Condensed Consolidating Statement of Cash Flows (Detail) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
CASH FLOWS FROM OPERATING ACTIVITIES
Net Cash Provided by (Used in) Operating Activities	$ 337,665	$ 331,598	$ 265,767
CASH FLOWS FROM INVESTING ACTIVITIES
Additions to Property, Plant, and Equipment	(131,957)	(56,938)	(89,563)
Acquisition Spending	(36,761)	(400,488)	(32,427)
Net Cash Used in Investing Activities	(168,718)	(457,426)	(121,990)
CASH FLOWS FROM FINANCING ACTIVITIES
Increase (Decrease) in Credit Facility	15,000	(157,000)	52,000
Repayment of Senior Notes	(81,214)	(8,000)	(57,045)
Issuance of Long-term Debt		350,000
Payment of Debt Issuance Costs		(6,637)
Dividends Paid to Stockholders	(19,438)	(19,341)	(20,020)
Purchase and Retirement of Common Stock	(61,078)	(60,013)	(123,530)
Proceeds from Stock Option Exercises	24,264	22,108	2,866
Shares Redeemed to Settle Employee Taxes on Stock Compensation	(4,974)	(4,468)	(4,273)
Excess Tax Benefits from Share Based Payment Arrangements		10,349	4,102
Net Cash Provided by (Used in) Financing Activities	(127,440)	126,998	(145,900)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS AND RESTRICTED CASH	41,507	1,170	(2,123)
CASH AND CASH EQUIVALENTS AND RESTRICTED CASH AT BEGINNING OF PERIOD	6,561	5,391	7,514
CASH AND CASH EQUIVALENTS AND RESTRICTED CASH AT END OF PERIOD	48,068	6,561	5,391
Eliminations [Member]
CASH FLOWS FROM INVESTING ACTIVITIES
Investment in Subsidiaries	36,761	400,488	32,427
Net Cash Used in Investing Activities	36,761	400,488	32,427
CASH FLOWS FROM FINANCING ACTIVITIES
Intra-entity Activity, net	(36,761)	(400,488)	(32,427)
Net Cash Provided by (Used in) Financing Activities	(36,761)	(400,488)	(32,427)
Parent [Member]
CASH FLOWS FROM OPERATING ACTIVITIES
Net Cash Provided by (Used in) Operating Activities	(83,947)	(64,376)	(37,985)
CASH FLOWS FROM INVESTING ACTIVITIES
Additions to Property, Plant, and Equipment	(142)	(697)
Investment in Subsidiaries	(36,761)	(400,488)	(32,427)
Net Cash Used in Investing Activities	(36,903)	(401,185)	(32,427)
CASH FLOWS FROM FINANCING ACTIVITIES
Increase (Decrease) in Credit Facility	15,000	(157,000)	52,000
Repayment of Senior Notes	(81,214)	(8,000)	(57,045)
Issuance of Long-term Debt		350,000
Payment of Debt Issuance Costs		(6,637)
Dividends Paid to Stockholders	(19,438)	(19,341)	(20,020)
Purchase and Retirement of Common Stock	(61,078)	(60,013)	(123,530)
Proceeds from Stock Option Exercises	24,264	22,108	2,866
Shares Redeemed to Settle Employee Taxes on Stock Compensation	(4,974)	(4,468)	(4,273)
Excess Tax Benefits from Share Based Payment Arrangements		10,349	4,102
Intra-entity Activity, net	287,643	340,240	216,175
Net Cash Provided by (Used in) Financing Activities	160,203	467,238	70,275
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS AND RESTRICTED CASH	39,353	1,677	(137)
CASH AND CASH EQUIVALENTS AND RESTRICTED CASH AT BEGINNING OF PERIOD	5,184	3,507	3,644
CASH AND CASH EQUIVALENTS AND RESTRICTED CASH AT END OF PERIOD	44,537	5,184	3,507
Guarantor Subsidiaries [Member]
CASH FLOWS FROM OPERATING ACTIVITIES
Net Cash Provided by (Used in) Operating Activities	421,612	395,974	303,752
CASH FLOWS FROM INVESTING ACTIVITIES
Additions to Property, Plant, and Equipment	(131,815)	(56,241)	(89,563)
Acquisition Spending	(36,761)	(400,488)	(32,427)
Net Cash Used in Investing Activities	(168,576)	(456,729)	(121,990)
CASH FLOWS FROM FINANCING ACTIVITIES
Intra-entity Activity, net	(250,882)	60,248	(183,748)
Net Cash Provided by (Used in) Financing Activities	(250,882)	60,248	(183,748)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS AND RESTRICTED CASH	2,154	(507)	(1,986)
CASH AND CASH EQUIVALENTS AND RESTRICTED CASH AT BEGINNING OF PERIOD	1,377	1,884	3,870
CASH AND CASH EQUIVALENTS AND RESTRICTED CASH AT END OF PERIOD	$ 3,531	$ 1,377	$ 1,884