Reportable Segments (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Segment Reporting Information [Line Items]
Operating Revenue		$ 1,829	$ 1,801
Net income available to common stockholders		199	164
Plant, property, and equipment, gross		21,265		$ 21,010
Total Assets		21,623		21,622
Consumers Energy Company [Member]
Segment Reporting Information [Line Items]
Operating Revenue		1,737	1,723
Net income available to common stockholders		211	172
Plant, property, and equipment, gross		21,092		20,838
Total Assets		19,824		19,946
Electric Utility [Member]
Segment Reporting Information [Line Items]
Operating Revenue		1,036	1,013
Net income available to common stockholders		124	91
Plant, property, and equipment, gross	[1]	14,715		14,540
Total Assets	[1]	13,653		13,429
Electric Utility [Member] | Consumers Energy Company [Member]
Segment Reporting Information [Line Items]
Operating Revenue		1,036	1,013
Net income available to common stockholders		124	91
Plant, property, and equipment, gross	[1]	14,715		14,540
Total Assets	[1]	13,656		13,430
Gas Utility [Member]
Segment Reporting Information [Line Items]
Operating Revenue		701	710
Net income available to common stockholders		87	81
Plant, property, and equipment, gross	[1]	6,362		6,283
Total Assets	[1]	6,131		6,446
Gas Utility [Member] | Consumers Energy Company [Member]
Segment Reporting Information [Line Items]
Operating Revenue		701	710
Net income available to common stockholders		87	81
Plant, property, and equipment, gross	[1]	6,362		6,283
Total Assets	[1]	6,131		6,446
Enterprises [Member]
Segment Reporting Information [Line Items]
Operating Revenue		59	48
Net income available to common stockholders		12	6
Plant, property, and equipment, gross		158		157
Total Assets		269		269
Other [Member]
Segment Reporting Information [Line Items]
Operating Revenue		33	30
Net income available to common stockholders		(24)	$ (14)
Plant, property, and equipment, gross		30		30
Total Assets		1,570		1,478
Other [Member] | Consumers Energy Company [Member]
Segment Reporting Information [Line Items]
Plant, property, and equipment, gross		15		15
Total Assets		$ 37		$ 70

[1] Amounts include a portion of Consumers' other common assets attributable to both the electric and gas utility businesses.