Long-Term Debt - Additional Information (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2025	Dec. 31, 2024
Debt Instrument [Line Items]
Document Period End Date	Jun. 30, 2025
Long-term debt including current maturities	$ 1,300,000	$ 1,300,000
Debt Instrument, Unused Borrowing Capacity, Amount	305,000
Short-term borrowing	$ 245,300	196,500
Uncollateralized Senior Note Due December Two Thousand Thirty Four [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	2.98%
Debt instrument, maturity date	Dec. 20, 2034
Term Note Due January Two Thousand Twenty [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	$ 70,000	70,000
3.48% note, due May 31, 2038 [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	50,000	50,000
3.25% note, due April 30, 2032 [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	49,000	52,500
Equipment Security Note
Debt Instrument [Line Items]
Long-term debt including current maturities	$ 6,300	6,700
Debt Instrument, Interest Rate, Stated Percentage	2.46%
Debt instrument, maturity date	Sep. 24, 2031
Uncollateralized Senior Note Due March 15, 2042
Debt Instrument [Line Items]
Long-term debt including current maturities	$ 50,000	50,000
Debt Instrument, Interest Rate, Stated Percentage	2.95%
Debt instrument, maturity date	Mar. 15, 2042
Uncollateralized Senior Note Due March 14, 2038
Debt Instrument [Line Items]
Long-term debt including current maturities	$ 80,000
Debt Instrument, Interest Rate, Stated Percentage	5.43%
Debt instrument, maturity date	Mar. 14, 2038
Uncollateralized Senior Note Due January Two Thousand Thirty Seven
Debt Instrument [Line Items]
Long-term debt including current maturities	$ 50,000	$ 50,000
Debt Instrument, Interest Rate, Stated Percentage	2.49%
Debt instrument, maturity date	Jan. 25, 2037
Uncollateralized Senior Note Due October 2029
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.20%
Uncollateralized Senior Note Due MM YYYY
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.04%
Uncollateralized Senior Note Due September 2030
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.02%
Uncollateralized Senior Note Due August 2028
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.88%
Uncollateralized Senior Note Due August 2031
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.16%
Prudential [Member] | Uncollateralized Senior Note Due October 2029
Debt Instrument [Line Items]
Long-term debt including current maturities	$ 100,000
Prudential [Member] | Uncollateralized Senior Note Due MM YYYY
Debt Instrument [Line Items]
Long-term debt including current maturities	200,000
Prudential [Member] | Uncollateralized Senior Notes Issued August 2025
Debt Instrument [Line Items]
Long-term debt including current maturities	150,000
Prudential [Member] | Uncollateralized Senior Note Due September 2030
Debt Instrument [Line Items]
Long-term debt including current maturities	50,000
Prudential [Member] | Uncollateralized Senior Note Due August 2028
Debt Instrument [Line Items]
Long-term debt including current maturities	60,000
Prudential [Member] | Uncollateralized Senior Note Due August 2031
Debt Instrument [Line Items]
Long-term debt including current maturities	$ 90,000