Plant, Property, and Equipment (Schedule of Finance Leases and Other Financing Obligations) (Details) - Consumers Energy Company - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Finance Leases and Other Financing Obligations, Rollforward [Roll Forward]
Balance at beginning of period	$ 309	$ 312
Additions	26	0
Net retirements and other adjustments	5	(3)
Balance at end of period	340	309
Less accumulated depreciation and amortization	$ 239	$ 212