Stockholder's Equity - Accumulated Other Comprehensive Income (Loss) - Reclassifications of Accumulated Other Comprehensive Loss (Detail) - USD ($) shares in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Amortization of pension and postretirement items:
Tax benefit	$ (3,673,000)	$ (3,703,000)	$ (21,368,000)	$ (23,385,000)
Derivative, Gain (Loss) on Derivative, Net	2,338,000	(3,741,000)	343,000	$ (653,000)
Stock Issued During Period, Shares, Dividend Reinvestment Plan				0.1
Stock Issued During Period, Value, Dividend Reinvestment Plan				$ 136.26
Proceeds from Issuance of Common Stock, Dividend Reinvestment Plan				4,500,000
Interest Rate Swap [Member] | Derivatives designated as hedging instrument [Member] | Interest Expense [Member]
Amortization of pension and postretirement items:
Derivative, Gain (Loss) on Derivative, Net	$ 160,000	$ 0	$ 352,000	$ 0