Consolidated Statements Of Changes In Equity - USD ($) shares in Thousands, $ in Millions	Total	Common Stock	Other Paid-in Capital	Accumulated Other Comprehensive Loss	Retirement benefits liability	Investments	Derivative instruments	Accumulated Deficit	Noncontrolling Interests	Consumers Energy Company	Consumers Energy Company Common Stock	Consumers Energy Company Other Paid-in Capital	Consumers Energy Company Accumulated Other Comprehensive Loss	Consumers Energy Company Retirement benefits liability	Consumers Energy Company Investments	Consumers Energy Company Accumulated Deficit	Consumers Energy Company Cumulative Preferred Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of change in accounting principle					$ 0			$ 33						$ 0	$ 0	$ 0
Total Equity at Beginning of Period at Dec. 31, 2015	$ 3,975	$ 3	$ 4,837	$ (47)	(43)	$ (4)	$ 0	(855)	$ 37	$ 5,546	$ 841	$ 3,724	$ (6)	(19)	13	950	$ 37
Beginning of period (in shares) at Dec. 31, 2015		277,163
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued (in shares)		2,580
Common stock issued			90
Common stock repurchased (in shares)		(292)
Common stock repurchased			(11)
Common stock reissued (in shares)		0
Common stock reissued			0
Common stock reacquired (in shares)		(245)
Common stock reacquired			0
Stockholder contribution												275
Net income attributable to CMS Energy	551							551
Net loss arising during the period	(8)				(8)					(3)				(3)
Prior service credit adjustment	0				0
Amortization of net actuarial loss	2				2					1				1
Amortization of prior service credit	(1)				(1)
Reclassification adjustments included in net income										0					0
Unrealized gain on investments	1					1				3					3
Other-than-temporary impairment included in net income	3					3				2					2
Unrealized loss on derivative instruments	0						0
Net Income	553									616						616
Dividends declared on common stock								(345)								(499)
Dividends declared on preferred stock																(2)
Income attributable to noncontrolling interests	$ 2								2
Distributions and other changes in noncontrolling interests									(2)
Dividends declared per common share (in dollars per share)	$ 1.24
End of period (in shares) at Dec. 31, 2016		279,206
Total Equity at End of Period at Dec. 31, 2016	$ 4,290	$ 3	4,916	(50)	(50)	0	0	(616)	37	5,939	841	3,999	(3)	(21)	18	1,065	37
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of change in accounting principle					0			0						0	0	0
Common stock issued (in shares)		2,492
Common stock issued			102
Common stock repurchased (in shares)		(317)
Common stock repurchased			(14)
Common stock reissued (in shares)		360
Common stock reissued			15
Common stock reacquired (in shares)		(94)
Common stock reacquired			0
Stockholder contribution												450
Net income attributable to CMS Energy	460							460
Net loss arising during the period	(5)				(5)					(4)				(4)
Prior service credit adjustment	4				4
Amortization of net actuarial loss	2				2					1				1
Amortization of prior service credit	(1)				(1)
Reclassification adjustments included in net income										(9)					(9)
Unrealized gain on investments	0					0				3					3
Other-than-temporary impairment included in net income	0					0				0					0
Unrealized loss on derivative instruments	0						0
Net Income	462									$ 632						632
Dividends declared on common stock								(375)								(522)
Dividends declared on preferred stock																(2)
Income attributable to noncontrolling interests	$ 2								2
Distributions and other changes in noncontrolling interests									(2)
Dividends declared per common share (in dollars per share)	$ 1.33
End of period (in shares) at Dec. 31, 2017	281,600	281,647								84,100
Total Equity at End of Period at Dec. 31, 2017	$ 4,478	$ 3	5,019	(50)	(50)	0	0	(531)	37	$ 6,488	841	4,449	(12)	(24)	12	1,173	37
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of change in accounting principle					(11)			8					(19)	(5)	(12)	19
Common stock issued (in shares)		1,554
Common stock issued			59
Common stock repurchased (in shares)		(224)
Common stock repurchased			(10)
Common stock reissued (in shares)		423
Common stock reissued			20
Common stock reacquired (in shares)		(26)
Common stock reacquired			0
Stockholder contribution												250
Net income attributable to CMS Energy	657							657
Net loss arising during the period	(4)				(4)					6				6
Prior service credit adjustment	(1)				(1)
Amortization of net actuarial loss	4				4					2				2
Amortization of prior service credit	(1)				(1)
Reclassification adjustments included in net income										1					1
Unrealized gain on investments	0					0				(1)					(1)
Other-than-temporary impairment included in net income	0					0				0					0
Unrealized loss on derivative instruments	(2)						(2)
Net Income	659									$ 705						705
Dividends declared on common stock								(405)								(531)
Dividends declared on preferred stock																(2)
Income attributable to noncontrolling interests	$ 2								2
Distributions and other changes in noncontrolling interests									(2)
Dividends declared per common share (in dollars per share)	$ 1.43
End of period (in shares) at Dec. 31, 2018	283,400	283,374								84,100
Total Equity at End of Period at Dec. 31, 2018	$ 4,792	$ 3	$ 5,088	$ (65)	$ (63)	$ 0	$ (2)	$ (271)	$ 37	$ 6,920	$ 841	$ 4,699	$ (21)	$ (21)	$ 0	$ 1,364	$ 37