Reportable Segments (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Segment Reporting Information [Line Items]
Operating Revenue	$ 1,430	$ 1,445	$ 5,421	$ 4,830
Total Net Income Available to Common Stockholders	94	126	381	350
Plant, property, and equipment, gross	17,155		17,155		16,184
Total Assets	18,381		18,381		17,416
Consumers Energy Company [Member]
Segment Reporting Information [Line Items]
Operating Revenue	1,359	1,386	5,128	4,647
Total Net Income Available to Common Stockholders	119	152	448	413
Plant, property, and equipment, gross	17,013		17,013		16,044
Total Assets	16,919		16,919		16,179
Electric Utility [Member]
Segment Reporting Information [Line Items]
Operating Revenue	1,153	1,188	3,428	3,175
Total Net Income Available to Common Stockholders	128	156	326	315
Plant, property, and equipment, gross	11,790		11,790		11,186
Total Assets	11,029		11,029		10,487
Electric Utility [Member] | Consumers Energy Company [Member]
Segment Reporting Information [Line Items]
Operating Revenue	1,153	1,188	3,428	3,175
Total Net Income Available to Common Stockholders	128	156	326	315
Plant, property, and equipment, gross	11,790		11,790		11,186
Total Assets	11,029		11,029		10,487
Gas Utility [Member]
Segment Reporting Information [Line Items]
Operating Revenue	206	198	1,699	1,472
Total Net Income Available to Common Stockholders	(9)	(4)	121	97
Plant, property, and equipment, gross	5,208		5,208		4,843
Total Assets	5,242		5,242		4,784
Gas Utility [Member] | Consumers Energy Company [Member]
Segment Reporting Information [Line Items]
Operating Revenue	206	198	1,699	1,472
Total Net Income Available to Common Stockholders	(9)	(4)	121	97
Plant, property, and equipment, gross	5,208		5,208		4,843
Total Assets	5,242		5,242		4,784
Enterprises [Member]
Segment Reporting Information [Line Items]
Operating Revenue	51	44	235	136
Total Net Income Available to Common Stockholders	(7)	(4)	(3)	1
Plant, property, and equipment, gross	116		116		115
Total Assets	318		318		332
Other [Member]
Segment Reporting Information [Line Items]
Operating Revenue	20	15	59	47
Total Net Income Available to Common Stockholders	(18)	(22)	(63)	(63)
Plant, property, and equipment, gross	41		41		40
Total Assets	1,792		1,792		1,813
Other [Member] | Consumers Energy Company [Member]
Segment Reporting Information [Line Items]
Operating Revenue			1
Total Net Income Available to Common Stockholders			1	1
Plant, property, and equipment, gross	15		15		15
Total Assets	$ 648		$ 648		$ 908