Note 2 - Ownership Interests and Advances (Details Textual) - USD ($) $ in Thousands	9 Months Ended
Sep. 30, 2023	Sep. 30, 2022
Impairment of Other Method Securities	$ 200	$ 0

The amount of impairment of other method securities.

No definition available.

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