Note 9 - Commitments and Contingencies - Operating Lease Cash Flow (Details) $ in Thousands	Mar. 31, 2021 USD ($)
2021 (nine months ending December 31), Operating lease payments	$ 447
2021 (nine months ending December 31), Expected sublease receipts	396
2022, Operating lease payments	601
2022), Expected sublease receipts	540
2023, Operating lease payments	607
2023), Expected sublease receipts	556
2024, Operating lease payments	613
2024), Expected sublease receipts	573
2025, Operating lease payments	619
2025), Expected sublease receipts	590
2026, Operating lease payments	207
2026), Expected sublease receipts	199
Thereafter, Operating lease payments	0
Thereafter, Expected sublease receipt	0
Total future minimum lease payments, Operating lease payments	3,094
Total future minimum lease payments, Expected sublease receipt	2,854
Less imputed interest, Operating lease payments	(792)
Total operating lease liabilities, Operating lease payments	$ 2,302

Total amount of sublease expected receipts.

No definition available.

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- Definition

Amount of expected sublease receipts for year one.

+ References

No definition available.

+ Details

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Balance Type:	debit
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- Definition

Amount of expected sublease receipts for remainder of fiscal year.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
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- Definition

Amount of expected sublease receipts after year six.

+ References

No definition available.

+ Details

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Namespace Prefix:	sfe_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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- Definition

Amount of expected sublease receipts for year five.

+ References

No definition available.

+ Details

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Namespace Prefix:	sfe_
Data Type:	xbrli:monetaryItemType
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- Definition

Amount of expected sublease receipts for year four.

+ References

No definition available.

+ Details

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Namespace Prefix:	sfe_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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- Definition

Amount of expected sublease receipts for year three.

+ References

No definition available.

+ Details

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Namespace Prefix:	sfe_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of expected sublease receipts for year two.

+ References

No definition available.

+ Details

Name:	sfe_LesseeSubleaseexpectedReceiptsYearTwo
Namespace Prefix:	sfe_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of lessee's undiscounted obligation for lease payment for operating lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=121609121&loc=SL77918701-209980

+ Details

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Balance Type:	credit
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- Definition

Amount of lessee's undiscounted obligation for lease payment for operating lease due after fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

+ Details

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- Definition

Amount of lessee's undiscounted obligation for lease payment for operating lease to be paid in next fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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- Definition

Amount of lessee's undiscounted obligation for lease payment for operating lease to be paid in fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

+ Details

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- Definition

Amount of lessee's undiscounted obligation for lease payment for operating lease to be paid in fourth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

+ Details

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- Definition

Amount of lessee's undiscounted obligation for lease payment for operating lease to be paid in third fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of lessee's undiscounted obligation for lease payment for operating lease to be paid in second fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

+ Details

Name:	us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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- Definition

Amount of lessee's undiscounted obligation for lease payment for operating lease having initial or remaining lease term in excess of one year to be paid in remainder of current fiscal year.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=121609121&loc=SL77918701-209980

+ Details

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Balance Type:	credit
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- Definition

Amount of lessee's undiscounted obligation for lease payments in excess of discounted obligation for lease payments for operating lease.

+ References

+ Details

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- Definition

Present value of lessee's discounted obligation for lease payments from operating lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 45
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121603541&loc=SL77918627-209977

+ Details

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Balance Type:	credit
Period Type:	instant