Leases and Palisades Financing - Palisades Financing (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($) MW	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2007
Other Commitments [Line Items]
Non‑current lease liabilities	$ 11,951	$ 10,615
Finance Obligation
2020	1,111
2021	538
2022	1,354
Total minimum payments	13,188	11,683
Less discount	(27)	(21)
Current lease liabilities	1,111	974
Consumers Energy Company
Other Commitments [Line Items]
Non‑current lease liabilities	7,048	6,779
Finance Obligation
2020	202
2021	27
2022	653
Total minimum payments	7,322	6,862
Less discount	23	16
Current lease liabilities	$ 202	26
Financing Obligation | Consumers Energy Company | Palisades Power Purchase Agreement
Other Commitments [Line Items]
Finance obligation term				15 years
Annual average capacity (in MW) | MW	798
Amortization and interest expense	$ 15	$ 16	$ 17
Right-of-use assets	29
Non‑current lease liabilities	16
Finance Obligation
2020	14
2021	14
2022	3
Total minimum payments	31
Less discount	2
Financing obligation	29
Current lease liabilities	13
Transfers Accounted for as Secured Borrowings, Associated Liabilities, Carrying Amount	$ 29