Consolidated Statements Of Cash Flows (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Cash Flows from Operating Activities
Net income	$ 202	$ 204
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization	222	199
Deferred income taxes and investment tax credit	99	102
Postretirement benefits expense	23	6
Other non-cash operating activities	19	19
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	(48)	(313)
Decrease (increase) in inventories	378	345
Increase (decrease) in accounts payable and accrued refunds	(36)	105
Other current and non-current assets and liabilities	(68)	(54)
Net cash provided by operating activities	760	611
Cash Flows from Investing Activities
Capital expenditures (excludes assets placed under capital lease)	(348)	(304)
Cost to retire property	(10)	(14)
Increase in EnerBank notes receivable	(29)	(29)
Other investing activities	(35)	1
Net cash used in investing activities	(422)	(346)
Cash Flows from Financing Activities
Proceeds from issuance of debt	100	550
Proceeds from EnerBank notes, net	40	16
Issuance of common stock	4	33
Retirement of long-term debt	(11)	(26)
Payment of dividends on common stock	(80)	(72)
Payment of capital lease obligations and other financing costs	(16)	(10)
Increase (decrease) in notes payable	(60)	(170)
Net cash provided by (used in) financing activities	(23)	321
Net Increase (Decrease) in Cash and Cash Equivalents	315	586
Cash and Cash Equivalents, Beginning of Period	207	172
Cash and Cash Equivalents, End of Period	522	758
Non-Cash Transactions
Capital expenditures not paid	117	116
Consumers Energy Company [Member]
Cash Flows from Operating Activities
Net income	215	221
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization	220	197
Deferred income taxes and investment tax credit	39	46
Postretirement benefits expense	23	6
Other non-cash operating activities	17	16
Postretirement benefits contributions	(30)	(1)
Cash provided by (used in) changes in assets and liabilities
Decrease (increase) in accounts receivable, notes receivable, and accrued revenue	(43)	(303)
Decrease (increase) in inventories	374	338
Increase (decrease) in accounts payable and accrued refunds	(32)	108
Other current and non-current assets and liabilities	3	18
Net cash provided by operating activities	786	646
Cash Flows from Investing Activities
Capital expenditures (excludes assets placed under capital lease)	(345)	(302)
Cost to retire property	(10)	(14)
Other investing activities	(28)	1
Net cash used in investing activities	(383)	(315)
Cash Flows from Financing Activities
Retirement of long-term debt	(11)	(11)
Payment of dividends on common stock	(122)	(135)
Stockholder contribution	150	150
Payment of capital lease obligations and other financing costs	(6)	(5)
Increase (decrease) in notes payable	(60)	(170)
Net cash provided by (used in) financing activities	(49)	(171)
Net Increase (Decrease) in Cash and Cash Equivalents	354	160
Cash and Cash Equivalents, Beginning of Period	71	18
Cash and Cash Equivalents, End of Period	425	178
Non-Cash Transactions
Capital expenditures not paid	$ 117	$ 116