Stock-Based Compensation (Schedule Of Restricted Stock Granted) (Details)	12 Months Ended
	Dec. 31, 2017 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Granted	734,603
Consumers Energy Company [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Granted	703,022
Time-Lapsed Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Granted	164,640
Time-Lapsed Restricted Stock [Member] | Consumers Energy Company [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Granted	159,260
Market-Based Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Granted	157,064
Market-Based Restricted Stock [Member] | Consumers Energy Company [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Granted	149,870
Performance-Based Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Granted	157,064
Performance-Based Restricted Stock [Member] | Consumers Energy Company [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Granted	149,870
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Granted	12,388
Restricted Stock Units (RSUs) [Member] | Consumers Energy Company [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Granted	11,970
Time-Lapsed Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Granted	11,444
Time-Lapsed Restricted Stock Units [Member] | Consumers Energy Company [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Granted	11,055
Dividends On Market-Based Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Granted	24,137
Dividends On Market-Based Awards [Member] | Consumers Energy Company [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Granted	22,976
Dividends On Performance-Based Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Granted	22,894
Dividends On Performance-Based Awards [Member] | Consumers Energy Company [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Granted	21,791
Dividends On Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Granted	944
Dividends On Restricted Stock Units [Member] | Consumers Energy Company [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Granted	915
Additional Market-Based Shares Based On Achievement Of Condition [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Granted	113,079
Additional Market-Based Shares Based On Achievement Of Condition [Member] | Consumers Energy Company [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Granted	107,823
Additional Performance-Based Shares Based On Achievement Of Condition [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Granted	83,337
Additional Performance-Based Shares Based On Achievement Of Condition [Member] | Consumers Energy Company [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Granted	79,462