Consolidated Statements of Changes In Equity (Unaudited) - USD ($) $ in Millions	Total	Common Stock	Other Paid-in Capital	Accumulated Other Comprehensive Loss	Retirement benefits liability	Investments	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 Preferred Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of change in accounting principle					$ 0		$ 0						$ 0	$ 0	$ 0
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
Increase (Decrease) in Stockholders' Equity [Roll Forward]
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	0				0
Unrealized gain (loss) on investments	2					2			2					2
Reclassification adjustments included in net income	0					0			(8)					(8)
Net income	464						463	1	496						496
Dividends declared on common stock							(281)								(347)
Dividends declared on preferred stock															(1)
Distributions and other changes in noncontrolling interests								(1)
Total Equity at End of Period at Sep. 30, 2017	4,572	3	5,013	(47)	(49)	2	(434)	37	6,532	841	4,449	(8)	(20)	12	1,213	37
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of change in accounting principle					0		0						0	0	0
Total Equity at Beginning of Period at Jun. 30, 2017	4,486	3	5,006	(48)	(49)	1	(512)	37	6,462	841	4,449	(8)	(20)	12	1,143	37
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued			7
Common stock repurchased			0
Common stock reissued			0
Stockholder contribution											0
Amortization of net actuarial loss	0				0				0				0
Amortization of prior service credit	0				0
Unrealized gain (loss) on investments	1					1			0					0
Reclassification adjustments included in net income	0					0			0					0
Net income	172						172	0	181						181
Dividends declared on common stock							(94)								(111)
Dividends declared on preferred stock															0
Distributions and other changes in noncontrolling interests								0
Total Equity at End of Period at Sep. 30, 2017	4,572	3	5,013	(47)	(49)	2	(434)	37	6,532	841	4,449	(8)	(20)	12	1,213	37
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of change in accounting principle					(11)		8						(5)	(12)	19
Total Equity at Beginning 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]
Common stock issued			54
Common stock repurchased			(10)
Common stock reissued			20
Stockholder contribution											250
Amortization of net actuarial loss	3				3				2				2
Amortization of prior service credit	(1)				(1)
Unrealized gain (loss) on investments	(1)					(1)			(1)					(1)
Reclassification adjustments included in net income	1					1			1					1
Net income	550						549	1	574						574
Dividends declared on common stock							(304)								(392)
Dividends declared on preferred stock															(1)
Distributions and other changes in noncontrolling interests								(1)
Total Equity at End of Period at Sep. 30, 2018	4,786	3	5,083	(59)	(59)	0	(278)	37	6,923	841	4,699	(27)	(27)	0	1,373	37
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of change in accounting principle					0		0						0	0	0
Total Equity at Beginning of Period at Jun. 30, 2018	4,709	3	5,076	(61)	(60)	(1)	(346)	37	6,888	841	4,699	(29)	(28)	(1)	1,340	37
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued			7
Common stock repurchased			0
Common stock reissued			0
Stockholder contribution											0
Amortization of net actuarial loss	1				1				1				1
Amortization of prior service credit	0				0
Unrealized gain (loss) on investments	0					0			0					0
Reclassification adjustments included in net income	1					1			1					1
Net income	169						169	0	180						180
Dividends declared on common stock							(101)								(147)
Dividends declared on preferred stock															0
Distributions and other changes in noncontrolling interests								0
Total Equity at End of Period at Sep. 30, 2018	$ 4,786	$ 3	$ 5,083	$ (59)	$ (59)	$ 0	$ (278)	$ 37	$ 6,923	$ 841	$ 4,699	(27)	$ (27)	$ 0	$ 1,373	$ 37
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of change in accounting principle												$ (19)