Note 10 - Accumulated Other Comprehensive Loss - AOCI Reclass (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Other income (expense), net	$ (190)	$ 586	$ (705)	$ 1,401
Income before Income Tax Provision	4,533	6,795	11,774	12,066
Tax impact	(1,070)	(2,860)	(2,817)	(5,112)
Total reclassifications for the period	3,463	3,935	8,957	6,954
Reclassification out of Accumulated Other Comprehensive Income [Member]
Income before Income Tax Provision		201		50
Tax impact		(80)		(19)
Total reclassifications for the period		121		31
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Investment Gain (Loss) Attributable to Parent [Member]
Other income (expense), net		201		201
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Other-than-Temporary Impairment Attributable to Parent [Member]
Other income (expense), net				$ (151)