Consolidated Statements Of Changes In Equity - USD ($) shares in Millions, $ 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 Income (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 Income (Loss) [Member]	Retirement Benefits Liability [Member]	Investments [Member]	Retained Earnings (Accumulated Deficit) [Member]	Noncontrolling Interest [Member]	Total
Total Equity, beginning at Dec. 31, 2014	$ 841	$ 3,574	$ (7)	$ (26)	$ 19	$ 832	$ 37	$ 5,277	$ 3	$ 4,774	$ (49)	$ (48)	$ (1)	$ (1,058)	$ 37	$ 3,707
Common stock issued										56
Common stock repurchased										(11)
Common stock reissued										10
Stockholder contribution		150
Amortization of net actuarial loss				3				3				4				4
Amortization of prior service credit												(1)				(1)
Unrealized gain (loss) on investments					(2)			(2)					(3)			(3)
Reclassification adjustments included in net income					(5)			5
Net income attributable to CMS Energy																417
Net income						459		459						417		418
Dividends declared on common stock						(359)								(240)
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, 2015	841	3,724	(11)	(23)	12	931	37	5,522	3	4,829	(49)	(45)	(4)	(881)		3,939
Total Equity, beginning at Jun. 30, 2015	841	3,724	(12)	(24)	12	876	37	5,466	3	4,812	(48)	(46)	(2)	(949)	37	3,855
Common stock issued										17
Common stock repurchased
Stockholder contribution
Amortization of net actuarial loss				1				1				2				2
Amortization of prior service credit												(1)				(1)
Unrealized gain (loss) on investments													(2)			(2)
Reclassification adjustments included in net income
Net income attributable to CMS Energy																148
Net income						160		160						148		148
Dividends declared on common stock						(105)								(80)
Total Equity, end at Sep. 30, 2015	841	3,724	(11)	(23)	12	931	37	5,522	3	4,829	(49)	(45)	(4)	(881)		3,939
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
Beginning of period, shares at Dec. 31, 2015								84.1								277.2
Common stock issued										82
Common stock repurchased										(11)
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 income attributable to CMS Energy																474
Net income						499		$ 499						474		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)
End of period, shares at Sep. 30, 2016								84.1								279.1
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)		$ 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)
Stockholder contribution
Amortization of net actuarial loss												1				1
Unrealized gain (loss) on investments					(2)			(2)					1			1
Reclassification adjustments included in net income
Net income attributable to CMS Energy																186
Net income						195		$ 195						186		$ 186
Dividends declared on common stock						(148)								(87)
End of period, shares at Sep. 30, 2016								84.1								279.1
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)		$ 4,296
Cumulative effect of change in accounting principle														$ 33