Consolidated Statements Of Cash Flows - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Cash Flows from Operating Activities
Net Income	$ 464	$ 475
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization	652	597
Deferred income taxes and investment tax credit	198	219
Other non-cash operating activities and reconciling adjustments	78	54
Cash provided by (used in) changes in assets and liabilities
Decrease (increase) in accounts and notes receivable and accrued revenue	185	51
Decrease (increase) in inventories	(161)	35
Increase (decrease) in accounts payable and accrued refunds	(6)	(24)
Other current and non-current assets and liabilities	(211)	(166)
Net cash provided by operating activities	1,199	1,241
Cash Flows from Investing Activities
Capital expenditures (excludes assets placed under capital lease)	(1,208)	(1,224)
Decrease (increase) in EnerBank notes receivable	(87)	(87)
Proceeds from the sale of EnerBank notes receivable	19
Cost to retire property and other investing activities	(78)	(87)
Net cash used in investing activities	(1,354)	(1,398)
Cash Flows from Financing Activities
Proceeds from issuance of debt	1,108	775
Issuance of common stock	80	69
Net increase (decrease) in EnerBank certificates of deposit	40	64
Payment of dividends on common and preferred stock	(282)	(260)
Retirement of long-term debt	(668)	(215)
Decrease in notes payable	(168)	(174)
Payment of capital lease obligations and other financing costs	(39)	(22)
Net cash provided by (used in) financing activities	71	237
Net Increase (Decrease) in Cash and Cash Equivalents, Including Restricted Amounts	(84)	80
Cash and Cash Equivalents, Including Restricted Amounts, Beginning of Period	257	288
Cash and Cash Equivalents, Including Restricted Amounts, End of Period	173	368
Non-cash transactions
Capital expenditures not paid	153	159
Note receivable recorded for future refund of use taxes paid and capitalized		29
Consumers Energy Company [Member]
Cash Flows from Operating Activities
Net Income	496	499
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization	646	592
Deferred income taxes and investment tax credit	204	220
Other non-cash operating activities and reconciling adjustments	71	45
Cash provided by (used in) changes in assets and liabilities
Decrease (increase) in accounts and notes receivable and accrued revenue	184	72
Decrease (increase) in inventories	(161)	35
Increase (decrease) in accounts payable and accrued refunds	(10)	(31)
Other current and non-current assets and liabilities	(221)	(144)
Net cash provided by operating activities	1,209	1,288
Cash Flows from Investing Activities
Capital expenditures (excludes assets placed under capital lease)	(1,196)	(1,214)
Cost to retire property and other investing activities	(82)	(87)
Net cash used in investing activities	(1,278)	(1,301)
Cash Flows from Financing Activities
Proceeds from issuance of debt	534	446
Stockholder contribution	450	275
Payment of dividends on common and preferred stock	(348)	(362)
Retirement of long-term debt	(443)	(185)
Decrease in notes payable	(168)	(174)
Payment of capital lease obligations and other financing costs	(23)	(8)
Net cash provided by (used in) financing activities	2	(8)
Net Increase (Decrease) in Cash and Cash Equivalents, Including Restricted Amounts	(67)	(21)
Cash and Cash Equivalents, Including Restricted Amounts, Beginning of Period	152	71
Cash and Cash Equivalents, Including Restricted Amounts, End of Period	85	50
Non-cash transactions
Capital expenditures not paid	$ 140	145
Note receivable recorded for future refund of use taxes paid and capitalized		$ 29