Schedule I - Condensed Financial Information of Registrant (Condensed Balance Sheets) (Details) - USD ($) $ in Millions		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Notes and accrued interest receivable		$ 180	$ 128
Accounts receivable, including intercompany and related parties		12	11
Prepayments and other current assets		81	77
Total current assets		2,280	2,320
Less accumulated depreciation and amortization		6,056	5,747
Total plant, property, and equipment	[1]	15,715	14,705
Other		353	343
Total other non-current assets		3,627	3,274
Total Assets		21,622	20,299	$ 19,143
Current portion of long-term debt		886	706
Accounts and notes payable, including intercompany and related parties		12	9
Accrued interest, including intercompany		98	106
Accrued taxes		348	349
Other liabilities current		199	142
Total current liabilities		2,655	2,302
Long-term debt		8,640	8,400
Net unamortized discounts		(15)	(12)
Postretirement benefits		789	591
Other non-current liabilities		290	313
Total non-current liabilities		14,677	14,022
Common stockholders' equity		4,253	3,938
Total Liabilities and Equity		21,622	20,299
CMS Energy [Member]
Notes and accrued interest receivable		2	88
Accounts receivable, including intercompany and related parties		7	9
Accrued taxes		51
Prepayments and other current assets		1
Total current assets		61	97
Plant, property, and equipment, gross			16
Less accumulated depreciation and amortization			16
Total plant, property, and equipment
Noncurrent notes receivable		3
Deferred income taxes		366	340
Invetment in subsidiaries		6,674	6,240
Other investments - DB SERP		26	26
Other		4	5
Total other non-current assets		7,073	6,611
Total Assets		7,134	6,708
Accounts and notes payable, including intercompany and related parties		141	74
Accrued interest, including intercompany		28	38
Accrued taxes			23
Other liabilities current		10	5
Total current liabilities		179	140
Long-term debt		2,678	2,605
Postretirement benefits		21	22
Other non-current liabilities		3	3
Total non-current liabilities		2,702	2,630
Common stockholders' equity		4,253	3,938
Total Liabilities and Equity		$ 7,134	$ 6,708

[1] For the year ended December 31, 2016, Consumers' plant additions were $2.3 billion and plant retirements were $285 million. For the year ended December 31, 2015, Consumers' plant additions were $1.4 billion and plant retirements were $187 million.