Consumers Energy (CMS-PB) 10-Q 25 Oct 18 2018 Q3 Quarterly report Financial data

Document And Entity Information

Document And Entity Information - shares	9 Months Ended
	Sep. 30, 2018	Oct. 09, 2018
Document Information [Line Items]
Entity Registrant Name	CMS Energy Corporation
Trading Symbol	cms
Entity Central Index Key	811,156
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	false
Document Type	10-Q
Document Period End Date	Sep. 30, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q3
Amendment Flag	false
Entity Common Stock, Shares Outstanding		283,331,416
Consumers Energy Company
Document Information [Line Items]
Entity Registrant Name	Consumers Energy Company
Entity Central Index Key	201,533
Entity Filer Category	Non-accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Common Stock, Shares Outstanding		84,108,789

Consolidated Statements of Inco

Consolidated Statements of Income (Unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Operating Revenue	$ 1,599	$ 1,527	$ 5,044	$ 4,805
Operating Expenses
Fuel for electric generation	150	144	397	386
Purchased power – related parties	21	21	59	64
Maintenance and other operating expenses	366	304	1,002	909
Depreciation and amortization	206	193	689	652
General taxes	67	62	222	209
Total operating expenses	1,305	1,197	4,132	3,846
Operating Income	294	330	912	959
Other Income (Expense)
Interest income	2	3	8	10
Allowance for equity funds used during construction	2	1	4	5
Income (loss) from equity method investees	(1)	3	6	10
Nonoperating retirement benefits, net	22	3	68	10
Other income	1	2	2	4
Other expense	(4)	(2)	(15)	(6)
Total other income	22	10	73	33
Interest Charges
Interest on long-term debt	101	101	304	304
Other interest expense	14	10	35	26
Allowance for borrowed funds used during construction	(1)	0	(2)	(2)
Total interest charges	114	111	337	328
Income Before Income Taxes	202	229	648	664
Income Tax Expense	33	57	98	200
Net Income	169	172	550	464
Income Attributable to Noncontrolling Interests	0	0	1	1
Net Income Available to Common Stockholders	$ 169	$ 172	$ 549	$ 463
Basic earnings per average common share (in dollars per share)	$ 0.60	$ 0.61	$ 1.95	$ 1.65
Diluted earnings per average common share (in dollars per share)	0.59	0.61	1.94	1.65
Dividends declared per common share (in dollars per share)	$ 0.3575	$ 0.3325	$ 1.0725	$ 0.9975
Consumers Energy Company
Operating Revenue	$ 1,502	$ 1,437	$ 4,752	$ 4,536
Operating Expenses
Fuel for electric generation	122	115	310	304
Purchased and interchange power	440	424	1,206	1,124
Purchased power – related parties	22	23	61	67
Cost of gas sold	45	42	530	479
Maintenance and other operating expenses	334	274	914	824
Depreciation and amortization	203	191	681	646
General taxes	65	60	216	203
Total operating expenses	1,231	1,129	3,918	3,647
Operating Income	271	308	834	889
Other Income (Expense)
Interest income	2	2	6	8
Allowance for equity funds used during construction	2	1	4	5
Interest and dividend income – related parties	1	0	1	0
Nonoperating retirement benefits, net	21	3	63	8
Other income	0	1	1	15
Other expense	(4)	(2)	(9)	(6)
Total other income	22	5	66	30
Interest Charges
Interest on long-term debt	69	66	203	198
Other interest expense	5	4	14	11
Allowance for borrowed funds used during construction	(1)	0	(2)	(2)
Total interest charges	73	70	215	207
Income Before Income Taxes	220	243	685	712
Income Tax Expense	40	62	111	216
Net Income	180	181	574	496
Preferred Stock Dividends	0	0	1	1
Net Income Available to Common Stockholders	180	181	573	495
Purchased and interchange power
Operating Expenses
Cost of sales	447	426	1,222	1,132
Cost of gas sold
Operating Expenses
Cost of sales	$ 48	$ 47	$ 541	$ 494

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Net income	$ 169	$ 172	$ 550	$ 464
Retirement Benefits Liability
Amortization of net actuarial loss, net of tax of $- for all periods	1	0	3	1
Amortization of prior service credit	0	0	(1)	0
Investments
Unrealized gain (loss) on investments	0	1	(1)	2
Reclassification adjustments included in net income	1	0	1	0
Other Comprehensive Income	2	1	2	3
Comprehensive Income	171	173	552	467
Comprehensive Income Attributable to Noncontrolling Interests	0	0	1	1
Comprehensive Income Attributable to CMS Energy	171	173	551	466
Consumers Energy Company
Net income	180	181	574	496
Retirement Benefits Liability
Amortization of net actuarial loss, net of tax of $- for all periods	1	0	2	1
Investments
Unrealized gain (loss) on investments	0	0	(1)	2
Reclassification adjustments included in net income	1	0	1	(8)
Other Comprehensive Income	2	0	2	(5)
Comprehensive Income	$ 182	$ 181	$ 576	$ 491

Consolidated Statements Of Co_2

Consolidated Statements Of Comprehensive Income (Parenthetical) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Amortization of net actuarial loss TAX	$ 0	$ 1	$ 0	$ 1
Amortization of prior service credit TAX	0	0	0	0
Unrealized gain (loss) on investments TAX	0	0	0	1
Reclassification adjustments included in net income TAX	0	0	0	0
Consumers Energy Company
Amortization of net actuarial loss TAX	0	0	0	0
Unrealized gain (loss) on investments TAX	0	0	0	1
Reclassification adjustments included in net income TAX	$ 0	$ 0	$ 0	$ (5)

Consolidated Statements Of Cash

Consolidated Statements Of Cash Flows (Unaudited) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash Flows from Operating Activities
Net income	$ 550	$ 464
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization	689	652
Deferred income taxes and investment tax credit	90	198
Other non-cash operating activities and reconciling adjustments	47	78
Cash provided by (used in) changes in assets and liabilities
Accounts and notes receivable and accrued revenue	299	185
Inventories	(76)	(161)
Accounts payable and accrued refunds	(46)	(6)
Other current and non-current assets and liabilities	12	(211)
Net cash provided by operating activities	1,565	1,199
Cash Flows from Investing Activities
Capital expenditures (excludes assets placed under capital lease)	(1,572)	(1,208)
Increase in EnerBank notes receivable	(200)	(87)
Purchase of notes receivable by EnerBank	(87)	0
Proceeds from DB SERP investments	146	0
Proceeds from the sale of EnerBank notes receivable	0	19
Cost to retire property and other investing activities	(102)	(78)
Net cash used in investing activities	(1,815)	(1,354)
Cash Flows from Financing Activities
Proceeds from issuance of debt	1,044	1,108
Retirement of debt	(705)	(668)
Increase in EnerBank certificates of deposit	288	40
Increase (decrease) in notes payable	110
Increase (decrease) in notes payable		(168)
Issuance of common stock	39	80
Payment of dividends on common and preferred stock	(305)	(282)
Payment of capital lease obligations and other financing costs	(59)	(39)
Net cash provided by financing activities	412	71
Net Increase (Decrease) in Cash and Cash Equivalents, Including Restricted Amounts	162	(84)
Cash and Cash Equivalents, Including Restricted Amounts, Beginning of Period	204	257
Cash and Cash Equivalents, Including Restricted Amounts, End of Period	366	173
Non-cash transactions
Capital expenditures not paid	159	153
Consumers Energy Company
Cash Flows from Operating Activities
Net income	574	496
Adjustments to reconcile net income to net cash provided by operating activities
Deferred income taxes and investment tax credit	40	204
Other non-cash operating activities and reconciling adjustments	33	71
Cash provided by (used in) changes in assets and liabilities
Accounts and notes receivable and accrued revenue	178	184
Inventories	(75)	(161)
Accounts payable and accrued refunds	(48)	(10)
Other current and non-current assets and liabilities	(128)	(221)
Net cash provided by operating activities	1,255	1,209
Cash Flows from Investing Activities
Capital expenditures (excludes assets placed under capital lease)	(1,339)	(1,196)
Proceeds from DB SERP investments	106	0
DB SERP investment in note receivable - related party	(106)	0
Cost to retire property and other investing activities	(96)	(82)
Net cash used in investing activities	(1,435)	(1,278)
Cash Flows from Financing Activities
Proceeds from issuance of debt	544	534
Retirement of debt	(330)	(443)
Increase (decrease) in notes payable	110
Increase (decrease) in notes payable		(168)
Stockholder contribution	250	450
Payment of dividends on common and preferred stock	(393)	(348)
Payment of capital lease obligations and other financing costs	(28)	(23)
Net cash provided by financing activities	153	2
Net Increase (Decrease) in Cash and Cash Equivalents, Including Restricted Amounts	(27)	(67)
Cash and Cash Equivalents, Including Restricted Amounts, Beginning of Period	65	152
Cash and Cash Equivalents, Including Restricted Amounts, End of Period	38	85
Non-cash transactions
Capital expenditures not paid	$ 128	$ 140

Consolidated Balance Sheets (Un

Consolidated Balance Sheets (Unaudited) - USD ($) $ in Millions		Sep. 30, 2018	Dec. 31, 2017
Current Assets
Cash and cash equivalents		$ 323	$ 182
Restricted cash and cash equivalents	[1]	42	17
Accounts receivable and accrued revenue, less allowance of $20 in both periods		710	1,032
Notes receivable, less allowance of $23 in 2018 and $20 in 2017		237	198
Notes receivable held for sale		26	2
Accounts receivable – related parties		15	12
Inventories at average cost
Gas in underground storage		551	458
Materials and supplies		140	133
Generating plant fuel stock		50	81
Deferred property taxes		167	257
Regulatory assets		10	20
Prepayments and other current assets		103	83
Total current assets		2,374	2,475
Plant, Property, and Equipment
Plant, property, and equipment, gross		23,751	22,506
Less accumulated depreciation and amortization		6,909	6,510
Plant, property, and equipment, net		16,842	15,996
Construction work in progress		948	765
Total plant, property, and equipment		17,790	16,761
Other Non-current Assets
Regulatory assets		1,655	1,764
Accounts and notes receivable		1,393	1,187
Investments		72	64
Other		629	799
Total other non-current assets		3,749	3,814
Total Assets		23,913	23,050
Current Liabilities
Current portion of long-term debt, capital leases, and financing obligation		1,971	1,103
Notes payable		279	170
Accounts payable		680	725
Accounts payable – related parties		9	15
Accrued rate refunds		14	33
Accrued interest		83	103
Accrued taxes		107	360
Regulatory liabilities		165	80
Other current liabilities		134	195
Total current liabilities		3,442	2,784
Non-current Liabilities
Long-term debt		8,869	9,123
Non-current portion of capital leases and financing obligation		75	91
Regulatory liabilities		3,745	3,715
Postretirement benefits		797	766
Asset retirement obligations		421	430
Deferred investment tax credit		101	87
Deferred income taxes		1,382	1,269
Other non-current liabilities		295	307
Total non-current liabilities		15,685	15,788
Commitments and contingencies
Common stockholders’ equity
Common stock, authorized 350.0 shares; outstanding 283.3 shares in 2018 and 281.6 shares in 2017		3	3
Other paid-in capital		5,083	5,019
Accumulated other comprehensive loss		(59)	(50)
Accumulated deficit		(278)	(531)
Total common stockholders’ equity		4,749	4,441
Noncontrolling interests		37	37
Total equity		4,786	4,478
Total Liabilities and Equity		23,913	23,050
Consumers Energy Company
Current Assets
Cash and cash equivalents		9	44
Restricted cash and cash equivalents	[1]	28	17
Accounts receivable and accrued revenue, less allowance of $20 in both periods		686	885
Notes receivable, less allowance of $23 in 2018 and $20 in 2017		17	17
Accounts receivable – related parties		8	2
Inventories at average cost
Gas in underground storage		551	458
Materials and supplies		135	128
Generating plant fuel stock		44	76
Deferred property taxes		167	257
Regulatory assets		10	20
Prepayments and other current assets		90	71
Total current assets		1,745	1,975
Plant, Property, and Equipment
Plant, property, and equipment, gross		23,322	22,318
Less accumulated depreciation and amortization		6,834	6,441
Plant, property, and equipment, net		16,488	15,877
Construction work in progress		937	753
Total plant, property, and equipment		17,425	16,630
Other Non-current Assets
Regulatory assets		1,655	1,764
Accounts and notes receivable		22	22
Notes receivable – related party		100	0
Other		545	708
Total other non-current assets		2,322	2,494
Total Assets		21,492	21,099
Current Liabilities
Current portion of long-term debt, capital leases, and financing obligation		898	365
Notes payable		279	170
Accounts payable		636	701
Accounts payable – related parties		13	19
Accrued rate refunds		14	33
Accrued interest		58	67
Accrued taxes		148	542
Regulatory liabilities		165	80
Other current liabilities		96	159
Total current liabilities		2,307	2,136
Non-current Liabilities
Long-term debt		5,239	5,561
Non-current portion of capital leases and financing obligation		75	91
Regulatory liabilities		3,745	3,715
Postretirement benefits		741	711
Asset retirement obligations		417	429
Deferred investment tax credit		101	87
Deferred income taxes		1,711	1,640
Other non-current liabilities		233	241
Total non-current liabilities		12,262	12,475
Commitments and contingencies
Common stockholders’ equity
Common stock, authorized 350.0 shares; outstanding 283.3 shares in 2018 and 281.6 shares in 2017		841	841
Other paid-in capital		4,699	4,449
Accumulated other comprehensive loss		(27)	(12)
Accumulated deficit		1,373	1,173
Total common stockholders’ equity		6,886	6,451
Preferred stock		37	37
Total equity		6,923	6,488
Total Liabilities and Equity		$ 21,492	$ 21,099
[1]	1 All assets and liabilities were classified as Level 1 with the exception of some commodity contracts, which were classified as Level 3.

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Accounts receivable and accrued revenue ALLOWANCE	$ 20	$ 20
Accounts and notes receivable ALLOWANCE	$ 23	$ 20
Common Stock, Shares Authorized (in shares)	350,000,000	350,000,000
Common Stock, Shares, Outstanding	283,300,000	281,600,000
Consumers Energy Company
Accounts receivable and accrued revenue ALLOWANCE	$ 20	$ 20
Common Stock, Shares Authorized (in shares)	125,000,000	125,000,000
Common Stock, Shares, Outstanding	84,100,000	84,100,000

Consolidated Statements of Chan

Consolidated Statements of Changes In Equity (Unaudited) - USD ($) $ in Millions	Total	Common Stock	Other Paid-in Capital	Accumulated Other Comprehensive Loss	Retirement benefits liability	Investments	Accumulated Deficit	Noncontrolling Interests	Consumers Energy Company	Consumers Energy CompanyCommon Stock	Consumers Energy CompanyOther Paid-in Capital	Consumers Energy CompanyAccumulated Other Comprehensive Loss	Consumers Energy CompanyRetirement benefits liability	Consumers Energy CompanyInvestments	Consumers Energy CompanyAccumulated Deficit	Consumers Energy CompanyPreferred Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of change in accounting principle					$ 0		$ 0						$ 0	$ 0	$ 0
Total Equity at Beginning of Period at Dec. 31, 2016	$ 4,290	$ 3	$ 4,916	$ (50)	(50)	$ 0	(616)	$ 37	$ 5,939	$ 841	$ 3,999	$ (3)	(21)	18	1,065	$ 37
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued			95
Common stock repurchased			(13)
Common stock reissued			15
Stockholder contribution											450
Amortization of net actuarial loss	1				1				1				1
Amortization of prior service credit	0				0
Unrealized gain (loss) on investments	2					2			2					2
Reclassification adjustments included in net income	0					0			(8)					(8)
Net income	464						463	1	496						496
Dividends declared on common stock							(281)								(347)
Dividends declared on preferred stock															(1)
Distributions and other changes in noncontrolling interests								(1)
Total Equity at End of Period at Sep. 30, 2017	4,572	3	5,013	(47)	(49)	2	(434)	37	6,532	841	4,449	(8)	(20)	12	1,213	37
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of change in accounting principle					0		0						0	0	0
Total Equity at Beginning of Period at Jun. 30, 2017	4,486	3	5,006	(48)	(49)	1	(512)	37	6,462	841	4,449	(8)	(20)	12	1,143	37
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued			7
Common stock repurchased			0
Common stock reissued			0
Stockholder contribution											0
Amortization of net actuarial loss	0				0				0				0
Amortization of prior service credit	0				0
Unrealized gain (loss) on investments	1					1			0					0
Reclassification adjustments included in net income	0					0			0					0
Net income	172						172	0	181						181
Dividends declared on common stock							(94)								(111)
Dividends declared on preferred stock															0
Distributions and other changes in noncontrolling interests								0
Total Equity at End of Period at Sep. 30, 2017	4,572	3	5,013	(47)	(49)	2	(434)	37	6,532	841	4,449	(8)	(20)	12	1,213	37
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of change in accounting principle					(11)		8						(5)	(12)	19
Total Equity at Beginning of Period at Dec. 31, 2017	4,478	3	5,019	(50)	(50)	0	(531)	37	6,488	841	4,449	(12)	(24)	12	1,173	37
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued			54
Common stock repurchased			(10)
Common stock reissued			20
Stockholder contribution											250
Amortization of net actuarial loss	3				3				2				2
Amortization of prior service credit	(1)				(1)
Unrealized gain (loss) on investments	(1)					(1)			(1)					(1)
Reclassification adjustments included in net income	1					1			1					1
Net income	550						549	1	574						574
Dividends declared on common stock							(304)								(392)
Dividends declared on preferred stock															(1)
Distributions and other changes in noncontrolling interests								(1)
Total Equity at End of Period at Sep. 30, 2018	4,786	3	5,083	(59)	(59)	0	(278)	37	6,923	841	4,699	(27)	(27)	0	1,373	37
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of change in accounting principle					0		0						0	0	0
Total Equity at Beginning of Period at Jun. 30, 2018	4,709	3	5,076	(61)	(60)	(1)	(346)	37	6,888	841	4,699	(29)	(28)	(1)	1,340	37
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued			7
Common stock repurchased			0
Common stock reissued			0
Stockholder contribution											0
Amortization of net actuarial loss	1				1				1				1
Amortization of prior service credit	0				0
Unrealized gain (loss) on investments	0					0			0					0
Reclassification adjustments included in net income	1					1			1					1
Net income	169						169	0	180						180
Dividends declared on common stock							(101)								(147)
Dividends declared on preferred stock															0
Distributions and other changes in noncontrolling interests								0
Total Equity at End of Period at Sep. 30, 2018	$ 4,786	$ 3	$ 5,083	$ (59)	$ (59)	$ 0	$ (278)	$ 37	$ 6,923	$ 841	$ 4,699	(27)	$ (27)	$ 0	$ 1,373	$ 37
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of change in accounting principle												$ (19)

New Accounting Standards

New Accounting Standards	9 Months Ended
	Sep. 30, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Standards	New Accounting Standards Implementation of New Accounting Standards ASU 2014-09, Revenue from Contracts with Customers: This standard, which was effective on January 1, 2018 for CMS Energy and Consumers, provides new guidance for recognizing revenue from contracts with customers. A primary objective of the standard is to provide a single, comprehensive revenue recognition model that will be applied across entities, industries, and capital markets. The new guidance replaced most of the previous revenue recognition requirements in GAAP, although certain guidance specific to rate-regulated utilities was retained. CMS Energy and Consumers had the option to apply the standard retrospectively to all prior periods presented or retrospectively with the cumulative effect of the standard recorded as an adjustment to beginning retained earnings. They also had the option to apply the standard only to contracts existing on the effective date. CMS Energy and Consumers applied the standard retrospectively to contracts existing on the effective date, and recorded an immaterial cumulative-effect reduction to beginning retained earnings for certain contract costs that can no longer be deferred under the new guidance. The implementation of this standard did not have a material impact on CMS Energy’s or Consumers’ consolidated net income, cash flows, or financial position. CMS Energy and Consumers did not identify any significant changes to their revenue recognition practices that were required by the new guidance, but in accordance with the standard, they have provided additional disclosures about their revenues in Note 11, Revenue . ASU 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities: This standard, which was effective on January 1, 2018 for CMS Energy and Consumers, is intended to improve the accounting for financial instruments. The standard requires investments in equity securities to be measured at fair value, with changes in fair value recognized in net income, except for certain investments such as those that qualify for equity-method accounting. The standard no longer permits unrealized gains and losses for certain equity investments to be recorded in AOCI. There are other targeted changes as well. Entities must apply the standard using a modified retrospective approach, with the cumulative effect of the standard recorded as an adjustment to beginning retained earnings. The implementation of the standard had no impact on CMS Energy’s consolidated financial statements. In accordance with the standard, as of January 1, 2018, Consumers removed a $19 million unrealized gain and the associated deferred taxes on its investment in CMS Energy common stock from AOCI and recorded the gain in retained earnings. In January 2018, Consumers transferred substantially all of its shares in CMS Energy common stock to a related charitable foundation and, in accordance with this standard, recognized all unrealized gains and losses on its remaining shares in net income for the three and nine months ended September 30, 2018 . The accounting treatment for this investment is reflected in Consumers’ consolidated financial statements only, and had no impact on CMS Energy’s consolidated financial statements. For further details on CMS Energy’s and Consumers’ investments in debt and equity securities, see Note 6, Financial Instruments . ASU 2018-02, Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income: This standard addresses the income tax effects stranded in AOCI as a result of the TCJA. Existing GAAP requires that the remeasurement of deferred tax assets and liabilities resulting from a change in tax laws or rates be presented in net income from continuing operations, even if the deferred taxes were associated with items that were originally recognized in AOCI. As a result, upon recognizing the effects of the TCJA, the tax effects of items in AOCI (referred to as stranded tax effects) no longer reflected the current income tax rate. To address this matter, this standard permits companies to reclassify to retained earnings the stranded tax effects of the TCJA. The standard is effective on January 1, 2019 for CMS Energy and Consumers, but early adoption is permitted. The new guidance is to be applied either in the period of adoption or retrospectively to each prior period in which the effect of the TCJA was recognized. CMS Energy and Consumers elected to adopt this standard early. Accordingly, as of January 1, 2018, CMS Energy reclassified $11 million of stranded tax effects from AOCI to retained earnings, which included $5 million reclassified at Consumers. At September 30, 2018 , CMS Energy and Consumers did not have any material stranded tax effects remaining in AOCI. New Accounting Standards Not Yet Effective ASU 2016-02, Leases: This standard establishes a new accounting model for leases. The standard will require entities to recognize lease assets and liabilities on the balance sheet for all leases with a term of more than one year, including operating leases, which are not recorded on the balance sheet under existing standards. The new guidance will also amend the definition of a lease to require that a lessee control the use of a specified asset, and not simply control or take the output of the asset. On the income statement, leases that meet existing capital lease criteria will generally be accounted for under a financing model, while operating leases will generally be accounted for under a straight-line expense model. The standard will be effective on January 1, 2019 for CMS Energy and Consumers, but early adoption is permitted. CMS Energy and Consumers are not adopting the standard early and will elect certain practical expedients permitted by the standard, under which they will not be required to perform lease assessments or reassessments for agreements existing on the effective date. They also will elect a transition method under which they will initially apply the standard on January 1, 2019, without adjusting amounts presented for prior periods. Under this method, the cumulative effect of applying the standard must be recorded as an adjustment to beginning retained earnings. CMS Energy and Consumers will recognize additional lease assets and liabilities for their operating leases under the standard. CMS Energy and Consumers are continuing to evaluate the standard; however, they do not expect that it will have a material impact on their consolidated net income or cash flows. ASU 2016-13, Measurement of Credit Losses on Financial Instruments: This standard, which will be effective January 1, 2020 for CMS Energy and Consumers, provides new guidance for estimating and recording credit losses on financial instruments. The standard will apply to the recognition of loan losses at EnerBank as well as to the recognition of uncollectible accounts expense at Consumers. Entities will apply the standard using a modified retrospective approach, with a cumulative-effect adjustment recorded to beginning retained earnings on the effective date. CMS Energy and Consumers are evaluating the impact of the standard on their consolidated financial statements.
Consumers Energy Company
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Standards	New Accounting Standards Implementation of New Accounting Standards ASU 2014-09, Revenue from Contracts with Customers: This standard, which was effective on January 1, 2018 for CMS Energy and Consumers, provides new guidance for recognizing revenue from contracts with customers. A primary objective of the standard is to provide a single, comprehensive revenue recognition model that will be applied across entities, industries, and capital markets. The new guidance replaced most of the previous revenue recognition requirements in GAAP, although certain guidance specific to rate-regulated utilities was retained. CMS Energy and Consumers had the option to apply the standard retrospectively to all prior periods presented or retrospectively with the cumulative effect of the standard recorded as an adjustment to beginning retained earnings. They also had the option to apply the standard only to contracts existing on the effective date. CMS Energy and Consumers applied the standard retrospectively to contracts existing on the effective date, and recorded an immaterial cumulative-effect reduction to beginning retained earnings for certain contract costs that can no longer be deferred under the new guidance. The implementation of this standard did not have a material impact on CMS Energy’s or Consumers’ consolidated net income, cash flows, or financial position. CMS Energy and Consumers did not identify any significant changes to their revenue recognition practices that were required by the new guidance, but in accordance with the standard, they have provided additional disclosures about their revenues in Note 11, Revenue . ASU 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities: This standard, which was effective on January 1, 2018 for CMS Energy and Consumers, is intended to improve the accounting for financial instruments. The standard requires investments in equity securities to be measured at fair value, with changes in fair value recognized in net income, except for certain investments such as those that qualify for equity-method accounting. The standard no longer permits unrealized gains and losses for certain equity investments to be recorded in AOCI. There are other targeted changes as well. Entities must apply the standard using a modified retrospective approach, with the cumulative effect of the standard recorded as an adjustment to beginning retained earnings. The implementation of the standard had no impact on CMS Energy’s consolidated financial statements. In accordance with the standard, as of January 1, 2018, Consumers removed a $19 million unrealized gain and the associated deferred taxes on its investment in CMS Energy common stock from AOCI and recorded the gain in retained earnings. In January 2018, Consumers transferred substantially all of its shares in CMS Energy common stock to a related charitable foundation and, in accordance with this standard, recognized all unrealized gains and losses on its remaining shares in net income for the three and nine months ended September 30, 2018 . The accounting treatment for this investment is reflected in Consumers’ consolidated financial statements only, and had no impact on CMS Energy’s consolidated financial statements. For further details on CMS Energy’s and Consumers’ investments in debt and equity securities, see Note 6, Financial Instruments . ASU 2018-02, Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income: This standard addresses the income tax effects stranded in AOCI as a result of the TCJA. Existing GAAP requires that the remeasurement of deferred tax assets and liabilities resulting from a change in tax laws or rates be presented in net income from continuing operations, even if the deferred taxes were associated with items that were originally recognized in AOCI. As a result, upon recognizing the effects of the TCJA, the tax effects of items in AOCI (referred to as stranded tax effects) no longer reflected the current income tax rate. To address this matter, this standard permits companies to reclassify to retained earnings the stranded tax effects of the TCJA. The standard is effective on January 1, 2019 for CMS Energy and Consumers, but early adoption is permitted. The new guidance is to be applied either in the period of adoption or retrospectively to each prior period in which the effect of the TCJA was recognized. CMS Energy and Consumers elected to adopt this standard early. Accordingly, as of January 1, 2018, CMS Energy reclassified $11 million of stranded tax effects from AOCI to retained earnings, which included $5 million reclassified at Consumers. At September 30, 2018 , CMS Energy and Consumers did not have any material stranded tax effects remaining in AOCI. New Accounting Standards Not Yet Effective ASU 2016-02, Leases: This standard establishes a new accounting model for leases. The standard will require entities to recognize lease assets and liabilities on the balance sheet for all leases with a term of more than one year, including operating leases, which are not recorded on the balance sheet under existing standards. The new guidance will also amend the definition of a lease to require that a lessee control the use of a specified asset, and not simply control or take the output of the asset. On the income statement, leases that meet existing capital lease criteria will generally be accounted for under a financing model, while operating leases will generally be accounted for under a straight-line expense model. The standard will be effective on January 1, 2019 for CMS Energy and Consumers, but early adoption is permitted. CMS Energy and Consumers are not adopting the standard early and will elect certain practical expedients permitted by the standard, under which they will not be required to perform lease assessments or reassessments for agreements existing on the effective date. They also will elect a transition method under which they will initially apply the standard on January 1, 2019, without adjusting amounts presented for prior periods. Under this method, the cumulative effect of applying the standard must be recorded as an adjustment to beginning retained earnings. CMS Energy and Consumers will recognize additional lease assets and liabilities for their operating leases under the standard. CMS Energy and Consumers are continuing to evaluate the standard; however, they do not expect that it will have a material impact on their consolidated net income or cash flows. ASU 2016-13, Measurement of Credit Losses on Financial Instruments: This standard, which will be effective January 1, 2020 for CMS Energy and Consumers, provides new guidance for estimating and recording credit losses on financial instruments. The standard will apply to the recognition of loan losses at EnerBank as well as to the recognition of uncollectible accounts expense at Consumers. Entities will apply the standard using a modified retrospective approach, with a cumulative-effect adjustment recorded to beginning retained earnings on the effective date. CMS Energy and Consumers are evaluating the impact of the standard on their consolidated financial statements.

Regulatory Matters

Regulatory Matters	9 Months Ended
	Sep. 30, 2018
Public Utilities, General Disclosures [Line Items]
Regulatory Matters	Regulatory Matters Regulatory matters are critical to Consumers. The Michigan Attorney General, ABATE, the MPSC Staff, and certain other parties typically participate in MPSC proceedings concerning Consumers, such as Consumers’ rate cases and PSCR and GCR processes. These parties often challenge various aspects of those proceedings, including the prudence of Consumers’ policies and practices, and seek cost disallowances and other relief. The parties also have appealed significant MPSC orders. Depending upon the specific issues, the outcomes of rate cases and proceedings, including judicial proceedings challenging MPSC orders or other actions, could negatively affect CMS Energy’s and Consumers’ liquidity, financial condition, and results of operations. Consumers cannot predict the outcome of these proceedings. There are multiple appeals pending that involve various issues concerning cost recovery from customers, the adequacy of the record evidence supporting the recovery of Smart Energy investments, and other matters. Consumers is unable to predict the outcome of these appeals. Electric Rate Case: In March 2017, Consumers filed an application with the MPSC seeking an annual rate increase of $173 million , based on a 10.5 percent authorized return on equity. The filing requested authority to recover new investment in system reliability, environmental compliance, and technology enhancements. In September 2017, Consumers reduced its requested annual rate increase to $148 million . In October 2017, Consumers self-implemented an annual rate increase of $130 million , subject to refund with interest and potential penalties . The MPSC issued an order in March 2018, authorizing an annual rate increase of $66 million , based on a 10.0 percent authorized return on equity. In June 2018, as a result of a petition for rehearing filed by Consumers, the MPSC issued an order adjusting the authorized annual rate increase to $72 million by allowing recovery of additional retirement benefit plan costs. In July 2018, Consumers filed a reconciliation of total revenues collected during self-implementation to those that would have been collected under final rates. The reconciliation indicated that a $36 million refund would be required, which was recorded on Consumers’ consolidated balance sheets as a current regulatory liability at September 30, 2018 . Gas Rate Case: In October 2017, Consumers filed an application with the MPSC seeking an annual rate increase of $178 million , based on a 10.5 percent authorized return on equity. In March 2018, Consumers reduced its requested revenue requirement to $145 million , before taking into consideration any impact of the TCJA. Consumers further reduced its requested revenue requirement to $83 million to reflect the impact of the TCJA, offset partially by an increase in the authorized return on equity to 10.75 percent to compensate for the anticipated negative effects of tax reform on Consumers’ cash flows from operating activities. In July 2018, Consumers reduced its requested revenue requirement to $60 million , based on a 10.0 percent authorized return on equity. In August 2018, the MPSC approved a settlement agreement authorizing an annual rate increase of $11 million , based on a 10.0 percent authorized return on equity. The settlement agreement did not incorporate recommendations by the MPSC Staff and administrative law judge to disallow cost recovery for certain historical capital expenditures. The MPSC also approved two rate adjustment mechanisms: a revenue decoupling mechanism and an investment recovery mechanism. The revenue decoupling mechanism will annually reconcile Consumers’ actual weather-normalized non-fuel revenues with the revenues approved by the MPSC. The investment recovery mechanism will provide for an additional annual rate increase of $9 million beginning in July 2019 and another $10 million beginning in July 2020 for incremental investments that Consumers plans to make in those years, subject to reconciliation. The investment recovery surcharge will remain in effect until rates are reset in a subsequent general rate case. Tax Cuts and Jobs Act : The TCJA, which changed existing federal tax law and included numerous provisions that affect businesses, was signed into law in December 2017. In February 2018, the MPSC ordered Consumers to file various proceedings to determine the reduction in its electric and gas revenue requirements as a result of the TCJA. The MPSC also ordered Consumers to implement bill credits to reflect that reduction until customer rates are adjusted through Consumers’ general rate cases. Consumers filed the first of these proceedings in March 2018, requesting a $49 million reduction in its annual gas revenue requirement. The MPSC approved this reduction in June 2018, with credits to customer bills beginning in July 2018; this credit ended with the settlement of the gas rate case in August 2018. Consumers filed the second proceeding in April 2018, requesting a $113 million reduction in its annual electric revenue requirement. The MPSC approved this reduction in July 2018, with credits to customer bills beginning in August 2018. These credits reduce rates prospectively for the impact of the TCJA but do not include potential refunds associated with Consumers’ remeasurement of its deferred income taxes. Consumers filed two more proceedings to address amounts collected from customers during 2018 through the implementation of the first two proceedings. Consumers filed the first of these proceedings in August 2018, requesting to refund $31 million to gas customers over six months beginning in December 2018. Consumers filed the second proceeding in September 2018, requesting to refund $70 million to electric customers over six months beginning in January 2019. Consumers has recorded a liability in an amount reflecting these proposed refunds. In October 2018, Consumers filed an application to address the December 31, 2017 remeasurement of its deferred income taxes and other impacts of the TCJA on customers. The application requested approval to begin returning $0.4 billion of net regulatory tax liabilities through the rates determined in Consumers’ next gas rate case and $1.2 billion through the rates determined in Consumers’ next-filed electric rate case. Consumers’ total $1.6 billion of net regulatory tax liabilities comprises: • A regulatory tax liability of $1.7 billion associated with plant assets that are subject to normalization, which is governed by the Internal Revenue Code. This requires that the regulatory tax liability be returned over the remaining book life of the related plant assets, the average of which is 44 years for gas plant assets and 36 years for electric plant assets. • A regulatory tax asset of $0.3 billion associated with plant assets that are not subject to normalization. Consumers proposed to collect this over 44 years from gas customers and over 27 years from electric customers. • A regulatory tax liability of $0.2 billion , which does not relate to plant assets. Consumers proposed to refund this amount to customers over 15 years . For additional details on the remeasurement, see Note 9, Income Taxes . Energy Waste Reduction Plan Incentive: Consumers filed its 2017 energy waste reduction reconciliation in May 2018, requesting the MPSC’s approval to collect from customers the maximum performance incentive of $31 million for exceeding its statutory savings targets in 2017. Consumers recognized incentive revenue under this program of $31 million in 2017.
Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Regulatory Matters	Regulatory Matters Regulatory matters are critical to Consumers. The Michigan Attorney General, ABATE, the MPSC Staff, and certain other parties typically participate in MPSC proceedings concerning Consumers, such as Consumers’ rate cases and PSCR and GCR processes. These parties often challenge various aspects of those proceedings, including the prudence of Consumers’ policies and practices, and seek cost disallowances and other relief. The parties also have appealed significant MPSC orders. Depending upon the specific issues, the outcomes of rate cases and proceedings, including judicial proceedings challenging MPSC orders or other actions, could negatively affect CMS Energy’s and Consumers’ liquidity, financial condition, and results of operations. Consumers cannot predict the outcome of these proceedings. There are multiple appeals pending that involve various issues concerning cost recovery from customers, the adequacy of the record evidence supporting the recovery of Smart Energy investments, and other matters. Consumers is unable to predict the outcome of these appeals. Electric Rate Case: In March 2017, Consumers filed an application with the MPSC seeking an annual rate increase of $173 million , based on a 10.5 percent authorized return on equity. The filing requested authority to recover new investment in system reliability, environmental compliance, and technology enhancements. In September 2017, Consumers reduced its requested annual rate increase to $148 million . In October 2017, Consumers self-implemented an annual rate increase of $130 million , subject to refund with interest and potential penalties . The MPSC issued an order in March 2018, authorizing an annual rate increase of $66 million , based on a 10.0 percent authorized return on equity. In June 2018, as a result of a petition for rehearing filed by Consumers, the MPSC issued an order adjusting the authorized annual rate increase to $72 million by allowing recovery of additional retirement benefit plan costs. In July 2018, Consumers filed a reconciliation of total revenues collected during self-implementation to those that would have been collected under final rates. The reconciliation indicated that a $36 million refund would be required, which was recorded on Consumers’ consolidated balance sheets as a current regulatory liability at September 30, 2018 . Gas Rate Case: In October 2017, Consumers filed an application with the MPSC seeking an annual rate increase of $178 million , based on a 10.5 percent authorized return on equity. In March 2018, Consumers reduced its requested revenue requirement to $145 million , before taking into consideration any impact of the TCJA. Consumers further reduced its requested revenue requirement to $83 million to reflect the impact of the TCJA, offset partially by an increase in the authorized return on equity to 10.75 percent to compensate for the anticipated negative effects of tax reform on Consumers’ cash flows from operating activities. In July 2018, Consumers reduced its requested revenue requirement to $60 million , based on a 10.0 percent authorized return on equity. In August 2018, the MPSC approved a settlement agreement authorizing an annual rate increase of $11 million , based on a 10.0 percent authorized return on equity. The settlement agreement did not incorporate recommendations by the MPSC Staff and administrative law judge to disallow cost recovery for certain historical capital expenditures. The MPSC also approved two rate adjustment mechanisms: a revenue decoupling mechanism and an investment recovery mechanism. The revenue decoupling mechanism will annually reconcile Consumers’ actual weather-normalized non-fuel revenues with the revenues approved by the MPSC. The investment recovery mechanism will provide for an additional annual rate increase of $9 million beginning in July 2019 and another $10 million beginning in July 2020 for incremental investments that Consumers plans to make in those years, subject to reconciliation. The investment recovery surcharge will remain in effect until rates are reset in a subsequent general rate case. Tax Cuts and Jobs Act : The TCJA, which changed existing federal tax law and included numerous provisions that affect businesses, was signed into law in December 2017. In February 2018, the MPSC ordered Consumers to file various proceedings to determine the reduction in its electric and gas revenue requirements as a result of the TCJA. The MPSC also ordered Consumers to implement bill credits to reflect that reduction until customer rates are adjusted through Consumers’ general rate cases. Consumers filed the first of these proceedings in March 2018, requesting a $49 million reduction in its annual gas revenue requirement. The MPSC approved this reduction in June 2018, with credits to customer bills beginning in July 2018; this credit ended with the settlement of the gas rate case in August 2018. Consumers filed the second proceeding in April 2018, requesting a $113 million reduction in its annual electric revenue requirement. The MPSC approved this reduction in July 2018, with credits to customer bills beginning in August 2018. These credits reduce rates prospectively for the impact of the TCJA but do not include potential refunds associated with Consumers’ remeasurement of its deferred income taxes. Consumers filed two more proceedings to address amounts collected from customers during 2018 through the implementation of the first two proceedings. Consumers filed the first of these proceedings in August 2018, requesting to refund $31 million to gas customers over six months beginning in December 2018. Consumers filed the second proceeding in September 2018, requesting to refund $70 million to electric customers over six months beginning in January 2019. Consumers has recorded a liability in an amount reflecting these proposed refunds. In October 2018, Consumers filed an application to address the December 31, 2017 remeasurement of its deferred income taxes and other impacts of the TCJA on customers. The application requested approval to begin returning $0.4 billion of net regulatory tax liabilities through the rates determined in Consumers’ next gas rate case and $1.2 billion through the rates determined in Consumers’ next-filed electric rate case. Consumers’ total $1.6 billion of net regulatory tax liabilities comprises: • A regulatory tax liability of $1.7 billion associated with plant assets that are subject to normalization, which is governed by the Internal Revenue Code. This requires that the regulatory tax liability be returned over the remaining book life of the related plant assets, the average of which is 44 years for gas plant assets and 36 years for electric plant assets. • A regulatory tax asset of $0.3 billion associated with plant assets that are not subject to normalization. Consumers proposed to collect this over 44 years from gas customers and over 27 years from electric customers. • A regulatory tax liability of $0.2 billion , which does not relate to plant assets. Consumers proposed to refund this amount to customers over 15 years . For additional details on the remeasurement, see Note 9, Income Taxes . Energy Waste Reduction Plan Incentive: Consumers filed its 2017 energy waste reduction reconciliation in May 2018, requesting the MPSC’s approval to collect from customers the maximum performance incentive of $31 million for exceeding its statutory savings targets in 2017. Consumers recognized incentive revenue under this program of $31 million in 2017.

Contingencies and Commitments

Contingencies and Commitments	9 Months Ended
	Sep. 30, 2018
Site Contingency [Line Items]
Contingencies and Commitments	Contingencies and Commitments CMS Energy and Consumers are involved in various matters that give rise to contingent liabilities. Depending on the specific issues, the resolution of these contingencies could negatively affect CMS Energy’s and Consumers’ liquidity, financial condition, and results of operations. In their disclosures of these matters, CMS Energy and Consumers provide an estimate of the possible loss or range of loss when such an estimate can be made. Disclosures that state that CMS Energy or Consumers cannot predict the outcome of a matter indicate that they are unable to estimate a possible loss or range of loss for the matter. CMS Energy Contingencies Gas Index Price Reporting Litigation: CMS Energy, along with CMS MST, CMS Field Services, Cantera Natural Gas, Inc., and Cantera Gas Company, were named as defendants in four class action lawsuits and one individual lawsuit arising as a result of alleged inaccurate natural gas price reporting to publications that report trade information. Allegations include price-fixing conspiracies, restraint of trade, and artificial inflation of natural gas retail prices in Kansas, Missouri, and Wisconsin. In 2016, CMS Energy entities reached a settlement with the plaintiffs in the Kansas and Missouri class action cases for an amount that was not material to CMS Energy. In August 2017, the federal district court approved the settlement. Plaintiffs are making claims for the following: treble damages, full consideration damages, exemplary damages, costs, interest, and/or attorneys’ fees. After removal to federal court, all of the cases were transferred to a single federal district court pursuant to the multidistrict litigation process. In 2010 and 2011, all claims against CMS Energy defendants were dismissed by the district court based on FERC preemption. In 2013, the U.S. Court of Appeals for the Ninth Circuit reversed the district court decision. The appellate court found that FERC preemption does not apply under the facts of these cases. The appellate court affirmed the district court’s denial of leave to amend to add federal antitrust claims. The matter was appealed to the U.S. Supreme Court, which in 2015 upheld the Ninth Circuit’s decision. The cases were remanded back to the federal district court. In 2016, the federal district court granted the defendants’ motion for summary judgment in the individual lawsuit filed in Kansas based on a release in a prior settlement involving similar allegations; the order of summary judgment was subsequently appealed. In March 2018, the U.S. Court of Appeals for the Ninth Circuit reversed the lower court’s ruling and remanded the case back to the federal district court. In March 2017, the federal district court denied plaintiffs’ motion for class certification in the two pending class action cases in Wisconsin. The plaintiffs appealed that decision to the U.S. Court of Appeals for the Ninth Circuit and in August 2018, the Ninth Circuit Court of Appeals reversed and remanded the matter back to the federal district court for further consideration. In June 2017, an unaffiliated company that is also a defendant in these cases filed for bankruptcy, which could increase the risk of loss to CMS Energy. These cases involve complex facts, a large number of similarly situated defendants with different factual positions, and multiple jurisdictions. Presently, any estimate of liability would be highly speculative; the amount of CMS Energy’s reasonably possible loss would be based on widely varying models previously untested in this context. If the outcome after appeals is unfavorable, these cases could negatively affect CMS Energy’s liquidity, financial condition, and results of operations. Bay Harbor: CMS Land retained environmental remediation obligations for the collection and treatment of leachate, a liquid consisting of water and other substances, at Bay Harbor after selling its interests in the development in 2002. Leachate is produced when water enters into cement kiln dust piles left over from former cement plant operations at the site. In 2012, CMS Land and the MDEQ finalized an agreement that established the final remedies and the future water quality criteria at the site. CMS Land completed all construction necessary to implement the remedies required by the agreement and will continue to maintain and operate a system to discharge treated leachate into Little Traverse Bay under an NPDES permit issued in 2010 and renewed in 2016. The renewed NPDES permit is valid through September 2020. Various claims have been brought against CMS Land or its affiliates, including CMS Energy, alleging environmental damage to property, loss of property value, insufficient disclosure of environmental matters, breach of agreement relating to access, or other matters. CMS Land and other parties have received a demand for payment from the EPA in the amount of $8 million , plus interest and costs. The EPA is seeking recovery under CERCLA of response costs allegedly incurred at Bay Harbor. These costs exceed what was agreed to in a 2005 order between CMS Land and the EPA and CMS Land believes that the claim was made beyond the appropriate statute of limitations. CMS Land has communicated to the EPA that it does not believe that this is a valid claim. The EPA has filed a lawsuit to collect these costs. At September 30, 2018 , CMS Energy had a recorded liability of $46 million for its remaining obligations for environmental remediation. CMS Energy calculated this liability based on discounted projected costs, using a discount rate of 4.34 percent and an inflation rate of one percent on annual operating and maintenance costs. The undiscounted amount of the remaining obligation is $58 million . CMS Energy expects to pay the following amounts for long-term liquid disposal and operating and maintenance costs during the remainder of 2018 and in each of the next five years: In Millions 2018 2019 2020 2021 2022 2023 CMS Energy Long-term liquid disposal and operating and maintenance costs $ 1 $ 4 $ 4 $ 4 $ 4 $ 4 CMS Energy’s estimate of response activity costs and the timing of expenditures could change if there are changes in circumstances or assumptions used in calculating the liability. Although a liability for its present estimate of remaining response activity costs has been recorded, CMS Energy cannot predict the ultimate financial impact or outcome of this matter. Equatorial Guinea Tax Claim: In 2002, CMS Energy sold its oil, gas, and methanol investments in Equatorial Guinea. The government of Equatorial Guinea claims that, in connection with the sale, CMS Energy owes $152 million in taxes, plus substantial penalties and interest that could be up to the amount of the taxes claimed. In 2015, the matter was proceeding to formal arbitration; however, since then, the government of Equatorial Guinea has stopped communicating. CMS Energy has concluded that the government’s tax claim is without merit and will continue to contest the claim, but cannot predict the financial impact or outcome of the matter. An unfavorable outcome could have a material adverse effect on CMS Energy’s liquidity, financial condition, and results of operations. Consumers Electric Utility Contingencies Electric Environmental Matters: Consumers’ operations are subject to environmental laws and regulations. Historically, Consumers has generally been able to recover, in customer rates, the costs to operate its facilities in compliance with these laws and regulations. Cleanup and Solid Waste: Consumers expects to incur remediation and other response activity costs at a number of sites under the NREPA. Consumers believes that these costs should be recoverable in rates, but cannot guarantee that outcome. Consumers estimates that its liability for NREPA sites for which it can estimate a range of loss will be between $3 million and $4 million . At September 30, 2018 , Consumers had a recorded liability of $3 million , the minimum amount in the range of its estimated probable NREPA liability, as no amount in the range was considered a better estimate than any other amount. Consumers is a potentially responsible party at a number of contaminated sites administered under CERCLA. CERCLA liability is joint and several. In 2010, Consumers received official notification from the EPA that identified Consumers as a potentially responsible party for cleanup of PCBs at the Kalamazoo River CERCLA site. The notification claimed that the EPA has reason to believe that Consumers disposed of PCBs and arranged for the disposal and treatment of PCB-containing materials at portions of the site. In 2011, Consumers received a follow-up letter from the EPA requesting that Consumers agree to participate in a removal action plan along with several other companies for an area of lower Portage Creek, which is connected to the Kalamazoo River. All parties, including Consumers, that were asked to participate in the removal action plan declined to accept liability. Until further information is received from the EPA, Consumers is unable to estimate a range of potential liability for cleanup of the river. Based on its experience, Consumers estimates that its share of the total liability for known CERCLA sites will be between $3 million and $8 million . Various factors, including the number and creditworthiness of potentially responsible parties involved with each site, affect Consumers’ share of the total liability. At September 30, 2018 , Consumers had a recorded liability of $3 million for its share of the total liability at these sites, the minimum amount in the range of its estimated probable CERCLA liability, as no amount in the range was considered a better estimate than any other amount. The timing of payments related to Consumers’ remediation and other response activities at its CERCLA and NREPA sites is uncertain. Consumers periodically reviews these cost estimates. A change in the underlying assumptions, such as an increase in the number of sites, different remediation techniques, the nature and extent of contamination, and legal and regulatory requirements, could affect its estimates of NREPA and CERCLA liability. Ludington PCB: In 1998, during routine maintenance activities, Consumers identified PCB as a component in certain paint, grout, and sealant materials at Ludington. Consumers removed part of the PCB material and replaced it with non-PCB material. Consumers has had several communications with the EPA regarding this matter, but cannot predict the financial impact or outcome. MCV PPA: In December 2017, the MCV Partnership initiated arbitration against Consumers, asserting a breach of contract associated with the MCV PPA. Under this PPA, Consumers pays the MCV Partnership a fixed energy charge based on Consumers’ annual average baseload coal generating plant operating and maintenance cost, fuel inventory, and administrative and general expenses. The MCV Partnership asserts that Consumers should have installed pollution control equipment on coal-fueled electric generating units years before they were retired. The MCV Partnership also asserts that Consumers should have installed pollution control equipment earlier on its remaining coal-fueled electric generating units. The assertion claims that these changes would have increased Consumers’ costs to operate and maintain the facilities and, thereby, the fixed energy charge paid to the MCV Partnership. Additionally, the MCV Partnership claims that Consumers improperly characterized certain costs included in the calculation of the fixed energy charge. The claim estimates damages and interest in excess of $270 million , the majority of which is related to the claim on the installation of pollution control equipment. Consumers believes that the MCV Partnership’s claim is without merit, but cannot predict the financial impact or outcome of the matter. Underwater Cables in Straits of Mackinac: Consumers owns certain underwater electric cables in the Straits of Mackinac, which were de-energized and retired in 1990. Consumers was notified that some of these cables were damaged as a result of vessel activity in April 2018. Following the notification, Consumers located, inspected, sampled, capped, and returned the damaged retired cables to their original location on the lake bottom, and did not find any substantive evidence of environmental contamination. Consumers is collaborating with the State of Michigan, local Native American tribes, and other stakeholders to evaluate the status of the cables and to determine if any additional action is advisable. Consumers cannot predict the outcome of this matter, but if Consumers is required to remove all the cables, it could incur additional costs of up to $10 million . Consumers has filed suit against the companies that own the vessels that allegedly caused the damage. Consumers will seek recovery from customers of any costs incurred. Consumers Gas Utility Contingencies Gas Environmental Matters: Consumers expects to incur remediation and other response activity costs at a number of sites under the NREPA. These sites include 23 former MGP facilities. Consumers operated the facilities on these sites for some part of their operating lives. For some of these sites, Consumers has no present ownership interest or may own only a portion of the original site. At September 30, 2018 , Consumers had a recorded liability of $78 million for its remaining obligations for these sites. This amount represents the present value of long-term projected costs, using a discount rate of 2.57 percent and an inflation rate of 2.5 percent . The undiscounted amount of the remaining obligation is $83 million . Consumers expects to pay the following amounts for remediation and other response activity costs during the remainder of 2018 and in each of the next five years: In Millions 2018 2019 2020 2021 2022 2023 Consumers Remediation and other response activity costs $ 6 $ 12 $ 16 $ 21 $ 7 $ 2 Consumers periodically reviews these cost estimates. Any significant change in the underlying assumptions, such as an increase in the number of sites, changes in remediation techniques, or legal and regulatory requirements, could affect Consumers’ estimates of annual response activity costs and the MGP liability. Pursuant to orders issued by the MPSC, Consumers defers its MGP-related remediation costs and recovers them from its customers over a ten -year period. At September 30, 2018 , Consumers had a regulatory asset of $135 million related to the MGP sites. Consumers estimates that its liability to perform remediation and other response activities at NREPA sites other than the MGP sites could reach $3 million . At September 30, 2018 , Consumers had a recorded liability of less than $1 million , the minimum amount in the range of its estimated probable liability, as no amount in the range was considered a better estimate than any other amount. Guarantees Presented in the following table are CMS Energy’s and Consumers’ guarantees at September 30, 2018 : In Millions Guarantee Description Issue Date Expiration Date Maximum Obligation Carrying Amount CMS Energy, including Consumers Indemnity obligations from stock and asset sale agreements 1 Various Indefinite $ 153 $ 3 Guarantees 2 Various Indefinite 39 — Consumers Guarantee 2 July 2011 Indefinite $ 30 $ — 1 These obligations arose from stock and asset sale agreements under which CMS Energy or a subsidiary of CMS Energy indemnified the purchaser for losses resulting from various matters, primarily claims related to taxes. CMS Energy believes the likelihood of material loss to be remote for the indemnity obligations not recorded as liabilities. 2 At Consumers, this obligation comprises a guarantee provided to the U.S. Department of Energy in connection with a settlement agreement regarding damages resulting from the department’s failure to accept spent nuclear fuel from nuclear power plants formerly owned by Consumers. At CMS Energy, the guarantee obligations comprise Consumers’ guarantee to the U.S. Department of Energy and CMS Energy’s 1994 guarantee of non-recourse revenue bonds issued by Genesee. Additionally, in the normal course of business, CMS Energy, Consumers, and certain other subsidiaries of CMS Energy have entered into various agreements containing tax and other indemnity provisions for which they are unable to estimate the maximum potential obligation. The carrying value of these indemnity obligations is $1 million . CMS Energy and Consumers consider the likelihood that they would be required to perform or incur substantial losses related to these indemnities to be remote. Other Contingencies In addition to the matters disclosed in this Note and Note 2, Regulatory Matters , there are certain other lawsuits and administrative proceedings before various courts and governmental agencies arising in the ordinary course of business to which CMS Energy, Consumers, and certain other subsidiaries of CMS Energy are parties. These other lawsuits and proceedings may involve personal injury, property damage, contracts, environmental matters, federal and state taxes, rates, licensing, employment, and other matters. Further, CMS Energy and Consumers occasionally self-report certain regulatory non-compliance matters that may or may not eventually result in administrative proceedings. CMS Energy and Consumers believe that the outcome of any one of these proceedings will not have a material negative effect on their consolidated results of operations, financial condition, or liquidity.
Consumers Energy Company
Site Contingency [Line Items]
Contingencies and Commitments	Contingencies and Commitments CMS Energy and Consumers are involved in various matters that give rise to contingent liabilities. Depending on the specific issues, the resolution of these contingencies could negatively affect CMS Energy’s and Consumers’ liquidity, financial condition, and results of operations. In their disclosures of these matters, CMS Energy and Consumers provide an estimate of the possible loss or range of loss when such an estimate can be made. Disclosures that state that CMS Energy or Consumers cannot predict the outcome of a matter indicate that they are unable to estimate a possible loss or range of loss for the matter. CMS Energy Contingencies Gas Index Price Reporting Litigation: CMS Energy, along with CMS MST, CMS Field Services, Cantera Natural Gas, Inc., and Cantera Gas Company, were named as defendants in four class action lawsuits and one individual lawsuit arising as a result of alleged inaccurate natural gas price reporting to publications that report trade information. Allegations include price-fixing conspiracies, restraint of trade, and artificial inflation of natural gas retail prices in Kansas, Missouri, and Wisconsin. In 2016, CMS Energy entities reached a settlement with the plaintiffs in the Kansas and Missouri class action cases for an amount that was not material to CMS Energy. In August 2017, the federal district court approved the settlement. Plaintiffs are making claims for the following: treble damages, full consideration damages, exemplary damages, costs, interest, and/or attorneys’ fees. After removal to federal court, all of the cases were transferred to a single federal district court pursuant to the multidistrict litigation process. In 2010 and 2011, all claims against CMS Energy defendants were dismissed by the district court based on FERC preemption. In 2013, the U.S. Court of Appeals for the Ninth Circuit reversed the district court decision. The appellate court found that FERC preemption does not apply under the facts of these cases. The appellate court affirmed the district court’s denial of leave to amend to add federal antitrust claims. The matter was appealed to the U.S. Supreme Court, which in 2015 upheld the Ninth Circuit’s decision. The cases were remanded back to the federal district court. In 2016, the federal district court granted the defendants’ motion for summary judgment in the individual lawsuit filed in Kansas based on a release in a prior settlement involving similar allegations; the order of summary judgment was subsequently appealed. In March 2018, the U.S. Court of Appeals for the Ninth Circuit reversed the lower court’s ruling and remanded the case back to the federal district court. In March 2017, the federal district court denied plaintiffs’ motion for class certification in the two pending class action cases in Wisconsin. The plaintiffs appealed that decision to the U.S. Court of Appeals for the Ninth Circuit and in August 2018, the Ninth Circuit Court of Appeals reversed and remanded the matter back to the federal district court for further consideration. In June 2017, an unaffiliated company that is also a defendant in these cases filed for bankruptcy, which could increase the risk of loss to CMS Energy. These cases involve complex facts, a large number of similarly situated defendants with different factual positions, and multiple jurisdictions. Presently, any estimate of liability would be highly speculative; the amount of CMS Energy’s reasonably possible loss would be based on widely varying models previously untested in this context. If the outcome after appeals is unfavorable, these cases could negatively affect CMS Energy’s liquidity, financial condition, and results of operations. Bay Harbor: CMS Land retained environmental remediation obligations for the collection and treatment of leachate, a liquid consisting of water and other substances, at Bay Harbor after selling its interests in the development in 2002. Leachate is produced when water enters into cement kiln dust piles left over from former cement plant operations at the site. In 2012, CMS Land and the MDEQ finalized an agreement that established the final remedies and the future water quality criteria at the site. CMS Land completed all construction necessary to implement the remedies required by the agreement and will continue to maintain and operate a system to discharge treated leachate into Little Traverse Bay under an NPDES permit issued in 2010 and renewed in 2016. The renewed NPDES permit is valid through September 2020. Various claims have been brought against CMS Land or its affiliates, including CMS Energy, alleging environmental damage to property, loss of property value, insufficient disclosure of environmental matters, breach of agreement relating to access, or other matters. CMS Land and other parties have received a demand for payment from the EPA in the amount of $8 million , plus interest and costs. The EPA is seeking recovery under CERCLA of response costs allegedly incurred at Bay Harbor. These costs exceed what was agreed to in a 2005 order between CMS Land and the EPA and CMS Land believes that the claim was made beyond the appropriate statute of limitations. CMS Land has communicated to the EPA that it does not believe that this is a valid claim. The EPA has filed a lawsuit to collect these costs. At September 30, 2018 , CMS Energy had a recorded liability of $46 million for its remaining obligations for environmental remediation. CMS Energy calculated this liability based on discounted projected costs, using a discount rate of 4.34 percent and an inflation rate of one percent on annual operating and maintenance costs. The undiscounted amount of the remaining obligation is $58 million . CMS Energy expects to pay the following amounts for long-term liquid disposal and operating and maintenance costs during the remainder of 2018 and in each of the next five years: In Millions 2018 2019 2020 2021 2022 2023 CMS Energy Long-term liquid disposal and operating and maintenance costs $ 1 $ 4 $ 4 $ 4 $ 4 $ 4 CMS Energy’s estimate of response activity costs and the timing of expenditures could change if there are changes in circumstances or assumptions used in calculating the liability. Although a liability for its present estimate of remaining response activity costs has been recorded, CMS Energy cannot predict the ultimate financial impact or outcome of this matter. Equatorial Guinea Tax Claim: In 2002, CMS Energy sold its oil, gas, and methanol investments in Equatorial Guinea. The government of Equatorial Guinea claims that, in connection with the sale, CMS Energy owes $152 million in taxes, plus substantial penalties and interest that could be up to the amount of the taxes claimed. In 2015, the matter was proceeding to formal arbitration; however, since then, the government of Equatorial Guinea has stopped communicating. CMS Energy has concluded that the government’s tax claim is without merit and will continue to contest the claim, but cannot predict the financial impact or outcome of the matter. An unfavorable outcome could have a material adverse effect on CMS Energy’s liquidity, financial condition, and results of operations. Consumers Electric Utility Contingencies Electric Environmental Matters: Consumers’ operations are subject to environmental laws and regulations. Historically, Consumers has generally been able to recover, in customer rates, the costs to operate its facilities in compliance with these laws and regulations. Cleanup and Solid Waste: Consumers expects to incur remediation and other response activity costs at a number of sites under the NREPA. Consumers believes that these costs should be recoverable in rates, but cannot guarantee that outcome. Consumers estimates that its liability for NREPA sites for which it can estimate a range of loss will be between $3 million and $4 million . At September 30, 2018 , Consumers had a recorded liability of $3 million , the minimum amount in the range of its estimated probable NREPA liability, as no amount in the range was considered a better estimate than any other amount. Consumers is a potentially responsible party at a number of contaminated sites administered under CERCLA. CERCLA liability is joint and several. In 2010, Consumers received official notification from the EPA that identified Consumers as a potentially responsible party for cleanup of PCBs at the Kalamazoo River CERCLA site. The notification claimed that the EPA has reason to believe that Consumers disposed of PCBs and arranged for the disposal and treatment of PCB-containing materials at portions of the site. In 2011, Consumers received a follow-up letter from the EPA requesting that Consumers agree to participate in a removal action plan along with several other companies for an area of lower Portage Creek, which is connected to the Kalamazoo River. All parties, including Consumers, that were asked to participate in the removal action plan declined to accept liability. Until further information is received from the EPA, Consumers is unable to estimate a range of potential liability for cleanup of the river. Based on its experience, Consumers estimates that its share of the total liability for known CERCLA sites will be between $3 million and $8 million . Various factors, including the number and creditworthiness of potentially responsible parties involved with each site, affect Consumers’ share of the total liability. At September 30, 2018 , Consumers had a recorded liability of $3 million for its share of the total liability at these sites, the minimum amount in the range of its estimated probable CERCLA liability, as no amount in the range was considered a better estimate than any other amount. The timing of payments related to Consumers’ remediation and other response activities at its CERCLA and NREPA sites is uncertain. Consumers periodically reviews these cost estimates. A change in the underlying assumptions, such as an increase in the number of sites, different remediation techniques, the nature and extent of contamination, and legal and regulatory requirements, could affect its estimates of NREPA and CERCLA liability. Ludington PCB: In 1998, during routine maintenance activities, Consumers identified PCB as a component in certain paint, grout, and sealant materials at Ludington. Consumers removed part of the PCB material and replaced it with non-PCB material. Consumers has had several communications with the EPA regarding this matter, but cannot predict the financial impact or outcome. MCV PPA: In December 2017, the MCV Partnership initiated arbitration against Consumers, asserting a breach of contract associated with the MCV PPA. Under this PPA, Consumers pays the MCV Partnership a fixed energy charge based on Consumers’ annual average baseload coal generating plant operating and maintenance cost, fuel inventory, and administrative and general expenses. The MCV Partnership asserts that Consumers should have installed pollution control equipment on coal-fueled electric generating units years before they were retired. The MCV Partnership also asserts that Consumers should have installed pollution control equipment earlier on its remaining coal-fueled electric generating units. The assertion claims that these changes would have increased Consumers’ costs to operate and maintain the facilities and, thereby, the fixed energy charge paid to the MCV Partnership. Additionally, the MCV Partnership claims that Consumers improperly characterized certain costs included in the calculation of the fixed energy charge. The claim estimates damages and interest in excess of $270 million , the majority of which is related to the claim on the installation of pollution control equipment. Consumers believes that the MCV Partnership’s claim is without merit, but cannot predict the financial impact or outcome of the matter. Underwater Cables in Straits of Mackinac: Consumers owns certain underwater electric cables in the Straits of Mackinac, which were de-energized and retired in 1990. Consumers was notified that some of these cables were damaged as a result of vessel activity in April 2018. Following the notification, Consumers located, inspected, sampled, capped, and returned the damaged retired cables to their original location on the lake bottom, and did not find any substantive evidence of environmental contamination. Consumers is collaborating with the State of Michigan, local Native American tribes, and other stakeholders to evaluate the status of the cables and to determine if any additional action is advisable. Consumers cannot predict the outcome of this matter, but if Consumers is required to remove all the cables, it could incur additional costs of up to $10 million . Consumers has filed suit against the companies that own the vessels that allegedly caused the damage. Consumers will seek recovery from customers of any costs incurred. Consumers Gas Utility Contingencies Gas Environmental Matters: Consumers expects to incur remediation and other response activity costs at a number of sites under the NREPA. These sites include 23 former MGP facilities. Consumers operated the facilities on these sites for some part of their operating lives. For some of these sites, Consumers has no present ownership interest or may own only a portion of the original site. At September 30, 2018 , Consumers had a recorded liability of $78 million for its remaining obligations for these sites. This amount represents the present value of long-term projected costs, using a discount rate of 2.57 percent and an inflation rate of 2.5 percent . The undiscounted amount of the remaining obligation is $83 million . Consumers expects to pay the following amounts for remediation and other response activity costs during the remainder of 2018 and in each of the next five years: In Millions 2018 2019 2020 2021 2022 2023 Consumers Remediation and other response activity costs $ 6 $ 12 $ 16 $ 21 $ 7 $ 2 Consumers periodically reviews these cost estimates. Any significant change in the underlying assumptions, such as an increase in the number of sites, changes in remediation techniques, or legal and regulatory requirements, could affect Consumers’ estimates of annual response activity costs and the MGP liability. Pursuant to orders issued by the MPSC, Consumers defers its MGP-related remediation costs and recovers them from its customers over a ten -year period. At September 30, 2018 , Consumers had a regulatory asset of $135 million related to the MGP sites. Consumers estimates that its liability to perform remediation and other response activities at NREPA sites other than the MGP sites could reach $3 million . At September 30, 2018 , Consumers had a recorded liability of less than $1 million , the minimum amount in the range of its estimated probable liability, as no amount in the range was considered a better estimate than any other amount. Guarantees Presented in the following table are CMS Energy’s and Consumers’ guarantees at September 30, 2018 : In Millions Guarantee Description Issue Date Expiration Date Maximum Obligation Carrying Amount CMS Energy, including Consumers Indemnity obligations from stock and asset sale agreements 1 Various Indefinite $ 153 $ 3 Guarantees 2 Various Indefinite 39 — Consumers Guarantee 2 July 2011 Indefinite $ 30 $ — 1 These obligations arose from stock and asset sale agreements under which CMS Energy or a subsidiary of CMS Energy indemnified the purchaser for losses resulting from various matters, primarily claims related to taxes. CMS Energy believes the likelihood of material loss to be remote for the indemnity obligations not recorded as liabilities. 2 At Consumers, this obligation comprises a guarantee provided to the U.S. Department of Energy in connection with a settlement agreement regarding damages resulting from the department’s failure to accept spent nuclear fuel from nuclear power plants formerly owned by Consumers. At CMS Energy, the guarantee obligations comprise Consumers’ guarantee to the U.S. Department of Energy and CMS Energy’s 1994 guarantee of non-recourse revenue bonds issued by Genesee. Additionally, in the normal course of business, CMS Energy, Consumers, and certain other subsidiaries of CMS Energy have entered into various agreements containing tax and other indemnity provisions for which they are unable to estimate the maximum potential obligation. The carrying value of these indemnity obligations is $1 million . CMS Energy and Consumers consider the likelihood that they would be required to perform or incur substantial losses related to these indemnities to be remote. Other Contingencies In addition to the matters disclosed in this Note and Note 2, Regulatory Matters , there are certain other lawsuits and administrative proceedings before various courts and governmental agencies arising in the ordinary course of business to which CMS Energy, Consumers, and certain other subsidiaries of CMS Energy are parties. These other lawsuits and proceedings may involve personal injury, property damage, contracts, environmental matters, federal and state taxes, rates, licensing, employment, and other matters. Further, CMS Energy and Consumers occasionally self-report certain regulatory non-compliance matters that may or may not eventually result in administrative proceedings. CMS Energy and Consumers believe that the outcome of any one of these proceedings will not have a material negative effect on their consolidated results of operations, financial condition, or liquidity.

Financings And Capitalization

Financings And Capitalization	9 Months Ended
	Sep. 30, 2018
Debt Instrument [Line Items]
Financings And Capitalization	Financings and Capitalization Financings: Presented in the following table is a summary of major long-term debt transactions during the nine months ended September 30, 2018 . Principal Interest Rate Issue/Retirement Date Maturity Date Debt issuances CMS Energy, parent only Junior subordinated notes 1 $ 200 5.625 % March 2018 March 2078 Junior subordinated notes 1 250 5.875 % September 2018 October 2078 Total CMS Energy, parent only $ 450 Consumers First mortgage bonds $ 550 4.05 % May 2018 May 2048 Total Consumers $ 550 Total CMS Energy $ 1,000 Debt retirements CMS Energy, parent only Term loan facility $ 180 variable March 2018 December 2018 Senior notes 2 100 8.75 % June 2018 June 2019 Term loan facility 45 variable August 2018 December 2018 Total CMS Energy, parent only $ 325 Consumers Tax-exempt pollution control revenue bonds $ 68 various April 2018 April 2018 First mortgage bonds 250 5.65 % May 2018 September 2018 Total Consumers $ 318 Total CMS Energy $ 643 1 These unsecured obligations rank subordinate and junior in right of payment to all of CMS Energy’s existing and future senior indebtedness. 2 CMS Energy retired these senior notes at a premium and recorded a loss on extinguishment of $5 million in other expense on its consolidated statements of income. In October 2018, under the over-allotment option included in a September 2018 underwriting agreement, CMS Energy issued and sold an additional $30 million of its 5.875 percent junior subordinated notes due 2078. Also in October 2018, CMS Energy redeemed $300 million of its 6.25 percent senior notes due 2020. CMS Energy retired this debt at a premium and recorded a loss on extinguishment of $11 million in other expense on its consolidated statements of income. In July 2018, Consumers entered into a bond purchase agreement to issue an aggregate principal amount of $500 million in first mortgage bonds through a private placement. In October 2018, the following first mortgage bonds were issued and funded: • $100 million of 3.68 percent first mortgage bonds due 2027 • $215 million of 4.01 percent first mortgage bonds due 2038 • $185 million of 4.28 percent first mortgage bonds due 2057 Revolving Credit Facilities: The following revolving credit facilities with banks were available at September 30, 2018 : In Millions Expiration Date Amount of Facility Amount Borrowed Letters of Credit Outstanding Amount Available CMS Energy, parent only June 5, 2023 1 $ 550 $ — $ 9 $ 541 Consumers June 5, 2023 2,3 $ 850 $ — $ 7 $ 843 November 23, 2019 3 250 — 25 225 September 9, 2019 3 30 — 30 — 1 In June 2018, CMS Energy amended this revolving credit facility, eliminating the security provided by Consumers common stock, and extending the expiration date to June 2023. 2 In June 2018, Consumers amended this revolving credit facility by increasing its borrowing capacity to $850 million and extending the expiration date to June 2023. 3 Obligations under this facility are secured by first mortgage bonds of Consumers. Short-term Borrowings: Under Consumers’ commercial paper program , Consumers may issue, in one or more placements , commercial paper notes with maturities of up to 365 days and that bear interest at fixed or floating rates. These issuances are supported by Consumers’ revolving credit facilities and may have an aggregate principal amount outstanding of up to $500 million . While the amount of outstanding commercial paper does not reduce the available capacity of the revolving credit facilities, Consumers does not intend to issue commercial paper in an amount exceeding the available capacity of the facilities. At September 30, 2018 , $279 million in commercial paper notes were outstanding under this program. Dividend Restrictions : At September 30, 2018 , payment of dividends by CMS Energy on its common stock was limited to $4.7 billion under provisions of the Michigan Business Corporation Act of 1972. Under the provisions of its articles of incorporation, at September 30, 2018 , Consumers had $1.3 billion of unrestricted retained earnings available to pay dividends on its common stock to CMS Energy. Provisions of the Federal Power Act and the Natural Gas Act appear to restrict dividends payable by Consumers to the amount of Consumers’ retained earnings. Several decisions from FERC suggest that, under a variety of circumstances, dividends from Consumers on its common stock would not be limited to amounts in Consumers’ retained earnings. Any decision by Consumers to pay dividends on its common stock in excess of retained earnings would be based on specific facts and circumstances and would be subject to a formal regulatory filing process. For the nine months ended September 30, 2018 , Consumers paid $392 million in dividends on its common stock to CMS Energy. Issuance of Common Stock: In March 2017, CMS Energy entered into an updated continuous equity offering program permitting it to sell, from time to time in “at the market” offerings, common stock having an aggregate sales price of up to $100 million . Presented in the following table are the transactions that CMS Energy entered into under the program: Number of Shares Issued Average Price Per Share Net Proceeds May 2018 638,898 $ 45.83 $ 29 June 2017 1,494,371 47.31 70 In August 2018, CMS Energy entered into an equity offering program under which it may sell, from time to time, shares of CMS Energy common stock having an aggregate sales price of up to $250 million . Under this program, CMS Energy may sell its common stock in privately negotiated “at the market” offerings, through forward purchases or otherwise. There was no activity under the new program in the third quarter of 2018.
Consumers Energy Company
Debt Instrument [Line Items]
Financings And Capitalization	Financings and Capitalization Financings: Presented in the following table is a summary of major long-term debt transactions during the nine months ended September 30, 2018 . Principal Interest Rate Issue/Retirement Date Maturity Date Debt issuances CMS Energy, parent only Junior subordinated notes 1 $ 200 5.625 % March 2018 March 2078 Junior subordinated notes 1 250 5.875 % September 2018 October 2078 Total CMS Energy, parent only $ 450 Consumers First mortgage bonds $ 550 4.05 % May 2018 May 2048 Total Consumers $ 550 Total CMS Energy $ 1,000 Debt retirements CMS Energy, parent only Term loan facility $ 180 variable March 2018 December 2018 Senior notes 2 100 8.75 % June 2018 June 2019 Term loan facility 45 variable August 2018 December 2018 Total CMS Energy, parent only $ 325 Consumers Tax-exempt pollution control revenue bonds $ 68 various April 2018 April 2018 First mortgage bonds 250 5.65 % May 2018 September 2018 Total Consumers $ 318 Total CMS Energy $ 643 1 These unsecured obligations rank subordinate and junior in right of payment to all of CMS Energy’s existing and future senior indebtedness. 2 CMS Energy retired these senior notes at a premium and recorded a loss on extinguishment of $5 million in other expense on its consolidated statements of income. In October 2018, under the over-allotment option included in a September 2018 underwriting agreement, CMS Energy issued and sold an additional $30 million of its 5.875 percent junior subordinated notes due 2078. Also in October 2018, CMS Energy redeemed $300 million of its 6.25 percent senior notes due 2020. CMS Energy retired this debt at a premium and recorded a loss on extinguishment of $11 million in other expense on its consolidated statements of income. In July 2018, Consumers entered into a bond purchase agreement to issue an aggregate principal amount of $500 million in first mortgage bonds through a private placement. In October 2018, the following first mortgage bonds were issued and funded: • $100 million of 3.68 percent first mortgage bonds due 2027 • $215 million of 4.01 percent first mortgage bonds due 2038 • $185 million of 4.28 percent first mortgage bonds due 2057 Revolving Credit Facilities: The following revolving credit facilities with banks were available at September 30, 2018 : In Millions Expiration Date Amount of Facility Amount Borrowed Letters of Credit Outstanding Amount Available CMS Energy, parent only June 5, 2023 1 $ 550 $ — $ 9 $ 541 Consumers June 5, 2023 2,3 $ 850 $ — $ 7 $ 843 November 23, 2019 3 250 — 25 225 September 9, 2019 3 30 — 30 — 1 In June 2018, CMS Energy amended this revolving credit facility, eliminating the security provided by Consumers common stock, and extending the expiration date to June 2023. 2 In June 2018, Consumers amended this revolving credit facility by increasing its borrowing capacity to $850 million and extending the expiration date to June 2023. 3 Obligations under this facility are secured by first mortgage bonds of Consumers. Short-term Borrowings: Under Consumers’ commercial paper program , Consumers may issue, in one or more placements , commercial paper notes with maturities of up to 365 days and that bear interest at fixed or floating rates. These issuances are supported by Consumers’ revolving credit facilities and may have an aggregate principal amount outstanding of up to $500 million . While the amount of outstanding commercial paper does not reduce the available capacity of the revolving credit facilities, Consumers does not intend to issue commercial paper in an amount exceeding the available capacity of the facilities. At September 30, 2018 , $279 million in commercial paper notes were outstanding under this program. Dividend Restrictions : At September 30, 2018 , payment of dividends by CMS Energy on its common stock was limited to $4.7 billion under provisions of the Michigan Business Corporation Act of 1972. Under the provisions of its articles of incorporation, at September 30, 2018 , Consumers had $1.3 billion of unrestricted retained earnings available to pay dividends on its common stock to CMS Energy. Provisions of the Federal Power Act and the Natural Gas Act appear to restrict dividends payable by Consumers to the amount of Consumers’ retained earnings. Several decisions from FERC suggest that, under a variety of circumstances, dividends from Consumers on its common stock would not be limited to amounts in Consumers’ retained earnings. Any decision by Consumers to pay dividends on its common stock in excess of retained earnings would be based on specific facts and circumstances and would be subject to a formal regulatory filing process. For the nine months ended September 30, 2018 , Consumers paid $392 million in dividends on its common stock to CMS Energy. Issuance of Common Stock: In March 2017, CMS Energy entered into an updated continuous equity offering program permitting it to sell, from time to time in “at the market” offerings, common stock having an aggregate sales price of up to $100 million . Presented in the following table are the transactions that CMS Energy entered into under the program: Number of Shares Issued Average Price Per Share Net Proceeds May 2018 638,898 $ 45.83 $ 29 June 2017 1,494,371 47.31 70 In August 2018, CMS Energy entered into an equity offering program under which it may sell, from time to time, shares of CMS Energy common stock having an aggregate sales price of up to $250 million . Under this program, CMS Energy may sell its common stock in privately negotiated “at the market” offerings, through forward purchases or otherwise. There was no activity under the new program in the third quarter of 2018.

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	Fair Value Measurements Accounting standards define fair value as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. When measuring fair value, CMS Energy and Consumers are required to incorporate all assumptions that market participants would use in pricing an asset or liability, including assumptions about risk. A fair value hierarchy prioritizes inputs used to measure fair value according to their observability in the market. The three levels of the fair value hierarchy are as follows: • Level 1 inputs are unadjusted quoted prices in active markets for identical assets or liabilities. • Level 2 inputs are observable, market-based inputs, other than Level 1 prices. Level 2 inputs may include quoted prices for similar assets or liabilities in active markets, quoted prices in inactive markets, and inputs derived from or corroborated by observable market data. • Level 3 inputs are unobservable inputs that reflect CMS Energy’s or Consumers’ own assumptions about how market participants would value their assets and liabilities. CMS Energy and Consumers classify fair value measurements within the fair value hierarchy based on the lowest level of input that is significant to the fair value measurement in its entirety. Assets and Liabilities Measured at Fair Value on a Recurring Basis Presented in the following table are CMS Energy’s and Consumers’ assets and liabilities recorded at fair value on a recurring basis: In Millions CMS Energy, including Consumers Consumers September 30 December 31 September 30 December 31 Assets 1 Cash equivalents $ 139 $ 74 $ — $ — Restricted cash equivalents 42 17 28 17 CMS Energy common stock — — 1 21 Nonqualified deferred compensation plan assets 14 14 11 10 DB SERP Cash equivalents 1 5 1 4 Debt securities — 141 — 102 Derivative instruments Commodity contracts 1 1 1 1 Total $ 197 $ 252 $ 42 $ 155 Liabilities 1 Nonqualified deferred compensation plan liabilities $ 14 $ 14 $ 11 $ 10 Derivative instruments Commodity contracts 1 1 1 — Total $ 15 $ 15 $ 12 $ 10 1 All assets and liabilities were classified as Level 1 with the exception of some commodity contracts, which were classified as Level 3. Cash Equivalents: Cash equivalents and restricted cash equivalents consist of money market funds with daily liquidity. Short-term debt instruments classified as cash equivalents on the consolidated balance sheets are not included since they are recorded at amortized cost. Nonqualified Deferred Compensation Plan Assets and Liabilities: The nonqualified deferred compensation plan assets consist of mutual funds, which are valued using the daily quoted net asset values. CMS Energy and Consumers value their nonqualified deferred compensation plan liabilities based on the fair values of the plan assets, as they reflect the amount owed to the plan participants in accordance with their investment elections. CMS Energy and Consumers report the assets in other non-current assets and the liabilities in other non-current liabilities on their consolidated balance sheets. DB SERP Assets: The DB SERP cash equivalents consist of a money market fund with daily liquidity and are reported in other non-current assets on CMS Energy and Consumers’ consolidated balance sheets. The DB SERP debt securities at December 31, 2017 consisted of U.S. Treasury debt securities that were valued at their daily quoted market prices. These debt securities were reported in other non-current assets on CMS Energy’s and Consumers’ consolidated balance sheets. In July 2018, CMS Energy and Consumers sold the DB SERP debt securities . For additional details about this sale, see Note 6, Financial Instruments . Derivative Instruments: CMS Energy and Consumers value their derivative instruments using either a market approach that incorporates information from market transactions, or an income approach that discounts future expected cash flows to a present value amount. CMS Energy values its exchange-traded derivative contracts based on Level 1 quoted prices. CMS Energy’s and Consumers’ remaining derivatives are classified as Level 3. The majority of these derivatives are FTRs held by Consumers. Consumers uses FTRs to manage price risk related to electricity transmission congestion. An FTR is a financial instrument that entitles its holder to receive compensation or requires its holder to remit payment for congestion-related transmission charges. Under regulatory accounting, all changes in fair value associated with FTRs are deferred as regulatory assets and liabilities until the instruments are settled. Due to the lack of quoted pricing information, Consumers determines the fair value of its FTRs based on Consumers’ average historical settlements. There was no material activity within the Level 3 category of financial assets and liabilities during the periods presented.
Consumers Energy Company
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	Fair Value Measurements Accounting standards define fair value as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. When measuring fair value, CMS Energy and Consumers are required to incorporate all assumptions that market participants would use in pricing an asset or liability, including assumptions about risk. A fair value hierarchy prioritizes inputs used to measure fair value according to their observability in the market. The three levels of the fair value hierarchy are as follows: • Level 1 inputs are unadjusted quoted prices in active markets for identical assets or liabilities. • Level 2 inputs are observable, market-based inputs, other than Level 1 prices. Level 2 inputs may include quoted prices for similar assets or liabilities in active markets, quoted prices in inactive markets, and inputs derived from or corroborated by observable market data. • Level 3 inputs are unobservable inputs that reflect CMS Energy’s or Consumers’ own assumptions about how market participants would value their assets and liabilities. CMS Energy and Consumers classify fair value measurements within the fair value hierarchy based on the lowest level of input that is significant to the fair value measurement in its entirety. Assets and Liabilities Measured at Fair Value on a Recurring Basis Presented in the following table are CMS Energy’s and Consumers’ assets and liabilities recorded at fair value on a recurring basis: In Millions CMS Energy, including Consumers Consumers September 30 December 31 September 30 December 31 Assets 1 Cash equivalents $ 139 $ 74 $ — $ — Restricted cash equivalents 42 17 28 17 CMS Energy common stock — — 1 21 Nonqualified deferred compensation plan assets 14 14 11 10 DB SERP Cash equivalents 1 5 1 4 Debt securities — 141 — 102 Derivative instruments Commodity contracts 1 1 1 1 Total $ 197 $ 252 $ 42 $ 155 Liabilities 1 Nonqualified deferred compensation plan liabilities $ 14 $ 14 $ 11 $ 10 Derivative instruments Commodity contracts 1 1 1 — Total $ 15 $ 15 $ 12 $ 10 1 All assets and liabilities were classified as Level 1 with the exception of some commodity contracts, which were classified as Level 3. Cash Equivalents: Cash equivalents and restricted cash equivalents consist of money market funds with daily liquidity. Short-term debt instruments classified as cash equivalents on the consolidated balance sheets are not included since they are recorded at amortized cost. Nonqualified Deferred Compensation Plan Assets and Liabilities: The nonqualified deferred compensation plan assets consist of mutual funds, which are valued using the daily quoted net asset values. CMS Energy and Consumers value their nonqualified deferred compensation plan liabilities based on the fair values of the plan assets, as they reflect the amount owed to the plan participants in accordance with their investment elections. CMS Energy and Consumers report the assets in other non-current assets and the liabilities in other non-current liabilities on their consolidated balance sheets. DB SERP Assets: The DB SERP cash equivalents consist of a money market fund with daily liquidity and are reported in other non-current assets on CMS Energy and Consumers’ consolidated balance sheets. The DB SERP debt securities at December 31, 2017 consisted of U.S. Treasury debt securities that were valued at their daily quoted market prices. These debt securities were reported in other non-current assets on CMS Energy’s and Consumers’ consolidated balance sheets. In July 2018, CMS Energy and Consumers sold the DB SERP debt securities . For additional details about this sale, see Note 6, Financial Instruments . Derivative Instruments: CMS Energy and Consumers value their derivative instruments using either a market approach that incorporates information from market transactions, or an income approach that discounts future expected cash flows to a present value amount. CMS Energy values its exchange-traded derivative contracts based on Level 1 quoted prices. CMS Energy’s and Consumers’ remaining derivatives are classified as Level 3. The majority of these derivatives are FTRs held by Consumers. Consumers uses FTRs to manage price risk related to electricity transmission congestion. An FTR is a financial instrument that entitles its holder to receive compensation or requires its holder to remit payment for congestion-related transmission charges. Under regulatory accounting, all changes in fair value associated with FTRs are deferred as regulatory assets and liabilities until the instruments are settled. Due to the lack of quoted pricing information, Consumers determines the fair value of its FTRs based on Consumers’ average historical settlements. There was no material activity within the Level 3 category of financial assets and liabilities during the periods presented.

Financial Instruments

Financial Instruments	9 Months Ended
	Sep. 30, 2018
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial Instruments	Financial Instruments Presented in the following table are the carrying amounts and fair values, by level within the fair value hierarchy, of CMS Energy’s and Consumers’ financial instruments that are not recorded at fair value. The table excludes cash, cash equivalents, short-term financial instruments, and trade accounts receivable and payable whose carrying amounts approximate their fair values. For information about assets and liabilities recorded at fair value and for additional details regarding the fair value hierarchy, see Note 5, Fair Value Measurements . In Millions September 30, 2018 December 31, 2017 Fair Value Fair Value Carrying Level Carrying Level Amount Total 1 2 3 Amount Total 1 2 3 CMS Energy, including Consumers Assets Long-term receivables 1 $ 22 $ 22 $ — $ — $ 22 $ 21 $ 21 $ — $ — $ 21 Notes receivable 2 1,640 1,730 — — 1,730 1,371 1,464 — — 1,464 Securities held to maturity 22 21 — 21 — 16 16 — 16 — Liabilities Long-term payables 3 26 26 — — 26 27 26 — — 26 Long-term debt 4 10,817 10,798 445 9,088 1,265 10,204 10,715 — 9,363 1,352 Consumers Assets Long-term receivables 1 $ 22 $ 22 $ — $ — $ 22 $ 21 $ 21 $ — $ — $ 21 Notes receivable 5 17 17 — — 17 17 17 — — 17 Notes receivable – related party 6 107 105 — — 105 — — — — — Liabilities Long-term debt 7 6,115 6,083 — 4,818 1,265 5,904 6,236 — 4,883 1,353 1 Includes current accounts receivable of $15 million at September 30, 2018 and $14 million December 31, 2017 . 2 Includes current portion of notes receivable of $263 million at September 30, 2018 and $200 million at December 31, 2017 . For further details, see Note 7, Notes Receivable . 3 Includes current portion of long-term payables of $3 million at September 30, 2018 and December 31, 2017 . 4 Includes current portion of long-term debt of $1.9 billion at September 30, 2018 and $1.1 billion at December 31, 2017 . 5 Includes current portion of notes receivable of $17 million at September 30, 2018 and December 31, 2017 . 6 Includes current portion of notes receivable – related party of $7 million at September 30, 2018 . For further details on this note receivable, see the DB SERP discussion below. 7 Includes current portion of long-term debt of $876 million at September 30, 2018 and $343 million at December 31, 2017 . The effects of third-party credit enhancements were excluded from the fair value measurements of long-term debt. The principal amount of CMS Energy’s long-term debt supported by third-party credit enhancements was $35 million at September 30, 2018 and $103 million at December 31, 2017 . The entirety of these amounts was at Consumers. Presented in the following table are CMS Energy’s and Consumers’ investment securities classified as available for sale or held to maturity: In Millions September 30, 2018 December 31, 2017 Cost Unrealized Gains Unrealized Losses Fair Value Cost Unrealized Gains Unrealized Losses Fair Value CMS Energy, including Consumers Available for sale DB SERP Debt securities $ — $ — $ — $ — $ 141 $ — $ — $ 141 Held to maturity Debt securities 22 — (1 ) 21 16 — — 16 Consumers Available for sale DB SERP Debt securities $ — $ — $ — $ — $ 102 $ — $ — $ 102 CMS Energy common stock — — — — 2 19 — 21 DB SERP: The DB SERP debt securities classified as available for sale at December 31, 2017 were U.S. Treasury debt securities with maturities ranging from one to ten years . In July 2018, CMS Energy and Consumers sold the DB SERP debt securities and CMS Energy issued a $146 million demand note payable to the DB SERP rabbi trust. The demand note bears interest at an annual rate of 4.10 percent and has a maturity date of 2028. The demand note payable and associated DB SERP investment were eliminated on CMS Energy’s consolidated balance sheets. The portion of the demand note attributable to Consumers was recorded as a note receivable – related party on Consumers’ consolidated balance sheets at September 30, 2018. Held-to-maturity Debt Securities: Debt securities classified as held to maturity consisted primarily of mortgage-backed securities and Utah Housing Corporation bonds held by EnerBank. CMS Energy Common Stock: In January 2018, Consumers implemented ASU 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities . In accordance with the standard, as of January 1, 2018, Consumers removed a $19 million unrealized gain on its investment in CMS Energy common stock from AOCI and recorded the gain in retained earnings. In January 2018, Consumers transferred substantially all of its shares in CMS Energy common stock to a related charitable foundation. Consumers’ remaining equity investment in CMS Energy common stock was $1 million at September 30, 2018 . In accordance with the new standard, as of January 1, 2018, Consumers’ investment in CMS Energy common stock was no longer classified as available for sale. Therefore, this amount is not presented in the table above. There were no material changes in the fair value of Consumers’ investment in CMS Energy common stock during the nine months ended September 30, 2018 . For further details on CMS Energy’s and Consumers’ accounting for this new standard, see Note 1, New Accounting Standards .
Consumers Energy Company
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial Instruments	Financial Instruments Presented in the following table are the carrying amounts and fair values, by level within the fair value hierarchy, of CMS Energy’s and Consumers’ financial instruments that are not recorded at fair value. The table excludes cash, cash equivalents, short-term financial instruments, and trade accounts receivable and payable whose carrying amounts approximate their fair values. For information about assets and liabilities recorded at fair value and for additional details regarding the fair value hierarchy, see Note 5, Fair Value Measurements . In Millions September 30, 2018 December 31, 2017 Fair Value Fair Value Carrying Level Carrying Level Amount Total 1 2 3 Amount Total 1 2 3 CMS Energy, including Consumers Assets Long-term receivables 1 $ 22 $ 22 $ — $ — $ 22 $ 21 $ 21 $ — $ — $ 21 Notes receivable 2 1,640 1,730 — — 1,730 1,371 1,464 — — 1,464 Securities held to maturity 22 21 — 21 — 16 16 — 16 — Liabilities Long-term payables 3 26 26 — — 26 27 26 — — 26 Long-term debt 4 10,817 10,798 445 9,088 1,265 10,204 10,715 — 9,363 1,352 Consumers Assets Long-term receivables 1 $ 22 $ 22 $ — $ — $ 22 $ 21 $ 21 $ — $ — $ 21 Notes receivable 5 17 17 — — 17 17 17 — — 17 Notes receivable – related party 6 107 105 — — 105 — — — — — Liabilities Long-term debt 7 6,115 6,083 — 4,818 1,265 5,904 6,236 — 4,883 1,353 1 Includes current accounts receivable of $15 million at September 30, 2018 and $14 million December 31, 2017 . 2 Includes current portion of notes receivable of $263 million at September 30, 2018 and $200 million at December 31, 2017 . For further details, see Note 7, Notes Receivable . 3 Includes current portion of long-term payables of $3 million at September 30, 2018 and December 31, 2017 . 4 Includes current portion of long-term debt of $1.9 billion at September 30, 2018 and $1.1 billion at December 31, 2017 . 5 Includes current portion of notes receivable of $17 million at September 30, 2018 and December 31, 2017 . 6 Includes current portion of notes receivable – related party of $7 million at September 30, 2018 . For further details on this note receivable, see the DB SERP discussion below. 7 Includes current portion of long-term debt of $876 million at September 30, 2018 and $343 million at December 31, 2017 . The effects of third-party credit enhancements were excluded from the fair value measurements of long-term debt. The principal amount of CMS Energy’s long-term debt supported by third-party credit enhancements was $35 million at September 30, 2018 and $103 million at December 31, 2017 . The entirety of these amounts was at Consumers. Presented in the following table are CMS Energy’s and Consumers’ investment securities classified as available for sale or held to maturity: In Millions September 30, 2018 December 31, 2017 Cost Unrealized Gains Unrealized Losses Fair Value Cost Unrealized Gains Unrealized Losses Fair Value CMS Energy, including Consumers Available for sale DB SERP Debt securities $ — $ — $ — $ — $ 141 $ — $ — $ 141 Held to maturity Debt securities 22 — (1 ) 21 16 — — 16 Consumers Available for sale DB SERP Debt securities $ — $ — $ — $ — $ 102 $ — $ — $ 102 CMS Energy common stock — — — — 2 19 — 21 DB SERP: The DB SERP debt securities classified as available for sale at December 31, 2017 were U.S. Treasury debt securities with maturities ranging from one to ten years . In July 2018, CMS Energy and Consumers sold the DB SERP debt securities and CMS Energy issued a $146 million demand note payable to the DB SERP rabbi trust. The demand note bears interest at an annual rate of 4.10 percent and has a maturity date of 2028. The demand note payable and associated DB SERP investment were eliminated on CMS Energy’s consolidated balance sheets. The portion of the demand note attributable to Consumers was recorded as a note receivable – related party on Consumers’ consolidated balance sheets at September 30, 2018. Held-to-maturity Debt Securities: Debt securities classified as held to maturity consisted primarily of mortgage-backed securities and Utah Housing Corporation bonds held by EnerBank. CMS Energy Common Stock: In January 2018, Consumers implemented ASU 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities . In accordance with the standard, as of January 1, 2018, Consumers removed a $19 million unrealized gain on its investment in CMS Energy common stock from AOCI and recorded the gain in retained earnings. In January 2018, Consumers transferred substantially all of its shares in CMS Energy common stock to a related charitable foundation. Consumers’ remaining equity investment in CMS Energy common stock was $1 million at September 30, 2018 . In accordance with the new standard, as of January 1, 2018, Consumers’ investment in CMS Energy common stock was no longer classified as available for sale. Therefore, this amount is not presented in the table above. There were no material changes in the fair value of Consumers’ investment in CMS Energy common stock during the nine months ended September 30, 2018 . For further details on CMS Energy’s and Consumers’ accounting for this new standard, see Note 1, New Accounting Standards .

Notes Receivable

Notes Receivable	9 Months Ended
	Sep. 30, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes Receivable	Notes Receivable Presented in the following table are details of CMS Energy’s and Consumers’ current and non-current notes receivable: In Millions September 30, 2018 December 31, 2017 CMS Energy, including Consumers Current EnerBank notes receivable, net of allowance for loan losses $ 217 $ 178 EnerBank notes receivable held for sale 26 2 Michigan tax settlement 20 20 Non-current EnerBank notes receivable 1,377 1,171 Total notes receivable $ 1,640 $ 1,371 Consumers Current Michigan tax settlement $ 17 $ 17 DB SERP note receivable – related party 7 — Non-current DB SERP note receivable – related party 100 — Total notes receivable $ 124 $ 17 EnerBank notes receivable are unsecured consumer installment loans for financing home improvements. EnerBank records its notes receivable at cost, less an allowance for loan losses. At September 30, 2018 , $26 million of notes receivable were reclassified as held for sale; the fair value of the notes receivable held for sale exceeded their carrying value. These notes are expected to be sold later this year. Authorized contractors pay fees to EnerBank to provide borrowers with same-as-cash, zero interest, or reduced interest loans. Unearned income associated with the loan fees, which is recorded as a reduction to notes receivable on CMS Energy’s consolidated balance sheets, was $82 million at September 30, 2018 and $84 million at December 31, 2017 . Unearned income associated with loan fees for notes receivable held for sale was $6 million at September 30, 2018 . During the three months ended September 30, 2018 , EnerBank purchased a portfolio of secured and unsecured consumer retail installment contracts with a principal value of $77 million at September 30, 2018 . The allowance for loan losses is a valuation allowance to reflect estimated credit losses. The allowance is increased by the provision for loan losses and decreased by loan charge-offs net of recoveries. Management estimates the allowance balance required by taking into consideration historical loan loss experience, the nature and volume of the portfolio, economic conditions, and other factors. Loan losses are charged against the allowance when the loss is confirmed, but no later than the point at which a loan becomes 120 days past due. Loans that are 30 days or more past due are considered delinquent. The balance of EnerBank’s delinquent consumer loans was $15 million at September 30, 2018 and $14 million at December 31, 2017 . At September 30, 2018 and December 31, 2017 , $1 million of EnerBank’s loans had been modified as troubled debt restructurings. For additional details about the DB SERP note receivable – related party, see Note 6, Financial Instruments .
Consumers Energy Company
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes Receivable	Notes Receivable Presented in the following table are details of CMS Energy’s and Consumers’ current and non-current notes receivable: In Millions September 30, 2018 December 31, 2017 CMS Energy, including Consumers Current EnerBank notes receivable, net of allowance for loan losses $ 217 $ 178 EnerBank notes receivable held for sale 26 2 Michigan tax settlement 20 20 Non-current EnerBank notes receivable 1,377 1,171 Total notes receivable $ 1,640 $ 1,371 Consumers Current Michigan tax settlement $ 17 $ 17 DB SERP note receivable – related party 7 — Non-current DB SERP note receivable – related party 100 — Total notes receivable $ 124 $ 17 EnerBank notes receivable are unsecured consumer installment loans for financing home improvements. EnerBank records its notes receivable at cost, less an allowance for loan losses. At September 30, 2018 , $26 million of notes receivable were reclassified as held for sale; the fair value of the notes receivable held for sale exceeded their carrying value. These notes are expected to be sold later this year. Authorized contractors pay fees to EnerBank to provide borrowers with same-as-cash, zero interest, or reduced interest loans. Unearned income associated with the loan fees, which is recorded as a reduction to notes receivable on CMS Energy’s consolidated balance sheets, was $82 million at September 30, 2018 and $84 million at December 31, 2017 . Unearned income associated with loan fees for notes receivable held for sale was $6 million at September 30, 2018 . During the three months ended September 30, 2018 , EnerBank purchased a portfolio of secured and unsecured consumer retail installment contracts with a principal value of $77 million at September 30, 2018 . The allowance for loan losses is a valuation allowance to reflect estimated credit losses. The allowance is increased by the provision for loan losses and decreased by loan charge-offs net of recoveries. Management estimates the allowance balance required by taking into consideration historical loan loss experience, the nature and volume of the portfolio, economic conditions, and other factors. Loan losses are charged against the allowance when the loss is confirmed, but no later than the point at which a loan becomes 120 days past due. Loans that are 30 days or more past due are considered delinquent. The balance of EnerBank’s delinquent consumer loans was $15 million at September 30, 2018 and $14 million at December 31, 2017 . At September 30, 2018 and December 31, 2017 , $1 million of EnerBank’s loans had been modified as troubled debt restructurings. For additional details about the DB SERP note receivable – related party, see Note 6, Financial Instruments .

Retirement Benefits

Retirement Benefits	9 Months Ended
	Sep. 30, 2018
Defined Benefit Plan Disclosure [Line Items]
Retirement Benefits	Retirement Benefits CMS Energy and Consumers provide pension, OPEB, and other retirement benefits to employees under a number of different plans. In November 2017, CMS Energy and Consumers approved certain amendments to the OPEB Plan, resulting in higher OPEB Plan credits in 2018 compared to 2017. Presented in the following table are the costs (credits) and other changes in plan assets and benefit obligations incurred in CMS Energy’s and Consumers’ retirement benefits plans: In Millions DB Pension Plans OPEB Plan Three Months Ended Nine Months Ended Three Months Ended Nine Months Ended September 30 2018 2017 2018 2017 2018 2017 2018 2017 CMS Energy, including Consumers Net periodic cost (credit) Service cost $ 12 $ 12 $ 36 $ 34 $ 4 $ 5 $ 13 $ 15 Interest cost 22 23 67 67 9 13 27 39 Expected return on plan assets (38 ) (39 ) (112 ) (115 ) (24 ) (22 ) (73 ) (67 ) Amortization of: Net loss 19 20 56 60 3 7 11 23 Prior service cost (credit) 1 1 2 3 (16 ) (8 ) (50 ) (26 ) Net periodic cost (credit) $ 16 $ 17 $ 49 $ 49 $ (24 ) $ (5 ) $ (72 ) $ (16 ) Consumers Net periodic cost (credit) Service cost $ 12 $ 11 $ 35 $ 33 $ 4 $ 5 $ 12 $ 14 Interest cost 22 22 64 65 8 12 25 38 Expected return on plan assets (35 ) (38 ) (104 ) (112 ) (22 ) (21 ) (68 ) (63 ) Amortization of: Net loss 17 19 53 58 4 8 12 24 Prior service cost (credit) 1 1 2 3 (17 ) (8 ) (49 ) (25 ) Net periodic cost (credit) $ 17 $ 15 $ 50 $ 47 $ (23 ) $ (4 ) $ (68 ) $ (12 )
Consumers Energy Company
Defined Benefit Plan Disclosure [Line Items]
Retirement Benefits	Retirement Benefits CMS Energy and Consumers provide pension, OPEB, and other retirement benefits to employees under a number of different plans. In November 2017, CMS Energy and Consumers approved certain amendments to the OPEB Plan, resulting in higher OPEB Plan credits in 2018 compared to 2017. Presented in the following table are the costs (credits) and other changes in plan assets and benefit obligations incurred in CMS Energy’s and Consumers’ retirement benefits plans: In Millions DB Pension Plans OPEB Plan Three Months Ended Nine Months Ended Three Months Ended Nine Months Ended September 30 2018 2017 2018 2017 2018 2017 2018 2017 CMS Energy, including Consumers Net periodic cost (credit) Service cost $ 12 $ 12 $ 36 $ 34 $ 4 $ 5 $ 13 $ 15 Interest cost 22 23 67 67 9 13 27 39 Expected return on plan assets (38 ) (39 ) (112 ) (115 ) (24 ) (22 ) (73 ) (67 ) Amortization of: Net loss 19 20 56 60 3 7 11 23 Prior service cost (credit) 1 1 2 3 (16 ) (8 ) (50 ) (26 ) Net periodic cost (credit) $ 16 $ 17 $ 49 $ 49 $ (24 ) $ (5 ) $ (72 ) $ (16 ) Consumers Net periodic cost (credit) Service cost $ 12 $ 11 $ 35 $ 33 $ 4 $ 5 $ 12 $ 14 Interest cost 22 22 64 65 8 12 25 38 Expected return on plan assets (35 ) (38 ) (104 ) (112 ) (22 ) (21 ) (68 ) (63 ) Amortization of: Net loss 17 19 53 58 4 8 12 24 Prior service cost (credit) 1 1 2 3 (17 ) (8 ) (49 ) (25 ) Net periodic cost (credit) $ 17 $ 15 $ 50 $ 47 $ (23 ) $ (4 ) $ (68 ) $ (12 )

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2018
Income Taxes [Line Items]
Income Taxes	Income Taxes Presented in the following table is a reconciliation of the statutory U.S. federal income tax rate to the effective income tax rate from continuing operations: Nine Months Ended September 30 2018 2017 CMS Energy, including Consumers U.S. federal income tax rate 21.0 % 35.0 % Increase (decrease) in income taxes from: State and local income taxes, net of federal effect 5.9 2.3 Accelerated flow-through of regulatory tax benefits 1 (5.0 ) (4.3 ) TCJA excess deferred taxes 2 (3.4 ) — Research and development tax credits, net 3 (1.6 ) (0.1 ) Production tax credits (2.0 ) (1.0 ) Other, net 0.2 (1.8 ) Effective tax rate 15.1 % 30.1 % Consumers U.S. federal income tax rate 21.0 % 35.0 % Increase (decrease) in income taxes from: State and local income taxes, net of federal effect 6.1 2.3 Accelerated flow-through of regulatory tax benefits 1 (4.4 ) (3.9 ) TCJA excess deferred taxes 2 (3.1 ) — Research and development tax credits, net 3 (1.5 ) (0.1 ) Production tax credits (1.6 ) (1.0 ) Other, net (0.3 ) (2.0 ) Effective tax rate 16.2 % 30.3 % 1 In 2013, the MPSC issued an order authorizing Consumers to accelerate the flow-through to electric and gas customers of certain income tax benefits associated primarily with the cost of removal of plant placed in service before 1993. Consumers implemented this regulatory treatment beginning in 2014. This change, which also accelerates Consumers’ recognition of the income tax benefits, reduced Consumers’ income tax expense by $30 million for the nine months ended September 30, 2018 and by $28 million for the nine months ended September 30, 2017 . 2 In December 2017, Consumers remeasured its deferred tax assets and liabilities at the new federal tax rate enacted by the TCJA and recorded a $1.8 billion regulatory liability. This regulatory liability relates to the excess deferred taxes arising from accelerated tax depreciation on assets in rate base that are governed by normalization provisions of the Internal Revenue Code. The normalization provisions require that the excess deferred taxes be refunded to customers over the remaining average service life of the associated assets. In January 2018, Consumers began to reduce this regulatory liability by crediting income tax expense. Consumers has fully reserved for the eventual refund of these excess deferred taxes that it has credited to income tax expense in a separate regulatory liability established by reducing revenue, and will continue to do so until these benefits are passed on to customers in accordance with an MPSC order, expected to be issued in 2019. At September 30, 2018 , this reserve for refund of these excess deferred taxes totaled $26 million . 3 In March 2018, Consumers finalized a study of research and development tax credits for the tax years 2012 through 2016. As a result, Consumers recognized an $8 million increase in the credit, net of reserves for uncertain tax positions.
Consumers Energy Company
Income Taxes [Line Items]
Income Taxes	Income Taxes Presented in the following table is a reconciliation of the statutory U.S. federal income tax rate to the effective income tax rate from continuing operations: Nine Months Ended September 30 2018 2017 CMS Energy, including Consumers U.S. federal income tax rate 21.0 % 35.0 % Increase (decrease) in income taxes from: State and local income taxes, net of federal effect 5.9 2.3 Accelerated flow-through of regulatory tax benefits 1 (5.0 ) (4.3 ) TCJA excess deferred taxes 2 (3.4 ) — Research and development tax credits, net 3 (1.6 ) (0.1 ) Production tax credits (2.0 ) (1.0 ) Other, net 0.2 (1.8 ) Effective tax rate 15.1 % 30.1 % Consumers U.S. federal income tax rate 21.0 % 35.0 % Increase (decrease) in income taxes from: State and local income taxes, net of federal effect 6.1 2.3 Accelerated flow-through of regulatory tax benefits 1 (4.4 ) (3.9 ) TCJA excess deferred taxes 2 (3.1 ) — Research and development tax credits, net 3 (1.5 ) (0.1 ) Production tax credits (1.6 ) (1.0 ) Other, net (0.3 ) (2.0 ) Effective tax rate 16.2 % 30.3 % 1 In 2013, the MPSC issued an order authorizing Consumers to accelerate the flow-through to electric and gas customers of certain income tax benefits associated primarily with the cost of removal of plant placed in service before 1993. Consumers implemented this regulatory treatment beginning in 2014. This change, which also accelerates Consumers’ recognition of the income tax benefits, reduced Consumers’ income tax expense by $30 million for the nine months ended September 30, 2018 and by $28 million for the nine months ended September 30, 2017 . 2 In December 2017, Consumers remeasured its deferred tax assets and liabilities at the new federal tax rate enacted by the TCJA and recorded a $1.8 billion regulatory liability. This regulatory liability relates to the excess deferred taxes arising from accelerated tax depreciation on assets in rate base that are governed by normalization provisions of the Internal Revenue Code. The normalization provisions require that the excess deferred taxes be refunded to customers over the remaining average service life of the associated assets. In January 2018, Consumers began to reduce this regulatory liability by crediting income tax expense. Consumers has fully reserved for the eventual refund of these excess deferred taxes that it has credited to income tax expense in a separate regulatory liability established by reducing revenue, and will continue to do so until these benefits are passed on to customers in accordance with an MPSC order, expected to be issued in 2019. At September 30, 2018 , this reserve for refund of these excess deferred taxes totaled $26 million . 3 In March 2018, Consumers finalized a study of research and development tax credits for the tax years 2012 through 2016. As a result, Consumers recognized an $8 million increase in the credit, net of reserves for uncertain tax positions.

Earnings Per Share - CMS Energy

Earnings Per Share - CMS Energy	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Earnings Per Share - CMS Energy	Earnings Per Share—CMS Energy Presented in the following table are CMS Energy’s basic and diluted EPS computations based on net income: In Millions, Except Per Share Amounts Three Months Ended Nine Months Ended September 30 2018 2017 2018 2017 Income available to common stockholders Net income $ 169 $ 172 $ 550 $ 464 Less income attributable to noncontrolling interests — — 1 1 Net income available to common stockholders – basic and diluted $ 169 $ 172 $ 549 $ 463 Average common shares outstanding Weighted-average shares – basic 282.5 280.8 282.1 279.8 Add dilutive nonvested stock awards 0.7 0.8 0.7 0.8 Weighted-average shares – diluted 283.2 281.6 282.8 280.6 Net income per average common share available to common stockholders Basic $ 0.60 $ 0.61 $ 1.95 $ 1.65 Diluted 0.59 0.61 1.94 1.65 Nonvested Stock Awards CMS Energy’s nonvested stock awards are composed of participating and non-participating securities. The participating securities accrue cash dividends when common stockholders receive dividends. Since the recipient is not required to return the dividends to CMS Energy if the recipient forfeits the award, the nonvested stock awards are considered participating securities. As such, the participating nonvested stock awards were included in the computation of basic EPS. The non-participating securities accrue stock dividends that vest concurrently with the stock award. If the recipient forfeits the award, the stock dividends accrued on the non-participating securities are also forfeited. Accordingly, the non-participating awards and stock dividends were included in the computation of diluted EPS, but not basic EPS.

Revenue

Revenue	9 Months Ended
	Sep. 30, 2018
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	Revenue Presented in the following tables are the components of operating revenue: In Millions Three Months Ended September 30, 2018 Electric Utility Gas Utility Enterprises 1 Other 2 Consolidated CMS Energy, including Consumers Consumers utility revenue $ 1,310 $ 188 $ — $ — $ 1,498 Other — — 21 — 21 Revenue recognized from contracts with customers 1,310 188 21 — 1,519 Leasing income — — 36 — 36 Financing income 3 — — 40 43 Consumers alternative revenue programs — 1 — — 1 Total operating revenue – CMS Energy $ 1,313 $ 189 $ 57 $ 40 $ 1,599 Consumers Consumers utility revenue Residential $ 625 $ 118 $ — $ — $ 743 Commercial 434 30 — — 464 Industrial 186 4 — — 190 Other 65 36 — — 101 Revenue recognized from contracts with customers 1,310 188 — — 1,498 Financing income 3 — — — 3 Alternative revenue programs — 1 — — 1 Total operating revenue – Consumers $ 1,313 $ 189 $ — $ — $ 1,502 In Millions Nine Months Ended September 30, 2018 Electric Utility Gas Utility Enterprises 1 Other 2 Consolidated CMS Energy, including Consumers Consumers utility revenue $ 3,473 $ 1,263 $ — $ — $ 4,736 Other — — 69 — 69 Revenue recognized from contracts with customers 3,473 1,263 69 — 4,805 Leasing income — — 112 — 112 Financing income 7 4 — 111 122 Consumers alternative revenue programs — 5 — — 5 Total operating revenue – CMS Energy $ 3,480 $ 1,272 $ 181 $ 111 $ 5,044 Consumers Consumers utility revenue Residential $ 1,601 $ 849 $ — $ — $ 2,450 Commercial 1,181 250 — — 1,431 Industrial 499 37 — — 536 Other 192 127 — — 319 Revenue recognized from contracts with customers 3,473 1,263 — — 4,736 Financing income 7 4 — — 11 Alternative revenue programs — 5 — — 5 Total operating revenue – Consumers $ 3,480 $ 1,272 $ — $ — $ 4,752 1 Amounts represent the enterprises segment’s operating revenue from independent power production and CMS ERM’s sales of energy commodities in support of the independent power production portfolio. 2 Amount represents EnerBank’s operating revenue from unsecured consumer installment loans for financing home improvements. Electric and Gas Utilities Consumers Utility Revenue: Consumers recognizes revenue primarily from the sale of electric and gas utility services at tariff-based rates regulated by the MPSC. Consumers’ customer base consists of a mix of residential, commercial, and diversified industrial customers. Consumers’ tariff-based sales performance obligations are described below. • Consumers has performance obligations for the service of standing ready to deliver electricity or natural gas to customers, and it satisfies these performance obligations over time. Consumers recognizes revenue at a fixed rate as it provides these services. These arrangements generally do not have fixed terms and remain in effect as long as the customer consumes the utility service. The rates are set by the MPSC through the rate-making process and represent the stand-alone selling price of Consumers’ service to stand ready to deliver. • Consumers has performance obligations for the service of delivering the commodity of electricity or natural gas to customers, and it satisfies these performance obligations upon delivery. Consumers recognizes revenue at a price per unit of electricity or natural gas delivered, based on the tariffs established by the MPSC. These arrangements generally do not have fixed terms and remain in effect as long as the customer consumes the utility service. The rates are set by the MPSC through the rate-making process and represent the stand-alone selling price of a bundled product comprising the commodity, electricity or natural gas, and the service of delivering such commodity. In some instances, Consumers has specific fixed-term contracts with large commercial and industrial customers to provide electricity or gas at certain tariff rates or to provide gas transportation services at contracted rates. The amount of electricity and gas to be delivered under these contracts and the associated future revenue to be received are generally dependent on the customers’ needs. Accordingly, Consumers recognizes revenues at the tariff or contracted rate as electricity or gas is delivered to the customer. Consumers also has other miscellaneous contracts with customers related to pole and other property rentals, appliance service plans, and utility contract work. Generally, these contracts are short term or evergreen in nature. Accounts Receivable and Unbilled Revenues: Accounts receivable comprise trade receivables and unbilled receivables. CMS Energy and Consumers record their accounts receivable at cost, which approximates fair value. CMS Energy and Consumers establish an allowance for uncollectible accounts based on historical losses, management’s assessment of existing economic conditions, customer payment trends, and other factors. CMS Energy and Consumers assess late payment fees on trade receivables based on contractual past-due terms established with customers. CMS Energy and Consumers charge off accounts deemed uncollectible to operating expense. Uncollectible expense for CMS Energy, including Consumers, was $22 million for the nine months ended September 30, 2018 . Uncollectible expense for Consumers was $22 million for the nine months ended September 30, 2018 . Consumers’ customers are billed monthly in cycles having billing dates that do not generally coincide with the end of a calendar month. This results in customers having received electricity or natural gas that they have not been billed for as of the month-end. Consumers estimates its unbilled revenues by applying an average billed rate to total unbilled deliveries for each customer class. Unbilled revenues, which are recorded as accounts receivable on CMS Energy’s and Consumers’ consolidated balance sheets, were $271 million at September 30, 2018 and $481 million at December 31, 2017 . Alternative-Revenue Programs: Under a gas revenue decoupling mechanism authorized by the MPSC, Consumers is allowed to adjust future gas rates for differences between Consumers’ actual weather-normalized nonfuel revenues and the revenues approved by the MPSC. Consumers accounts for this program as an alternative-revenue program that meets the criteria for recognizing the effects of decoupling adjustments on revenue as gas is delivered.
Consumers Energy Company
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	Revenue Presented in the following tables are the components of operating revenue: In Millions Three Months Ended September 30, 2018 Electric Utility Gas Utility Enterprises 1 Other 2 Consolidated CMS Energy, including Consumers Consumers utility revenue $ 1,310 $ 188 $ — $ — $ 1,498 Other — — 21 — 21 Revenue recognized from contracts with customers 1,310 188 21 — 1,519 Leasing income — — 36 — 36 Financing income 3 — — 40 43 Consumers alternative revenue programs — 1 — — 1 Total operating revenue – CMS Energy $ 1,313 $ 189 $ 57 $ 40 $ 1,599 Consumers Consumers utility revenue Residential $ 625 $ 118 $ — $ — $ 743 Commercial 434 30 — — 464 Industrial 186 4 — — 190 Other 65 36 — — 101 Revenue recognized from contracts with customers 1,310 188 — — 1,498 Financing income 3 — — — 3 Alternative revenue programs — 1 — — 1 Total operating revenue – Consumers $ 1,313 $ 189 $ — $ — $ 1,502 In Millions Nine Months Ended September 30, 2018 Electric Utility Gas Utility Enterprises 1 Other 2 Consolidated CMS Energy, including Consumers Consumers utility revenue $ 3,473 $ 1,263 $ — $ — $ 4,736 Other — — 69 — 69 Revenue recognized from contracts with customers 3,473 1,263 69 — 4,805 Leasing income — — 112 — 112 Financing income 7 4 — 111 122 Consumers alternative revenue programs — 5 — — 5 Total operating revenue – CMS Energy $ 3,480 $ 1,272 $ 181 $ 111 $ 5,044 Consumers Consumers utility revenue Residential $ 1,601 $ 849 $ — $ — $ 2,450 Commercial 1,181 250 — — 1,431 Industrial 499 37 — — 536 Other 192 127 — — 319 Revenue recognized from contracts with customers 3,473 1,263 — — 4,736 Financing income 7 4 — — 11 Alternative revenue programs — 5 — — 5 Total operating revenue – Consumers $ 3,480 $ 1,272 $ — $ — $ 4,752 1 Amounts represent the enterprises segment’s operating revenue from independent power production and CMS ERM’s sales of energy commodities in support of the independent power production portfolio. 2 Amount represents EnerBank’s operating revenue from unsecured consumer installment loans for financing home improvements. Electric and Gas Utilities Consumers Utility Revenue: Consumers recognizes revenue primarily from the sale of electric and gas utility services at tariff-based rates regulated by the MPSC. Consumers’ customer base consists of a mix of residential, commercial, and diversified industrial customers. Consumers’ tariff-based sales performance obligations are described below. • Consumers has performance obligations for the service of standing ready to deliver electricity or natural gas to customers, and it satisfies these performance obligations over time. Consumers recognizes revenue at a fixed rate as it provides these services. These arrangements generally do not have fixed terms and remain in effect as long as the customer consumes the utility service. The rates are set by the MPSC through the rate-making process and represent the stand-alone selling price of Consumers’ service to stand ready to deliver. • Consumers has performance obligations for the service of delivering the commodity of electricity or natural gas to customers, and it satisfies these performance obligations upon delivery. Consumers recognizes revenue at a price per unit of electricity or natural gas delivered, based on the tariffs established by the MPSC. These arrangements generally do not have fixed terms and remain in effect as long as the customer consumes the utility service. The rates are set by the MPSC through the rate-making process and represent the stand-alone selling price of a bundled product comprising the commodity, electricity or natural gas, and the service of delivering such commodity. In some instances, Consumers has specific fixed-term contracts with large commercial and industrial customers to provide electricity or gas at certain tariff rates or to provide gas transportation services at contracted rates. The amount of electricity and gas to be delivered under these contracts and the associated future revenue to be received are generally dependent on the customers’ needs. Accordingly, Consumers recognizes revenues at the tariff or contracted rate as electricity or gas is delivered to the customer. Consumers also has other miscellaneous contracts with customers related to pole and other property rentals, appliance service plans, and utility contract work. Generally, these contracts are short term or evergreen in nature. Accounts Receivable and Unbilled Revenues: Accounts receivable comprise trade receivables and unbilled receivables. CMS Energy and Consumers record their accounts receivable at cost, which approximates fair value. CMS Energy and Consumers establish an allowance for uncollectible accounts based on historical losses, management’s assessment of existing economic conditions, customer payment trends, and other factors. CMS Energy and Consumers assess late payment fees on trade receivables based on contractual past-due terms established with customers. CMS Energy and Consumers charge off accounts deemed uncollectible to operating expense. Uncollectible expense for CMS Energy, including Consumers, was $22 million for the nine months ended September 30, 2018 . Uncollectible expense for Consumers was $22 million for the nine months ended September 30, 2018 . Consumers’ customers are billed monthly in cycles having billing dates that do not generally coincide with the end of a calendar month. This results in customers having received electricity or natural gas that they have not been billed for as of the month-end. Consumers estimates its unbilled revenues by applying an average billed rate to total unbilled deliveries for each customer class. Unbilled revenues, which are recorded as accounts receivable on CMS Energy’s and Consumers’ consolidated balance sheets, were $271 million at September 30, 2018 and $481 million at December 31, 2017 . Alternative-Revenue Programs: Under a gas revenue decoupling mechanism authorized by the MPSC, Consumers is allowed to adjust future gas rates for differences between Consumers’ actual weather-normalized nonfuel revenues and the revenues approved by the MPSC. Consumers accounts for this program as an alternative-revenue program that meets the criteria for recognizing the effects of decoupling adjustments on revenue as gas is delivered.

Cash And Cash Equivalents

Cash And Cash Equivalents	9 Months Ended
	Sep. 30, 2018
Cash and Cash Equivalents [Line Items]
Cash And Cash Equivalents	Cash and Cash Equivalents Presented in the following table are the components of total cash and cash equivalents, including restricted amounts, and their location on CMS Energy’s and Consumers’ consolidated balance sheets: In Millions September 30, 2018 December 31, 2017 CMS Energy, including Consumers Cash and cash equivalents $ 323 $ 182 Restricted cash and cash equivalents 42 17 Other non-current assets 1 5 Cash and cash equivalents, including restricted amounts $ 366 $ 204 Consumers Cash and cash equivalents $ 9 $ 44 Restricted cash and cash equivalents 28 17 Other non-current assets 1 4 Cash and cash equivalents, including restricted amounts $ 38 $ 65 Cash and Cash Equivalents: Cash and cash equivalents include short-term, highly liquid investments with original maturities of three months or less. Restricted Cash and Cash Equivalents: Restricted cash and cash equivalents are held primarily for the repayment of securitization bonds and funds held in escrow. Cash and cash equivalents may also be restricted to pay other contractual obligations such as leasing of coal rail cars. These amounts are classified as current assets since they relate to payments that could or will occur within one year. Other Non-current Assets: The cash equivalents classified as other non-current assets represent an investment in a money market fund held in the DB SERP rabbi trust. See Note 5, Fair Value Measurements for more information regarding the DB SERP.
Consumers Energy Company
Cash and Cash Equivalents [Line Items]
Cash And Cash Equivalents	Cash and Cash Equivalents Presented in the following table are the components of total cash and cash equivalents, including restricted amounts, and their location on CMS Energy’s and Consumers’ consolidated balance sheets: In Millions September 30, 2018 December 31, 2017 CMS Energy, including Consumers Cash and cash equivalents $ 323 $ 182 Restricted cash and cash equivalents 42 17 Other non-current assets 1 5 Cash and cash equivalents, including restricted amounts $ 366 $ 204 Consumers Cash and cash equivalents $ 9 $ 44 Restricted cash and cash equivalents 28 17 Other non-current assets 1 4 Cash and cash equivalents, including restricted amounts $ 38 $ 65 Cash and Cash Equivalents: Cash and cash equivalents include short-term, highly liquid investments with original maturities of three months or less. Restricted Cash and Cash Equivalents: Restricted cash and cash equivalents are held primarily for the repayment of securitization bonds and funds held in escrow. Cash and cash equivalents may also be restricted to pay other contractual obligations such as leasing of coal rail cars. These amounts are classified as current assets since they relate to payments that could or will occur within one year. Other Non-current Assets: The cash equivalents classified as other non-current assets represent an investment in a money market fund held in the DB SERP rabbi trust. See Note 5, Fair Value Measurements for more information regarding the DB SERP.

Reportable Segments

Reportable Segments	9 Months Ended
	Sep. 30, 2018
Segment Reporting Information [Line Items]
Reportable Segments	Reportable Segments Reportable segments consist of business units defined by the products and services they offer. CMS Energy and Consumers evaluate the performance of each segment based on its contribution to net income available to CMS Energy’s common stockholders. CMS Energy The reportable segments for CMS Energy are: • electric utility, consisting of regulated activities associated with the generation, transmission, and distribution of electricity in Michigan • gas utility, consisting of regulated activities associated with the transportation, storage, and distribution of natural gas in Michigan • enterprises, consisting of various subsidiaries engaging in domestic independent power production, the marketing of independent power production, and the development and operation of renewable generation CMS Energy presents EnerBank, corporate interest and other expenses, and Consumers’ other consolidated entities within other reconciling items. Consumers The reportable segments for Consumers are: • electric utility, consisting of regulated activities associated with the generation, transmission, and distribution of electricity in Michigan • gas utility, consisting of regulated activities associated with the transportation, storage, and distribution of natural gas in Michigan Consumers’ other consolidated entities are presented within other reconciling items. Presented in the following tables is financial information by reportable segment: In Millions Three Months Ended Nine Months Ended September 30 2018 2017 2018 2017 CMS Energy, including Consumers Operating revenue Electric utility $ 1,313 $ 1,247 $ 3,480 $ 3,360 Gas utility 189 190 1,272 1,176 Enterprises 57 58 181 172 Other reconciling items 40 32 111 97 Total operating revenue – CMS Energy $ 1,599 $ 1,527 $ 5,044 $ 4,805 Consumers Operating revenue Electric utility $ 1,313 $ 1,247 $ 3,480 $ 3,360 Gas utility 189 190 1,272 1,176 Total operating revenue – Consumers $ 1,502 $ 1,437 $ 4,752 $ 4,536 CMS Energy, including Consumers Net income (loss) available to common stockholders Electric utility $ 199 $ 176 $ 468 $ 394 Gas utility (19 ) 5 105 101 Enterprises 4 8 33 27 Other reconciling items (15 ) (17 ) (57 ) (59 ) Total net income available to common stockholders – CMS Energy $ 169 $ 172 $ 549 $ 463 Consumers Net income (loss) available to common stockholder Electric utility $ 199 $ 176 $ 468 $ 394 Gas utility (19 ) 5 105 101 Total net income available to common stockholder – Consumers $ 180 $ 181 $ 573 $ 495 In Millions September 30, 2018 December 31, 2017 CMS Energy, including Consumers Plant, property, and equipment, gross Electric utility 1 $ 15,772 $ 15,221 Gas utility 1 7,534 7,080 Enterprises 405 167 Other reconciling items 40 38 Total plant, property, and equipment, gross – CMS Energy $ 23,751 $ 22,506 Consumers Plant, property, and equipment, gross Electric utility 1 $ 15,772 $ 15,221 Gas utility 1 7,534 7,080 Other reconciling items 16 17 Total plant, property, and equipment, gross – Consumers $ 23,322 $ 22,318 CMS Energy, including Consumers Total assets Electric utility 1 $ 13,850 $ 13,906 Gas utility 1 7,513 7,139 Enterprises 538 342 Other reconciling items 2,012 1,663 Total assets – CMS Energy $ 23,913 $ 23,050 Consumers Total assets Electric utility 1 $ 13,914 $ 13,907 Gas utility 1 7,556 7,139 Other reconciling items 22 53 Total assets – Consumers $ 21,492 $ 21,099 1 Amounts include a portion of Consumers’ other common assets attributable to both the electric and gas utility businesses.
Consumers Energy Company
Segment Reporting Information [Line Items]
Reportable Segments	Reportable Segments Reportable segments consist of business units defined by the products and services they offer. CMS Energy and Consumers evaluate the performance of each segment based on its contribution to net income available to CMS Energy’s common stockholders. CMS Energy The reportable segments for CMS Energy are: • electric utility, consisting of regulated activities associated with the generation, transmission, and distribution of electricity in Michigan • gas utility, consisting of regulated activities associated with the transportation, storage, and distribution of natural gas in Michigan • enterprises, consisting of various subsidiaries engaging in domestic independent power production, the marketing of independent power production, and the development and operation of renewable generation CMS Energy presents EnerBank, corporate interest and other expenses, and Consumers’ other consolidated entities within other reconciling items. Consumers The reportable segments for Consumers are: • electric utility, consisting of regulated activities associated with the generation, transmission, and distribution of electricity in Michigan • gas utility, consisting of regulated activities associated with the transportation, storage, and distribution of natural gas in Michigan Consumers’ other consolidated entities are presented within other reconciling items. Presented in the following tables is financial information by reportable segment: In Millions Three Months Ended Nine Months Ended September 30 2018 2017 2018 2017 CMS Energy, including Consumers Operating revenue Electric utility $ 1,313 $ 1,247 $ 3,480 $ 3,360 Gas utility 189 190 1,272 1,176 Enterprises 57 58 181 172 Other reconciling items 40 32 111 97 Total operating revenue – CMS Energy $ 1,599 $ 1,527 $ 5,044 $ 4,805 Consumers Operating revenue Electric utility $ 1,313 $ 1,247 $ 3,480 $ 3,360 Gas utility 189 190 1,272 1,176 Total operating revenue – Consumers $ 1,502 $ 1,437 $ 4,752 $ 4,536 CMS Energy, including Consumers Net income (loss) available to common stockholders Electric utility $ 199 $ 176 $ 468 $ 394 Gas utility (19 ) 5 105 101 Enterprises 4 8 33 27 Other reconciling items (15 ) (17 ) (57 ) (59 ) Total net income available to common stockholders – CMS Energy $ 169 $ 172 $ 549 $ 463 Consumers Net income (loss) available to common stockholder Electric utility $ 199 $ 176 $ 468 $ 394 Gas utility (19 ) 5 105 101 Total net income available to common stockholder – Consumers $ 180 $ 181 $ 573 $ 495 In Millions September 30, 2018 December 31, 2017 CMS Energy, including Consumers Plant, property, and equipment, gross Electric utility 1 $ 15,772 $ 15,221 Gas utility 1 7,534 7,080 Enterprises 405 167 Other reconciling items 40 38 Total plant, property, and equipment, gross – CMS Energy $ 23,751 $ 22,506 Consumers Plant, property, and equipment, gross Electric utility 1 $ 15,772 $ 15,221 Gas utility 1 7,534 7,080 Other reconciling items 16 17 Total plant, property, and equipment, gross – Consumers $ 23,322 $ 22,318 CMS Energy, including Consumers Total assets Electric utility 1 $ 13,850 $ 13,906 Gas utility 1 7,513 7,139 Enterprises 538 342 Other reconciling items 2,012 1,663 Total assets – CMS Energy $ 23,913 $ 23,050 Consumers Total assets Electric utility 1 $ 13,914 $ 13,907 Gas utility 1 7,556 7,139 Other reconciling items 22 53 Total assets – Consumers $ 21,492 $ 21,099 1 Amounts include a portion of Consumers’ other common assets attributable to both the electric and gas utility businesses.

New Accounting Standards (Polic

New Accounting Standards (Policies)	9 Months Ended
	Sep. 30, 2018
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
New accounting standards	Implementation of New Accounting Standards ASU 2014-09, Revenue from Contracts with Customers: This standard, which was effective on January 1, 2018 for CMS Energy and Consumers, provides new guidance for recognizing revenue from contracts with customers. A primary objective of the standard is to provide a single, comprehensive revenue recognition model that will be applied across entities, industries, and capital markets. The new guidance replaced most of the previous revenue recognition requirements in GAAP, although certain guidance specific to rate-regulated utilities was retained. CMS Energy and Consumers had the option to apply the standard retrospectively to all prior periods presented or retrospectively with the cumulative effect of the standard recorded as an adjustment to beginning retained earnings. They also had the option to apply the standard only to contracts existing on the effective date. CMS Energy and Consumers applied the standard retrospectively to contracts existing on the effective date, and recorded an immaterial cumulative-effect reduction to beginning retained earnings for certain contract costs that can no longer be deferred under the new guidance. The implementation of this standard did not have a material impact on CMS Energy’s or Consumers’ consolidated net income, cash flows, or financial position. CMS Energy and Consumers did not identify any significant changes to their revenue recognition practices that were required by the new guidance, but in accordance with the standard, they have provided additional disclosures about their revenues in Note 11, Revenue . ASU 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities: This standard, which was effective on January 1, 2018 for CMS Energy and Consumers, is intended to improve the accounting for financial instruments. The standard requires investments in equity securities to be measured at fair value, with changes in fair value recognized in net income, except for certain investments such as those that qualify for equity-method accounting. The standard no longer permits unrealized gains and losses for certain equity investments to be recorded in AOCI. There are other targeted changes as well. Entities must apply the standard using a modified retrospective approach, with the cumulative effect of the standard recorded as an adjustment to beginning retained earnings. The implementation of the standard had no impact on CMS Energy’s consolidated financial statements. In accordance with the standard, as of January 1, 2018, Consumers removed a $19 million unrealized gain and the associated deferred taxes on its investment in CMS Energy common stock from AOCI and recorded the gain in retained earnings. In January 2018, Consumers transferred substantially all of its shares in CMS Energy common stock to a related charitable foundation and, in accordance with this standard, recognized all unrealized gains and losses on its remaining shares in net income for the three and nine months ended September 30, 2018 . The accounting treatment for this investment is reflected in Consumers’ consolidated financial statements only, and had no impact on CMS Energy’s consolidated financial statements. For further details on CMS Energy’s and Consumers’ investments in debt and equity securities, see Note 6, Financial Instruments . ASU 2018-02, Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income: This standard addresses the income tax effects stranded in AOCI as a result of the TCJA. Existing GAAP requires that the remeasurement of deferred tax assets and liabilities resulting from a change in tax laws or rates be presented in net income from continuing operations, even if the deferred taxes were associated with items that were originally recognized in AOCI. As a result, upon recognizing the effects of the TCJA, the tax effects of items in AOCI (referred to as stranded tax effects) no longer reflected the current income tax rate. To address this matter, this standard permits companies to reclassify to retained earnings the stranded tax effects of the TCJA. The standard is effective on January 1, 2019 for CMS Energy and Consumers, but early adoption is permitted. The new guidance is to be applied either in the period of adoption or retrospectively to each prior period in which the effect of the TCJA was recognized. CMS Energy and Consumers elected to adopt this standard early. Accordingly, as of January 1, 2018, CMS Energy reclassified $11 million of stranded tax effects from AOCI to retained earnings, which included $5 million reclassified at Consumers. At September 30, 2018 , CMS Energy and Consumers did not have any material stranded tax effects remaining in AOCI. New Accounting Standards Not Yet Effective ASU 2016-02, Leases: This standard establishes a new accounting model for leases. The standard will require entities to recognize lease assets and liabilities on the balance sheet for all leases with a term of more than one year, including operating leases, which are not recorded on the balance sheet under existing standards. The new guidance will also amend the definition of a lease to require that a lessee control the use of a specified asset, and not simply control or take the output of the asset. On the income statement, leases that meet existing capital lease criteria will generally be accounted for under a financing model, while operating leases will generally be accounted for under a straight-line expense model. The standard will be effective on January 1, 2019 for CMS Energy and Consumers, but early adoption is permitted. CMS Energy and Consumers are not adopting the standard early and will elect certain practical expedients permitted by the standard, under which they will not be required to perform lease assessments or reassessments for agreements existing on the effective date. They also will elect a transition method under which they will initially apply the standard on January 1, 2019, without adjusting amounts presented for prior periods. Under this method, the cumulative effect of applying the standard must be recorded as an adjustment to beginning retained earnings. CMS Energy and Consumers will recognize additional lease assets and liabilities for their operating leases under the standard. CMS Energy and Consumers are continuing to evaluate the standard; however, they do not expect that it will have a material impact on their consolidated net income or cash flows. ASU 2016-13, Measurement of Credit Losses on Financial Instruments: This standard, which will be effective January 1, 2020 for CMS Energy and Consumers, provides new guidance for estimating and recording credit losses on financial instruments. The standard will apply to the recognition of loan losses at EnerBank as well as to the recognition of uncollectible accounts expense at Consumers. Entities will apply the standard using a modified retrospective approach, with a cumulative-effect adjustment recorded to beginning retained earnings on the effective date. CMS Energy and Consumers are evaluating the impact of the standard on their consolidated financial statements.
Allowance For Loan Losses Policy	The allowance for loan losses is a valuation allowance to reflect estimated credit losses. The allowance is increased by the provision for loan losses and decreased by loan charge-offs net of recoveries. Management estimates the allowance balance required by taking into consideration historical loan loss experience, the nature and volume of the portfolio, economic conditions, and other factors. Loan losses are charged against the allowance when the loss is confirmed, but no later than the point at which a loan becomes 120 days past due.

Contingencies And Commitments (

Contingencies And Commitments (Tables)	9 Months Ended
	Sep. 30, 2018
Site Contingency [Line Items]
Guarantees	Presented in the following table are CMS Energy’s and Consumers’ guarantees at September 30, 2018 : In Millions Guarantee Description Issue Date Expiration Date Maximum Obligation Carrying Amount CMS Energy, including Consumers Indemnity obligations from stock and asset sale agreements 1 Various Indefinite $ 153 $ 3 Guarantees 2 Various Indefinite 39 — Consumers Guarantee 2 July 2011 Indefinite $ 30 $ — 1 These obligations arose from stock and asset sale agreements under which CMS Energy or a subsidiary of CMS Energy indemnified the purchaser for losses resulting from various matters, primarily claims related to taxes. CMS Energy believes the likelihood of material loss to be remote for the indemnity obligations not recorded as liabilities. 2 At Consumers, this obligation comprises a guarantee provided to the U.S. Department of Energy in connection with a settlement agreement regarding damages resulting from the department’s failure to accept spent nuclear fuel from nuclear power plants formerly owned by Consumers. At CMS Energy, the guarantee obligations comprise Consumers’ guarantee to the U.S. Department of Energy and CMS Energy’s 1994 guarantee of non-recourse revenue bonds issued by Genesee.
Consumers Energy Company
Site Contingency [Line Items]
Guarantees	Presented in the following table are CMS Energy’s and Consumers’ guarantees at September 30, 2018 : In Millions Guarantee Description Issue Date Expiration Date Maximum Obligation Carrying Amount CMS Energy, including Consumers Indemnity obligations from stock and asset sale agreements 1 Various Indefinite $ 153 $ 3 Guarantees 2 Various Indefinite 39 — Consumers Guarantee 2 July 2011 Indefinite $ 30 $ — 1 These obligations arose from stock and asset sale agreements under which CMS Energy or a subsidiary of CMS Energy indemnified the purchaser for losses resulting from various matters, primarily claims related to taxes. CMS Energy believes the likelihood of material loss to be remote for the indemnity obligations not recorded as liabilities. 2 At Consumers, this obligation comprises a guarantee provided to the U.S. Department of Energy in connection with a settlement agreement regarding damages resulting from the department’s failure to accept spent nuclear fuel from nuclear power plants formerly owned by Consumers. At CMS Energy, the guarantee obligations comprise Consumers’ guarantee to the U.S. Department of Energy and CMS Energy’s 1994 guarantee of non-recourse revenue bonds issued by Genesee.
Bay Harbor
Site Contingency [Line Items]
Expected Remediation Cost By Year	CMS Energy expects to pay the following amounts for long-term liquid disposal and operating and maintenance costs during the remainder of 2018 and in each of the next five years: In Millions 2018 2019 2020 2021 2022 2023 CMS Energy Long-term liquid disposal and operating and maintenance costs $ 1 $ 4 $ 4 $ 4 $ 4 $ 4
Gas Utility | Manufactured Gas Plant | Consumers Energy Company
Site Contingency [Line Items]
Expected Remediation Cost By Year	Consumers expects to pay the following amounts for remediation and other response activity costs during the remainder of 2018 and in each of the next five years: In Millions 2018 2019 2020 2021 2022 2023 Consumers Remediation and other response activity costs $ 6 $ 12 $ 16 $ 21 $ 7 $ 2

Financings And Capitalization (

Financings And Capitalization (Tables)	9 Months Ended
	Sep. 30, 2018
Debt Instrument [Line Items]
Major Long-Term Debt Transactions	Financings: Presented in the following table is a summary of major long-term debt transactions during the nine months ended September 30, 2018 . Principal Interest Rate Issue/Retirement Date Maturity Date Debt issuances CMS Energy, parent only Junior subordinated notes 1 $ 200 5.625 % March 2018 March 2078 Junior subordinated notes 1 250 5.875 % September 2018 October 2078 Total CMS Energy, parent only $ 450 Consumers First mortgage bonds $ 550 4.05 % May 2018 May 2048 Total Consumers $ 550 Total CMS Energy $ 1,000 Debt retirements CMS Energy, parent only Term loan facility $ 180 variable March 2018 December 2018 Senior notes 2 100 8.75 % June 2018 June 2019 Term loan facility 45 variable August 2018 December 2018 Total CMS Energy, parent only $ 325 Consumers Tax-exempt pollution control revenue bonds $ 68 various April 2018 April 2018 First mortgage bonds 250 5.65 % May 2018 September 2018 Total Consumers $ 318 Total CMS Energy $ 643 1 These unsecured obligations rank subordinate and junior in right of payment to all of CMS Energy’s existing and future senior indebtedness. 2 CMS Energy retired these senior notes at a premium and recorded a loss on extinguishment of $5 million in other expense on its consolidated statements of income.
Revolving Credit Facilities	Revolving Credit Facilities: The following revolving credit facilities with banks were available at September 30, 2018 : In Millions Expiration Date Amount of Facility Amount Borrowed Letters of Credit Outstanding Amount Available CMS Energy, parent only June 5, 2023 1 $ 550 $ — $ 9 $ 541 Consumers June 5, 2023 2,3 $ 850 $ — $ 7 $ 843 November 23, 2019 3 250 — 25 225 September 9, 2019 3 30 — 30 — 1 In June 2018, CMS Energy amended this revolving credit facility, eliminating the security provided by Consumers common stock, and extending the expiration date to June 2023. 2 In June 2018, Consumers amended this revolving credit facility by increasing its borrowing capacity to $850 million and extending the expiration date to June 2023. 3 Obligations under this facility are secured by first mortgage bonds of Consumers.
Issuance of Common Stock	Presented in the following table are the transactions that CMS Energy entered into under the program: Number of Shares Issued Average Price Per Share Net Proceeds May 2018 638,898 $ 45.83 $ 29 June 2017 1,494,371 47.31 70
Consumers Energy Company
Debt Instrument [Line Items]
Major Long-Term Debt Transactions	Financings: Presented in the following table is a summary of major long-term debt transactions during the nine months ended September 30, 2018 . Principal Interest Rate Issue/Retirement Date Maturity Date Debt issuances CMS Energy, parent only Junior subordinated notes 1 $ 200 5.625 % March 2018 March 2078 Junior subordinated notes 1 250 5.875 % September 2018 October 2078 Total CMS Energy, parent only $ 450 Consumers First mortgage bonds $ 550 4.05 % May 2018 May 2048 Total Consumers $ 550 Total CMS Energy $ 1,000 Debt retirements CMS Energy, parent only Term loan facility $ 180 variable March 2018 December 2018 Senior notes 2 100 8.75 % June 2018 June 2019 Term loan facility 45 variable August 2018 December 2018 Total CMS Energy, parent only $ 325 Consumers Tax-exempt pollution control revenue bonds $ 68 various April 2018 April 2018 First mortgage bonds 250 5.65 % May 2018 September 2018 Total Consumers $ 318 Total CMS Energy $ 643 1 These unsecured obligations rank subordinate and junior in right of payment to all of CMS Energy’s existing and future senior indebtedness. 2 CMS Energy retired these senior notes at a premium and recorded a loss on extinguishment of $5 million in other expense on its consolidated statements of income.
Revolving Credit Facilities	Revolving Credit Facilities: The following revolving credit facilities with banks were available at September 30, 2018 : In Millions Expiration Date Amount of Facility Amount Borrowed Letters of Credit Outstanding Amount Available CMS Energy, parent only June 5, 2023 1 $ 550 $ — $ 9 $ 541 Consumers June 5, 2023 2,3 $ 850 $ — $ 7 $ 843 November 23, 2019 3 250 — 25 225 September 9, 2019 3 30 — 30 — 1 In June 2018, CMS Energy amended this revolving credit facility, eliminating the security provided by Consumers common stock, and extending the expiration date to June 2023. 2 In June 2018, Consumers amended this revolving credit facility by increasing its borrowing capacity to $850 million and extending the expiration date to June 2023. 3 Obligations under this facility are secured by first mortgage bonds of Consumers.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets And Liabilities Measured At Fair Value On A Recurring Basis	Presented in the following table are CMS Energy’s and Consumers’ assets and liabilities recorded at fair value on a recurring basis: In Millions CMS Energy, including Consumers Consumers September 30 December 31 September 30 December 31 Assets 1 Cash equivalents $ 139 $ 74 $ — $ — Restricted cash equivalents 42 17 28 17 CMS Energy common stock — — 1 21 Nonqualified deferred compensation plan assets 14 14 11 10 DB SERP Cash equivalents 1 5 1 4 Debt securities — 141 — 102 Derivative instruments Commodity contracts 1 1 1 1 Total $ 197 $ 252 $ 42 $ 155 Liabilities 1 Nonqualified deferred compensation plan liabilities $ 14 $ 14 $ 11 $ 10 Derivative instruments Commodity contracts 1 1 1 — Total $ 15 $ 15 $ 12 $ 10 1 All assets and liabilities were classified as Level 1 with the exception of some commodity contracts, which were classified as Level 3.
Consumers Energy Company
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets And Liabilities Measured At Fair Value On A Recurring Basis	Presented in the following table are CMS Energy’s and Consumers’ assets and liabilities recorded at fair value on a recurring basis: In Millions CMS Energy, including Consumers Consumers September 30 December 31 September 30 December 31 Assets 1 Cash equivalents $ 139 $ 74 $ — $ — Restricted cash equivalents 42 17 28 17 CMS Energy common stock — — 1 21 Nonqualified deferred compensation plan assets 14 14 11 10 DB SERP Cash equivalents 1 5 1 4 Debt securities — 141 — 102 Derivative instruments Commodity contracts 1 1 1 1 Total $ 197 $ 252 $ 42 $ 155 Liabilities 1 Nonqualified deferred compensation plan liabilities $ 14 $ 14 $ 11 $ 10 Derivative instruments Commodity contracts 1 1 1 — Total $ 15 $ 15 $ 12 $ 10 1 All assets and liabilities were classified as Level 1 with the exception of some commodity contracts, which were classified as Level 3.

Financial Instruments (Tables)

Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2018
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Schedule Of Carrying Amounts And Fair Values Of Financial Instruments	Presented in the following table are the carrying amounts and fair values, by level within the fair value hierarchy, of CMS Energy’s and Consumers’ financial instruments that are not recorded at fair value. The table excludes cash, cash equivalents, short-term financial instruments, and trade accounts receivable and payable whose carrying amounts approximate their fair values. For information about assets and liabilities recorded at fair value and for additional details regarding the fair value hierarchy, see Note 5, Fair Value Measurements . In Millions September 30, 2018 December 31, 2017 Fair Value Fair Value Carrying Level Carrying Level Amount Total 1 2 3 Amount Total 1 2 3 CMS Energy, including Consumers Assets Long-term receivables 1 $ 22 $ 22 $ — $ — $ 22 $ 21 $ 21 $ — $ — $ 21 Notes receivable 2 1,640 1,730 — — 1,730 1,371 1,464 — — 1,464 Securities held to maturity 22 21 — 21 — 16 16 — 16 — Liabilities Long-term payables 3 26 26 — — 26 27 26 — — 26 Long-term debt 4 10,817 10,798 445 9,088 1,265 10,204 10,715 — 9,363 1,352 Consumers Assets Long-term receivables 1 $ 22 $ 22 $ — $ — $ 22 $ 21 $ 21 $ — $ — $ 21 Notes receivable 5 17 17 — — 17 17 17 — — 17 Notes receivable – related party 6 107 105 — — 105 — — — — — Liabilities Long-term debt 7 6,115 6,083 — 4,818 1,265 5,904 6,236 — 4,883 1,353 1 Includes current accounts receivable of $15 million at September 30, 2018 and $14 million December 31, 2017 . 2 Includes current portion of notes receivable of $263 million at September 30, 2018 and $200 million at December 31, 2017 . For further details, see Note 7, Notes Receivable . 3 Includes current portion of long-term payables of $3 million at September 30, 2018 and December 31, 2017 . 4 Includes current portion of long-term debt of $1.9 billion at September 30, 2018 and $1.1 billion at December 31, 2017 . 5 Includes current portion of notes receivable of $17 million at September 30, 2018 and December 31, 2017 . 6 Includes current portion of notes receivable – related party of $7 million at September 30, 2018 . For further details on this note receivable, see the DB SERP discussion below. 7 Includes current portion of long-term debt of $876 million at September 30, 2018 and $343 million at December 31, 2017 .
Schedule Of Investment Securities	Presented in the following table are CMS Energy’s and Consumers’ investment securities classified as available for sale or held to maturity: In Millions September 30, 2018 December 31, 2017 Cost Unrealized Gains Unrealized Losses Fair Value Cost Unrealized Gains Unrealized Losses Fair Value CMS Energy, including Consumers Available for sale DB SERP Debt securities $ — $ — $ — $ — $ 141 $ — $ — $ 141 Held to maturity Debt securities 22 — (1 ) 21 16 — — 16 Consumers Available for sale DB SERP Debt securities $ — $ — $ — $ — $ 102 $ — $ — $ 102 CMS Energy common stock — — — — 2 19 — 21
Consumers Energy Company
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Schedule Of Carrying Amounts And Fair Values Of Financial Instruments	Presented in the following table are the carrying amounts and fair values, by level within the fair value hierarchy, of CMS Energy’s and Consumers’ financial instruments that are not recorded at fair value. The table excludes cash, cash equivalents, short-term financial instruments, and trade accounts receivable and payable whose carrying amounts approximate their fair values. For information about assets and liabilities recorded at fair value and for additional details regarding the fair value hierarchy, see Note 5, Fair Value Measurements . In Millions September 30, 2018 December 31, 2017 Fair Value Fair Value Carrying Level Carrying Level Amount Total 1 2 3 Amount Total 1 2 3 CMS Energy, including Consumers Assets Long-term receivables 1 $ 22 $ 22 $ — $ — $ 22 $ 21 $ 21 $ — $ — $ 21 Notes receivable 2 1,640 1,730 — — 1,730 1,371 1,464 — — 1,464 Securities held to maturity 22 21 — 21 — 16 16 — 16 — Liabilities Long-term payables 3 26 26 — — 26 27 26 — — 26 Long-term debt 4 10,817 10,798 445 9,088 1,265 10,204 10,715 — 9,363 1,352 Consumers Assets Long-term receivables 1 $ 22 $ 22 $ — $ — $ 22 $ 21 $ 21 $ — $ — $ 21 Notes receivable 5 17 17 — — 17 17 17 — — 17 Notes receivable – related party 6 107 105 — — 105 — — — — — Liabilities Long-term debt 7 6,115 6,083 — 4,818 1,265 5,904 6,236 — 4,883 1,353 1 Includes current accounts receivable of $15 million at September 30, 2018 and $14 million December 31, 2017 . 2 Includes current portion of notes receivable of $263 million at September 30, 2018 and $200 million at December 31, 2017 . For further details, see Note 7, Notes Receivable . 3 Includes current portion of long-term payables of $3 million at September 30, 2018 and December 31, 2017 . 4 Includes current portion of long-term debt of $1.9 billion at September 30, 2018 and $1.1 billion at December 31, 2017 . 5 Includes current portion of notes receivable of $17 million at September 30, 2018 and December 31, 2017 . 6 Includes current portion of notes receivable – related party of $7 million at September 30, 2018 . For further details on this note receivable, see the DB SERP discussion below. 7 Includes current portion of long-term debt of $876 million at September 30, 2018 and $343 million at December 31, 2017 .
Schedule Of Investment Securities	Presented in the following table are CMS Energy’s and Consumers’ investment securities classified as available for sale or held to maturity: In Millions September 30, 2018 December 31, 2017 Cost Unrealized Gains Unrealized Losses Fair Value Cost Unrealized Gains Unrealized Losses Fair Value CMS Energy, including Consumers Available for sale DB SERP Debt securities $ — $ — $ — $ — $ 141 $ — $ — $ 141 Held to maturity Debt securities 22 — (1 ) 21 16 — — 16 Consumers Available for sale DB SERP Debt securities $ — $ — $ — $ — $ 102 $ — $ — $ 102 CMS Energy common stock — — — — 2 19 — 21

Notes Receivable (Tables)

Notes Receivable (Tables)	9 Months Ended
	Sep. 30, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Schedule Of Current And Non-Current Notes Receivable	Presented in the following table are details of CMS Energy’s and Consumers’ current and non-current notes receivable: In Millions September 30, 2018 December 31, 2017 CMS Energy, including Consumers Current EnerBank notes receivable, net of allowance for loan losses $ 217 $ 178 EnerBank notes receivable held for sale 26 2 Michigan tax settlement 20 20 Non-current EnerBank notes receivable 1,377 1,171 Total notes receivable $ 1,640 $ 1,371 Consumers Current Michigan tax settlement $ 17 $ 17 DB SERP note receivable – related party 7 — Non-current DB SERP note receivable – related party 100 — Total notes receivable $ 124 $ 17
Consumers Energy Company
Accounts, Notes, Loans and Financing Receivable [Line Items]
Schedule Of Current And Non-Current Notes Receivable	Presented in the following table are details of CMS Energy’s and Consumers’ current and non-current notes receivable: In Millions September 30, 2018 December 31, 2017 CMS Energy, including Consumers Current EnerBank notes receivable, net of allowance for loan losses $ 217 $ 178 EnerBank notes receivable held for sale 26 2 Michigan tax settlement 20 20 Non-current EnerBank notes receivable 1,377 1,171 Total notes receivable $ 1,640 $ 1,371 Consumers Current Michigan tax settlement $ 17 $ 17 DB SERP note receivable – related party 7 — Non-current DB SERP note receivable – related party 100 — Total notes receivable $ 124 $ 17

Retirement Benefits (Tables)

Retirement Benefits (Tables)	9 Months Ended
	Sep. 30, 2018
Defined Benefit Plan Disclosure [Line Items]
Schedule Of Net Benefit Costs	In November 2017, CMS Energy and Consumers approved certain amendments to the OPEB Plan, resulting in higher OPEB Plan credits in 2018 compared to 2017. Presented in the following table are the costs (credits) and other changes in plan assets and benefit obligations incurred in CMS Energy’s and Consumers’ retirement benefits plans: In Millions DB Pension Plans OPEB Plan Three Months Ended Nine Months Ended Three Months Ended Nine Months Ended September 30 2018 2017 2018 2017 2018 2017 2018 2017 CMS Energy, including Consumers Net periodic cost (credit) Service cost $ 12 $ 12 $ 36 $ 34 $ 4 $ 5 $ 13 $ 15 Interest cost 22 23 67 67 9 13 27 39 Expected return on plan assets (38 ) (39 ) (112 ) (115 ) (24 ) (22 ) (73 ) (67 ) Amortization of: Net loss 19 20 56 60 3 7 11 23 Prior service cost (credit) 1 1 2 3 (16 ) (8 ) (50 ) (26 ) Net periodic cost (credit) $ 16 $ 17 $ 49 $ 49 $ (24 ) $ (5 ) $ (72 ) $ (16 ) Consumers Net periodic cost (credit) Service cost $ 12 $ 11 $ 35 $ 33 $ 4 $ 5 $ 12 $ 14 Interest cost 22 22 64 65 8 12 25 38 Expected return on plan assets (35 ) (38 ) (104 ) (112 ) (22 ) (21 ) (68 ) (63 ) Amortization of: Net loss 17 19 53 58 4 8 12 24 Prior service cost (credit) 1 1 2 3 (17 ) (8 ) (49 ) (25 ) Net periodic cost (credit) $ 17 $ 15 $ 50 $ 47 $ (23 ) $ (4 ) $ (68 ) $ (12 )
Consumers Energy Company
Defined Benefit Plan Disclosure [Line Items]
Schedule Of Net Benefit Costs	In November 2017, CMS Energy and Consumers approved certain amendments to the OPEB Plan, resulting in higher OPEB Plan credits in 2018 compared to 2017. Presented in the following table are the costs (credits) and other changes in plan assets and benefit obligations incurred in CMS Energy’s and Consumers’ retirement benefits plans: In Millions DB Pension Plans OPEB Plan Three Months Ended Nine Months Ended Three Months Ended Nine Months Ended September 30 2018 2017 2018 2017 2018 2017 2018 2017 CMS Energy, including Consumers Net periodic cost (credit) Service cost $ 12 $ 12 $ 36 $ 34 $ 4 $ 5 $ 13 $ 15 Interest cost 22 23 67 67 9 13 27 39 Expected return on plan assets (38 ) (39 ) (112 ) (115 ) (24 ) (22 ) (73 ) (67 ) Amortization of: Net loss 19 20 56 60 3 7 11 23 Prior service cost (credit) 1 1 2 3 (16 ) (8 ) (50 ) (26 ) Net periodic cost (credit) $ 16 $ 17 $ 49 $ 49 $ (24 ) $ (5 ) $ (72 ) $ (16 ) Consumers Net periodic cost (credit) Service cost $ 12 $ 11 $ 35 $ 33 $ 4 $ 5 $ 12 $ 14 Interest cost 22 22 64 65 8 12 25 38 Expected return on plan assets (35 ) (38 ) (104 ) (112 ) (22 ) (21 ) (68 ) (63 ) Amortization of: Net loss 17 19 53 58 4 8 12 24 Prior service cost (credit) 1 1 2 3 (17 ) (8 ) (49 ) (25 ) Net periodic cost (credit) $ 17 $ 15 $ 50 $ 47 $ (23 ) $ (4 ) $ (68 ) $ (12 )

Income Taxes (Tables)

Income Taxes (Tables)	9 Months Ended
	Sep. 30, 2018
Income Taxes [Line Items]
Schedule Of Effective Income Tax Rate Reconciliation	Presented in the following table is a reconciliation of the statutory U.S. federal income tax rate to the effective income tax rate from continuing operations: Nine Months Ended September 30 2018 2017 CMS Energy, including Consumers U.S. federal income tax rate 21.0 % 35.0 % Increase (decrease) in income taxes from: State and local income taxes, net of federal effect 5.9 2.3 Accelerated flow-through of regulatory tax benefits 1 (5.0 ) (4.3 ) TCJA excess deferred taxes 2 (3.4 ) — Research and development tax credits, net 3 (1.6 ) (0.1 ) Production tax credits (2.0 ) (1.0 ) Other, net 0.2 (1.8 ) Effective tax rate 15.1 % 30.1 % Consumers U.S. federal income tax rate 21.0 % 35.0 % Increase (decrease) in income taxes from: State and local income taxes, net of federal effect 6.1 2.3 Accelerated flow-through of regulatory tax benefits 1 (4.4 ) (3.9 ) TCJA excess deferred taxes 2 (3.1 ) — Research and development tax credits, net 3 (1.5 ) (0.1 ) Production tax credits (1.6 ) (1.0 ) Other, net (0.3 ) (2.0 ) Effective tax rate 16.2 % 30.3 % 1 In 2013, the MPSC issued an order authorizing Consumers to accelerate the flow-through to electric and gas customers of certain income tax benefits associated primarily with the cost of removal of plant placed in service before 1993. Consumers implemented this regulatory treatment beginning in 2014. This change, which also accelerates Consumers’ recognition of the income tax benefits, reduced Consumers’ income tax expense by $30 million for the nine months ended September 30, 2018 and by $28 million for the nine months ended September 30, 2017 . 2 In December 2017, Consumers remeasured its deferred tax assets and liabilities at the new federal tax rate enacted by the TCJA and recorded a $1.8 billion regulatory liability. This regulatory liability relates to the excess deferred taxes arising from accelerated tax depreciation on assets in rate base that are governed by normalization provisions of the Internal Revenue Code. The normalization provisions require that the excess deferred taxes be refunded to customers over the remaining average service life of the associated assets. In January 2018, Consumers began to reduce this regulatory liability by crediting income tax expense. Consumers has fully reserved for the eventual refund of these excess deferred taxes that it has credited to income tax expense in a separate regulatory liability established by reducing revenue, and will continue to do so until these benefits are passed on to customers in accordance with an MPSC order, expected to be issued in 2019. At September 30, 2018 , this reserve for refund of these excess deferred taxes totaled $26 million . 3 In March 2018, Consumers finalized a study of research and development tax credits for the tax years 2012 through 2016. As a result, Consumers recognized an $8 million increase in the credit, net of reserves for uncertain tax positions
Consumers Energy Company
Income Taxes [Line Items]
Schedule Of Effective Income Tax Rate Reconciliation	Presented in the following table is a reconciliation of the statutory U.S. federal income tax rate to the effective income tax rate from continuing operations: Nine Months Ended September 30 2018 2017 CMS Energy, including Consumers U.S. federal income tax rate 21.0 % 35.0 % Increase (decrease) in income taxes from: State and local income taxes, net of federal effect 5.9 2.3 Accelerated flow-through of regulatory tax benefits 1 (5.0 ) (4.3 ) TCJA excess deferred taxes 2 (3.4 ) — Research and development tax credits, net 3 (1.6 ) (0.1 ) Production tax credits (2.0 ) (1.0 ) Other, net 0.2 (1.8 ) Effective tax rate 15.1 % 30.1 % Consumers U.S. federal income tax rate 21.0 % 35.0 % Increase (decrease) in income taxes from: State and local income taxes, net of federal effect 6.1 2.3 Accelerated flow-through of regulatory tax benefits 1 (4.4 ) (3.9 ) TCJA excess deferred taxes 2 (3.1 ) — Research and development tax credits, net 3 (1.5 ) (0.1 ) Production tax credits (1.6 ) (1.0 ) Other, net (0.3 ) (2.0 ) Effective tax rate 16.2 % 30.3 % 1 In 2013, the MPSC issued an order authorizing Consumers to accelerate the flow-through to electric and gas customers of certain income tax benefits associated primarily with the cost of removal of plant placed in service before 1993. Consumers implemented this regulatory treatment beginning in 2014. This change, which also accelerates Consumers’ recognition of the income tax benefits, reduced Consumers’ income tax expense by $30 million for the nine months ended September 30, 2018 and by $28 million for the nine months ended September 30, 2017 . 2 In December 2017, Consumers remeasured its deferred tax assets and liabilities at the new federal tax rate enacted by the TCJA and recorded a $1.8 billion regulatory liability. This regulatory liability relates to the excess deferred taxes arising from accelerated tax depreciation on assets in rate base that are governed by normalization provisions of the Internal Revenue Code. The normalization provisions require that the excess deferred taxes be refunded to customers over the remaining average service life of the associated assets. In January 2018, Consumers began to reduce this regulatory liability by crediting income tax expense. Consumers has fully reserved for the eventual refund of these excess deferred taxes that it has credited to income tax expense in a separate regulatory liability established by reducing revenue, and will continue to do so until these benefits are passed on to customers in accordance with an MPSC order, expected to be issued in 2019. At September 30, 2018 , this reserve for refund of these excess deferred taxes totaled $26 million . 3 In March 2018, Consumers finalized a study of research and development tax credits for the tax years 2012 through 2016. As a result, Consumers recognized an $8 million increase in the credit, net of reserves for uncertain tax positions

Earnings Per Share - CMS Ener_2

Earnings Per Share - CMS Energy (Tables)	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Basic And Diluted EPS Computations	Presented in the following table are CMS Energy’s basic and diluted EPS computations based on net income: In Millions, Except Per Share Amounts Three Months Ended Nine Months Ended September 30 2018 2017 2018 2017 Income available to common stockholders Net income $ 169 $ 172 $ 550 $ 464 Less income attributable to noncontrolling interests — — 1 1 Net income available to common stockholders – basic and diluted $ 169 $ 172 $ 549 $ 463 Average common shares outstanding Weighted-average shares – basic 282.5 280.8 282.1 279.8 Add dilutive nonvested stock awards 0.7 0.8 0.7 0.8 Weighted-average shares – diluted 283.2 281.6 282.8 280.6 Net income per average common share available to common stockholders Basic $ 0.60 $ 0.61 $ 1.95 $ 1.65 Diluted 0.59 0.61 1.94 1.65

Revenue (Tables)

Revenue (Tables)	9 Months Ended
	Sep. 30, 2018
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Components Of Operating Revenue	Presented in the following tables are the components of operating revenue: In Millions Three Months Ended September 30, 2018 Electric Utility Gas Utility Enterprises 1 Other 2 Consolidated CMS Energy, including Consumers Consumers utility revenue $ 1,310 $ 188 $ — $ — $ 1,498 Other — — 21 — 21 Revenue recognized from contracts with customers 1,310 188 21 — 1,519 Leasing income — — 36 — 36 Financing income 3 — — 40 43 Consumers alternative revenue programs — 1 — — 1 Total operating revenue – CMS Energy $ 1,313 $ 189 $ 57 $ 40 $ 1,599 Consumers Consumers utility revenue Residential $ 625 $ 118 $ — $ — $ 743 Commercial 434 30 — — 464 Industrial 186 4 — — 190 Other 65 36 — — 101 Revenue recognized from contracts with customers 1,310 188 — — 1,498 Financing income 3 — — — 3 Alternative revenue programs — 1 — — 1 Total operating revenue – Consumers $ 1,313 $ 189 $ — $ — $ 1,502 In Millions Nine Months Ended September 30, 2018 Electric Utility Gas Utility Enterprises 1 Other 2 Consolidated CMS Energy, including Consumers Consumers utility revenue $ 3,473 $ 1,263 $ — $ — $ 4,736 Other — — 69 — 69 Revenue recognized from contracts with customers 3,473 1,263 69 — 4,805 Leasing income — — 112 — 112 Financing income 7 4 — 111 122 Consumers alternative revenue programs — 5 — — 5 Total operating revenue – CMS Energy $ 3,480 $ 1,272 $ 181 $ 111 $ 5,044 Consumers Consumers utility revenue Residential $ 1,601 $ 849 $ — $ — $ 2,450 Commercial 1,181 250 — — 1,431 Industrial 499 37 — — 536 Other 192 127 — — 319 Revenue recognized from contracts with customers 3,473 1,263 — — 4,736 Financing income 7 4 — — 11 Alternative revenue programs — 5 — — 5 Total operating revenue – Consumers $ 3,480 $ 1,272 $ — $ — $ 4,752 1 Amounts represent the enterprises segment’s operating revenue from independent power production and CMS ERM’s sales of energy commodities in support of the independent power production portfolio. 2 Amount represents EnerBank’s operating revenue from unsecured consumer installment loans for financing home improvements.
Consumers Energy Company
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Components Of Operating Revenue	Presented in the following tables are the components of operating revenue: In Millions Three Months Ended September 30, 2018 Electric Utility Gas Utility Enterprises 1 Other 2 Consolidated CMS Energy, including Consumers Consumers utility revenue $ 1,310 $ 188 $ — $ — $ 1,498 Other — — 21 — 21 Revenue recognized from contracts with customers 1,310 188 21 — 1,519 Leasing income — — 36 — 36 Financing income 3 — — 40 43 Consumers alternative revenue programs — 1 — — 1 Total operating revenue – CMS Energy $ 1,313 $ 189 $ 57 $ 40 $ 1,599 Consumers Consumers utility revenue Residential $ 625 $ 118 $ — $ — $ 743 Commercial 434 30 — — 464 Industrial 186 4 — — 190 Other 65 36 — — 101 Revenue recognized from contracts with customers 1,310 188 — — 1,498 Financing income 3 — — — 3 Alternative revenue programs — 1 — — 1 Total operating revenue – Consumers $ 1,313 $ 189 $ — $ — $ 1,502 In Millions Nine Months Ended September 30, 2018 Electric Utility Gas Utility Enterprises 1 Other 2 Consolidated CMS Energy, including Consumers Consumers utility revenue $ 3,473 $ 1,263 $ — $ — $ 4,736 Other — — 69 — 69 Revenue recognized from contracts with customers 3,473 1,263 69 — 4,805 Leasing income — — 112 — 112 Financing income 7 4 — 111 122 Consumers alternative revenue programs — 5 — — 5 Total operating revenue – CMS Energy $ 3,480 $ 1,272 $ 181 $ 111 $ 5,044 Consumers Consumers utility revenue Residential $ 1,601 $ 849 $ — $ — $ 2,450 Commercial 1,181 250 — — 1,431 Industrial 499 37 — — 536 Other 192 127 — — 319 Revenue recognized from contracts with customers 3,473 1,263 — — 4,736 Financing income 7 4 — — 11 Alternative revenue programs — 5 — — 5 Total operating revenue – Consumers $ 3,480 $ 1,272 $ — $ — $ 4,752 1 Amounts represent the enterprises segment’s operating revenue from independent power production and CMS ERM’s sales of energy commodities in support of the independent power production portfolio. 2 Amount represents EnerBank’s operating revenue from unsecured consumer installment loans for financing home improvements.

Cash And Cash Equivalents (Tabl

Cash And Cash Equivalents (Tables)	9 Months Ended
	Sep. 30, 2018
Cash and Cash Equivalents [Line Items]
Schedule Of Cash And Cash Equivalents, Including Restricted Amounts	Presented in the following table are the components of total cash and cash equivalents, including restricted amounts, and their location on CMS Energy’s and Consumers’ consolidated balance sheets: In Millions September 30, 2018 December 31, 2017 CMS Energy, including Consumers Cash and cash equivalents $ 323 $ 182 Restricted cash and cash equivalents 42 17 Other non-current assets 1 5 Cash and cash equivalents, including restricted amounts $ 366 $ 204 Consumers Cash and cash equivalents $ 9 $ 44 Restricted cash and cash equivalents 28 17 Other non-current assets 1 4 Cash and cash equivalents, including restricted amounts $ 38 $ 65
Consumers Energy Company
Cash and Cash Equivalents [Line Items]
Schedule Of Cash And Cash Equivalents, Including Restricted Amounts	Presented in the following table are the components of total cash and cash equivalents, including restricted amounts, and their location on CMS Energy’s and Consumers’ consolidated balance sheets: In Millions September 30, 2018 December 31, 2017 CMS Energy, including Consumers Cash and cash equivalents $ 323 $ 182 Restricted cash and cash equivalents 42 17 Other non-current assets 1 5 Cash and cash equivalents, including restricted amounts $ 366 $ 204 Consumers Cash and cash equivalents $ 9 $ 44 Restricted cash and cash equivalents 28 17 Other non-current assets 1 4 Cash and cash equivalents, including restricted amounts $ 38 $ 65

Reportable Segments (Tables)

Reportable Segments (Tables)	9 Months Ended
	Sep. 30, 2018
Segment Reporting Information [Line Items]
Schedule Of Financial Information By Reportable Segments	Presented in the following tables is financial information by reportable segment: In Millions Three Months Ended Nine Months Ended September 30 2018 2017 2018 2017 CMS Energy, including Consumers Operating revenue Electric utility $ 1,313 $ 1,247 $ 3,480 $ 3,360 Gas utility 189 190 1,272 1,176 Enterprises 57 58 181 172 Other reconciling items 40 32 111 97 Total operating revenue – CMS Energy $ 1,599 $ 1,527 $ 5,044 $ 4,805 Consumers Operating revenue Electric utility $ 1,313 $ 1,247 $ 3,480 $ 3,360 Gas utility 189 190 1,272 1,176 Total operating revenue – Consumers $ 1,502 $ 1,437 $ 4,752 $ 4,536 CMS Energy, including Consumers Net income (loss) available to common stockholders Electric utility $ 199 $ 176 $ 468 $ 394 Gas utility (19 ) 5 105 101 Enterprises 4 8 33 27 Other reconciling items (15 ) (17 ) (57 ) (59 ) Total net income available to common stockholders – CMS Energy $ 169 $ 172 $ 549 $ 463 Consumers Net income (loss) available to common stockholder Electric utility $ 199 $ 176 $ 468 $ 394 Gas utility (19 ) 5 105 101 Total net income available to common stockholder – Consumers $ 180 $ 181 $ 573 $ 495 In Millions September 30, 2018 December 31, 2017 CMS Energy, including Consumers Plant, property, and equipment, gross Electric utility 1 $ 15,772 $ 15,221 Gas utility 1 7,534 7,080 Enterprises 405 167 Other reconciling items 40 38 Total plant, property, and equipment, gross – CMS Energy $ 23,751 $ 22,506 Consumers Plant, property, and equipment, gross Electric utility 1 $ 15,772 $ 15,221 Gas utility 1 7,534 7,080 Other reconciling items 16 17 Total plant, property, and equipment, gross – Consumers $ 23,322 $ 22,318 CMS Energy, including Consumers Total assets Electric utility 1 $ 13,850 $ 13,906 Gas utility 1 7,513 7,139 Enterprises 538 342 Other reconciling items 2,012 1,663 Total assets – CMS Energy $ 23,913 $ 23,050 Consumers Total assets Electric utility 1 $ 13,914 $ 13,907 Gas utility 1 7,556 7,139 Other reconciling items 22 53 Total assets – Consumers $ 21,492 $ 21,099 1 Amounts include a portion of Consumers’ other common assets attributable to both the electric and gas utility businesses.
Consumers Energy Company
Segment Reporting Information [Line Items]
Schedule Of Financial Information By Reportable Segments	Presented in the following tables is financial information by reportable segment: In Millions Three Months Ended Nine Months Ended September 30 2018 2017 2018 2017 CMS Energy, including Consumers Operating revenue Electric utility $ 1,313 $ 1,247 $ 3,480 $ 3,360 Gas utility 189 190 1,272 1,176 Enterprises 57 58 181 172 Other reconciling items 40 32 111 97 Total operating revenue – CMS Energy $ 1,599 $ 1,527 $ 5,044 $ 4,805 Consumers Operating revenue Electric utility $ 1,313 $ 1,247 $ 3,480 $ 3,360 Gas utility 189 190 1,272 1,176 Total operating revenue – Consumers $ 1,502 $ 1,437 $ 4,752 $ 4,536 CMS Energy, including Consumers Net income (loss) available to common stockholders Electric utility $ 199 $ 176 $ 468 $ 394 Gas utility (19 ) 5 105 101 Enterprises 4 8 33 27 Other reconciling items (15 ) (17 ) (57 ) (59 ) Total net income available to common stockholders – CMS Energy $ 169 $ 172 $ 549 $ 463 Consumers Net income (loss) available to common stockholder Electric utility $ 199 $ 176 $ 468 $ 394 Gas utility (19 ) 5 105 101 Total net income available to common stockholder – Consumers $ 180 $ 181 $ 573 $ 495 In Millions September 30, 2018 December 31, 2017 CMS Energy, including Consumers Plant, property, and equipment, gross Electric utility 1 $ 15,772 $ 15,221 Gas utility 1 7,534 7,080 Enterprises 405 167 Other reconciling items 40 38 Total plant, property, and equipment, gross – CMS Energy $ 23,751 $ 22,506 Consumers Plant, property, and equipment, gross Electric utility 1 $ 15,772 $ 15,221 Gas utility 1 7,534 7,080 Other reconciling items 16 17 Total plant, property, and equipment, gross – Consumers $ 23,322 $ 22,318 CMS Energy, including Consumers Total assets Electric utility 1 $ 13,850 $ 13,906 Gas utility 1 7,513 7,139 Enterprises 538 342 Other reconciling items 2,012 1,663 Total assets – CMS Energy $ 23,913 $ 23,050 Consumers Total assets Electric utility 1 $ 13,914 $ 13,907 Gas utility 1 7,556 7,139 Other reconciling items 22 53 Total assets – Consumers $ 21,492 $ 21,099 1 Amounts include a portion of Consumers’ other common assets attributable to both the electric and gas utility businesses.

New Accounting Standards (Detai

New Accounting Standards (Details) - USD ($) $ in Millions	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
Accumulated Deficit
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of change in accounting principle		$ 0	$ 8	$ 0	$ 0
Retirement benefits liability
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of change in accounting principle		0	(11)	0	0
Retirement benefits liability | Accounting Standards Update 2018-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of change in accounting principle			(11)
Consumers Energy Company | Accounting Standards Update 2016-01
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of change in accounting principle			19
Consumers Energy Company | Accumulated Deficit
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of change in accounting principle		0	19	0	0
Consumers Energy Company | Accumulated Deficit | Accounting Standards Update 2016-01
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of change in accounting principle			19
Consumers Energy Company | Accumulated Other Comprehensive Loss
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of change in accounting principle	$ (19)
Consumers Energy Company | Retirement benefits liability
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of change in accounting principle		$ 0	(5)	$ 0	$ 0
Consumers Energy Company | Retirement benefits liability | Accounting Standards Update 2018-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of change in accounting principle			$ (5)

Regulatory Matters (Narrative)

Regulatory Matters (Narrative) (Details) - USD ($) $ in Millions

1 Months Ended

3 Months Ended

9 Months Ended

12 Months Ended

Jul. 31, 2020

Jul. 31, 2019

Oct. 25, 2018

Aug. 31, 2018

Jul. 31, 2018

Jun. 30, 2018

Mar. 31, 2018

Oct. 31, 2017

Sep. 30, 2017

Mar. 31, 2017

Sep. 30, 2018

Sep. 30, 2017

Sep. 30, 2018

Sep. 30, 2017

Dec. 31, 2017

May 31, 2018

Public Utilities, General Disclosures [Line Items]

Regulatory liabilities, current

$ 165

$ 165

$ 80

Regulatory liabilities, noncurrent

3,745

3,745

3,715

Regulatory assets

1,655

1,655

1,764

Revenue

1,599

$ 1,527

5,044

$ 4,805

Consumers Energy Company

Public Utilities, General Disclosures [Line Items]

Regulatory liabilities, current

165

165

80

Regulatory liabilities, noncurrent

3,745

3,745

3,715

Regulatory assets

1,655

1,655

1,764

Revenue

1,502

$ 1,437

4,752

$ 4,536

Income Taxes, Net | Consumers Energy Company

Public Utilities, General Disclosures [Line Items]

Regulatory liabilities, noncurrent

1,600

1,600

Income Taxes Subject To Normalization | Consumers Energy Company

Public Utilities, General Disclosures [Line Items]

Regulatory liabilities, noncurrent

1,700

1,700

Income Taxes Not Subject To Normalization | Consumers Energy Company

Public Utilities, General Disclosures [Line Items]

Regulatory assets

300

300

Taxes Not Related To Plant Assets | Consumers Energy Company

Public Utilities, General Disclosures [Line Items]

Regulatory liabilities, noncurrent

200

200

Electric Rate Case | Consumers Energy Company

Public Utilities, General Disclosures [Line Items]

Annual rate increase requested

$ 173

Rate of return on equity requested

10.50%

Annual rate increase requested, amended

$ 148

Annual rate increase self-implemented

$ 130

Annual rate increase authorized

$ 72

$ 66

Rate of return on equity authorized

10.00%

Electric Rate Case | Revenue Subject to Refund - Other | Consumers Energy Company

Public Utilities, General Disclosures [Line Items]

Regulatory liabilities, current

36

36

Gas Rate Case | Consumers Energy Company

Public Utilities, General Disclosures [Line Items]

Annual rate increase requested

$ 178

Rate of return on equity requested

10.50%

Annual rate increase requested, amended

$ 60

$ 145

Annual rate increase authorized

$ 11

Rate of return on equity authorized

10.00%

Authorized amended return on equity

10.00%

Electric Rate Case Tax Reform Rate Change | Consumers Energy Company

Public Utilities, General Disclosures [Line Items]

Annual rate increase authorized

$ (113)

Electric Rate Case Tax Reform Rate Change | Revenue Subject to Refund - Tax Reform Rate Change | Consumers Energy Company

Public Utilities, General Disclosures [Line Items]

Regulatory liabilities, current

70

70

Electric Rate Case Tax Reform Rate Change | Income Taxes, Net | Consumers Energy Company

Public Utilities, General Disclosures [Line Items]

Regulatory liabilities, noncurrent

1,200

1,200

Gas Rate Case Tax Reform Rate Change | Consumers Energy Company

Public Utilities, General Disclosures [Line Items]

Annual rate increase requested, amended

$ 83

Annual rate increase authorized

$ (49)

Authorized amended return on equity

10.75%

Gas Rate Case Tax Reform Rate Change | Revenue Subject to Refund - Tax Reform Rate Change | Consumers Energy Company

Public Utilities, General Disclosures [Line Items]

Regulatory liabilities, current

31

31

Gas Rate Case Tax Reform Rate Change | Income Taxes, Net | Consumers Energy Company

Public Utilities, General Disclosures [Line Items]

Regulatory liabilities, noncurrent

$ 400

$ 400

Energy Waste Reduction Plan | Consumers Energy Company

Public Utilities, General Disclosures [Line Items]

Requested recovery/collection

$ 31

Revenue

$ 31

Scenario, Forecast | Gas Rate Case | Consumers Energy Company

Public Utilities, General Disclosures [Line Items]

Annual rate increase authorized

$ 10

$ 9

Subsequent Event | Taxes Not Related To Plant Assets | Consumers Energy Company

Public Utilities, General Disclosures [Line Items]

Regulatory liability remaining life (in years)

15 years

Subsequent Event | Electric Rate Case Tax Reform Rate Change | Income Taxes Subject To Normalization | Consumers Energy Company

Public Utilities, General Disclosures [Line Items]

Regulatory liability remaining life (in years)

36 years

Subsequent Event | Electric Rate Case Tax Reform Rate Change | Income Taxes Not Subject To Normalization | Consumers Energy Company

Public Utilities, General Disclosures [Line Items]

Regulatory asset remaining life (in years)

27 years

Subsequent Event | Gas Rate Case Tax Reform Rate Change | Income Taxes Subject To Normalization | Consumers Energy Company

Public Utilities, General Disclosures [Line Items]

Regulatory liability remaining life (in years)

44 years

Subsequent Event | Gas Rate Case Tax Reform Rate Change | Income Taxes Not Subject To Normalization | Consumers Energy Company

Public Utilities, General Disclosures [Line Items]

Regulatory asset remaining life (in years)

44 years

Contingencies And Commitments_2

Contingencies And Commitments (Contingencies And Commitments) (Details) $ in Millions	9 Months Ended
	Sep. 30, 2018USD ($)sitelawsuit	Dec. 31, 2017USD ($)
Loss Contingencies [Line Items]
Regulatory assets	$ 1,655	$ 1,764
Consumers Energy Company
Loss Contingencies [Line Items]
Regulatory assets	1,655	$ 1,764
Bay Harbor
Loss Contingencies [Line Items]
Demand for payment by USEPA	8
Accrual for obligations for environmental remediation	$ 46
Discounted projected costs rate	4.34%
Remaining undiscounted obligation amount	$ 58
Accrual for environmental loss contingencies, inflation rate	1.00%
Electric Utility | NREPA | Consumers Energy Company
Loss Contingencies [Line Items]
Accrual for obligations for environmental remediation	$ 3
Electric Utility | NREPA | Minimum | Consumers Energy Company
Loss Contingencies [Line Items]
Remediation and other response activity costs	3
Electric Utility | NREPA | Maximum | Consumers Energy Company
Loss Contingencies [Line Items]
Remediation and other response activity costs	4
Electric Utility | CERCLA Liability | Consumers Energy Company
Loss Contingencies [Line Items]
Accrual for obligations for environmental remediation	3
Electric Utility | CERCLA Liability | Minimum | Consumers Energy Company
Loss Contingencies [Line Items]
Remediation and other response activity costs	3
Electric Utility | CERCLA Liability | Maximum | Consumers Energy Company
Loss Contingencies [Line Items]
Remediation and other response activity costs	8
Gas Utility | NREPA | Maximum | Consumers Energy Company
Loss Contingencies [Line Items]
Accrual for obligations for environmental remediation	1
Remediation and other response activity costs	3
Gas Utility | Manufactured Gas Plant | Consumers Energy Company
Loss Contingencies [Line Items]
Accrual for obligations for environmental remediation	$ 78
Discounted projected costs rate	2.57%
Remaining undiscounted obligation amount	$ 83
Number of former MGPs | site	23
Regulatory assets	$ 135
Authorized recovery, collection period	10 years
Accrual for environmental loss contingencies, inflation rate	2.50%
Equatorial Guinea Tax Claim
Loss Contingencies [Line Items]
Foreign government tax claim on sale	$ 152
Class Action Lawsuits
Loss Contingencies [Line Items]
Number of lawsuits | lawsuit	4
Individual Lawsuits
Loss Contingencies [Line Items]
Number of lawsuits | lawsuit	1
MCV PPA | Consumers Energy Company
Loss Contingencies [Line Items]
Remediation and other response activity costs	$ 270
Underwater cables Straits of Mackinac | Consumers Energy Company
Loss Contingencies [Line Items]
Remediation and other response activity costs	$ 10

Contingencies And Commitments_3

Contingencies And Commitments (Expected Remediation Cost By Year) (Details) $ in Millions	Sep. 30, 2018USD ($)
Bay Harbor
Site Contingency [Line Items]
2,018	$ 1
2,019	4
2,020	4
2,021	4
2,022	4
2,023	4
Gas Utility | Manufactured Gas Plant | Consumers Energy Company
Site Contingency [Line Items]
2,018	6
2,019	12
2,020	16
2,021	21
2,022	7
2,023	$ 2

Contingencies And Commitments_4

Contingencies And Commitments (Guarantees) (Details) $ in Millions	9 Months Ended
	Sep. 30, 2018USD ($)
Guarantees
Guarantees And Other Contingencies [Line Items]
Guarantee Description	Guarantees
Expiration Date	Indefinite	[1]
Maximum Obligation	$ 39	[1]
Carrying Amount	$ 0	[1]
Guarantees | Consumers Energy Company
Guarantees And Other Contingencies [Line Items]
Guarantee Description	Guarantee
Expiration Date	Indefinite	[1]
Maximum Obligation	$ 30	[1]
Carrying Amount	$ 0	[1]
Indemnity Obligations From Stock And Asset Sales Agreements
Guarantees And Other Contingencies [Line Items]
Guarantee Description	Indemnity obligations from stock and asset sales agreements
Expiration Date	Indefinite	[2]
Maximum Obligation	$ 153	[2]
Carrying Amount	3	[2]
Tax And Other Indemnity Obligations | Consumers Energy Company
Guarantees And Other Contingencies [Line Items]
Carrying Amount	$ 1
[1]	At Consumers, this obligation comprises a guarantee provided to the U.S. Department of Energy in connection with a settlement agreement regarding damages resulting from the department’s failure to accept spent nuclear fuel from nuclear power plants formerly owned by Consumers. At CMS Energy, the guarantee obligations comprise Consumers’ guarantee to the U.S. Department of Energy and CMS Energy’s 1994 guarantee of non-recourse revenue bonds issued by Genesee.
[2]	These obligations arose from stock and asset sale agreements under which CMS Energy or a subsidiary of CMS Energy indemnified the purchaser for losses resulting from various matters, primarily claims related to taxes. CMS Energy believes the likelihood of material loss to be remote for the indemnity obligations not recorded as liabilities.

Financings And Capitalization_2

Financings And Capitalization (Major Long-Term Debt Transactions) (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018USD ($)		Sep. 30, 2018USD ($)
Debt Instrument [Line Items]
Principal balance	$ 1,000		$ 1,000
Debt retirement, principal			643
Consumers Energy Company
Debt Instrument [Line Items]
Principal balance	550		550
Debt retirement, principal			318
First mortgage bonds | Consumers Energy Company
Debt Instrument [Line Items]
Principal balance	$ 550		$ 550
Interest Rate	4.05%		4.05%
Debt issuance date			May 2018
Maturity Date			2048-05
Tax-exempt pollution control revenue bonds | Consumers Energy Company
Debt Instrument [Line Items]
Debt retirement, principal			$ 68
Maturity Date			2018-04
Debt retirement date			April 2018
First mortgage bonds | Consumers Energy Company
Debt Instrument [Line Items]
Debt retirement, principal			$ 250
Interest Rate	5.65%		5.65%
Maturity Date			2018-09
Debt retirement date			May 2018
CMS Energy Corporation
Debt Instrument [Line Items]
Principal balance	$ 450	[1]	$ 450	[1]
Debt retirement, principal			325
CMS Energy Corporation | Junior subordinated notes 5.625% due March 2078
Debt Instrument [Line Items]
Principal balance	$ 200	[1]	$ 200	[1]
Interest Rate	5.625%	[1]	5.625%	[1]
Debt issuance date			March 2018	[1]
Maturity Date	2078-03	[1]	2078-03	[1]
CMS Energy Corporation | Junior subordinated notes 5.875% due October 2078
Debt Instrument [Line Items]
Principal balance	$ 250	[1]	$ 250	[1]
Interest Rate	5.875%	[1]	5.875%	[1]
Debt issuance date			September 2018	[1]
Maturity Date			2078-10	[1]
CMS Energy Corporation | Term loan facility due December 2018
Debt Instrument [Line Items]
Debt retirement, principal			$ 180
Maturity Date	2018-12		2018-12
Debt retirement date			March 2018
CMS Energy Corporation | Term loan facility due August 2018
Debt Instrument [Line Items]
Debt retirement, principal			$ 45
Maturity Date			2018-12
Debt retirement date			August 2,018
CMS Energy Corporation | Senior notes 8.75% due June 2019
Debt Instrument [Line Items]
Debt retirement, principal			$ 100	[2]
Interest Rate	8.75%	[2]	8.75%	[2]
Maturity Date			2019-06	[2]
Debt retirement date			June 2018	[2]
Loss on extinguishment of debt			$ 5
[1]	These unsecured obligations rank subordinate and junior in right of payment to all of CMS Energy’s existing and future senior indebtedness.
[2]	CMS Energy retired these senior notes at a premium and recorded a loss on extinguishment of $5 million in other expense on its consolidated statements of income.

Financings And Capitalization_3

Financings And Capitalization (Narrative) (Details) - USD ($) $ in Millions		1 Months Ended			9 Months Ended
		Oct. 25, 2018	Aug. 31, 2018	Mar. 31, 2017	Sep. 30, 2018	Jul. 31, 2018
Financing And Capitalization [Line Items]
Principal balance					$ 1,000
Debt retirement, principal					643
Unrestricted retained earnings					4,700
Common stock dividends from Consumers					392
Stock offering program maximum value			$ 250	$ 100
Consumers Energy Company
Financing And Capitalization [Line Items]
Principal balance					550
Debt retirement, principal					318
Unrestricted retained earnings					1,300
Consumers Energy Company | Commercial Paper
Financing And Capitalization [Line Items]
Short-term debt, authorized borrowings					500
Short-term debt					279
October 2018 First Mortgage Bonds | Consumers Energy Company
Financing And Capitalization [Line Items]
Principal balance						$ 500
Subsequent Event | 3.68% First Mortgage Bonds Due 2027 | Consumers Energy Company
Financing And Capitalization [Line Items]
Principal balance		$ 100
Interest Rate		3.68%
Subsequent Event | 4.01% First Mortgage Bonds Due 2038 | Consumers Energy Company
Financing And Capitalization [Line Items]
Principal balance		$ 215
Interest Rate		4.01%
Subsequent Event | 4.28% First Mortgage Bonds Due 2057 | Consumers Energy Company
Financing And Capitalization [Line Items]
Principal balance		$ 185
Interest Rate		4.28%
CMS Energy Corporation
Financing And Capitalization [Line Items]
Principal balance	[1]				450
Debt retirement, principal					$ 325
CMS Energy Corporation | Subsequent Event | 5.875% Junior Subordinated Notes Due 2078
Financing And Capitalization [Line Items]
Principal balance		$ 30
Interest Rate	[1]	5.875%
CMS Energy Corporation | Subsequent Event | 6.25% Senior Notes Due 2020
Financing And Capitalization [Line Items]
Interest Rate	[1]	6.25%
Loss on extinguishment of debt		$ 11
Debt retirement, principal		$ 300
[1]	These unsecured obligations rank subordinate and junior in right of payment to all of CMS Energy’s existing and future senior indebtedness.

Financings And Capitalization_4

Financings And Capitalization (Revolving Credit Facilities) (Details) $ in Millions	Sep. 30, 2018USD ($)
Revolving Credit Facilities June 5, 2023 | Consumers Energy Company
Line of Credit Facility [Line Items]
Amount of Facility	$ 850	[1],[2]
Amount Borrowed	0	[1],[2]
Letters of Credit Outstanding	7	[1],[2]
Amount Available	843	[1],[2]
Revolving Credit Facilities November 23, 2019 | Consumers Energy Company
Line of Credit Facility [Line Items]
Amount of Facility	250	[3]
Amount Borrowed	0	[3]
Letters of Credit Outstanding	25	[3]
Amount Available	225	[3]
Revolving Credit Facilities September 9, 2019 | Consumers Energy Company
Line of Credit Facility [Line Items]
Amount of Facility	30	[3]
Amount Borrowed	0	[3]
Letters of Credit Outstanding	30	[3]
Amount Available	0	[3]
CMS Energy Corporation | Revolving Credit Facilities June 5, 2023
Line of Credit Facility [Line Items]
Amount of Facility	550	[4]
Amount Borrowed	0	[4]
Letters of Credit Outstanding	9	[4]
Amount Available	$ 541	[4]
[1]	In June 2018, Consumers amended this revolving credit facility by increasing its borrowing capacity to $850 million and extending the expiration date to June 2023.
[2]	Obligations under this facility are secured by first mortgage bonds of Consumers.
[3]	These unsecured obligations rank subordinate and junior in right of payment to all of CMS Energy’s existing and future senior indebtedness.
[4]	In June 2018, CMS Energy amended this revolving credit facility, eliminating the security provided by Consumers common stock, and extending the expiration date to June 2023.

Financings and Capitalization_5

Financings and Capitalization (Issuance of Common Stock) (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended
	May 31, 2018	Jun. 30, 2017
Debt Disclosure [Abstract]
Number of shares issued (in shares)	638,898	1,494,371
Average price per share (in dollars per share)	$ 45.83	$ 47.31
Net Proceeds (In Millions)	$ 29	$ 70

Fair Value Measurements (Assets

Fair Value Measurements (Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Millions		Sep. 30, 2018	Dec. 31, 2017
Assets
Cash equivalents	[1]	$ 139	$ 74
Restricted cash and cash equivalents	[1]	42	17
Nonqualified deferred compensation plan assets	[1]	14	14
DB SERP
Cash equivalents	[1]	1	5
Derivative instruments
Commodity contracts	[1]	1	1
Total	[1]	197	252
Liabilities
Nonqualified deferred compensation plan liabilities	[1]	14	14
Derivative instruments
Commodity contracts	[1]	1	1
Total	[1]	15	15
Consumers Energy Company
Assets
Cash equivalents	[1]	0	0
Restricted cash and cash equivalents	[1]	28	17
Nonqualified deferred compensation plan assets	[1]	11	10
DB SERP
Cash equivalents		1	4
Derivative instruments
Commodity contracts	[1]	1	1
Total	[1]	42	155
Liabilities
Nonqualified deferred compensation plan liabilities	[1]	11	10
Derivative instruments
Commodity contracts	[1]	1	0
Total	[1]	12	10
DB SERP
DB SERP
Cash equivalents	[1]	1	5
Debt securities	[1]	0	141
DB SERP | Consumers Energy Company
DB SERP
Cash equivalents	[1]	1	4
Debt securities	[1]	0	102
Common Stock | Consumers Energy Company
Assets
CMS Energy common stock	[1]	$ 1	$ 21
[1]	1 All assets and liabilities were classified as Level 1 with the exception of some commodity contracts, which were classified as Level 3.

Financial Instruments (Schedule

Financial Instruments (Schedule Of Carrying Amounts And Fair Values Of Financial Instruments) (Details) - USD ($) $ in Millions		Sep. 30, 2018	Dec. 31, 2017
Assets
Securities held to maturity		$ 21	$ 16
Liabilities
Other current liabilities		134	195
Long-term debt, current		1,900	1,100
Current portion of notes receivable		237	198
DIG Note Payable
Liabilities
Other current liabilities		3	3
Carrying Amount
Assets
Long-term receivables		22	21	[1]
Notes receivable	[2]	1,640	1,371
Securities held to maturity		22	16
Liabilities
Long-term debt	[3]	10,817	10,204
Long-term payables	[4]	26	27
Fair Value
Assets
Long-term receivables	[1]	22	21
Notes receivable	[2]	1,730	1,464
Securities held to maturity		21	16
Liabilities
Long-term debt	[3]	10,798	10,715
Long-term payables	[4]	26	26
Consumers Energy Company
Liabilities
Other current liabilities		96	159
Long-term debt, current		876	343
Current portion of notes receivable		17	17
Current portion notes receivable related party		7	0
Consumers Energy Company | Carrying Amount
Assets
Long-term receivables	[1]	22	21
Notes receivable	[5]	17	17
Notes Receivable Affiliate, Fair Value Disclosure	[6]	107	0
Liabilities
Long-term debt	[7]	6,115	5,904
Consumers Energy Company | Fair Value
Assets
Long-term receivables	[1]	22	21
Notes receivable	[5]	17	17
Notes Receivable Affiliate, Fair Value Disclosure	[6]	105	0
Liabilities
Long-term debt	[7]	6,083	6,236
EnerBank
Liabilities
Current notes receivable		263	200
Other Receivables | Consumers Energy Company
Liabilities
Accounts receivable, current		15	14
Fair Value, Inputs, Level 1 | Fair Value
Assets
Long-term receivables	[1]	0	0
Notes receivable	[2]	0	0
Securities held to maturity		0	0
Liabilities
Long-term debt	[3]	445	0
Long-term payables	[4]	0	0
Fair Value, Inputs, Level 1 | Consumers Energy Company | Fair Value
Assets
Long-term receivables	[1]	0	0
Notes receivable	[5]	0	0
Notes Receivable Affiliate, Fair Value Disclosure	[6]	0	0
Liabilities
Long-term debt	[7]	0	0
Fair Value, Inputs, Level 2 | Fair Value
Assets
Long-term receivables	[1]	0	0
Notes receivable	[2]	0	0
Securities held to maturity		21	16
Liabilities
Long-term debt	[3]	9,088	9,363
Long-term payables	[4]	0	0
Fair Value, Inputs, Level 2 | Consumers Energy Company | Fair Value
Assets
Long-term receivables	[1]	0	0
Notes receivable	[5]	0	0
Notes Receivable Affiliate, Fair Value Disclosure	[6]	0	0
Liabilities
Long-term debt	[7]	4,818	4,883
Fair Value, Inputs, Level 3 | Fair Value
Assets
Long-term receivables	[1]	22	21
Notes receivable	[2]	1,730	1,464
Securities held to maturity		0	0
Liabilities
Long-term debt	[3]	1,265	1,352
Long-term payables	[4]	26	26
Fair Value, Inputs, Level 3 | Consumers Energy Company | Fair Value
Assets
Long-term receivables	[1]	22	21
Notes receivable	[5]	17	17
Notes Receivable Affiliate, Fair Value Disclosure	[6]	105	0
Liabilities
Long-term debt	[7]	1,265	1,353
Michigan tax settlement
Liabilities
Current portion of notes receivable		20	20
Michigan tax settlement | Consumers Energy Company
Liabilities
Current portion of notes receivable		$ 17	$ 17
[1]	Includes current accounts receivable of $15 million at September 30, 2018 and $14 million December 31, 2017.
[2]	Includes current portion of notes receivable of $263 million at September 30, 2018 and $200 million at December 31, 2017. For further details, see Note 7, Notes Receivable.
[3]	Includes current portion of long-term debt of $1.9 billion at September 30, 2018 and $1.1 billion at December 31, 2017.
[4]	Includes current portion of long-term payables of $3 million at September 30, 2018 and December 31, 2017.
[5]	Includes current portion of notes receivable of $17 million at September 30, 2018 and December 31, 2017.
[6]	Includes current portion of notes receivable – related party of $7 million at September 30, 2018. For further details on this note receivable, see the DB SERP discussion below.
[7]	Includes current portion of long-term debt of $876 million at September 30, 2018 and $343 million at December 31, 2017.

Financial Instruments (Narrativ

Financial Instruments (Narrative) (Details) - USD ($) $ in Millions		9 Months Ended
		Sep. 30, 2018	Jul. 31, 2018	Dec. 31, 2017
Financial Instruments [Line Items]
Portion of long-term debt supported by third-party credit enhancements		$ 35		$ 103
Consumers Energy Company
Financial Instruments [Line Items]
Portion of long-term debt supported by third-party credit enhancements		$ 35		103
DB SERP | Minimum
Financial Instruments [Line Items]
Debt security term		1 year
DB SERP | Maximum
Financial Instruments [Line Items]
Debt security term		10 years
CMS Energy Note Payable
Financial Instruments [Line Items]
Notes payable			$ 146
Interest Rate			4.10%
Common Stock | Consumers Energy Company
Financial Instruments [Line Items]
Equity investment	[1]	$ 1		$ 21
[1]	1 All assets and liabilities were classified as Level 1 with the exception of some commodity contracts, which were classified as Level 3.

Financial Instruments (Schedu_2

Financial Instruments (Schedule Of Investment Securities) (Details) - USD ($) $ in Millions		Sep. 30, 2018	Dec. 31, 2017
Held to maturity
Cost		$ 22	$ 16
Unrealized Gains		0	0
Unrealized Losses		(1)	0
Securities held to maturity		21	16
Common Stock | Consumers Energy Company
Available for sale
CMS Energy common stock cost			2
CMS Energy common stock - unrealized gains			19
CMS Energy Common Stock - unrealized losses			0
CMS Energy common stock - fair value			21
DB SERP
Available for sale
Cost		0	141
Unrealized Gains		0	0
Unrealized Losses		0	0
Fair Value	[1]	0	141
DB SERP | Consumers Energy Company
Available for sale
Cost		0	102
Unrealized Gains		0	0
Unrealized Losses		0	0
Fair Value	[1]	$ 0	102
Accounting Standards Update 2016-01 | Consumers Energy Company
Held to maturity
Cumulative effect of change in accounting principle			$ 19
[1]	1 All assets and liabilities were classified as Level 1 with the exception of some commodity contracts, which were classified as Level 3.

Notes Receivable (Schedule Of C

Notes Receivable (Schedule Of Current And Non-Current Notes Receivable) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Current
Current portion of notes receivable	$ 237	$ 198
EnerBank notes receivable held for sale	26	2
Non-current
Total notes receivable	1,640	1,371
Consumers Energy Company
Current
Current portion of notes receivable	17	17
DB SERP note receivable – related party	7	0
Non-current
Notes receivable – related party	100	0
Total notes receivable	124	17
EnerBank
Current
EnerBank notes receivable held for sale	26
Non-current
Noncurrent notes receivable	1,377	1,171
EnerBank notes receivable, net of allowance for loan losses | EnerBank
Current
Current portion of notes receivable	217	178
EnerBank notes receivable held for sale | EnerBank
Current
EnerBank notes receivable held for sale	26	2
Michigan tax settlement
Current
Current portion of notes receivable	20	20
Michigan tax settlement | Consumers Energy Company
Current
Current portion of notes receivable	$ 17	$ 17

Notes Receivable (Narrative) (D

Notes Receivable (Narrative) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes receivable	$ 1,640	$ 1,371
EnerBank notes receivable held for sale	26	2
EnerBank
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unearned income	82	84
Delinquent loans	15	14
Loans modified as troubled debt restructurings	1	$ 1
EnerBank notes receivable held for sale	26
Receivable Held For Sale | EnerBank
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unearned income	6
Retail Installment Contracts | EnerBank
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes receivable	$ 77

Retirement Benefits (Schedule O

Retirement Benefits (Schedule Of Net Benefit Costs) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
DB Pension Plans
Net periodic cost (credit)
Service cost	$ 12	$ 12	$ 36	$ 34
Interest cost	22	23	67	67
Expected return on plan assets	(38)	(39)	(112)	(115)
Amortization of:
Net loss	19	20	56	60
Prior service cost (credit)	1	1	2	3
Net periodic cost (credit)	16	17	49	49
DB Pension Plans | Consumers Energy Company
Net periodic cost (credit)
Service cost	12	11	35	33
Interest cost	22	22	64	65
Expected return on plan assets	(35)	(38)	(104)	(112)
Amortization of:
Net loss	17	19	53	58
Prior service cost (credit)	1	1	2	3
Net periodic cost (credit)	17	15	50	47
OPEB Plan
Net periodic cost (credit)
Service cost	4	5	13	15
Interest cost	9	13	27	39
Expected return on plan assets	(24)	(22)	(73)	(67)
Amortization of:
Net loss	3	7	11	23
Prior service cost (credit)	(16)	(8)	(50)	(26)
Net periodic cost (credit)	(24)	(5)	(72)	(16)
OPEB Plan | Consumers Energy Company
Net periodic cost (credit)
Service cost	4	5	12	14
Interest cost	8	12	25	38
Expected return on plan assets	(22)	(21)	(68)	(63)
Amortization of:
Net loss	4	8	12	24
Prior service cost (credit)	(17)	(8)	(49)	(25)
Net periodic cost (credit)	$ (23)	$ (4)	$ (68)	$ (12)

Income Taxes (Schedule Of Effec

Income Taxes (Schedule Of Effective Income Tax Rate Reconciliation) (Details) - USD ($) $ in Millions		1 Months Ended	9 Months Ended
		Mar. 31, 2018	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Income Taxes [Line Items]
U.S. federal income tax rate			21.00%	35.00%
Increase (decrease) in income taxes from:
State and local income taxes, net of federal effect			5.90%	2.30%
Accelerated flow-through of regulatory tax benefits	[1]		(5.00%)	(4.30%)
TCJA excess deferred taxes	[2]		(3.40%)	0.00%
Research and development tax credits, net	[3]		(1.60%)	(0.10%)
Production tax credits			(2.00%)	(1.00%)
Other, net			0.20%	(1.80%)
Effective tax rate			15.10%	30.10%
Consumers Energy Company
Income Taxes [Line Items]
U.S. federal income tax rate			21.00%	35.00%
Increase (decrease) in income taxes from:
State and local income taxes, net of federal effect			6.10%	2.30%
Accelerated flow-through of regulatory tax benefits	[1]		(4.40%)	(3.90%)
TCJA excess deferred taxes	[2]		(3.10%)	0.00%
Research and development tax credits, net	[3]		(1.50%)	(0.10%)
Production tax credits			(1.60%)	(1.00%)
Other, net			(0.30%)	(2.00%)
Effective tax rate			16.20%	30.30%
Reduction of income tax expense			$ 30	$ 28
Research Tax Credit Carryforward | Consumers Energy Company
Increase (decrease) in income taxes from:
Increase in credit		$ 8
Revenue Subject to Refund - Tax Reform DFIT Change | Consumers Energy Company
Increase (decrease) in income taxes from:
Regulatory liabilities			$ 26
Plant, Property, And Equipment (Subject To Normalization) | Consumers Energy Company
Increase (decrease) in income taxes from:
Regulatory liabilities					$ 1,800
[1]	In 2013, the MPSC issued an order authorizing Consumers to accelerate the flow-through to electric and gas customers of certain income tax benefits associated primarily with the cost of removal of plant placed in service before 1993. Consumers implemented this regulatory treatment beginning in 2014. This change, which also accelerates Consumers’ recognition of the income tax benefits, reduced Consumers’ income tax expense by $30 million for the nine months ended September 30, 2018 and by $28 million for the nine months ended September 30, 2017.
[2]	In December 2017, Consumers remeasured its deferred tax assets and liabilities at the new federal tax rate enacted by the TCJA and recorded a $1.8 billion regulatory liability. This regulatory liability relates to the excess deferred taxes arising from accelerated tax depreciation on assets in rate base that are governed by normalization provisions of the Internal Revenue Code. The normalization provisions require that the excess deferred taxes be refunded to customers over the remaining average service life of the associated assets. In January 2018, Consumers began to reduce this regulatory liability by crediting income tax expense. Consumers has fully reserved for the eventual refund of these excess deferred taxes that it has credited to income tax expense in a separate regulatory liability established by reducing revenue, and will continue to do so until these benefits are passed on to customers in accordance with an MPSC order, expected to be issued in 2019. At September 30, 2018, this reserve for refund of these excess deferred taxes totaled $26 million.
[3]	In March 2018, Consumers finalized a study of research and development tax credits for the tax years 2012 through 2016. As a result, Consumers recognized an $8 million increase in the credit, net of reserves for uncertain tax positions

Earnings Per Share - CMS Ener_3

Earnings Per Share - CMS Energy (Basic And Diluted EPS Computations) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income available to common stockholders
Net income	$ 169	$ 172	$ 550	$ 464
Income Attributable to Noncontrolling Interests	0	0	1	1
Net Income Available to Common Stockholders	$ 169	$ 172	$ 549	$ 463
Average common shares outstanding
Weighted average shares - basic (in shares)	282.5	280.8	282.1	279.8
Dilutive nonvested stock awards (in shares)	0.7	0.8	0.7	0.8
Weighted average shares - diluted (in shares)	283.2	281.6	282.8	280.6
Net income per average common share available to common stockholders
Basic earnings per average common share (in dollars per share)	$ 0.60	$ 0.61	$ 1.95	$ 1.65
Diluted earnings per average common share (in dollars per share)	$ 0.59	$ 0.61	$ 1.94	$ 1.65

Revenue (Components Of Operatin

Revenue (Components Of Operating Revenue) (Details) - USD ($) $ in Millions		3 Months Ended			9 Months Ended
		Sep. 30, 2018		Sep. 30, 2017	Sep. 30, 2018		Sep. 30, 2017
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		$ 1,519			$ 4,805
Leasing income		36			112
Financing income		43			122
Alternative revenue programs		1			5
Total operating revenue		1,599		$ 1,527	5,044		$ 4,805
Other
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		21			69
Consumers Energy Company
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		1,498			4,736
Financing income		3			11
Alternative revenue programs		1			5
Total operating revenue		1,502		1,437	4,752		4,536
Consumers Energy Company | Residential
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		743			2,450
Consumers Energy Company | Commercial
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		464			1,431
Consumers Energy Company | Industrial
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		190			536
Consumers Energy Company | Other
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		101			319
Operating Segments | Electric Utility
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		1,310			3,473
Financing income		3			7
Total operating revenue		1,313		1,247	3,480		3,360
Operating Segments | Gas Utility
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		188			1,263
Financing income		0			4
Alternative revenue programs		1			5
Total operating revenue		189		190	1,272		1,176
Operating Segments | Enterprises
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	[1]	21			69
Leasing income	[1]	36			112
Total operating revenue		57	[1]	58	181	[1]	172
Operating Segments | Enterprises | Other
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	[1]	21			69
Operating Segments | Consumers Energy Company | Electric Utility
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		1,310			3,473
Financing income		3			7
Total operating revenue		1,313		1,247	3,480		3,360
Operating Segments | Consumers Energy Company | Electric Utility | Residential
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		625			1,601
Operating Segments | Consumers Energy Company | Electric Utility | Commercial
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		434			1,181
Operating Segments | Consumers Energy Company | Electric Utility | Industrial
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		186			499
Operating Segments | Consumers Energy Company | Electric Utility | Other
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		65			192
Operating Segments | Consumers Energy Company | Gas Utility
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		188			1,263
Financing income		0			4
Alternative revenue programs		1			5
Total operating revenue		189		190	1,272		1,176
Operating Segments | Consumers Energy Company | Gas Utility | Residential
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		118			849
Operating Segments | Consumers Energy Company | Gas Utility | Commercial
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		30			250
Operating Segments | Consumers Energy Company | Gas Utility | Industrial
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		4			37
Operating Segments | Consumers Energy Company | Gas Utility | Other
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers		36			127
Other reconciling items
Disaggregation of Revenue [Line Items]
Financing income	[2]	40			111
Total operating revenue		40	[2]	$ 32	111	[2]	$ 97
Other reconciling items | Consumers Energy Company
Disaggregation of Revenue [Line Items]
Total operating revenue		$ 0			$ 0
[1]	Amounts represent the enterprises segment’s operating revenue from independent power production and CMS ERM’s sales of energy commodities in support of the independent power production portfolio.
[2]	Amount represents EnerBank’s operating revenue from unsecured consumer installment loans for financing home improvements.

Revenue (Narrative) (Details)

Revenue (Narrative) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Uncollectable expense	$ 22
Unbilled receivables	280	$ 481
Consumers Energy Company
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Uncollectable expense	22
Unbilled receivables	$ 271	$ 481

Cash And Cash Equivalents (Sche

Cash And Cash Equivalents (Schedule Of Cash And Cash Equivalents, Including Restricted Amounts) (Details) - USD ($) $ in Millions		Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents		$ 323	$ 182
Restricted cash and cash equivalents	[1]	42	17
Other non-current assets	[1]	1	5
Cash and cash equivalents, including restricted amounts		366	204	$ 173	$ 257
Consumers Energy Company
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents		9	44
Restricted cash and cash equivalents	[1]	28	17
Other non-current assets		1	4
Cash and cash equivalents, including restricted amounts		$ 38	$ 65	$ 85	$ 152
[1]	1 All assets and liabilities were classified as Level 1 with the exception of some commodity contracts, which were classified as Level 3.

Reportable Segments (Details)

Reportable Segments (Details) - USD ($) $ in Millions		3 Months Ended			9 Months Ended
		Sep. 30, 2018		Sep. 30, 2017	Sep. 30, 2018		Sep. 30, 2017	Dec. 31, 2017
Segment Reporting Information [Line Items]
Operating Revenue		$ 1,599		$ 1,527	$ 5,044		$ 4,805
Net income (loss) available to common stockholders		169		172	549		463
Plant, property, and equipment, gross		23,751			23,751			$ 22,506
Total Assets		23,913			23,913			23,050
Consumers Energy Company
Segment Reporting Information [Line Items]
Operating Revenue		1,502		1,437	4,752		4,536
Net income (loss) available to common stockholder		180		181	573		495
Plant, property, and equipment, gross		23,322			23,322			22,318
Total Assets		21,492			21,492			21,099
Operating Segments | Electric Utility
Segment Reporting Information [Line Items]
Operating Revenue		1,313		1,247	3,480		3,360
Net income (loss) available to common stockholders		199		176	468		394
Plant, property, and equipment, gross	[1]	15,772			15,772			15,221
Total Assets	[1]	13,850			13,850			13,906
Operating Segments | Electric Utility | Consumers Energy Company
Segment Reporting Information [Line Items]
Operating Revenue		1,313		1,247	3,480		3,360
Net income (loss) available to common stockholder		199		176	468		394
Plant, property, and equipment, gross	[1]	15,772			15,772			15,221
Total Assets	[1]	13,914			13,914			13,907
Operating Segments | Gas Utility
Segment Reporting Information [Line Items]
Operating Revenue		189		190	1,272		1,176
Net income (loss) available to common stockholders		(19)		5	105		101
Plant, property, and equipment, gross	[1]	7,534			7,534			7,080
Total Assets	[1]	7,513			7,513			7,139
Operating Segments | Gas Utility | Consumers Energy Company
Segment Reporting Information [Line Items]
Operating Revenue		189		190	1,272		1,176
Net income (loss) available to common stockholder		(19)		5	105		101
Plant, property, and equipment, gross	[1]	7,534			7,534			7,080
Total Assets	[1]	7,556			7,556			7,139
Operating Segments | Enterprises
Segment Reporting Information [Line Items]
Operating Revenue		57	[2]	58	181	[2]	172
Net income (loss) available to common stockholders		4		8	33		27
Plant, property, and equipment, gross		405			405			167
Total Assets		538			538			342
Other reconciling items
Segment Reporting Information [Line Items]
Operating Revenue		40	[3]	32	111	[3]	97
Net income (loss) available to common stockholders		(15)		$ (17)	(57)		$ (59)
Plant, property, and equipment, gross		40			40			38
Total Assets		2,012			2,012			1,663
Other reconciling items | Consumers Energy Company
Segment Reporting Information [Line Items]
Operating Revenue		0			0
Plant, property, and equipment, gross		16			16			17
Total Assets		$ 22			$ 22			$ 53
[1]	Amounts include a portion of Consumers’ other common assets attributable to both the electric and gas utility businesses.
[2]	Amounts represent the enterprises segment’s operating revenue from independent power production and CMS ERM’s sales of energy commodities in support of the independent power production portfolio.
[3]	Amount represents EnerBank’s operating revenue from unsecured consumer installment loans for financing home improvements.