Loan Servicing, Mortgage Origination, and Loans Held for Sale (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Loans held for sale, loan servicing and mortgage origination
Residential mortgages serviced for others	$ 6,600,000		$ 6,600,000		$ 6,100,000
Contractually specified servicing fees earned	$ 4,200	$ 3,800	$ 12,100	$ 10,500
Contractually Specified Servicing Fee Income, Statement of Income or Comprehensive Income [Extensible Enumeration]	Revenue from Contract with Customer, Excluding Assessed Tax	Revenue from Contract with Customer, Excluding Assessed Tax	Revenue from Contract with Customer, Excluding Assessed Tax	Revenue from Contract with Customer, Excluding Assessed Tax
Mortgage servicing rights	$ 90,459		$ 90,459		$ 65,620
Changes in the fair value of MSRs and its offsetting hedge.
Increase in fair value of MSRs	$ 2,661	$ 1,659	$ 18,274	$ 7,543
Servicing Asset, Fair Value, Change in Fair Value, Valuation Input, Statement of Income or Comprehensive Income [Extensible Enumeration]	Revenue from Contract with Customer, Excluding Assessed Tax	Revenue from Contract with Customer, Excluding Assessed Tax	Revenue from Contract with Customer, Excluding Assessed Tax	Revenue from Contract with Customer, Excluding Assessed Tax
Decay of MSRs	$ (2,530)	$ (3,427)	$ (8,052)	$ (11,276)
Loss related to derivatives	(3,572)	(577)	(17,963)	(4,178)
Net effect on statements of income	$ (3,441)	$ (2,345)	$ (7,741)	$ (7,911)
Characteristics and sensitivity analysis of the MSR
Composition of residential loans serviced for others	100.00%		100.00%		100.00%
Weighted average life (in years)			8 years 5 months 4 days		7 years 4 months 6 days
Constant Prepayment rate (CPR) (as a percent)			6.40%		8.40%
Weighted average discount rate (as a percent)			10.20%		9.00%
Effect on fair value due to change in interest rates:
25 basis point increase	$ 510		$ 510		$ 3,961
50 basis point increase	925		925		7,261
25 basis point decrease	(628)		(628)		(4,371)
50 basis point decrease	(1,389)		(1,389)		(8,966)
Custodial escrow balances maintained in connection with the loan servicing	$ 74,700		$ 74,700		$ 29,600
Fixed-rate mortgage loans
Characteristics and sensitivity analysis of the MSR
Composition of residential loans serviced for others	100.00%		100.00%		99.90%
Adjustable-rate mortgage loans
Characteristics and sensitivity analysis of the MSR
Composition of residential loans serviced for others					0.10%

Not applicable.

No definition available.

Name:	ssb_ChangesInFairValueOfMortgageServicingRightsMSRAndOffsettingHedgeAbstract
Namespace Prefix:	ssb_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the value of residential mortgages serviced for others, which are acquired through merger transaction.

+ References

No definition available.

+ Details

Name:	ssb_ResidentialMortgagesServicedForOthers
Namespace Prefix:	ssb_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Represents the percentage of residential mortgages serviced for others, which are acquired through merger transaction.

+ References

No definition available.

+ Details

Name:	ssb_ResidentialMortgagesServicedForOthersPercentage
Namespace Prefix:	ssb_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The hypothetical financial impact of a 25 basis point decrease in interest rates on the fair value of transferor's interests in transferred financial assets (including any servicing assets or servicing liabilities) as of the balance sheet date.

+ References

No definition available.

+ Details

Name:	ssb_SensitivityAnalysisOfFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesImpactOf25BasisPointDecreaseInInterestRates
Namespace Prefix:	ssb_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The hypothetical financial impact of a 25 basis point increase in interest rates on the fair value of transferor's interests in transferred financial assets (including any servicing assets or servicing liabilities) as of the balance sheet date.

+ References

No definition available.

+ Details

Name:	ssb_SensitivityAnalysisOfFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesImpactOf25BasisPointIncreaseInInterestRates
Namespace Prefix:	ssb_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The hypothetical financial impact of a 50 basis point decrease in interest rates on the fair value of transferor's interests in transferred financial assets (including any servicing assets or servicing liabilities) as of the balance sheet date.

+ References

No definition available.

+ Details

Name:	ssb_SensitivityAnalysisOfFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesImpactOf50BasisPointDecreaseInInterestRates
Namespace Prefix:	ssb_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The hypothetical financial impact of a 50 basis point increase in interest rates on the fair value of transferor's interests in transferred financial assets (including any servicing assets or servicing liabilities) as of the balance sheet date.

+ References

No definition available.

+ Details

Name:	ssb_SensitivityAnalysisOfFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesImpactOf50BasisPointIncreaseInInterestRates
Namespace Prefix:	ssb_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- References

No definition available.

+ Details

Name:	ssb_SensitivityAnalysisOfFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesImpactOfChangeInAssumptionAbstract
Namespace Prefix:	ssb_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of increase (decrease) in fair value from changes in the assumptions or model used to calculate the fair value of a contract to service financial assets under which the benefits of servicing are expected to more than adequately compensate the servicer.

+ References

No definition available.

+ Details

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

- Definition

Indicates line item in statement of income or comprehensive income that includes contractually specified servicing fee income.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI https://asc.fasb.org/extlink&oid=128311188&loc=d3e122596-111746

+ Details

Name:	us-gaap_ContractuallySpecifiedServicingFeeIncomeStatementOfIncomeOrComprehensiveIncomeExtensibleEnumeration
Namespace Prefix:	us-gaap_
Data Type:	enum2:enumerationSetItemType
Balance Type:	na
Period Type:	duration

- Definition

All amounts that, per contract, are due to the servicer in exchange for servicing the financial asset and would no longer be received by a servicer if the beneficial owners of the serviced assets (or their trustees or agents) were to exercise their actual or potential authority under the contract to shift the servicing to another servicer. Depending on the servicing contract, those fees may include some or all of the difference between the interest rate collected on the asset being serviced and the rate to be paid to the beneficial owners of the asset.

+ References

+ Details

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

- Definition

The designation of funds furnished by a borrower to a lender to assure future payments of the borrower's real estate taxes and insurance obligations with respect to a mortgaged property. Escrow deposits may be made for a variety of other purposes such as earnest money and contingent payments. This element excludes replacement reserves which are an escrow separately provided for within the US GAAP taxonomy.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.10)
-URI https://asc.fasb.org/extlink&oid=126897435&loc=d3e534808-122878

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 954
-SubTopic 440
-Section 50
-Paragraph 1
-Subparagraph (d)
-URI https://asc.fasb.org/extlink&oid=6491277&loc=d3e6429-115629

+ Details

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

- Definition

Aggregate amount of servicing assets that are subsequently measured at fair value and servicing assets that are subsequently measured using the amortization method.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 45
-Paragraph 2
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=6469459&loc=d3e122501-111745

+ Details

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

- Definition

Indicates line item in statement of income or comprehensive income that includes increase (decrease) in fair value from change in input used to calculate fair value of contract to service financial asset under which benefit of servicing is expected to more than adequately compensate servicer.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=128311188&loc=d3e122625-111746

+ Details

Name:	us-gaap_ServicingAssetAtFairValueChangeInFairValueValuationInputStatementOfIncomeOrComprehensiveIncomeExtensibleEnumeration
Namespace Prefix:	us-gaap_
Data Type:	enum2:enumerationSetItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of increase (decrease) in fair value from changes in the inputs used to calculate the fair value of contract to service financial assets under which the benefits of servicing are expected to more than adequately compensate the servicer.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 50
-Paragraph 3
-Subparagraph (a)(4)(i)
-URI https://asc.fasb.org/extlink&oid=128311188&loc=d3e122625-111746

+ Details

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

- Definition

Amount of increase (decrease) in fair value from changes classified as other for a contract to service financial assets under which the benefits of servicing are expected to more than adequately compensate the servicer.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 50
-Paragraph 3
-Subparagraph (a)(5)
-URI https://asc.fasb.org/extlink&oid=128311188&loc=d3e122625-111746

+ Details

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

- Definition

The increase (decrease) in the fair value of servicing assets that are subsequently measured at fair value.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=128311188&loc=d3e122625-111746

+ Details

Name:	us-gaap_ServicingAssetAtFairValuePeriodIncreaseDecrease
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration

- References

No definition available.

+ Details

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

- Definition

Discount rate used to estimate the fair value of servicing assets and servicing liabilities.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 50
-Paragraph 2
-Subparagraph (d)
-URI https://asc.fasb.org/extlink&oid=128311188&loc=d3e122596-111746

+ Details

Name:	us-gaap_ServicingAssetsAndServicingLiabilitiesAtFairValueAssumptionsUsedToEstimateFairValueDiscountRate
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Estimated rate of prepayments of principal on servicing assets and servicing liabilities.

+ References

+ Details

Name:	us-gaap_ServicingAssetsAndServicingLiabilitiesAtFairValueAssumptionsUsedToEstimateFairValuePrepaymentSpeed
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Weighted average life of financial assets and financial liabilities, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 50
-Paragraph 2
-Subparagraph (d)
-URI https://asc.fasb.org/extlink&oid=128311188&loc=d3e122596-111746

+ Details

Name:	us-gaap_ServicingAssetsAndServicingLiabilitiesAtFairValueAssumptionsUsedToEstimateFairValueWeightedAverageLife1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
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_ServicingAssetsAtFairValueLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

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

- Details

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