Note 9 - Income Taxes - Schedule of Summary of Operating Loss Carryforwards (Details) $ in Thousands	Dec. 31, 2020 USD ($)
2021	$ 3,728
2022	48,848
2023	52,512
2024	50,140
2025 and thereafter	170,189
Deferred Tax Assets, Operating Loss Carryforwards, Subject to Expiration	$ 325,417

Represent net operating loss carryforwards expiring in year five and thereafter.

No definition available.

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

- Definition

Represents net operating loss carryforwards expiring in year four.

+ References

No definition available.

+ Details

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

- Definition

Represents net operating loss carryforwards expiring in year one.

+ References

No definition available.

+ Details

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

- Definition

Represents net operating loss carryforwards expiring in 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

Represents net operating loss carryforwards expiring in year two.

+ References

No definition available.

+ Details

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

- Definition

Amount before allocation of valuation allowances of deferred tax asset attributable to deductible operating loss carryforwards that are subject to expiration dates.

+ References

No definition available.

+ Details

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