3) Loans Held For Sale: Schedule of Mortgage Fee Income for Loans Held for Sale (Details) - USD ($)	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Mortgage fee income	$ 298,933,110	$ 131,976,082
Loans Held For Sale
Loan fees	43,432,532	28,660,966
Interest Income	10,628,581	6,978,930
Secondary gains	231,759,342	93,581,956
Change in fair value of loan commitments	7,637,377	899,417
Change in fair value of loans held for sale	10,413,492	2,498,097
Provision for loan loss reserve	(4,938,214)	(643,284)
Mortgage fee income	$ 298,933,110	$ 131,976,082

Represents the monetary amount of Change in fair value of loan commitments, during the indicated time period.

No definition available.

Name:	snfc_ChangeInFairValueOfLoanCommitments
Namespace Prefix:	snfc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Represents the monetary amount of Change in fair value of loans held for sale, during the indicated time period.

+ References

No definition available.

+ Details

Name:	snfc_ChangeInFairValueOfLoanHeldForSale
Namespace Prefix:	snfc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Represents the monetary amount of Loan fees, during the indicated time period.

+ References

No definition available.

+ Details

Name:	snfc_LoanFees
Namespace Prefix:	snfc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Represents the monetary amount of Mortgage Fee Income, during the indicated time period.

+ References

No definition available.

+ Details

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

- Definition

Represents the monetary amount of Secondary gains, during the indicated time period.

+ References

No definition available.

+ Details

Name:	snfc_SecondaryGains
Namespace Prefix:	snfc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The amount of interest income and other income recognized during the period. Included in this element is interest derived from investments in debt securities, cash and cash equivalents, and other investments which reflect the time value of money or transactions in which the payments are for the use or forbearance of money and other income from ancillary business-related activities (that is, excluding major activities considered part of the normal operations of the business).

+ References

No definition available.

+ Details

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

- Definition

Amount of expense related to estimated loss from loan and lease transactions.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3602-108585

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04.11)
-URI http://asc.fasb.org/extlink&oid=120399700&loc=SL114874048-224260

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=121611835&loc=SL6953423-111524

+ Details

Name:	us-gaap_ProvisionForLoanAndLeaseLosses
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

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