Loans and Allowance for Credit Losses - Purchased With Credit Deterioration (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020
Financing Receivable, Credit Quality Indicator [Line Items]
Non-credit related discount	$ (21,500)	$ (57,300)
Landmark Bank
Financing Receivable, Credit Quality Indicator [Line Items]
Unpaid principal balance	66,662
PCD allowance for credit loss at acquisition	(2,359)
Non-credit related discount	(2,577)
Fair value of PCD loans	61,726
Landmark Bank \| Other Consumer and Other
Financing Receivable, Credit Quality Indicator [Line Items]
Unpaid principal balance	67
PCD allowance for credit loss at acquisition	(1)
Non-credit related discount	(2)
Fair value of PCD loans	64
Landmark Bank \| Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Unpaid principal balance	11,046
PCD allowance for credit loss at acquisition	(350)
Non-credit related discount	(160)
Fair value of PCD loans	10,536
Landmark Bank \| Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Unpaid principal balance	55,549
PCD allowance for credit loss at acquisition	(2,008)
Non-credit related discount	(2,415)
Fair value of PCD loans	51,126
Landmark Bank \| Consumer \| Credit cards
Financing Receivable, Credit Quality Indicator [Line Items]
Unpaid principal balance	0
PCD allowance for credit loss at acquisition	0
Non-credit related discount	0
Fair value of PCD loans	0
Triumph
Financing Receivable, Credit Quality Indicator [Line Items]
Unpaid principal balance	121,284
PCD allowance for credit loss at acquisition	(11,092)
Non-credit related discount	(1,594)
Fair value of PCD loans	108,598
Triumph \| Other Consumer and Other
Financing Receivable, Credit Quality Indicator [Line Items]
Unpaid principal balance	15
PCD allowance for credit loss at acquisition	0
Non-credit related discount	(1)
Fair value of PCD loans	14
Triumph \| Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Unpaid principal balance	40,466
PCD allowance for credit loss at acquisition	(2,999)
Non-credit related discount	(279)
Fair value of PCD loans	37,188
Triumph \| Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Unpaid principal balance	80,803
PCD allowance for credit loss at acquisition	(8,093)
Non-credit related discount	(1,314)
Fair value of PCD loans	71,396
Triumph \| Consumer \| Credit cards
Financing Receivable, Credit Quality Indicator [Line Items]
Unpaid principal balance	0
PCD allowance for credit loss at acquisition	0
Non-credit related discount	0
Fair value of PCD loans	$ 0

Financing Receivable, Purchased With Credit Deterioration, Fair Value

No definition available.

Name:	sfnc_FinancingReceivablePurchasedWithCreditDeteriorationFairValue
Namespace Prefix:	sfnc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Financing Receivable, Purchased With Credit Deterioration, Unpaid Principal Balance

+ References

No definition available.

+ Details

Name:	sfnc_FinancingReceivablePurchasedWithCreditDeteriorationUnpaidPrincipalBalance
Namespace Prefix:	sfnc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of allowance for credit loss at acquisition date of financing receivable purchased with credit deterioration.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 19
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=124255953&loc=SL82919265-210447

+ Details

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

- Definition

Amount of discount (premium) attributable to other factors on financing receivable purchased with credit deterioration.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 19
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=124255953&loc=SL82919265-210447

+ Details

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

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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

- Details

Name:	us-gaap_BusinessAcquisitionAxis=sfnc_LandmarkBankMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=sfnc_OtherLoansMember
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_FinancingReceivablePortfolioSegmentAxis=sfnc_RealEstatePortfolioSegmentMember
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=us-gaap_CreditCardReceivablesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=sfnc_TriumphMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: