Schedule I - Condensed Financial Information of Registrant (Condensed Balance Sheets) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Current Assets
Notes and accrued interest receivable	$ 223	$ 233
Accounts receivable – intercompany and related parties	17	14
Prepayments and other current assets	86	101
Total current assets	2,331	2,468
Other Non‑current Assets
Other	739	478
Total other non‑current assets	5,580	3,935
Total Assets	26,837	24,529	$ 23,050
Current Liabilities
Accounts and notes payable – intercompany	13	10
Accrued interest, including intercompany	104	94
Accrued taxes	437	398
Other current liabilities	186	147
Total current liabilities	2,704	2,624
Non‑current Liabilities
Long-term debt	11,951	10,615
Postretirement benefits	674	436
Other non‑current liabilities	383	294
Total non‑current liabilities	19,078	17,113
Equity
Common stockholders’ equity	5,018	4,755
Total Liabilities and Equity	26,837	24,529
CMS Energy
Current Assets
Notes and accrued interest receivable	2	2
Accounts receivable – intercompany and related parties	9	7
Federal income tax receivable	18	44
Accrued taxes	0	26
Prepayments and other current assets	1	1
Total current assets	30	80
Other Non‑current Assets
Deferred income taxes	126	180
Investments in subsidiaries	8,526	7,706
Other investments	4	3
Other	16	10
Total other non‑current assets	8,672	7,899
Total Assets	8,702	7,979
Current Liabilities
Current portion of long-term debt	0	180
Accounts and notes payable – intercompany	123	113
Accrued interest, including intercompany	34	32
Accrued taxes	5	0
Other current liabilities	38	7
Total current liabilities	200	332
Non‑current Liabilities
Long-term debt	3,334	2,750
Notes payable – intercompany	112	116
Postretirement benefits	21	17
Other non‑current liabilities	17	9
Total non‑current liabilities	3,484	2,892
Equity
Total Liabilities and Equity	$ 8,702	$ 7,979