11) Reinsurance, Commitments and Contingencies: Other Contingencies and Commitments (Details)	Sep. 30, 2020 USD ($)
Text Block [Abstract]
Commitments to fund new residential construction loans	$ 187,305,000
Commitments to fund new residential construction loans funded	$ 124,409,000

Represents the monetary amount of Commitments to fund new residential construction loans funded, as of the indicated date.

No definition available.

Name:	snfc_CommitmentsToFundNewResidentialConstructionLoansFunded
Namespace Prefix:	snfc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant