Reportable Segments (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended										12 Months Ended
	Dec. 31, 2013		Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012		Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Segment Reporting Information [Line Items]
Operating Revenue	$ 1,736		$ 1,445	$ 1,406	$ 1,979	$ 1,670		$ 1,507	$ 1,333	$ 1,743	$ 6,566		$ 6,253		$ 6,503
Depreciation and amortization											628		598		546
Income (loss) from equity method investees											13	[1]	17	[1]	9	[1]
Interest charges											398		389		415
Income Tax Expense											302		245		191
Total Net Income Available to Common Stockholders	102		126	80	144	67		148	100	67	452		382		415
Plant, property, and equipment, gross	16,184					15,592					16,184		15,592		14,751
Investments in equity method investees	59	[1]				57	[1]				59	[1]	57	[1]	50	[1]
Total Assets	17,416					17,131					17,416		17,131		16,452
Capital Expenditures											1,408	[2]	1,266	[2]	928	[2]
Consumers Energy Company [Member]
Segment Reporting Information [Line Items]
Operating Revenue	1,674		1,386	1,342	1,919	1,608		1,448	1,282	1,675	6,321		6,013		6,253
Depreciation and amortization											622		592		542
Interest charges											245		244		265
Income Tax Expense											346		297		267
Total Net Income Available to Common Stockholders	119		152	99	162	78		162	121	76	532		437		465
Plant, property, and equipment, gross	16,044					15,456					16,044		15,456		14,621
Total Assets	16,179					16,275					16,179		16,275		15,662
Capital Expenditures											1,403	[2]	1,261	[2]	922	[2]
Electric Utility [Member]
Segment Reporting Information [Line Items]
Operating Revenue											4,173		4,031		3,913
Depreciation and amortization											484		459		412
Interest charges											179		179		192
Income Tax Expense											242		227		190
Total Net Income Available to Common Stockholders											363		325		333
Plant, property, and equipment, gross	11,186					11,041					11,186		11,041		10,400
Total Assets	10,487	[3]				10,423	[3]				10,487	[3]	10,423	[3]	9,938	[3]
Capital Expenditures											996	[2]	921	[2]	661	[2]
Electric Utility [Member] | Consumers Energy Company [Member]
Segment Reporting Information [Line Items]
Operating Revenue											4,173		4,031		3,913
Depreciation and amortization											484		459		412
Interest charges											179		179		192
Income Tax Expense											242		227		190
Total Net Income Available to Common Stockholders											363		325		333
Plant, property, and equipment, gross	11,186					11,041					11,186		11,041		10,400
Total Assets	10,487	[3]				10,423	[3]				10,487	[3]	10,423	[3]	9,938	[3]
Capital Expenditures											996	[2]	921	[2]	661	[2]
Gas Utility [Member]
Segment Reporting Information [Line Items]
Operating Revenue											2,148		1,982		2,340
Depreciation and amortization											138		133		130
Interest charges											64		63		71
Income Tax Expense											104		70		77
Total Net Income Available to Common Stockholders											168		110		130
Plant, property, and equipment, gross	4,843					4,400					4,843		4,400		4,206
Total Assets	4,784	[3]				5,016	[3]				4,784	[3]	5,016	[3]	4,956	[3]
Capital Expenditures											407	[2]	340	[2]	261	[2]
Gas Utility [Member] | Consumers Energy Company [Member]
Segment Reporting Information [Line Items]
Operating Revenue											2,148		1,982		2,340
Depreciation and amortization											138		133		130
Interest charges											64		63		71
Income Tax Expense											104		70		77
Total Net Income Available to Common Stockholders											168		110		130
Plant, property, and equipment, gross	4,843					4,400					4,843		4,400		4,206
Total Assets	4,784	[3]				5,016	[3]				4,784	[3]	5,016	[3]	4,956	[3]
Capital Expenditures											407	[2]	340	[2]	261	[2]
Enterprises [Member]
Segment Reporting Information [Line Items]
Operating Revenue											181		183		204
Depreciation and amortization											3		4		3
Income (loss) from equity method investees											13	[1]	17	[1]	9	[1]
Income Tax Expense											(4)		(1)		(24)
Total Net Income Available to Common Stockholders											2		16		32
Plant, property, and equipment, gross	115					113					115		113		109
Investments in equity method investees	57	[1]				55	[1]				57	[1]	55	[1]	49	[1]
Total Assets	332					181					332		181		242
Capital Expenditures											1	[2]	1	[2]	5	[2]
Other [Member]
Segment Reporting Information [Line Items]
Operating Revenue											64		57		46
Depreciation and amortization											3		2		1
Interest charges											155		147		152
Income Tax Expense											(40)		(51)		(52)
Total Net Income Available to Common Stockholders											(81)		(69)		(80)
Plant, property, and equipment, gross	40					38					40		38		36
Investments in equity method investees	2	[1]				2	[1]				2	[1]	2	[1]	1	[1]
Total Assets	1,813					1,511					1,813		1,511		1,316
Capital Expenditures											4	[2]	4	[2]	1	[2]
Other [Member] | Consumers Energy Company [Member]
Segment Reporting Information [Line Items]
Interest charges											2		2		2
Total Net Income Available to Common Stockholders											1		2		2
Plant, property, and equipment, gross	15					15					15		15		15
Total Assets	$ 908					$ 836					$ 908		$ 836		$ 768

[1] Consumers had no significant equity method investments.

[2] Amounts include purchase of capital lease additions. Amounts also include a portion of Consumers’ capital expenditures for plant and equipment attributable to both the electric and gas utility businesses.

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