Consolidated Statements Of Cash Flows - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Cash Flows from Operating Activities
Net income	$ 418	$ 382
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization	564	503
Deferred income taxes and investment tax credit	210	178
Postretirement benefits expense	68	17
Other non-cash operating activities	56	64
Postretirement benefits contributions	(35)	(5)
Cash provided by (used in) changes in assets and liabilities
Decrease (increase) in accounts receivable, notes receivable, and accrued revenue	219	111
Decrease (increase) in inventories	54	(161)
Increase (decrease) in accounts payable and accrued refunds	(34)	(14)
Other current and non-current assets and liabilities	(100)	(113)
Net cash provided by operating activities	1,420	962
Cash Flows from Investing Activities
Capital expenditures (excludes assets placed under capital lease)	(1,102)	(1,125)
Cost to retire property	(60)	(62)
Increase in EnerBank notes receivable	(186)	(164)
Sale of notes receivable	48
Other investing activities	(40)	4
Net cash used in investing activities	(1,340)	(1,347)
Cash Flows from Financing Activities
Proceeds from issuance of debt	100	1,428
Net increase in EnerBank certificates of deposit	135	147
Issuance of common stock	40	40
Retirement of long-term debt	(148)	(488)
Payment of dividends on common and preferred stock	(241)	(220)
Increase (decrease) in notes payable	8	(170)
Payment of capital lease obligations and other financing costs	(31)	(31)
Net cash provided by (used in) financing activities	(137)	706
Net Increase (Decrease) in Cash and Cash Equivalents	(57)	321
Cash and Cash Equivalents, Beginning of Period	207	172
Cash and Cash Equivalents, End of Period	150	493
Non-Cash Transactions
Capital expenditures not paid	147	168
Consumers Energy Company [Member]
Cash Flows from Operating Activities
Net income	459	449
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization	560	498
Deferred income taxes and investment tax credit	33	64
Postretirement benefits expense	68	18
Other non-cash operating activities	48	54
Postretirement benefits contributions	(33)	(3)
Cash provided by (used in) changes in assets and liabilities
Decrease (increase) in accounts receivable, notes receivable, and accrued revenue	221	120
Decrease (increase) in inventories	53	(163)
Increase (decrease) in accounts payable and accrued refunds	(30)	(6)
Other current and non-current assets and liabilities	48	(83)
Net cash provided by operating activities	1,427	948
Cash Flows from Investing Activities
Capital expenditures (excludes assets placed under capital lease)	(1,093)	(1,123)
Cost to retire property	(60)	(62)
Other investing activities	(33)	3
Net cash used in investing activities	(1,186)	(1,182)
Cash Flows from Financing Activities
Proceeds from issuance of debt		878
Retirement of long-term debt	(48)	(208)
Payment of dividends on common and preferred stock	(360)	(376)
Stockholder contribution	150	495
Return of stockholder contribution		(178)
Increase (decrease) in notes payable	8	(170)
Payment of capital lease obligations and other financing costs	(19)	(25)
Net cash provided by (used in) financing activities	(269)	416
Net Increase (Decrease) in Cash and Cash Equivalents	(28)	182
Cash and Cash Equivalents, Beginning of Period	71	18
Cash and Cash Equivalents, End of Period	43	200
Non-Cash Transactions
Capital expenditures not paid	$ 147	$ 168