Consolidated Statements Of Cash Flows - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Cash Flows from Operating Activities
Net income	$ 289	$ 270
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization	414	391
Deferred income taxes and investment tax credit	127	135
Other non-cash operating activities	33	84
Cash provided by (used in) changes in assets and liabilities
Decrease (increase) in accounts receivable, notes receivable, and accrued revenue	97	194
Decrease (increase) in inventories	198	235
Increase (decrease) in accounts payable and accrued refunds	(21)	(35)
Other current and non-current assets and liabilities	(36)	(12)
Net cash provided by operating activities	1,101	1,262
Cash Flows from Investing Activities
Capital expenditures (excludes assets placed under capital lease)	(817)	(675)
Increase in EnerBank notes receivable	(43)	(99)
Proceeds from the sale of EnerBank notes receivable		48
Cost to retire property and other investing activities	(50)	(56)
Net cash used in investing activities	(910)	(782)
Cash Flows from Financing Activities
Proceeds from issuance of debt	329	100
Proceeds from EnerBank certificates of deposit, net	12	39
Issuance of common stock	66	27
Retirement of long-term debt	(42)	(137)
Payment of dividends on common and preferred stock	(173)	(161)
Decrease in notes payable	(249)	(60)
Payment of capital lease obligations and other financing costs	(15)	(18)
Net cash used in financing activities	(72)	(210)
Net Increase in Cash and Cash Equivalents	119	270
Cash and Cash Equivalents, Beginning of Period	266	207
Cash and Cash Equivalents, End of Period	385	477
Non-Cash Transactions
Capital expenditures not paid	178	148
Refund of capitalized sales and use tax not received	29
Consumers Energy Company [Member]
Cash Flows from Operating Activities
Net income	304	299
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization	410	388
Deferred income taxes and investment tax credit	130	24
Other non-cash operating activities	27	78
Cash provided by (used in) changes in assets and liabilities
Decrease (increase) in accounts receivable, notes receivable, and accrued revenue	119	195
Decrease (increase) in inventories	197	233
Increase (decrease) in accounts payable and accrued refunds	(15)	(34)
Other current and non-current assets and liabilities	(40)	68
Net cash provided by operating activities	1,132	1,251
Cash Flows from Investing Activities
Capital expenditures (excludes assets placed under capital lease)	(813)	(667)
Cost to retire property and other investing activities	(51)	(47)
Net cash used in investing activities	(864)	(714)
Cash Flows from Financing Activities
Retirement of long-term debt	(12)	(37)
Payment of dividends on common and preferred stock	(214)	(255)
Stockholder contribution	275	150
Decrease in notes payable	(249)	(60)
Payment of capital lease obligations and other financing costs	(1)	(9)
Net cash used in financing activities	(201)	(211)
Net Increase in Cash and Cash Equivalents	67	326
Cash and Cash Equivalents, Beginning of Period	50	71
Cash and Cash Equivalents, End of Period	117	397
Non-Cash Transactions
Capital expenditures not paid	162	$ 148
Refund of capitalized sales and use tax not received	$ 29