Consolidated Statements Of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash Flows from Operating Activities
Net Income	$ 241	$ 199
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization	279	262
Deferred income taxes and investment tax credit	37	90
Other non-cash operating activities and reconciling adjustments	10	21
Cash provided by (used in) changes in assets and liabilities
Decrease (increase) in accounts and notes receivable and accrued revenue	7	37
Decrease (increase) in inventories	228	201
Increase (decrease) in accounts payable and accrued refunds	(92)	(40)
Other current and non-current assets and liabilities	(2)	(124)
Net cash provided by operating activities	708	646
Cash Flows from Investing Activities
Capital expenditures (excludes assets placed under capital lease)	(422)	(365)
Decrease (increase) in EnerBank notes receivable	(5)	14
Proceeds from the sale of EnerBank notes receivable		19
Cost to retire property and other investing activities	(29)	(14)
Net cash used in investing activities	(456)	(346)
Cash Flows from Financing Activities
Proceeds from issuance of debt	250	923
Decrease in EnerBank certificates of deposit	(9)	(29)
Issuance of common stock	3	3
Retirement of debt	(180)	(475)
Payment of dividends on common stock	(101)	(94)
Decrease in notes payable	(170)	(398)
Payment of capital lease obligations and other financing costs	(22)	(24)
Net cash used in financing activities	(229)	(94)
Net Increase in Cash and Cash Equivalents, Including Restricted Amounts	23	206
Cash and Cash Equivalents, Including Restricted Amounts, Beginning of Period	204	257
Cash and Cash Equivalents, Including Restricted Amounts, End of Period	227	463
Non-cash transactions
Capital expenditures not paid	102	112
Consumers Energy Company [Member]
Cash Flows from Operating Activities
Net Income	242	211
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization	277	260
Deferred income taxes and investment tax credit	3	69
Other non-cash operating activities and reconciling adjustments	7	22
Cash provided by (used in) changes in assets and liabilities
Decrease (increase) in accounts and notes receivable and accrued revenue	5	43
Decrease (increase) in inventories	226	197
Increase (decrease) in accounts payable and accrued refunds	(88)	(38)
Other current and non-current assets and liabilities	48	(116)
Net cash provided by operating activities	720	648
Cash Flows from Investing Activities
Capital expenditures (excludes assets placed under capital lease)	(414)	(361)
Cost to retire property and other investing activities	(30)	(21)
Net cash used in investing activities	(444)	(382)
Cash Flows from Financing Activities
Proceeds from issuance of debt		349
Retirement of debt		(250)
Payment of dividends on common stock	(119)	(148)
Stockholder contribution	100	250
Decrease in notes payable	(170)	(398)
Payment of capital lease obligations and other financing costs	(6)	(9)
Net cash used in financing activities	(195)	(206)
Net Increase in Cash and Cash Equivalents, Including Restricted Amounts	81	60
Cash and Cash Equivalents, Including Restricted Amounts, Beginning of Period	65	152
Cash and Cash Equivalents, Including Restricted Amounts, End of Period	146	212
Non-cash transactions
Capital expenditures not paid	$ 90	$ 101