Consolidated Statements Of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Cash Flows from Operating Activities
Net income	$ 199	$ 164
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization	262	238
Deferred income taxes and investment tax credit	90	68
Other non-cash operating activities and reconciling adjustments	21	21
Cash provided by (used in) changes in assets and liabilities
Decrease (increase) in accounts and notes receivable and accrued revenue	37	16
Decrease (increase) in inventories	201	274
Increase (decrease) in accounts payable and accrued refunds	(40)	(48)
Other current and non-current assets and liabilities	(124)	(101)
Net cash provided by operating activities	646	632
Cash Flows from Investing Activities
Capital expenditures (excludes assets placed under capital lease)	(365)	(407)
Decrease (increase) in EnerBank notes receivable	14	(16)
Proceeds from the sale of EnerBank notes receivable	19
Cost to retire property and other investing activities	(14)	(21)
Net cash used in investing activities	(346)	(444)
Cash Flows from Financing Activities
Proceeds from issuance of debt	923	30
Issuance of common stock	3	63
Net increase (decrease) in EnerBank certificates of deposit	(29)	14
Payment of dividends on common stock	(94)	(86)
Retirement of long-term debt	(475)	(30)
Decrease in notes payable	(398)	(249)
Payment of capital lease obligations and other financing costs	(24)	(12)
Net cash used in financing activities	(94)	(270)
Net Increase (Decrease) in Cash and Cash Equivalents, Including Restricted Amounts	206	(82)
Cash and Cash Equivalents, Including Restricted Amounts, Beginning of Period	257	288
Cash and Cash Equivalents, Including Restricted Amounts, End of Period	463	206
Non-cash transactions
Capital expenditures not paid	112	173
Consumers Energy Company [Member]
Cash Flows from Operating Activities
Net income	211	172
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization	260	237
Deferred income taxes and investment tax credit	69	62
Other non-cash operating activities and reconciling adjustments	22	17
Cash provided by (used in) changes in assets and liabilities
Decrease (increase) in accounts and notes receivable and accrued revenue	43	33
Decrease (increase) in inventories	197	270
Increase (decrease) in accounts payable and accrued refunds	(38)	(42)
Other current and non-current assets and liabilities	(116)	(84)
Net cash provided by operating activities	648	665
Cash Flows from Investing Activities
Capital expenditures (excludes assets placed under capital lease)	(361)	(406)
Cost to retire property and other investing activities	(21)	(19)
Net cash used in investing activities	(382)	(425)
Cash Flows from Financing Activities
Proceeds from issuance of debt	349
Stockholder contribution	250	150
Payment of dividends on common stock	(148)	(155)
Retirement of long-term debt	(250)
Decrease in notes payable	(398)	(249)
Payment of capital lease obligations and other financing costs	(9)	(1)
Net cash used in financing activities	(206)	(255)
Net Increase (Decrease) in Cash and Cash Equivalents, Including Restricted Amounts	60	(15)
Cash and Cash Equivalents, Including Restricted Amounts, Beginning of Period	152	71
Cash and Cash Equivalents, Including Restricted Amounts, End of Period	212	56
Non-cash transactions
Capital expenditures not paid	$ 101	$ 154