10) Derivative Instruments: Schedule of Gains and Losses on Derivatives (Details) - USD ($)	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Text Block [Abstract]
Gain (Loss) on Derivatives, Loan Commitments	$ 314,466	$ 3,275,032
Gain (Loss) on Derivatives, Call and put options	$ 26,762	$ (737,860)

Represents the monetary amount of Gain (Loss) on Derivatives, Call and put options, during the indicated time period.

No definition available.

Name:	snfc_GainLossOnDerivativesCallAndPutOptions
Namespace Prefix:	snfc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration