XML 46 R28.htm IDEA: XBRL DOCUMENT
v3.10.0.1

Retirement Benefits (Tables) | 6 Months Ended
--- | ---
Jun. 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 |  | Six Months Ended |  | Three Months Ended |  | Six Months Ended
June 30 | 2018 |  | 2017 |  |  | 2018 |  | 2017 |  |  | 2018 |  | 2017 |  |  | 2018 |  | 2017 |
CMS Energy, including Consumers
Net periodic cost (credit) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Service cost |  | $ | 12 |  |  | $ | 11 |  |  |  | $ | 24 |  |  | $ | 22 |  |  |  | $ | 5 |  |  | $ | 5 |  |  |  | $ | 9 |  |  | $ | 10 |
Interest cost |  | 23 |  |  | 22 |  |  |  | 45 |  |  | 44 |  |  |  | 9 |  |  | 13 |  |  |  | 18 |  |  | 26 |
Expected return on plan assets |  | (37 | ) |  | (38 | ) |  |  | (74 | ) |  | (76 | ) |  |  | (25 | ) |  | (23 | ) |  |  | (49 | ) |  | (45 | )
Amortization of: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net loss |  | 19 |  |  | 20 |  |  |  | 37 |  |  | 40 |  |  |  | 4 |  |  | 8 |  |  |  | 8 |  |  | 16 |
Prior service cost (credit) |  | — |  |  | 1 |  |  |  | 1 |  |  | 2 |  |  |  | (17 | ) |  | (9 | ) |  |  | (34 | ) |  | (18 | )
Net periodic cost (credit) |  | $ | 17 |  |  | $ | 16 |  |  |  | $ | 33 |  |  | $ | 32 |  |  |  | $ | (24 | ) |  | $ | (6 | ) |  |  | $ | (48 | ) |  | $ | (11 | )
Consumers
Net periodic cost (credit) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Service cost |  | $ | 11 |  |  | $ | 11 |  |  |  | $ | 23 |  |  | $ | 22 |  |  |  | $ | 4 |  |  | $ | 4 |  |  |  | $ | 8 |  |  | $ | 9 |
Interest cost |  | 21 |  |  | 22 |  |  |  | 42 |  |  | 43 |  |  |  | 9 |  |  | 13 |  |  |  | 17 |  |  | 26 |
Expected return on plan assets |  | (34 | ) |  | (37 | ) |  |  | (69 | ) |  | (74 | ) |  |  | (23 | ) |  | (21 | ) |  |  | (46 | ) |  | (42 | )
Amortization of: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net loss |  | 18 |  |  | 19 |  |  |  | 36 |  |  | 39 |  |  |  | 4 |  |  | 8 |  |  |  | 8 |  |  | 16 |
Prior service cost (credit) |  | — |  |  | 1 |  |  |  | 1 |  |  | 2 |  |  |  | (16 | ) |  | (8 | ) |  |  | (32 | ) |  | (17 | )
Net periodic cost (credit) |  | $ | 16 |  |  | $ | 16 |  |  |  | $ | 33 |  |  | $ | 32 |  |  |  | $ | (22 | ) |  | $ | (4 | ) |  |  | $ | (45 | ) |  | $ | (8 | )
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 |  | Six Months Ended |  | Three Months Ended |  | Six Months Ended
June 30 | 2018 |  | 2017 |  |  | 2018 |  | 2017 |  |  | 2018 |  | 2017 |  |  | 2018 |  | 2017 |
CMS Energy, including Consumers
Net periodic cost (credit) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Service cost |  | $ | 12 |  |  | $ | 11 |  |  |  | $ | 24 |  |  | $ | 22 |  |  |  | $ | 5 |  |  | $ | 5 |  |  |  | $ | 9 |  |  | $ | 10 |
Interest cost |  | 23 |  |  | 22 |  |  |  | 45 |  |  | 44 |  |  |  | 9 |  |  | 13 |  |  |  | 18 |  |  | 26 |
Expected return on plan assets |  | (37 | ) |  | (38 | ) |  |  | (74 | ) |  | (76 | ) |  |  | (25 | ) |  | (23 | ) |  |  | (49 | ) |  | (45 | )
Amortization of: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net loss |  | 19 |  |  | 20 |  |  |  | 37 |  |  | 40 |  |  |  | 4 |  |  | 8 |  |  |  | 8 |  |  | 16 |
Prior service cost (credit) |  | — |  |  | 1 |  |  |  | 1 |  |  | 2 |  |  |  | (17 | ) |  | (9 | ) |  |  | (34 | ) |  | (18 | )
Net periodic cost (credit) |  | $ | 17 |  |  | $ | 16 |  |  |  | $ | 33 |  |  | $ | 32 |  |  |  | $ | (24 | ) |  | $ | (6 | ) |  |  | $ | (48 | ) |  | $ | (11 | )
Consumers
Net periodic cost (credit) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Service cost |  | $ | 11 |  |  | $ | 11 |  |  |  | $ | 23 |  |  | $ | 22 |  |  |  | $ | 4 |  |  | $ | 4 |  |  |  | $ | 8 |  |  | $ | 9 |
Interest cost |  | 21 |  |  | 22 |  |  |  | 42 |  |  | 43 |  |  |  | 9 |  |  | 13 |  |  |  | 17 |  |  | 26 |
Expected return on plan assets |  | (34 | ) |  | (37 | ) |  |  | (69 | ) |  | (74 | ) |  |  | (23 | ) |  | (21 | ) |  |  | (46 | ) |  | (42 | )
Amortization of: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net loss |  | 18 |  |  | 19 |  |  |  | 36 |  |  | 39 |  |  |  | 4 |  |  | 8 |  |  |  | 8 |  |  | 16 |
Prior service cost (credit) |  | — |  |  | 1 |  |  |  | 1 |  |  | 2 |  |  |  | (16 | ) |  | (8 | ) |  |  | (32 | ) |  | (17 | )
Net periodic cost (credit) |  | $ | 16 |  |  | $ | 16 |  |  |  | $ | 33 |  |  | $ | 32 |  |  |  | $ | (22 | ) |  | $ | (4 | ) |  |  | $ | (45 | ) |  | $ | (8 | )

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_DefinedBenefitPlanDisclosureLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of the components of net benefit costs for pension plans and/or other employee benefit plans including service cost, interest cost, expected return on plan assets, gain (loss), prior service cost or credit, transition asset or obligation, and gain (loss) recognized due to settlements or curtailments. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
Name: | us-gaap_ScheduleOfNetBenefitCostsTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | dei_LegalEntityAxis=cms_ConsumersEnergyCompanyMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |