Note 8 - Commitments and Contingencies (Details Textual)			3 Months Ended	9 Months Ended	12 Months Ended
	Jan. 15, 2019 USD ($)	Apr. 25, 2013	Dec. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)	Mar. 31, 2019 USD ($)	Mar. 31, 2018 USD ($)	Mar. 31, 2016 USD ($)
Accrual for Environmental Loss Contingencies, Period Increase (Decrease), Total					$ 8,312,000
Accrual for Environmental Loss Contingencies, Ending Balance			$ 18,569,000	$ 18,569,000
Other Assets [Member]
Escrow Deposit			5,646,000	5,646,000	22,100,000
Greatbatch, Inc. v AVX Corporation [Member]
Loss Contingency, Damages Awarded, Value	$ 22,100,000						$ 37,500,000
Loss Contingency Accrual, Adjustment					13,900,000	$ 1,500,000
Presidio Components v. American Technical Ceramics Corp. [Member]
Loss Contingency Accrual, Ending Balance			25,919,000	25,919,000
Loss Contingency Accrual, Period Increase (Decrease), Total			$ (11,664,000)	$ (11,664,000)
Greatbatch, Inc. v AVX Corporation And Presidio Components v. American Technical Ceramics Corp. [Member]
Loss Contingency, Pending Claims, Number, Ending Balance			2	2
Unfavorable Regulatory Action - Environmental Matters [Member]
Loss Contingency Accrual, Ending Balance			$ 22,482,000	$ 22,482,000	26,371,000
Loss Contingency, Accrual, Current			2,660,000	2,660,000	5,749,000
Loss Contingency, Accrual, Noncurrent			19,822,000	19,822,000	$ 20,622,000
Unfavorable Regulatory Action - Patent Infringement Matters [Member] | Greatbatch, Inc. v AVX Corporation [Member]
Loss Contingency Accrual, Ending Balance			$ 48,019	$ 48,019
Unfavorable Regulatory Action - Patent Infringement Matters [Member] | Greatbatch, Inc. v AVX Corporation [Member] | Minimum [Member]
Loss Contingency, Patents Allegedly Infringed, Number		1
Unfavorable Regulatory Action - Patent Infringement Matters [Member] | Greatbatch, Inc. v AVX Corporation [Member] | Maximum [Member]
Loss Contingency, Patents Allegedly Infringed, Number		6