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Stockholders' Equity (Details) - USD ($)
$ in Thousands
 12 Months Ended
May 03, 2021
Dec. 31, 2023
Dec. 31, 2022
Class of Stock [Line Items]      
Total capitalization   $ 2,267,065 $ 2,041,138
OTP      
Class of Stock [Line Items]      
Equity to total capitalization ratio   54.20%  
Net assets restricted from distribution   $ 771,300  
Minimum | Minnesota Public Utilities Commission | OTP      
Class of Stock [Line Items]      
Public utilities, requested equity capital structure (as a percent)   48.30%  
Maximum | OTP      
Class of Stock [Line Items]      
Total capitalization   $ 2,000,000  
Maximum | Minnesota Public Utilities Commission | OTP      
Class of Stock [Line Items]      
Public utilities, requested equity capital structure (as a percent)   59.10%  
Second Shelf Registration      
Class of Stock [Line Items]      
Shelf registration (in shares) 1,500,000    
Number of shares issued (in shares)   105,663  
Number of shares available for grant (in shares)   1,145,330  
Cumulative Preferred Shares      
Class of Stock [Line Items]      
Preferred stock, shares authorized (in shares)   1,500,000  
Preferred stock, shares outstanding (in shares)   0 0
Cumulative Preference Shares      
Class of Stock [Line Items]      
Preferred stock, shares authorized (in shares)   1,000,000  
Preferred stock, shares outstanding (in shares)   0