Represents commitment to fund convertible bridge loan.

No definition available.

Name:	sfe_CommitmentToFundConvertibleBridgeLoan
Namespace Prefix:	sfe_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The amount of funding for convertible bridge loans in the period.

+ References

No definition available.

+ Details

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

- Definition

Represents the ownership percentage of an other method investment.

+ References

No definition available.

+ Details

Name:	sfe_OtherMethodInvestmentOwnershipPercentage
Namespace Prefix:	sfe_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of gain (loss) from sale of other method investment.

+ References

No definition available.

+ Details

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Namespace Prefix:	sfe_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

This item represents the carrying amount on the entity's balance sheet of its investment in common stock of an equity method investee. This is not an indicator of the fair value of the investment, rather it is the initial cost adjusted for the entity's share of earnings and losses of the investee, adjusted for any distributions (dividends) and other than temporary impairment (OTTI) losses recognized.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 323
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481664/323-10-45-1

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 323
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)(3)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481687/323-10-50-3

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(10))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 25
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-25

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The cash outflow associated with the purchase of or advances to an equity method investments, which are investments in joint ventures and entities in which the entity has an equity ownership interest normally of 20 to 50 percent and exercises significant influence.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482740/230-10-45-13

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=sfe_TriceMedicalIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=us-gaap_EquityMethodInvesteeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionAxis=sfe_CreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=sfe_InfoBionicIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementScenarioAxis=sfe_ApproximateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=sfe_meQuilibriumMember
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Note 3 - Acquisitions of Ownership Interests (Details Textual) - USD ($) $ in Thousands	3 Months Ended			12 Months Ended
	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2023	Dec. 31, 2022
Payments to Acquire Equity Method Investments				$ 3,000	$ (0)
Equity Method Investments				8,497	8,846
Prognos Health, Inc. [Member]
Payments to Acquire Equity Method Investments		$ 3,000
Equity Method Investments		$ 14,600			12,600
Convertible Bridge Loan					2,000
Trice Medical, Inc. [Member]
Equity Method Investments			$ 12,000		11,800
Convertible Bridge Loan			$ 300		100
Trice Medical, Inc. [Member] \| Equity Method Investee [Member] \| Credit Facility [Member]
Commitment To Fund Convertible Bridge Loan				$ 300	300
InfoBionic, Inc. [Member]
Other Method Investment, Realized Gain (Loss)	$ 1,700
InfoBionic, Inc. [Member] \| Approximate [Member]
Other Method Investment, Ownership Percentage	5.00%
Syapse, Inc. [Member]
Equity Method Investments					25,000
Convertible Bridge Loan					1,600
Clutch Holdings [Member]
Equity Method Investments					16,900
Convertible Bridge Loan					1,400
meQuilibrium [Member]
Equity Method Investments					14,000
Convertible Bridge Loan					$ 500