Income Taxes (Schedule of Effective Income Rate Reconciliation) (Details) - USD ($) $ in Millions	1 Months Ended		9 Months Ended
	Jun. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Income Taxes [Line Items]
U.S. federal income tax rate			21.00%	21.00%
Increase (decrease) in income taxes from:
State and local income taxes, net of federal effect			7.20%	5.40%
Renewable energy tax credits			(5.70%)	(6.30%)
TCJA excess deferred taxes			(3.50%)	(3.80%)
Deferred tax adjustment			0.00%	(1.90%)
Taxes attributable to noncontrolling interests			1.20%	1.10%
Other, net			0.10%	(0.20%)
Effective tax rate			20.30%	15.30%
Consumers Energy Company
Income Taxes [Line Items]
U.S. federal income tax rate			21.00%	21.00%
Increase (decrease) in income taxes from:
State and local income taxes, net of federal effect			6.50%	5.00%
Renewable energy tax credits			(3.60%)	(4.40%)
TCJA excess deferred taxes			(3.00%)	(3.50%)
Deferred tax adjustment			0.00%	(1.80%)
Other, net			(0.20%)	(0.20%)
Effective tax rate			20.70%	16.10%
Change in tax policy	$ 12
Consumers Energy Company | Tax Year 2018 And 2019
Increase (decrease) in income taxes from:
Income tax benefit from statutory time limit expiration		$ 16