Consolidated Statements of Comprehensive Income - USD ($) shares in Thousands	12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Sales	$ 273,800,000	$ 249,176,000	$ 234,684,000
Cost of sales	175,993,000	169,862,000	158,388,000
Gross profit	97,807,000	79,314,000	76,296,000
Operating expenses:
General and administrative	24,290,000	22,799,000	21,301,000
Advertising	19,255,000	17,663,000	21,837,000
Depreciation	2,126,000	1,369,000	770,000
Total operating expenses	45,671,000	41,831,000	43,908,000
Income from operations	52,136,000	37,483,000	32,388,000
Other income (expense):
Interest income, net	658,000	141,000	190,000
Realized loss on sale of short term investments			(74,000)
Other, net	995,000	300,000	63,000
Total other income	1,653,000	441,000	179,000
Income before provision for income taxes	53,789,000	37,924,000	32,567,000
Total provision for income taxes	16,506,000	14,105,000	12,000,000
Net income	37,283,000	23,819,000	20,567,000
Net change in unrealized gain on short term investments	0	0	54,000
Comprehensive income	$ 37,283,000	$ 23,819,000	$ 20,621,000
Net income per common share:
Basic (in dollars per share)	$ 1.83	$ 1.18	$ 1.02
Diluted (in dollars per share)	$ 1.82	$ 1.17	$ 1.02
Weighted average number of common shares outstanding:
Basic (in shares)	20,346	20,232	20,124
Diluted (in shares)	20,433	20,378	20,254
Cash dividends declared per common share (in dollars per share)	$ 0.85	$ 0.76	$ 0.72