SCHEDULE II VALUATION AND QUALIFYING ACCOUNTS (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Provision for doubtful accounts and sales allowances
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	$ 603	$ 564	$ 1,221
Charged to Expenses or Other Accounts	784	621	719
Deductions	(514)	(582)	(1,376)
Balance at End of Year	873	603	564
Provision for returns
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	10,541	7,314	6,194
Charged to Expenses or Other Accounts	30,472	35,485	27,635
Deductions	(30,788)	(32,258)	(26,515)
Balance at End of Year	10,225	10,541	7,314
Provision for promotions and rebates
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	31,747	27,737	15,401
Charged to Expenses or Other Accounts	183,929	150,085	111,244
Deductions	(177,392)	(146,075)	(98,908)
Balance at End of Year	38,284	31,747	27,737
Valuation allowance for deferred tax assets
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	2,209	1,962	1,940
Charged to Expenses or Other Accounts	981	1,130	1,962
Deductions	(676)	(883)	(1,940)
Balance at End of Year	$ 2,514	$ 2,209	$ 1,962