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	Derivative instruments	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
Total Equity at Beginning of Period at Dec. 31, 2016	$ 4,290	$ 3	$ 4,916	$ (50)	$ (50)		$ 0	$ (616)	$ 37	$ 5,939	$ 841	$ 3,999	$ (3)	$ (21)	$ 18	$ 1,065	$ 37
Beginning of period (in shares) at Dec. 31, 2016		279,206
Increase (Decrease) in Stockholders' Equity [Roll Forward]
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 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										3					3
Unrealized loss on derivative instruments	0						0
Reclassification adjustments included in net income	0						0
Net income attributable to CMS Energy	460							460
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)
End of period (in shares) at Dec. 31, 2017		281,647
Total Equity at End of Period at Dec. 31, 2017	$ 4,478	$ 3	5,019	(50)	(50)		0	(531)	37	6,488	841	4,449	(12)	(24)	12	1,173	37
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends declared per common share (in dollars per share)	$ 1.33
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 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										(1)					(1)
Unrealized loss on derivative instruments	(2)					$ (2)
Reclassification adjustments included in net income	0					0
Net income attributable to CMS Energy	657							657
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)
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)	(2)	$ (2)	(271)	37	$ 6,920	841	4,699	(21)	(21)	0	1,364	37
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends declared per common share (in dollars per share)	$ 1.43
Common stock issued (in shares)		710
Common stock issued			35
Common stock repurchased (in shares)		(181)
Common stock repurchased			(10)
Common stock reissued (in shares)		8
Common stock reissued			0
Common stock reacquired (in shares)		(47)
Common stock reacquired			0
Stockholder contribution												675
Net loss arising during the period	$ (7)				(7)					(8)				(8)
Prior service credit adjustment	0				0
Amortization of net actuarial loss	3				3					1				1
Amortization of prior service credit	(2)				(2)
Reclassification adjustments included in net income										0					0
Unrealized gain on investments										0					0
Unrealized loss on derivative instruments	(3)					(3)
Reclassification adjustments included in net income	1					1
Net income attributable to CMS Energy	680							680
Net Income	682									$ 743						743
Dividends declared on common stock								(434)								(592)
Dividends declared on preferred stock																(2)
Income attributable to noncontrolling interests	$ 2								2
Distributions and other changes in noncontrolling interests									(2)
End of period (in shares) at Dec. 31, 2019	283,900	283,864								84,100
Total Equity at End of Period at Dec. 31, 2019	$ 5,055	$ 3	$ 5,113	$ (73)	$ (69)	$ (4)		$ (25)	$ 37	$ 7,737	$ 841	$ 5,374	$ (28)	$ (28)	$ 0	$ 1,513	$ 37
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends declared per common share (in dollars per share)	$ 1.53