Investment Securities - Schedule of Income Earned on Securities (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Non-taxable:
Total	$ 31,013	$ 46,898	$ 62,895	$ 94,155
Held-to-maturity
Taxable:
Taxable	0	10,224	0	20,623
Non-taxable:
Non-taxable	0	10,052	0	20,103
Available-for-sale
Taxable:
Taxable	25,472	21,009	51,783	42,194
Non-taxable:
Non-taxable	$ 5,541	$ 5,613	$ 11,112	$ 11,235

Interest income, securities, operating, by non-0taxable status [abstract]

No definition available.

Name:	sfnc_InterestIncomeSecuritiesOperatingByNonTaxableStatusAbstract
Namespace Prefix:	sfnc_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- References

No definition available.

+ Details

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

- Definition

Amount of operating interest income, including amortization and accretion of premiums and discounts, on securities exempt from state, federal and other income tax.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name Regulation S-K (SK)
-Number 229
-Section 1402
-Paragraph a
-Publisher SEC

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 942
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(2))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478524/942-220-S99-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Name Regulation S-K (SK)
-Number 229
-Section 1402
-Paragraph b
-Subparagraph (1)(Instruction 4)
-Publisher SEC

+ Details

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

- Definition

Amount of operating interest income, including amortization and accretion of premiums and discounts, on securities subject to state, federal and other income tax.

+ References

+ Details

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

- Definition

Amount before accretion (amortization) of purchase discount (premium) of interest income on nonoperating securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (ee)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-32

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 22
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-22

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 48
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482785/280-10-55-48

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(7)(b))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483621/220-10-S99-2

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 270
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482964/270-10-50-1

+ Details

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

- Details

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

- Details

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