Stockholders' Equity	12 Months Ended
Stockholders' Equity	Dec. 31, 2020
Equity [Abstract]
Stockholders' Equity	Stockholders' Equity Capital Structure In addition to authorized and outstanding common shares, the Company has 1.5 million authorized no par value cumulated preferred shares and 1.0 million authorized no par value cumulative preference shares. No cumulative preferred or cumulative preference shares were outstanding at December 31, 2020 or 2019. Shelf Registrations On May 3, 2018 we filed a shelf registration statement with the Securities and Exchange Commission (SEC) under which the Company may offer for sale, from time to time, either separately or together in any combination, equity, debt or other securities described in the shelf registration statement, which expires on May 3, 2021. On November 8, 2019, we entered into a Distribution Agreement with KeyBanc Capital Markets Inc.(KeyBanc). Pursuant to the terms of the Distribution Agreement, we may offer and sell our common shares from time to time under an At-the-Market offering program through KeyBanc, as the distribution agent, for the offer and sale of the shares up to an aggregate sales price of $75.0 million. In 2020, we received net proceeds of $37.0 million, net of commissions paid to KeyBank of $0.5 million from the issuance of 868,484 shares under this program. In total from inception of the program through December 31, 2020, we have received proceeds of $54.4 million from the issuance of shares under this program. On May 3, 2018, we filed a second shelf registration statement with the SEC for the issuance of up to 1,500,000 common shares under an Automatic Dividend Reinvestment and Share Purchase Plan (the Plan), which permits shares purchased by participants in the Plan to be either new issue common shares or common shares purchased in the open market. The shelf registration for the Plan expires on May 3, 2021. In 2020, we received proceeds of $13.4 million from the sale of 320,173 shares under this program. As of December 31, 2020, 899,859 shares remain available for purchase or issuance under the Plan. Dividend Restrictions Otter Tail Corporation is a holding company with no significant operations of its own. The primary source of funds for payments of dividends to our shareholders is from dividends paid or distributions made by our subsidiaries. As a result of certain statutory limitations or regulatory or financing agreements, restrictions could occur on the amount of distributions allowed to be made by our subsidiaries. Both the OTC Credit Agreement and OTP Credit Agreement contain restrictions on the payment of cash dividends upon a default or event of default, including failure to maintain certain financial covenants. As of December 31, 2020, we were in compliance with these financial covenants. Under the Federal Power Act, a public utility may not pay dividends from any funds properly included in a capital account. What constitutes “funds properly included in a capital account” is undefined in the Federal Power Act or the related regulations; however, the FERC has consistently interpreted the provision to allow dividends to be paid as long as i) the source of the dividends is clearly disclosed, ii) the dividend is not excessive and iii) there is no self-dealing on the part of corporate officials. The MPUC indirectly limits the amount of dividends OTP can pay to the Company by requiring an equity-to-total-capitalization ratio between 47.5% and 58.1% based on OTP’s 2020 capital structure petition effective by order of the MPUC on July 15, 2020. As of December 31, 2020, OTP’s equity-to-total-capitalization ratio including short-term debt was 53.7% and its net assets restricted from distribution totaled approximately $634 million. Under the 2020 capital structure petition, total capitalization for OTP cannot exceed $1.7 billion.