Consolidated Statements Of Income (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating Revenue	$ 7,179	$ 6,566	$ 6,253
Operating Expenses
Fuel for electric generation	673	621	598
Purchased and interchange power	1,602	1,387	1,364
Purchased power - related parties	90	90	87
Cost of gas sold	1,493	1,228	1,150
Maintenance and other operating expenses	1,232	1,236	1,224
Depreciation and amortization	685	628	598
General taxes	252	234	229
Total operating expenses	6,027	5,424	5,250
Operating Income	1,152	1,142	1,003
Other Income (Expense)
Interest income	5	3	5
Allowance for equity funds used during construction	8	6	8
Income from equity method investees	15	13	17
Other income	11	10	11
Other expense	(55)	(20)	(33)
Total other income (expense)	(16)	12	8
Interest Charges
Interest on long-term debt	393	385	372
Other interest expense	17	16	21
Allowance for borrowed funds used during construction	(3)	(3)	(4)
Total interest charges	407	398	389
Income Before Income Taxes	729	756	622
Income Tax Expense	250	302	245
Income From Continuing Operations	479	454	377
Income From Discontinued Operations, Net of Tax			7
Net Income	479	454	384
Income Attributable to Noncontrolling Interests	2	2	2
Net Income Attributable to Common Stockholders
Amounts attributable to continuing operations	477	452	375
Amounts attributable to discontinued operations			7
Income Attributable to Noncontrolling Interests
Amounts attributable to continuing operations	2	2	2
Amounts attributable to discontinued operations
Income attributable to noncontrolling interests	2	2	2
Basic Earnings Per Average Common Share
Basic earnings from continuing operations	$ 1.76	$ 1.71	$ 1.43
Basic earnings from discontinued operations			$ 0.03
Basic earnings attributable to common stock	$ 1.76	$ 1.71	$ 1.46
Diluted Earnings Per Average Common Share
Diluted earnings from continuing operations	$ 1.74	$ 1.66	$ 1.39
Diluted earnings from discontinued operations			$ 0.03
Diluted earnings attributable to common stock	$ 1.74	$ 1.66	$ 1.42
Net income attributable to CMS Energy	477	452	382
Basic Earnings Per Average Common Share	$ 1.76	$ 1.71	$ 1.46
Diluted Earnings Per Average Common Share	$ 1.74	$ 1.66	$ 1.42
Consumers Energy Company [Member]
Operating Revenue	6,800	6,321	6,013
Operating Expenses
Fuel for electric generation	567	541	517
Purchased and interchange power	1,564	1,361	1,339
Purchased power - related parties	89	89	86
Cost of gas sold	1,375	1,187	1,110
Maintenance and other operating expenses	1,146	1,174	1,162
Depreciation and amortization	678	622	592
General taxes	246	229	223
Total operating expenses	5,665	5,203	5,029
Operating Income	1,135	1,118	984
Other Income (Expense)
Interest income	4	2	4
Interest and dividend income - related parties	1	1	1
Allowance for equity funds used during construction	8	6	8
Other income	10	14	16
Other expense	(35)	(16)	(33)
Total other income (expense)	(12)	7	(4)
Interest Charges
Interest on long-term debt	243	237	232
Other interest expense	10	11	16
Allowance for borrowed funds used during construction	(3)	(3)	(4)
Total interest charges	250	245	244
Income Before Income Taxes	873	880	736
Income Tax Expense	306	346	297
Net Income	567	534	439
Preferred Stock Dividends and Distribution	2	2	2
Net Income Available to Common Stockholder	$ 565	$ 532	$ 437