Consolidated Statements Of Changes In Equity - USD ($) $ in Millions	Consumers Energy Company [Member] CMS Energy Common Stock [Member]	Consumers Energy Company [Member] Other Paid-in Capital [Member]	Consumers Energy Company [Member] Accumulated Other Comprehensive (Loss) [Member]	Consumers Energy Company [Member] Retirement Benefits Liability [Member]	Consumers Energy Company [Member] Investments [Member]	Consumers Energy Company [Member] Retained Earnings (Accumulated Deficit) [Member]	Consumers Energy Company [Member] Preferred Stock [Member]	Consumers Energy Company [Member]	CMS Energy Common Stock [Member]	Other Paid-in Capital [Member]	Accumulated Other Comprehensive (Loss) [Member]	Retirement Benefits Liability [Member]	Investments [Member]	Retained Earnings (Accumulated Deficit) [Member]	Noncontrolling Interest [Member]	Total
Cumulative effect of change in accounting principle														$ 33
Total Equity, beginning at Dec. 31, 2015	$ 841	$ 3,724	$ (6)	$ (19)	$ 13	$ 950	$ 37	$ 5,546	$ 3	$ 4,837	$ (47)	$ (43)	$ (4)	(855)	$ 37	$ 3,975
Common stock issued										82
Common stock repurchased										(11)
Common stock reissued
Stockholder contribution		275
Amortization of net actuarial loss												2				2
Amortization of prior service credit												(1)				(1)
Unrealized gain (loss) on investments					3			3					1			1
Reclassification adjustments included in net income, net of tax
Net income (loss) attributable to CMS Energy														474		474
Net Income						499		499								475
Dividends declared on common stock						(361)								(259)
Dividends declared on preferred stock						(1)
Income Attributable to Noncontrolling Interests															1	1
Distributions, and other changes in noncontrolling interests															(1)
Total Equity, end at Sep. 30, 2016	841	3,999	(3)	(19)	16	1,087	37	5,961	3	4,908	(45)	(42)	(3)	(607)	37	4,296
Total Equity, beginning at Jun. 30, 2016	841	3,999	(1)	(19)	18	1,040	37	5,916	3	4,906	(47)	(43)	(4)	(706)	37	4,193
Common stock issued										3
Common stock repurchased										(1)
Common stock reissued
Stockholder contribution
Amortization of net actuarial loss												1				1
Amortization of prior service credit
Unrealized gain (loss) on investments					(2)			(2)					1			1
Reclassification adjustments included in net income, net of tax
Net income (loss) attributable to CMS Energy														186		186
Net Income						195		195								186
Dividends declared on common stock						(148)								(87)
Distributions, and other changes in noncontrolling interests
Total Equity, end at Sep. 30, 2016	841	3,999	(3)	(19)	16	1,087	37	5,961	3	4,908	(45)	(42)	(3)	(607)	37	4,296
Total Equity, beginning at Dec. 31, 2016	841	3,999	(3)	(21)	18	1,065	37	5,939	3	4,916	(50)	(50)		(616)	37	4,290
Common stock issued										95
Common stock repurchased										(13)
Common stock reissued										15
Stockholder contribution		450
Amortization of net actuarial loss				1				1				1				1
Amortization of prior service credit
Unrealized gain (loss) on investments					2			2					2			2
Reclassification adjustments included in net income, net of tax					(8)			(8)
Net income (loss) attributable to CMS Energy														463		463
Net Income						496		496								464
Dividends declared on common stock						(347)								(281)
Dividends declared on preferred stock						(1)
Income Attributable to Noncontrolling Interests															1	1
Distributions, and other changes in noncontrolling interests															(1)
Total Equity, end at Sep. 30, 2017	841	4,449	(8)	(20)	12	1,213	37	6,532	3	5,013	(47)	(49)	2	(434)	37	4,572
Total Equity, beginning at Jun. 30, 2017	841	4,449	(8)	(20)	12	1,143	37	6,462	3	5,006	(48)	(49)	1	(512)	37	4,486
Common stock issued										7
Common stock repurchased
Common stock reissued
Stockholder contribution
Amortization of net actuarial loss
Amortization of prior service credit
Unrealized gain (loss) on investments													1			1
Reclassification adjustments included in net income, net of tax
Net income (loss) attributable to CMS Energy														172		172
Net Income						181		181								172
Dividends declared on common stock						(111)								(94)
Distributions, and other changes in noncontrolling interests
Total Equity, end at Sep. 30, 2017	$ 841	$ 4,449	$ (8)	$ (20)	$ 12	$ 1,213	$ 37	$ 6,532	$ 3	$ 5,013	$ (47)	$ (49)	$ 2	$ (434)	$ 37	$ 4,572