3) Investments: Residential Real Estate Held for Investment (Details) - USD ($)	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Impairment losses on residential real estate held for investment	$ 0	$ 0
Residential Real Estate
Foreclosed Residential Real Estate included in Residential Real Estate Held for Investment	$ 9,040,000		$ 12,434,000

Represents the monetary amount of Foreclosed Residential Real Estate included in Residential Real Estate Held for Investment, as of the indicated date.

No definition available.

Name:	snfc_ForeclosedResidentialRealEstateIncludedInResidentialRealEstateHeldForInvestment
Namespace Prefix:	snfc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant