3) Investments: Schedule of Major categories of net investment income (Details) - USD ($)	3 Months Ended	6 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Gross investment income	$ 16,287,935	$ 13,757,989	$ 32,968,164	$ 27,207,158
Investment Income, Investment Expense	(3,325,190)	(3,217,154)	(6,604,920)	(6,624,655)
Net investment income	12,962,745	10,540,835	26,363,244	20,582,503
Fixed Maturities
Gross investment income	3,143,072	2,528,689	6,067,786	5,032,554
Equity Securities
Gross investment income	111,122	74,730	203,164	152,651
Mortgage Loans Real Estate
Gross investment income	5,582,152	4,525,817	11,236,042	8,629,184
Real Estate
Gross investment income	2,787,881	2,096,927	5,941,267	4,007,221
Policy Student and Other Loans
Gross investment income	257,527	106,905	491,492	195,042
Insurance Assignments
Gross investment income	4,383,398	3,906,832	8,682,602	8,118,952
Other Investments {1}
Gross investment income	398	52,130	25,421	106,678
Cash and Cash Equivalents
Gross investment income	$ 22,385	$ 465,959	$ 320,390	$ 964,876

Represents the monetary amount of Gross investment income, during the indicated time period.

No definition available.

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

- Definition

Amount of expenses related to the generation of investment income.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.9)
-URI http://asc.fasb.org/extlink&oid=120395209&loc=SL114868664-224227

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04.2)
-URI http://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263

+ Details

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

- Definition

Amount, after investment expense, of income earned from investments in securities and real estate. Includes, but is not limited to, real estate investment, policy loans, dividends, and interest. Excludes realized gain (loss) on investments.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(2))
-URI http://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263

+ Details

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

- Details

Name:	us-gaap_FinancialInstrumentAxis=snfc_FixedMaturities1Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=snfc_EquitySecurities1Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=snfc_MortgageLoansRealEstateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=snfc_RealEstate1Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=snfc_PolicyStudentAndOtherLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=snfc_InsuranceAssignmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=snfc_OtherInvestments1Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=snfc_CashAndCashEquivalents1Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: