Consolidated Statements Of Cash Flows - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Cash Flows from Operating Activities
Net Income	$ 292	$ 289
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization	459	414
Deferred income taxes and investment tax credit	132	127
Other non-cash operating activities and reconciling adjustments	47	33
Cash provided by (used in) changes in assets and liabilities
Decrease (increase) in accounts and notes receivable and accrued revenue	154	97
Decrease (increase) in inventories	44	198
Increase (decrease) in accounts payable and accrued refunds	37	(21)
Other current and non-current assets and liabilities	(46)	(36)
Net cash provided by operating activities	1,119	1,101
Cash Flows from Investing Activities
Capital expenditures (excludes assets placed under capital lease)	(746)	(817)
Decrease (increase) in EnerBank notes receivable	(25)	(43)
Proceeds from the sale of EnerBank notes receivable	19
Cost to retire property and other investing activities	(54)	(51)
Net cash used in investing activities	(806)	(911)
Cash Flows from Financing Activities
Proceeds from issuance of debt	923	329
Issuance of common stock	76	66
Net increase (decrease) in EnerBank certificates of deposit	(27)	12
Payment of dividends on common and preferred stock	(188)	(173)
Retirement of long-term debt	(488)	(42)
Decrease in notes payable	(398)	(249)
Payment of capital lease obligations and other financing costs	(27)	(15)
Net cash used in financing activities	(129)	(72)
Net Increase in Cash and Cash Equivalents, Including Restricted Amounts	184	118
Cash and Cash Equivalents, Including Restricted Amounts, Beginning of Period	257	288
Cash and Cash Equivalents, Including Restricted Amounts, End of Period	441	406
Non-cash transactions
Capital expenditures not paid	146	178
Note receivable recorded for future refund of use taxes paid and capitalized		29
Consumers Energy Company [Member]
Cash Flows from Operating Activities
Net Income	315	304
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization	455	410
Deferred income taxes and investment tax credit	157	130
Other non-cash operating activities and reconciling adjustments	44	27
Cash provided by (used in) changes in assets and liabilities
Decrease (increase) in accounts and notes receivable and accrued revenue	158	119
Decrease (increase) in inventories	43	197
Increase (decrease) in accounts payable and accrued refunds	38	(15)
Other current and non-current assets and liabilities	(85)	(40)
Net cash provided by operating activities	1,125	1,132
Cash Flows from Investing Activities
Capital expenditures (excludes assets placed under capital lease)	(741)	(813)
Cost to retire property and other investing activities	(61)	(52)
Net cash used in investing activities	(802)	(865)
Cash Flows from Financing Activities
Proceeds from issuance of debt	349
Stockholder contribution	450	275
Payment of dividends on common and preferred stock	(237)	(214)
Retirement of long-term debt	(263)	(12)
Decrease in notes payable	(398)	(249)
Payment of capital lease obligations and other financing costs	(12)	(1)
Net cash used in financing activities	(111)	(201)
Net Increase in Cash and Cash Equivalents, Including Restricted Amounts	212	66
Cash and Cash Equivalents, Including Restricted Amounts, Beginning of Period	152	71
Cash and Cash Equivalents, Including Restricted Amounts, End of Period	364	137
Non-cash transactions
Capital expenditures not paid	$ 133	162
Note receivable recorded for future refund of use taxes paid and capitalized		$ 29