Consolidated Statements Of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash Flows from Operating Activities
Net Income	$ 659	$ 462	$ 553
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization	933	881	811
Deferred income taxes and investment tax credit	182	417	264
Bad debt expense	54	49	50
Other non-cash operating activities and reconciling adjustments	22	82	52
Postretirement benefits contributions	(252)	(12)	(108)
Cash provided by (used in) changes in assets and liabilities
Accounts and notes receivable and accrued revenue	15	(66)	(155)
Inventories	14	(46)	146
Accounts payable and accrued rate refunds	22	49	59
Other current and non-current assets and liabilities	54	(111)	(43)
Net cash provided by operating activities	1,703	1,705	1,629
Cash Flows from Investing Activities
Capital expenditures (excludes assets placed under capital lease)	(2,074)	(1,665)	(1,672)
Increase in EnerBank notes receivable	(307)	(138)	(136)
Purchase of notes receivable by EnerBank	(225)	0	0
Proceeds from DB SERP investments	146	0	0
Proceeds from the sale of EnerBank notes receivable	0	50	0
Cost to retire property and other investing activities	(146)	(115)	(107)
Net cash used in investing activities	(2,606)	(1,868)	(1,915)
Cash Flows from Financing Activities
Proceeds from issuance of debt	2,767	1,633	1,049
Retirement of debt	(1,870)	(980)	(728)
Increase in EnerBank certificates of deposit	513	47	100
Increase (decrease) in notes payable	(73)	(228)
Increase (decrease) in notes payable			149
Issuance of common stock	41	83	72
Payment of dividends on common and preferred stock	(407)	(377)	(347)
Debt prepayment costs	(36)	(22)	(18)
Payment of capital lease obligations and other financing costs	(61)	(46)	(22)
Net cash provided by financing activities	874	110	255
Net Decrease in Cash and Cash Equivalents, Including Restricted Amounts	(29)	(53)	(31)
Cash and Cash Equivalents, Including Restricted Amounts, Beginning of Period	204	257	288
Cash and Cash Equivalents, Including Restricted Amounts, End of Period	175	204	257
Cash transactions
Interest paid (net of amounts capitalized)	458	418	427
Income taxes paid (refunds received), net	(123)	5	32
Non-cash transactions
Capital expenditures not paid	158	172	138
Note receivable recorded for future refund of use taxes paid and capitalized	0	0	29
Other assets placed under capital lease	0	3	13
Consumers Energy Company
Cash Flows from Operating Activities
Net Income	705	632	616
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization	921	872	803
Deferred income taxes and investment tax credit	123	163	289
Bad debt expense		29	31
Other non-cash operating activities and reconciling adjustments	13	59	25
Postretirement benefits contributions	(242)	(8)	(98)
Cash provided by (used in) changes in assets and liabilities
Accounts and notes receivable and accrued revenue	(26)	(63)	(138)
Inventories	15	(45)	145
Accounts payable and accrued rate refunds	12	43	57
Other current and non-current assets and liabilities	(101)	33	(49)
Net cash provided by operating activities	1,449	1,715	1,681
Cash Flows from Investing Activities
Capital expenditures (excludes assets placed under capital lease)	(1,822)	(1,632)	(1,656)
DB SERP investment in note receivable – related party	(106)	0	0
Proceeds from DB SERP investments	106	0	0
Cost to retire property and other investing activities	(149)	(119)	(112)
Net cash used in investing activities	(1,971)	(1,751)	(1,768)
Cash Flows from Financing Activities
Proceeds from issuance of debt	2,106	834	446
Retirement of debt	(1,193)	(555)	(198)
Increase (decrease) in notes payable	(73)	(228)
Increase (decrease) in notes payable			149
Stockholder contribution	250	450	275
Payment of dividends on common and preferred stock	(533)	(524)	(501)
Debt prepayment costs	(20)	(4)	0
Payment of capital lease obligations and other financing costs	(24)	(24)	(3)
Net cash provided by financing activities	513	(51)	168
Net Decrease in Cash and Cash Equivalents, Including Restricted Amounts	(9)	(87)	81
Cash and Cash Equivalents, Including Restricted Amounts, Beginning of Period	65	152	71
Cash and Cash Equivalents, Including Restricted Amounts, End of Period	56	65	152
Cash transactions
Interest paid (net of amounts capitalized)	287	266	256
Income taxes paid (refunds received), net	156	(1)	50
Non-cash transactions
Capital expenditures not paid	143	160	127
Note receivable recorded for future refund of use taxes paid and capitalized	0	0	29
Other assets placed under capital lease	$ 0	$ 3	$ 13