New Accounting Standards	6 Months Ended
New Accounting Standards	Jun. 30, 2017
New Accounting Standards	1:New Accounting Standards Implementation of New Accounting Standards ASU 2017‑07, Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost: This standard was issued to improve the reporting of net benefit cost by employers that offer defined benefit pension plans and other postretirement benefit plans. The required effective date of the standard for CMS Energy and Consumers is January 1, 2018, but early adoption was permitted in the first interim period of 2017. CMS Energy and Consumers elected to adopt the standard as of January 1, 2017. The standard requires employers to report the service cost component of net benefit cost in the same line item on the income statement as other employee compensation costs, while presenting the other cost components separately outside of operating income. This change is to be applied retrospectively to all prior periods presented. Accordingly, for the three months and six months ended June 30, 2017 and 2016, CMS Energy and Consumers have presented the service cost component of their retirement benefits plans in maintenance and other operating expenses on the consolidated statements of income, while presenting the other components in nonoperating retirement benefits, net, under other income (expense). Prior to this standard, CMS Energy and Consumers had presented all of the cost components in maintenance and other operating expenses. Under a practical expedient permitted by the standard, CMS Energy and Consumers used benefit cost amounts disclosed for prior periods as the basis for retrospective application. In addition, under this standard, only the service cost component is eligible for capitalization as part of the cost of an asset. This change is to be applied prospectively upon adoption. Accordingly, for the three months and six months ended June 30, 2017, CMS Energy and Consumers capitalized a portion of the service cost component of their retirement benefits plans to plant, property, and equipment, while recognizing the other components in net income. In prior periods, a portion of all cost components was capitalized. For further details on the net periodic cost of CMS Energy’s and Consumers’ retirement benefits plans, see Note 8, Retirement Benefits. 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. New Accounting Standards Not Yet Effective ASU 2014‑09, Revenue from Contracts with Customers: This standard 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 will replace most of the existing revenue recognition requirements in GAAP, although certain guidance specific to rate-regulated utilities will be retained. The standard will be effective on January 1, 2018 for CMS Energy and Consumers, but early adoption in 2017 is permitted. Entities will have the option to apply the standard retrospectively to all prior periods presented, or to apply it retrospectively only to contracts existing at the effective date, with the cumulative effect of the standard recorded as an adjustment to beginning retained earnings. CMS Energy and Consumers are not adopting the standard early, and are still assessing how they will apply the standard upon adoption. CMS Energy and Consumers are continuing to evaluate the impact of the standard on their consolidated financial statements; however, they have determined that the standard will have no impact on a majority of their revenues and they have not yet identified any changes in their revenue recognition practices that may be required. ASU 2016‑01, Recognition and Measurement of Financial Assets and Financial Liabilities: This standard, which will be effective January 1, 2018 for CMS Energy and Consumers, is intended to improve the accounting for financial instruments. The standard will require 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 will no longer permit unrealized gains and losses for certain equity investments to be recorded in AOCI. CMS Energy and Consumers presently record unrealized gains and losses on certain equity investments, including the mutual funds in the DB SERP and Consumers’ investment in CMS Energy common stock, in AOCI, except that unrealized losses determined to be other than temporary are reported in earnings. For further details on these investments, see Note 6, Financial Instruments. Entities will apply the standard using a modified retrospective approach, with a cumulative-effect adjustment recorded to beginning retained earnings on the effective date. 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. As a result, CMS Energy and Consumers expect to recognize additional lease assets and liabilities for their operating leases under this standard. 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 continuing to evaluate the impact of the standard on their consolidated financial statements and do not presently expect to adopt the standard early. 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 [Member]
New Accounting Standards	1:New Accounting Standards Implementation of New Accounting Standards ASU 2017‑07, Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost: This standard was issued to improve the reporting of net benefit cost by employers that offer defined benefit pension plans and other postretirement benefit plans. The required effective date of the standard for CMS Energy and Consumers is January 1, 2018, but early adoption was permitted in the first interim period of 2017. CMS Energy and Consumers elected to adopt the standard as of January 1, 2017. The standard requires employers to report the service cost component of net benefit cost in the same line item on the income statement as other employee compensation costs, while presenting the other cost components separately outside of operating income. This change is to be applied retrospectively to all prior periods presented. Accordingly, for the three months and six months ended June 30, 2017 and 2016, CMS Energy and Consumers have presented the service cost component of their retirement benefits plans in maintenance and other operating expenses on the consolidated statements of income, while presenting the other components in nonoperating retirement benefits, net, under other income (expense). Prior to this standard, CMS Energy and Consumers had presented all of the cost components in maintenance and other operating expenses. Under a practical expedient permitted by the standard, CMS Energy and Consumers used benefit cost amounts disclosed for prior periods as the basis for retrospective application. In addition, under this standard, only the service cost component is eligible for capitalization as part of the cost of an asset. This change is to be applied prospectively upon adoption. Accordingly, for the three months and six months ended June 30, 2017, CMS Energy and Consumers capitalized a portion of the service cost component of their retirement benefits plans to plant, property, and equipment, while recognizing the other components in net income. In prior periods, a portion of all cost components was capitalized. For further details on the net periodic cost of CMS Energy’s and Consumers’ retirement benefits plans, see Note 8, Retirement Benefits. 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. New Accounting Standards Not Yet Effective ASU 2014‑09, Revenue from Contracts with Customers: This standard 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 will replace most of the existing revenue recognition requirements in GAAP, although certain guidance specific to rate-regulated utilities will be retained. The standard will be effective on January 1, 2018 for CMS Energy and Consumers, but early adoption in 2017 is permitted. Entities will have the option to apply the standard retrospectively to all prior periods presented, or to apply it retrospectively only to contracts existing at the effective date, with the cumulative effect of the standard recorded as an adjustment to beginning retained earnings. CMS Energy and Consumers are not adopting the standard early, and are still assessing how they will apply the standard upon adoption. CMS Energy and Consumers are continuing to evaluate the impact of the standard on their consolidated financial statements; however, they have determined that the standard will have no impact on a majority of their revenues and they have not yet identified any changes in their revenue recognition practices that may be required. ASU 2016‑01, Recognition and Measurement of Financial Assets and Financial Liabilities: This standard, which will be effective January 1, 2018 for CMS Energy and Consumers, is intended to improve the accounting for financial instruments. The standard will require 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 will no longer permit unrealized gains and losses for certain equity investments to be recorded in AOCI. CMS Energy and Consumers presently record unrealized gains and losses on certain equity investments, including the mutual funds in the DB SERP and Consumers’ investment in CMS Energy common stock, in AOCI, except that unrealized losses determined to be other than temporary are reported in earnings. For further details on these investments, see Note 6, Financial Instruments. Entities will apply the standard using a modified retrospective approach, with a cumulative-effect adjustment recorded to beginning retained earnings on the effective date. 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. As a result, CMS Energy and Consumers expect to recognize additional lease assets and liabilities for their operating leases under this standard. 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 continuing to evaluate the impact of the standard on their consolidated financial statements and do not presently expect to adopt the standard early. 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.