Income Taxes (Schedule Of Effective Income Tax Rate Reconciliation) (Details) - USD ($) $ in Millions	1 Months Ended	6 Months Ended
	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
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		5.40%	5.60%
TCJA excess deferred taxes		(3.50%)	(3.40%)
Production tax credits		(2.50%)	(1.70%)
Accelerated flow-through of regulatory tax benefits		(1.50%)	(5.00%)
Research and development tax credits, net		(0.20%)	(2.20%)
Other, net		(0.60%)	0.30%
Effective tax rate		18.10%	14.60%
Regulatory liabilities, noncurrent		$ 3,786		$ 3,681
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		5.70%	5.80%
TCJA excess deferred taxes		(3.20%)	(3.20%)
Production tax credits		(1.30%)	(1.50%)
Accelerated flow-through of regulatory tax benefits		(1.80%)	(4.70%)
Research and development tax credits, net		(0.20%)	(2.10%)
Other, net		(0.40%)	0.00%
Effective tax rate		19.80%	15.30%
Reduction of income tax expense		$ 7	$ 22
Regulatory liabilities, noncurrent		3,786		$ 3,681
Research Tax Credit Carryforward | Consumers Energy Company
Increase (decrease) in income taxes from:
Increase in credit	$ 8
Plant, Property, And Equipment (Subject To Normalization) | Consumers Energy Company
Increase (decrease) in income taxes from:
Regulatory liabilities					$ 1,800
TCJA Reserve For Refund | Consumers Energy Company
Increase (decrease) in income taxes from:
Regulatory liabilities, noncurrent		$ 53