Schedule of Components of Deferred Income Taxes (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Mar. 31, 2020
Income Tax Disclosure [Abstract]
Items Giving Rise to Deferred Tax Liabilities - Excess Tax Depreciation and Amortization	$ (220,269)	$ (199,096)
Items Giving Rise to Deferred Tax Liabilities - State Income Taxes, net	(21,923)	(12,225)
Items Giving Rise to Deferred Tax Liabilities - Depletable Assets	(3,540)
Items Giving Rise to Deferred Tax Liabilities - Right of Use Assets	(6,271)	(5,441)
Items Giving Rise to Deferred Tax Liabilities - Other	(6,332)	(5,764)
Items Giving Rise to Deferred Tax Liabilities - Total Deferred Tax Liabilities	(258,335)	(222,526)
Items Giving Rise to Deferred Tax Assets - Change in Accruals	12,046	9,373
Items Giving Rise to Deferred Tax Assets - Depletable Assets		12,632
Items Giving Rise to Deferred Tax Assets - Inventory	1,243	7,217
Items Giving Rise to Deferred Tax Assets - Bad Debts	1,812	2,642
Items Giving Rise to Deferred Tax Assets - Long-term Incentive Compensation Plan	3,396	5,590
Items Giving Rise to Deferred Tax Assets - Credits and Other Carryforwards	17,338	19,861
Items Giving Rise to Deferred Tax Assets - Lease Liability	9,369	11,384
Items Giving Rise to Deferred Tax Assets - Pension	906	937
Items Giving Rise to Deferred Tax Assets - Subtotal	46,110	69,636
Items Giving Rise to Deferred Tax Assets - Valuation Allowance	(13,761)	(13,777)
Items Giving Rise to Deferred Tax Assets - Total Deferred Tax Assets	$ 32,349	$ 55,859