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Short-Term and Long-Term Borrowings - Narrative (Details) - USD ($)
 12 Months Ended
Dec. 31, 2023
Dec. 31, 2022
Debt Instrument [Line Items]    
Line of credit facility, maximum borrowing capacity $ 340,000,000  
Debt, weighted average interest rate (as a percent) 6.70% 5.61%
Debt instrument, redemption price, percentage 100.00%  
Minimum    
Debt Instrument [Line Items]    
Interest and dividend coverage ratio 1.50  
Minimum | Benchmark rate    
Debt Instrument [Line Items]    
Debt instrument, basis spread on variable rate (as a percent) 0.00%  
Maximum    
Debt Instrument [Line Items]    
Debt to total capitalization ratio 60.00%  
Maximum | Benchmark rate    
Debt Instrument [Line Items]    
Debt instrument, basis spread on variable rate (as a percent) 2.00%  
OTP Credit Agreement    
Debt Instrument [Line Items]    
Line of credit facility, maximum borrowing capacity $ 170,000,000  
Line of credit facility, increased current borrowing capacity, accordion provision 250,000,000  
OTC Credit Agreement    
Debt Instrument [Line Items]    
Line of credit facility, maximum borrowing capacity 170,000,000  
Line of credit facility, increased current borrowing capacity, accordion provision 290,000,000  
Revolving Credit Facility | OTP Credit Agreement    
Debt Instrument [Line Items]    
Line of credit facility, maximum borrowing capacity 170,000,000  
Revolving Credit Facility | OTC Credit Agreement    
Debt Instrument [Line Items]    
Line of credit facility, maximum borrowing capacity 170,000,000  
Letter of Credit | OTP Credit Agreement    
Debt Instrument [Line Items]    
Line of credit facility, maximum borrowing capacity 50,000,000  
Letter of Credit | OTC Credit Agreement    
Debt Instrument [Line Items]    
Line of credit facility, maximum borrowing capacity $ 40,000,000