Adoption of Accounting Principles and Recently Issued Accounting Pronouncements	12 Months Ended
Dec. 31, 2016
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Adoption of Accounting Principles and Recently Issued Accounting Pronouncements	Adoption of Accounting Principles and Recently Issued Accounting Pronouncements - MGE Energy and MGE. a. Revenue from Contracts with Customers. In May 2014, the FASB issued authoritative guidance within the Codification's Revenue Recognition topic that provides guidance on the recognition, measurement, and disclosure of revenue from contracts with customers. The new standard establishes a five step model for recognizing and measuring revenue from contracts with customers and replaces existing guidance on revenue recognition. The objective of the new standard is to provide a single, comprehensive revenue recognition model for all contracts with customers to improve comparability within industries, across industries and across capital markets. The underlying principle is that an entity will recognize revenue to depict the transfer of goods or services to customers at an amount that the entity expects to be entitled to in exchange for those goods or services. MGE Energy and MGE have been assessing the impact of this guidance on revenue streams within the scope of the new standard. All retail electric and gas revenues are tariff rates approved by the PSCW. Based on our evaluation of the new standard, retail revenues will be recognized within the period in which utility service is provided to the customer and the performance obligation is fulfilled, consistent with our current revenue recognition model. Electric revenues for sales to the market represent wholesale sales made to third parties who are not ultimate users of the electricity. These sales may also include bilateral sales to other utilities or power marketers. Revenues for sales to the market will be recognized when the sale is completed within the market operated by MISO, similar to the recognition under our current revenue recognition model. In addition, revenues from the transportation of gas will continue to be recognized upon the performance of services for the respective customer. Based on our assessment of the new standard, revenue recognition for retail revenues, sales to the market, and transportation of gas will be consistent with our current revenue recognition model. However, additional disclosures regarding the nature, amount, timing, and uncertainty of these revenue streams and related cash flows arising from contracts with customers will be required as a result of the new standard. The Power and Utilities Task Force of the AICPA is formulating a utility industry-specific interpretation of the guidance regarding the collectability threshold of probable within the new standard. The collectability criterion could impact the timing of revenue recognition for uncollectible accounts. The Power and Utilities Task Force of the AICPA is also requesting the FASB issue an industry-specific clarification regarding the accounting treatment of upfront contributions in the aid of construction, also known as CIAC. The final clarification on this topic could result in a material impact on the consolidated financial statements. Management continues to analyze newly-released interpretative guidance and assess the related impacts to the current revenue recognition model. This authoritative guidance will become effective January 1, 2018, and MGE Energy and MGE anticipate adopting the standard upon the effective date. Adoption of this standard is permitted under one of two methods: the full retrospective method or the modified retrospective method. MGE Energy and MGE are continuing to assess the permitted implementation methods and the impact on our financial statements. b. Consolidation. In February 2015, the FASB issued authoritative guidance within the Codification's Consolidation topic that provides guidance on the evaluation of certain legal entities for consolidation purposes. This authoritative guidance became effective January 1, 2016. This guidance had no impact on our financial statements. c. Debt Issuance Costs. In April 2015, the FASB issued authoritative guidance within the Codification's Interest topic that provides guidance on the presentation of debt issuance costs in financial statements. This authoritative guidance became effective January 1, 2016, and changed the presentation of debt issuance costs on the balance sheet. Prior to the authoritative guidance, debt issuance costs were treated as a deferred asset, and beginning January 1, 2016, these costs are included as a direct deduction to the related debt liability on the consolidated balance sheets. As of December 31, 2016, assets (other deferred assets and other) and liabilities (long-term debt) decreased approximately $3.9 million as a cumulative result of the guidance. In addition, this guidance was applied retrospectively to all prior periods presented, resulting in a decrease to assets and liabilities of $4.3 million for the year ended December 31, 2015. d. Financial Instruments. In January 2016, the FASB issued authoritative guidance within the Codification's Financial Instruments topic that provides guidance on the recognition and measurement of financial instruments. This authoritative guidance will become effective January 1, 2018, and will require equity investments to be measured at fair value with changes in fair value recognized in net income rather than in other comprehensive income. As a result of this guidance, MGE Energy and MGE will no longer have any other comprehensive income. This standard will be applied using a modified retrospective approach, with a cumulative effect adjustment recorded to opening retained earnings as of the beginning of all prior periods presented. e. Leases. In February 2016, the FASB issued authoritative guidance within the Codification's Leases topic that provides guidance on the classification, recognition, measurement, and disclosure of leases. The new leasing standard establishes that a lease conveys the right to control the use of identified property, plant, or equipment for a period of time in exchange for consideration. Under the new guidance, lessees will be required to recognize all leases with terms greater than one year, including operating leases, on the consolidated balance sheet by recording a right-of-use asset and lease liability. Prior to the authoritative guidance, only capital leases were recognized on the balance sheet by lessees. The new accounting guidance as applied by lessors is materially consistent from that applied under current GAAP. Management has begun utilizing a bottoms-up approach to analyze the impact of the standard on our lease portfolio. MGE Energy and MGE have been reviewing current accounting policies and procedures to identify potential differences in accounting treatment that would result from applying the requirements of the new standard to our existing lease portfolio. In addition, we are identifying appropriate changes to our business processes, systems, and controls to support recognition and disclosure requirements under the new standard. This authoritative guidance will become effective January 1, 2019, with early adoption permitted. The new leasing standard requires entities to recognize and measure leases at the beginning of the earliest comparative period presented using a modified retrospective approach. MGE Energy and MGE are currently assessing the impact this pronouncement will have on our financial statements. f. Restricted Cash. In November 2016, the FASB issued authoritative guidance within the Codification's Statement of Cash Flows topic that provides guidance on the classification and presentation of changes in restricted cash within the statement of cash flows. The new standard was issued to eliminate a current diversity in practice for the accounting treatment of restricted cash. Under the new guidance, reporting entities will be required to explain the changes in the total of restricted and unrestricted cash and cash equivalents when reconciling the beginning and ending balances on the statement of cash flows. Prior to the authoritative guidance, changes in restricted cash were presented as either cash flows from operating, investing, or financing activities within the statement of cash flows, as appropriate based on the nature of the restriction. Also under the new standard, reporting entities will be required to provide a reconciliation from the balance sheet to the statement of cash flows and disclose the nature of the restrictions of cash. This authoritative guidance will become effective January 1, 2018. Upon the effective date, MGE Energy and MGE will change the presentation of restricted cash to reflect this change in accounting guidance. MGE Energy and MGE will also retrospectively apply the guidance to all prior periods presented. As of December 31, 2016, MGE Energy and MGE had $5.1 million of restricted cash classified within other current assets on the consolidated balance sheets.

Adoption of Accounting Principles and Recently Issued Accounting Pronouncements - MGE Energy and MGE.

a. Revenue from Contracts with Customers.

In May 2014, the FASB issued authoritative guidance within the Codification's Revenue Recognition topic that provides guidance on the recognition, measurement, and disclosure of revenue from contracts with customers. The new standard establishes a five step model for recognizing and measuring revenue from contracts with customers and replaces existing guidance on revenue recognition. The objective of the new standard is to provide a single, comprehensive revenue recognition model for all contracts with customers to improve comparability within industries, across industries and across capital markets. The underlying principle is that an entity will recognize revenue to depict the transfer of goods or services to customers at an amount that the entity expects to be entitled to in exchange for those goods or services.

MGE Energy and MGE have been assessing the impact of this guidance on revenue streams within the scope of the new standard. All retail electric and gas revenues are tariff rates approved by the PSCW. Based on our evaluation of the new standard, retail revenues will be recognized within the period in which utility service is provided to the customer and the performance obligation is fulfilled, consistent with our current revenue recognition model. Electric revenues for sales to the market represent wholesale sales made to third parties who are not ultimate users of the electricity. These sales may also include bilateral sales to other utilities or power marketers. Revenues for sales to the market will be recognized when the sale is completed within the market operated by MISO, similar to the recognition under our current revenue recognition model. In addition, revenues from the transportation of gas will continue to be recognized upon the performance of services for the respective customer. Based on our assessment of the new standard, revenue recognition for retail revenues, sales to the market, and transportation of gas will be consistent with our current revenue recognition model. However, additional disclosures regarding the nature, amount, timing, and uncertainty of these revenue streams and related cash flows arising from contracts with customers will be required as a result of the new standard.

The Power and Utilities Task Force of the AICPA is formulating a utility industry-specific interpretation of the guidance regarding the collectability threshold of probable within the new standard. The collectability criterion could impact the timing of revenue recognition for uncollectible accounts. The Power and Utilities Task Force of the AICPA is also requesting the FASB issue an industry-specific clarification regarding the accounting treatment of upfront contributions in the aid of construction, also known as CIAC. The final clarification on this topic could result in a material impact on the consolidated financial statements. Management continues to analyze newly-released interpretative guidance and assess the related impacts to the current revenue recognition model.

This authoritative guidance will become effective January 1, 2018, and MGE Energy and MGE anticipate adopting the standard upon the effective date. Adoption of this standard is permitted under one of two methods: the full retrospective method or the modified retrospective method. MGE Energy and MGE are continuing to assess the permitted implementation methods and the impact on our financial statements.

b. Consolidation.

In February 2015, the FASB issued authoritative guidance within the Codification's Consolidation topic that provides guidance on the evaluation of certain legal entities for consolidation purposes. This authoritative guidance became effective January 1, 2016. This guidance had no impact on our financial statements.

c. Debt Issuance Costs.

In April 2015, the FASB issued authoritative guidance within the Codification's Interest topic that provides guidance on the presentation of debt issuance costs in financial statements. This authoritative guidance became effective January 1, 2016, and changed the presentation of debt issuance costs on the balance sheet. Prior to the authoritative guidance, debt issuance costs were treated as a deferred asset, and beginning January 1, 2016, these costs are included as a direct deduction to the related debt liability on the consolidated balance sheets. As of December 31, 2016, assets (other deferred assets and other) and liabilities (long-term debt) decreased approximately $3.9 million as a cumulative result of the guidance. In addition, this guidance was applied retrospectively to all prior periods presented, resulting in a decrease to assets and liabilities of $4.3 million for the year ended December 31, 2015.

d. Financial Instruments.

In January 2016, the FASB issued authoritative guidance within the Codification's Financial Instruments topic that provides guidance on the recognition and measurement of financial instruments. This authoritative guidance will become effective January 1, 2018, and will require equity investments to be measured at fair value with changes in fair value recognized in net income rather than in other comprehensive income. As a result of this guidance, MGE Energy and MGE will no longer have any other comprehensive income. This standard will be applied using a modified retrospective approach, with a cumulative effect adjustment recorded to opening retained earnings as of the beginning of all prior periods presented.

e. Leases.

In February 2016, the FASB issued authoritative guidance within the Codification's Leases topic that provides guidance on the classification, recognition, measurement, and disclosure of leases. The new leasing standard establishes that a lease conveys the right to control the use of identified property, plant, or equipment for a period of time in exchange for consideration. Under the new guidance, lessees will be required to recognize all leases with terms greater than one year, including operating leases, on the consolidated balance sheet by recording a right-of-use asset and lease liability. Prior to the authoritative guidance, only capital leases were recognized on the balance sheet by lessees. The new accounting guidance as applied by lessors is materially consistent from that applied under current GAAP.

Management has begun utilizing a bottoms-up approach to analyze the impact of the standard on our lease portfolio. MGE Energy and MGE have been reviewing current accounting policies and procedures to identify potential differences in accounting treatment that would result from applying the requirements of the new standard to our existing lease portfolio. In addition, we are identifying appropriate changes to our business processes, systems, and controls to support recognition and disclosure requirements under the new standard. This authoritative guidance will become effective January 1, 2019, with early adoption permitted. The new leasing standard requires entities to recognize and measure leases at the beginning of the earliest comparative period presented using a modified retrospective approach. MGE Energy and MGE are currently assessing the impact this pronouncement will have on our financial statements.

f. Restricted Cash.

In November 2016, the FASB issued authoritative guidance within the Codification's Statement of Cash Flows topic that provides guidance on the classification and presentation of changes in restricted cash within the statement of cash flows. The new standard was issued to eliminate a current diversity in practice for the accounting treatment of restricted cash. Under the new guidance, reporting entities will be required to explain the changes in the total of restricted and unrestricted cash and cash equivalents when reconciling the beginning and ending balances on the statement of cash flows. Prior to the authoritative guidance, changes in restricted cash were presented as either cash flows from operating, investing, or financing activities within the statement of cash flows, as appropriate based on the nature of the restriction. Also under the new standard, reporting entities will be required to provide a reconciliation from the balance sheet to the statement of cash flows and disclose the nature of the restrictions of cash. This authoritative guidance will become effective January 1, 2018. Upon the effective date, MGE Energy and MGE will change the presentation of restricted cash to reflect this change in accounting guidance. MGE Energy and MGE will also retrospectively apply the guidance to all prior periods presented. As of December 31, 2016, MGE Energy and MGE had $5.1 million of restricted cash classified within other current assets on the consolidated balance sheets.