Reportable Segments (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013	Dec. 31, 2013
Segment Reporting Information [Line Items]
Operating Revenue	$ 2,523		$ 1,979
Total Net Income Available to Common Stockholders	204		144
Plant, property, and equipment, gross	16,322			16,184
Total Assets	17,924			17,416
Consumers Energy Company [Member]
Segment Reporting Information [Line Items]
Operating Revenue	2,382		1,919
Total Net Income Available to Common Stockholders	221		162
Plant, property, and equipment, gross	16,181			16,044
Total Assets	16,312			16,179
Electric Utility [Member]
Segment Reporting Information [Line Items]
Operating Revenue	1,224		961
Total Net Income Available to Common Stockholders	100		66
Plant, property, and equipment, gross	11,270			11,186
Total Assets	10,719	[1]		10,487	[1]
Electric Utility [Member] | Consumers Energy Company [Member]
Segment Reporting Information [Line Items]
Operating Revenue	1,224		961
Total Net Income Available to Common Stockholders	100		66
Plant, property, and equipment, gross	11,270			11,186
Total Assets	10,719	[1]		10,487	[1]
Gas Utility [Member]
Segment Reporting Information [Line Items]
Operating Revenue	1,158		958
Total Net Income Available to Common Stockholders	121		96
Plant, property, and equipment, gross	4,896			4,843
Total Assets	4,554	[1]		4,784	[1]
Gas Utility [Member] | Consumers Energy Company [Member]
Segment Reporting Information [Line Items]
Operating Revenue	1,158		958
Total Net Income Available to Common Stockholders	121		96
Plant, property, and equipment, gross	4,896			4,843
Total Assets	4,554	[1]		4,784	[1]
Enterprises [Member]
Segment Reporting Information [Line Items]
Operating Revenue	122		44
Total Net Income Available to Common Stockholders	2		4
Plant, property, and equipment, gross	116			115
Total Assets	310			332
Other [Member]
Segment Reporting Information [Line Items]
Operating Revenue	19		16
Total Net Income Available to Common Stockholders	(19)		(22)
Plant, property, and equipment, gross	40			40
Total Assets	2,341			1,813
Other [Member] | Consumers Energy Company [Member]
Segment Reporting Information [Line Items]
Plant, property, and equipment, gross	15			15
Total Assets	$ 1,039			$ 908

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