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
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										8
Common stock repurchased										(12)
Common stock reissued										15
Stockholder contribution		250
Amortization of net actuarial loss
Unrealized gain (loss) on investments					2			2					$ 1			1
Reclassification adjustments included in net income					(8)			(8)
Net Income						211		211						199		199
Dividends declared on common stock						(148)								(94)
Total Equity, end at Mar. 31, 2017	841	4,249	(9)	(21)	12	1,128	37	6,246	3	4,927	(49)	(50)	1	(511)	37	4,407
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																$ 70
Number of Shares Issued																1,494,371
End of period, shares at Dec. 31, 2017								84,100,000								281,600,000
Total Equity, end at Dec. 31, 2017	841	4,449	(12)	(24)	12	1,173	37	$ 6,488	3	5,019	(50)	(50)		(531)	37	$ 4,478
Common stock issued										8
Common stock repurchased										(10)
Common stock reissued										20
Stockholder contribution		100
Amortization of net actuarial loss				1				1				1				1
Unrealized gain (loss) on investments					(1)			(1)					(1)			(1)
Reclassification adjustments included in net income
Net Income						242		$ 242						241		$ 241
Dividends declared on common stock						(119)								(101)
End of period, shares at Mar. 31, 2018								84,100,000								282,500,000
Total Equity, end at Mar. 31, 2018	$ 841	$ 4,549	$ (29)	(28)	(1)	1,315	$ 37	$ 6,713	$ 3	$ 5,037	$ (61)	(60)	$ (1)	(383)	$ 37	$ 4,633
Cumulative effect of change in accounting principle				$ (5)	$ (12)	$ 19						$ (11)		$ 8