Note 12 - Inventories (Details Textual) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Inventory, LIFO Reserve, Effect on Income, Net, Total	$ 30,400	$ 9,800
Effect Of LIFO Earnings Per Share Basic	$ (3.14)	$ (1)
Effect Of LIFO Earnings Per Share Diluted	$ (3.14)	$ (1)
Effect of LIFO Inventory Liquidation on Income	$ 28,700	$ 0

The effect of using the LIFO method on the amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

No definition available.

+ Details

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- Definition

The effect of using the LIFO methond on the amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

+ References

No definition available.

+ Details

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Namespace Prefix:	senea_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

The effect of liquidating LIFO (last in first out) inventory layers on income.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 330
-SubTopic 10
-Section S99
-Paragraph 3
-Subparagraph (SAB Topic 11.F)
-URI http://asc.fasb.org/extlink&oid=27011343&loc=d3e100079-122729

+ Details

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Period Type:	duration

- Definition

The difference between the change in the inventory reserve representing the cumulative difference in cost between the first in, first out and the last in, first out inventory valuation methods and any LIFO decrement which have been reflected in the statement of income during the period.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
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