Schedule I - Condensed Financial Information of Registrant (Condensed Statements of Income) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating Expenses
Other operating expense									$ (1,610)	$ (1,280)	$ (1,356)
Total operating expenses									(6,183)	(5,188)	(5,509)
Operating Loss	$ 204	$ 260	$ 252	$ 430	$ 307	$ 340	$ 248	$ 335	1,146	1,230	1,115
Other Income (Expense)
Non-operating retirement benefits, net									165	118	91
Interest income									3	4	7
Other income									9	6	4
Other expense									(18)	(62)	(13)
Total other income									177	84	109
Interest Charges
Interest on long-term debt									481	483	439
Intercompany interest expense and other									10	12	16
Total interest charges									500	505	460
Income Before Income Taxes									823	809	764
Income tax expense (benefit)									95	115	131
Income From Continuing Operations	114	153	153	308	138	198	129	229	728	694	633
Income From Discontinued Operations, Net of Tax	520	30	18	34	24	12	8	14	602	58	49
Net Income Attributable to CMS Energy	639	189	176	349					1,353	755	680
Preferred Stock Dividends	2	3	0	0					5	0	0
Net Income Available to Common Stockholders	$ 637	$ 186	$ 176	$ 349	$ 158	$ 218	$ 136	$ 243	1,348	755	680
CMS Energy
Operating Expenses
Other operating expense									(7)	(6)	(38)
Total operating expenses									(7)	(6)	(38)
Operating Loss									(7)	(6)	(38)
Other Income (Expense)
Equity earnings of subsidiaries									1,482	909	826
Non-operating retirement benefits, net									(1)	(1)	(1)
Interest income									1	1	1
Other income									1	1	1
Other expense									0	(19)	0
Total other income									1,483	891	827
Interest Charges
Interest on long-term debt									183	178	156
Intercompany interest expense and other									7	7	10
Total interest charges									190	185	166
Income Before Income Taxes									1,286	700	623
Income tax expense (benefit)									(60)	(55)	(57)
Income From Continuing Operations									1,346	755	680
Income From Discontinued Operations, Net of Tax									7	0	0
Net Income Attributable to CMS Energy									1,353	755	680
Preferred Stock Dividends									5	0	0
Net Income Available to Common Stockholders									$ 1,348	$ 755	$ 680