Reportable Segments (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended			6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013	Jun. 30, 2014		Jun. 30, 2013	Dec. 31, 2013
Segment Reporting Information [Line Items]
Operating Revenue	$ 1,468		$ 1,406	$ 3,991		$ 3,385
Total Net Income Available to Common Stockholders	83		80	287		224
Plant, property, and equipment, gross	16,583			16,583			16,184
Total Assets	17,719			17,719			17,416
Consumers Energy Company [Member]
Segment Reporting Information [Line Items]
Operating Revenue	1,387		1,342	3,769		3,261
Total Net Income Available to Common Stockholders	108		99	329		261
Plant, property, and equipment, gross	16,441			16,441			16,044
Total Assets	16,387			16,387			16,179
Electric Utility [Member]
Segment Reporting Information [Line Items]
Operating Revenue	1,051		1,026	2,275		1,987
Total Net Income Available to Common Stockholders	98		93	198		159
Plant, property, and equipment, gross	11,424	[1]		11,424	[1]		11,186	[1]
Total Assets	10,787	[1]		10,787	[1]		10,487	[1]
Electric Utility [Member] | Consumers Energy Company [Member]
Segment Reporting Information [Line Items]
Operating Revenue	1,051		1,026	2,275		1,987
Total Net Income Available to Common Stockholders	98		93	198		159
Plant, property, and equipment, gross	11,424	[1]		11,424	[1]		11,186	[1]
Total Assets	10,787	[1]		10,787	[1]		10,487	[1]
Gas Utility [Member]
Segment Reporting Information [Line Items]
Operating Revenue	335		316	1,493		1,274
Total Net Income Available to Common Stockholders	9		5	130		101
Plant, property, and equipment, gross	5,002	[1]		5,002	[1]		4,843	[1]
Total Assets	4,837	[1]		4,837	[1]		4,784	[1]
Gas Utility [Member] | Consumers Energy Company [Member]
Segment Reporting Information [Line Items]
Operating Revenue	335		316	1,493		1,274
Total Net Income Available to Common Stockholders	9		5	130		101
Plant, property, and equipment, gross	5,002	[1]		5,002	[1]		4,843	[1]
Total Assets	4,837	[1]		4,837	[1]		4,784	[1]
Enterprises [Member]
Segment Reporting Information [Line Items]
Operating Revenue	62		48	184		92
Total Net Income Available to Common Stockholders	2		1	4		5
Plant, property, and equipment, gross	116			116			115
Total Assets	314			314			332
Other [Member]
Segment Reporting Information [Line Items]
Operating Revenue	20		16	39		32
Total Net Income Available to Common Stockholders	(26)		(19)	(45)		(41)
Plant, property, and equipment, gross	41			41			40
Total Assets	1,781			1,781			1,813
Other [Member] | Consumers Energy Company [Member]
Segment Reporting Information [Line Items]
Operating Revenue	1			1
Total Net Income Available to Common Stockholders	1		1	1		1
Plant, property, and equipment, gross	15			15			15
Total Assets	$ 763			$ 763			$ 908

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