Reportable Segments (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Segment Reporting Information [Line Items]
Operating Revenue	$ 1,445	$ 1,492	$ 3,504	$ 3,445
Net income (loss) available to common stockholders	93	139	306	380
Plant, property, and equipment, gross	24,263		24,263		$ 24,400
Total Assets	25,292		25,292		24,529
Consumers Energy Company
Segment Reporting Information [Line Items]
Operating Revenue	1,334	1,395	3,277	3,250
Net income (loss) available to common stockholder	97	151	323	393
Plant, property, and equipment, gross	23,833		23,833		23,963
Total Assets	22,416		22,416		22,025
Operating Segments | Electric Utility
Segment Reporting Information [Line Items]
Operating Revenue	1,027	1,089	2,130	2,167
Net income (loss) available to common stockholders	90	130	195	269
Plant, property, and equipment, gross	15,660		15,660		16,027
Total Assets	14,396		14,396		14,079
Operating Segments | Electric Utility | Consumers Energy Company
Segment Reporting Information [Line Items]
Operating Revenue	1,027	1,089	2,130	2,167
Net income (loss) available to common stockholder	90	130	195	269
Plant, property, and equipment, gross	15,660		15,660		16,027
Total Assets	14,459		14,459		14,143
Operating Segments | Gas Utility
Segment Reporting Information [Line Items]
Operating Revenue	307	306	1,147	1,083
Net income (loss) available to common stockholders	8	21	129	124
Plant, property, and equipment, gross	8,154		8,154		7,919
Total Assets	7,890		7,890		7,806
Operating Segments | Gas Utility | Consumers Energy Company
Segment Reporting Information [Line Items]
Operating Revenue	307	306	1,147	1,083
Net income (loss) available to common stockholder	8	21	129	124
Plant, property, and equipment, gross	8,154		8,154		7,919
Total Assets	7,937		7,937		7,853
Operating Segments | Enterprises
Segment Reporting Information [Line Items]
Operating Revenue	58	61	125	124
Net income (loss) available to common stockholders	10	14	11	29
Plant, property, and equipment, gross	405		405		412
Total Assets	522		522		540
Operating Segments | Enterprises | Consumers Energy Company
Segment Reporting Information [Line Items]
Operating Revenue	0	0	0	0
Other reconciling items
Segment Reporting Information [Line Items]
Operating Revenue	53	36	102	71
Net income (loss) available to common stockholders	(15)	(26)	(29)	(42)
Plant, property, and equipment, gross	44		44		42
Total Assets	2,484		2,484		2,104
Other reconciling items | Consumers Energy Company
Segment Reporting Information [Line Items]
Operating Revenue	0	0	0	0
Net income (loss) available to common stockholder	(1)	$ 0	(1)	$ 0
Plant, property, and equipment, gross	19		19		17
Total Assets	$ 20		$ 20		$ 29