LOANS HELD FOR INVESTMENT, Investment in loans Disaggregated Based on Method of Evaluating Impairment (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Recorded Investment [Abstract]
Individually Evaluated	$ 5,567	$ 7,771
Collectively Evaluated	2,574,926	2,429,806
Allowance for Loan Losses [Abstract]
Individually Evaluated	355	1,344
Collectively Evaluated	39,430	40,754
Commercial Real Estate [Member]
Recorded Investment [Abstract]
Individually Evaluated	0	1,101
Collectively Evaluated	806,538	754,343
Allowance for Loan Losses [Abstract]
Individually Evaluated	0	584
Collectively Evaluated	13,903	16,661
Commercial [Member] \| Specialized [Member]
Recorded Investment [Abstract]
Individually Evaluated	0	0
Collectively Evaluated	351,609	378,725
Allowance for Loan Losses [Abstract]
Individually Evaluated	0	0
Collectively Evaluated	3,355	4,363
Commercial [Member] \| General [Member]
Recorded Investment [Abstract]
Individually Evaluated	3,601	5,078
Collectively Evaluated	480,363	454,946
Allowance for Loan Losses [Abstract]
Individually Evaluated	189	585
Collectively Evaluated	9,729	7,881
Consumer [Member] \| 1-4 Family Residential [Member]
Recorded Investment [Abstract]
Individually Evaluated	1,966	1,592
Collectively Evaluated	405,915	386,098
Allowance for Loan Losses [Abstract]
Individually Evaluated	166	175
Collectively Evaluated	5,163	5,093
Consumer [Member] \| Auto Loans [Member]
Recorded Investment [Abstract]
Individually Evaluated	0	0
Collectively Evaluated	299,703	240,719
Allowance for Loan Losses [Abstract]
Individually Evaluated	0	0
Collectively Evaluated	3,958	3,653
Consumer [Member] \| Other Consumer [Member]
Recorded Investment [Abstract]
Individually Evaluated	0	0
Collectively Evaluated	78,124	68,113
Allowance for Loan Losses [Abstract]
Individually Evaluated	0	0
Collectively Evaluated	1,443	1,357
Construction [Member]
Recorded Investment [Abstract]
Individually Evaluated	0	0
Collectively Evaluated	152,674	146,862
Allowance for Loan Losses [Abstract]
Individually Evaluated	0	0
Collectively Evaluated	$ 1,879	$ 1,746

No definition available.

Name:	us-gaap_FinancingReceivableAllowanceForCreditLossAdditionalInformationAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (g)
-URI https://asc.fasb.org/extlink&oid=123577603&loc=SL6953423-111524

+ Details

Name:	us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

+ References

+ Details

Name:	us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The balance of financing receivables that were collectively evaluated for impairment.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (h)
-URI https://asc.fasb.org/extlink&oid=123577603&loc=SL6953423-111524

+ Details

Name:	us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The balance of financing receivables that were individually evaluated for impairment.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (h)
-URI https://asc.fasb.org/extlink&oid=123577603&loc=SL6953423-111524

+ Details

Name:	us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- References

No definition available.

+ Details

Name:	us-gaap_ImpairedFinancingReceivableRecordedInvestmentAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialRealEstatePortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=spfi_CommercialSpecializedLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=spfi_CommercialGeneralLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ConsumerPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=spfi_ConsumerOneToFourFamilyResidentialLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_AutomobileLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=spfi_ConsumerOtherLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ConstructionLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: