Schedule I - Condensed Financial Information of Registrant (Condensed Statements of Income) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Other operating expense									$ (1,207)	$ (1,238)	$ (1,232)
General taxes									281	262	252
Total operating expenses									(5,102)	(5,293)	(6,027)
Operating Loss	$ 290	$ 386	$ 285	$ 336	$ 245	$ 317	$ 204	$ 397	1,297	1,163	1,152
Interest income									6	12	5
Total other income									(36)	29	(16)
Interest on long-term debt									411	386	393
Intercompany interest expense and other									29	14	17
Total interest charges									435	396	407
Income Before Income Taxes									826	796	729
Income Tax Expense									273	271	250
Net income attributable to CMS Energy	$ 77	$ 186	$ 124	$ 164	$ 106	$ 148	$ 67	$ 202	551	523	477
CMS Energy [Member]
Other operating expense									(15)	(9)	(6)
Total operating expenses									(15)	(9)	(6)
Operating Loss									(15)	(9)	(6)
Equity earnings of subsidiaries									660	625	585
Interest income									1	1	1
Other expense									(19)	(9)	(20)
Total other income									642	617	566
Interest on long-term debt									150	134	150
Intercompany interest expense and other									1	3	2
Total interest charges									151	137	152
Income Before Income Taxes									476	471	408
Income Tax Expense									(75)	(52)	(69)
Net income attributable to CMS Energy									$ 551	$ 523	$ 477