Significant Accounting Policies - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Mar. 31, 2023	May 17, 2022
Significant Accounting Policies [Line Items]
Allowance for doubtful accounts	$ 6,400	$ 6,700
Bad debt expense	200	300	$ 300
Write-offs of accounts receivable	600	600	100
Depreciable assets	$ 147,600	139,500	129,600
Basis of valuation	Property, Plant, and Equipment are stated at cost.
Property, Plant and Equipment, Depreciation Methods1	straight-line basis over the estimated useful lives
Goodwill impairment more likely than not a likelihood as greater percentage of fair value of reportable unit exceeds its carrying value	50.00%
Intangible Assets, Amortization Expense	$ 8,400	$ 7,900	$ 6,800
Amortization expense, expected, for fiscal year 2026	10,300
Amortization expense, expected, for fiscal year 2027	10,100
Amortization expense, expected, for fiscal year 2028	10,000
Amortization expense, expected, for fiscal year 2029	9,800
Amortization expense, expected, for fiscal year 2030	$ 9,800
Number of additional shares authorized to be repurchased				7,500,000
Repurchase of shares	1,214,173	1,863,534	3,075,788
Shares repurchased average price	$ 245.67	$ 184.21	$ 126.05
Stock repurchase remaining number of shares authorized to be repurchased	4,669,497
Freight expense	$ 1,587,371	$ 1,573,976	$ 1,508,803
Accumulated other comprehensive loss	3,125	3,373
Net of income taxes for accumulated other comprehensive loss	1,000
Maintenance and repair expenses	$ 248,400	$ 220,100	$ 173,400
Stock options excluded from computation of diluted earnings per share	4,404	16,609	52,375
Stock options, average exercise price per share	$ 240.32	$ 133.91	$ 127.06
Freight [Member]
Significant Accounting Policies [Line Items]
Freight expense	$ 211,200	$ 215,300	$ 229,600
Minimum [Member]
Significant Accounting Policies [Line Items]
Long term supply agreements term of termination notice period	2 years
Revenue from contract with customer collection terms	30 days
Maximum [Member]
Significant Accounting Policies [Line Items]
Long term supply agreements term of termination notice period	3 years
Revenue from contract with customer collection terms	75 days