Short-Term Borrowings (Details) - USD ($)	1 Months Ended	3 Months Ended		6 Months Ended
	Feb. 28, 2021	Jun. 30, 2025	Sep. 30, 2023	Jun. 30, 2025	Dec. 31, 2024	Jun. 30, 2024	Dec. 31, 2023
Short-term Debt [Line Items]
Notional Amount of Nonderivative Instruments	$ 40,000,000	$ 50,000,000.0	$ 30,000,000	$ 50,000,000.0
Line of Credit Facility, Remaining Borrowing Capacity		197,100,000		197,100,000
Short-term borrowing		$ 245,300,000		$ 245,300,000	$ 196,500,000
Short-term Debt, Weighted Average Interest Rate, at Point in Time		5.08%		5.08%	5.06%
Draws on letters of credit				$ 7,600,000
Revolving Line of Credit, Short-term
Short-term Debt [Line Items]
Aggregate Investment, Maximum		$ 250,000,000.0		$ 250,000,000.0
Interest Rate Credit Adjustment		10		10
Line of Credit Facility, Interest Rate Description				1.05 percent
Line of Credit Facility [Line Items]
Line of Credit Facility, Increase Request		$ 50,000,000.0		$ 50,000,000.0
3.48% note, due May 31, 2038 [Member]
Short-term Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		3.48%		3.48%
Revolving Line of Credit, Total
Short-term Debt [Line Items]
Aggregate Investment, Maximum		$ 450,000,000.0		$ 450,000,000.0
Revolving Line of Credit, 5 year
Short-term Debt [Line Items]
Aggregate Investment, Maximum		200,000,000.0		$ 200,000,000.0
Line of Credit Facility, Interest Rate Description				1.25 percent
Line of Credit Facility [Line Items]
Line of Credit Facility, Increase Request		100,000,000.0		$ 100,000,000.0
Committed Line of Credit Facility Two [Member]
Short-term Debt [Line Items]
Debt Instrument, Description of Variable Rate Basis				LIBOR rate, plus 0.75 percent
Committed Line of Credit Facility Three [Member]
Short-term Debt [Line Items]
Debt Instrument, Description of Variable Rate Basis				Lender's base rate, plus 0.75 percent
Committed Line of Credit Facility Five [Member]
Short-term Debt [Line Items]
Debt Instrument, Description of Variable Rate Basis				Lender's base rate, plus 0.85 percent
Committed Line of Credit Facility Four [Member]
Short-term Debt [Line Items]
Debt Instrument, Description of Variable Rate Basis				LIBOR rate, plus 1.125 percent
Committed Line of Credit Facility Six [Member]
Short-term Debt [Line Items]
Debt Instrument, Description of Variable Rate Basis				LIBOR rate, plus 1.75 percent
Committed Line of Credit Facility Seven [Member]
Short-term Debt [Line Items]
Debt Instrument, Description of Variable Rate Basis				LIBOR rate, plus 1.75 percent
Committed Line of Credit Facility Eight [Member]
Short-term Debt [Line Items]
Debt Instrument, Description of Variable Rate Basis				LIBOR rate, plus 1.75 percent
Committed Line of Credit Facility Nine [Member]
Short-term Debt [Line Items]
Debt Instrument, Description of Variable Rate Basis				LIBOR rate, plus 1.75 percent
Committed Line of Credit Facility One [Member]
Short-term Debt [Line Items]
Debt Instrument, Description of Variable Rate Basis				LIBOR rate, plus 0.75 percent
Revolving Credit Facility
Short-term Debt [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		$ 450,000,000.0		$ 450,000,000.0
Interest Rate Swap Rate, Low Range [Member]
Short-term Debt [Line Items]
Fixed Swap Rate							0.20%
Interest Rate Swap Rate, High Range [Member]
Short-term Debt [Line Items]
Fixed Swap Rate		3.97%		3.97%	0.17%	3.98%	0.205%