Consolidated Statements Of Cash Flows - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Cash Flows from Operating Activities
Net income	$ 270	$ 288
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization	391	350
Deferred income taxes and investment tax credit	135	137
Postretirement benefits expense	45	11
Other non-cash operating activities	39	38
Postretirement benefits contributions	(33)	(4)
Cash provided by (used in) changes in assets and liabilities
Decrease (increase) in accounts receivable, notes receivable, and accrued revenue	194	(14)
Decrease (increase) in inventories	235	108
Increase (decrease) in accounts payable and accrued refunds	(35)	2
Other current and non-current assets and liabilities	21	21
Net cash provided by operating activities	1,262	937
Cash Flows from Investing Activities
Capital expenditures (excludes assets placed under capital lease)	(675)	(663)
Cost to retire property	(26)	(36)
Increase in EnerBank notes receivable	(99)	(86)
Proceeds from the sale of EnerBank notes receivable	48
Other investing activities	(30)	2
Net cash used in investing activities	(782)	(783)
Cash Flows from Financing Activities
Proceeds from issuance of debt	100	550
Proceeds from EnerBank notes, net	39	78
Issuance of common stock	27	37
Retirement of long-term debt	(137)	(301)
Payment of dividends on common and preferred stock	(161)	(146)
Increase (decrease) in notes payable	(60)	(170)
Payment of capital lease obligations and other financing costs	(18)	(16)
Net cash provided by (used in) financing activities	(210)	32
Net Increase (Decrease) in Cash and Cash Equivalents	270	186
Cash and Cash Equivalents, Beginning of Period	207	172
Cash and Cash Equivalents, End of Period	477	358
Non-Cash Transactions
Capital expenditures not paid	148	170
Consumers Energy Company [Member]
Cash Flows from Operating Activities
Net income	299	330
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization	388	346
Deferred income taxes and investment tax credit	24	66
Postretirement benefits expense	45	12
Other non-cash operating activities	33	32
Postretirement benefits contributions	(31)	(2)
Cash provided by (used in) changes in assets and liabilities
Decrease (increase) in accounts receivable, notes receivable, and accrued revenue	195	(6)
Decrease (increase) in inventories	233	101
Increase (decrease) in accounts payable and accrued refunds	(34)	10
Other current and non-current assets and liabilities	99	27
Net cash provided by operating activities	1,251	916
Cash Flows from Investing Activities
Capital expenditures (excludes assets placed under capital lease)	(667)	(660)
Cost to retire property	(26)	(36)
Other investing activities	(21)	2
Net cash used in investing activities	(714)	(694)
Cash Flows from Financing Activities
Retirement of long-term debt	(37)	(21)
Payment of dividends on common and preferred stock	(255)	(256)
Stockholder contribution	150	315
Increase (decrease) in notes payable	(60)	(170)
Payment of capital lease obligations and other financing costs	(9)	(10)
Net cash provided by (used in) financing activities	(211)	(142)
Net Increase (Decrease) in Cash and Cash Equivalents	326	80
Cash and Cash Equivalents, Beginning of Period	71	18
Cash and Cash Equivalents, End of Period	397	98
Non-Cash Transactions
Capital expenditures not paid	$ 148	$ 170