Schedule II - Valuation and Qualifying Accounts (Detail) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Allowance for Doubtful Accounts [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning Balance	$ 1,470	$ 1,153	$ 1,055
Charged (credited) to costs and expenses	8,357	7,139	5,885
Deductions	(7,800)	(6,822)	(5,787)
Ending Balance	2,027	1,470	1,153
Deferred Tax Asset Valuation Allowance [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning Balance	17,728	17,089	15,550
Charged (credited) to costs and expenses	11,321	639	1,539
Ending Balance	$ 29,049	$ 17,728	$ 17,089