Significant Accounting Policies - Additional Information (Detail) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2014	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
Significant Accounting Policies [Line Items]
Ownership percentage		50.00%
Allowance for doubtful accounts	$ 5,800,000	$ 7,100,000	$ 5,800,000
Notes receivable, total		3,300,000
Notes receivable, current		500,000
Notes Receivable basis spread on Prime rate		3.90%
Depreciable assets		69,700,000	67,300,000	55,100,000
Carrying value of plant		2,700,000
Carrying value of equipment		400,000
Amortization expense of intangibles		5,700,000	1,700,000	1,000,000
Amortization expense, expected, for fiscal years 2016		13,400,000
Amortization expense, expected, for fiscal years 2017		13,200,000
Amortization expense, expected, for fiscal years 2018		12,700,000
Amortization expense, expected, for fiscal years 2019		12,600,000
Amortization expense, expected, for fiscal years 2020		6,200,000
Stock repurchases approved by Board of Directors		31,610,605
Shares remain available for repurchase		717,300
Freight costs as cost of goods sold		124,000,000	113,100,000	83,200,000
Accumulated other comprehensive loss	5,482,000	12,067,000	5,482,000
Net of income taxes for accumulated other comprehensive loss		7,100,000
Interest payments		15,100,000	17,000,000	14,600,000
Income taxes paid		78,300,000	41,700,000	14,800,000
Maintenance and repair expenses	4,500,000	86,700,000	77,400,000	61,300,000
Stock options outstanding (in shares)		285,267	146,696	1,082,380
Stock options, average exercise price per share		$ 82.72	$ 65.12	$ 39.65
Notes Receivable [Member]
Significant Accounting Policies [Line Items]
Allowance for doubtful accounts	$ 300,000	$ 300,000	$ 300,000