schedule Of Restricted Stock Granted) (Details)	12 Months Ended
	Dec. 31, 2018 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	654,840
Consumers Energy Company
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	619,683
Time-lapse awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	122,615
Time-lapse awards | Consumers Energy Company
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	117,029
Market-based awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	134,179
Market-based awards | Consumers Energy Company
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	126,558
Performance-based awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	134,179
Performance-based awards | Consumers Energy Company
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	126,558
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	11,196
Restricted stock units | Consumers Energy Company
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	10,792
Dividend equivalents on market-based awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	21,154
Dividend equivalents on market-based awards | Consumers Energy Company
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	20,077
Dividend equivalents on performance-based awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	25,925
Dividend equivalents on performance-based awards | Consumers Energy Company
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	24,583
Dividend equivalents on restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	1,254
Dividend equivalents on restricted stock units | Consumers Energy Company
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	1,142
Additional market-based shares based on achievement of condition
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	88,987
Additional market-based shares based on achievement of condition | Consumers Energy Company
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	84,025
Additional performance-based shares based on achievement of condition
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	115,351
Additional performance-based shares based on achievement of condition | Consumers Energy Company
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	108,919