Fair Value - Assets and liabilities measured at fair value on a recurring basis (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2023	Dec. 31, 2022
Assets
Derivative financial instruments	$ 169,000	$ 209,800
Trading securities	31,321	31,263
Securities available for sale	4,784,388	5,326,822
SBA servicing asset	6,000	6,100
Liabilities
Derivative financial instruments	$ 803,500	$ 1,000
Changes in fair value of assets
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Revenue from Contract with Customer, Excluding Assessed Tax	Revenue from Contract with Customer, Excluding Assessed Tax
U.S. Treasuries
Assets
Securities available for sale	$ 73,890	$ 265,638
U.S. Government agencies
Assets
Trading securities	1,537	11,190
Securities available for sale	224,706	219,088
Residential mortgage pass-through securities issued or guaranteed by U.S. government agencies or sponsored enterprises
Assets
Trading securities	14,461
Securities available for sale	1,558,306	1,698,353
Commercial mortgage-backed securities issued by U.S. government agencies or sponsored enterprises
Assets
Trading securities		4,589
Securities available for sale	1,024,170	1,000,398
State and municipal obligations
Assets
Trading securities	14,620	13,993
Securities available for sale	977,461	1,064,852
Small Business Administration loan-backed securities
Assets
Securities available for sale	371,686	444,810
Corporate securities.
Assets
Securities available for sale	26,747	32,638
Significant Other Observable Inputs (Level 2)
Assets
Loans held for sale	50,888	28,968
Trading securities	31,321	31,263
Significant Unobservable Inputs (Level 3)
Assets
Mortgage servicing rights	85,164	86,610
SBA servicing asset	5,952	6,068
Changes in fair value of assets
Changes in hierarchy classifications of Level 3 assets	0
Changes in hierarchy classifications of Level 3 liabilities	0
Recurring basis
Assets
Derivative financial instruments	172,939	211,016
Loans held for sale	50,888	28,968
Trading securities	31,321	31,263
Securities available for sale	4,784,388	5,326,822
Mortgage servicing rights	85,164	86,610
SBA servicing asset	5,952	6,068
Fair value of Assets, Total	5,130,652	5,690,747
Liabilities
Derivative financial instruments	804,486	1,034,143
Recurring basis \| U.S. Treasuries
Assets
Securities available for sale	73,890	265,638
Recurring basis \| U.S. Government agencies
Assets
Securities available for sale	224,706	219,088
Recurring basis \| Residential mortgage pass-through securities issued or guaranteed by U.S. government agencies or sponsored enterprises
Assets
Securities available for sale	1,558,306	1,698,353
Recurring basis \| Residential Collateralized Mortgage-Obligations Issued By U.S. Government Agencies Or Sponsored Enterprises
Assets
Securities available for sale	527,422	601,045
Recurring basis \| Commercial mortgage-backed securities issued by U.S. government agencies or sponsored enterprises
Assets
Securities available for sale	1,024,170	1,000,398
Recurring basis \| State and municipal obligations
Assets
Securities available for sale	977,461	1,064,852
Recurring basis \| Small Business Administration loan-backed securities
Assets
Securities available for sale		444,810
Recurring basis \| Mortgage-backed securities
Assets
Securities available for sale	371,686
Recurring basis \| Corporate securities.
Assets
Securities available for sale	26,747	32,638
Recurring basis \| Significant Other Observable Inputs (Level 2)
Assets
Derivative financial instruments	172,939	211,016
Loans held for sale	50,888	28,968
Trading securities	31,321	31,263
Securities available for sale	4,784,388	5,326,822
Fair value of Assets, Total	5,039,536	5,598,069
Liabilities
Derivative financial instruments	804,486	1,034,143
Recurring basis \| Significant Other Observable Inputs (Level 2) \| U.S. Treasuries
Assets
Securities available for sale	73,890	265,638
Recurring basis \| Significant Other Observable Inputs (Level 2) \| U.S. Government agencies
Assets
Securities available for sale	224,706	219,088
Recurring basis \| Significant Other Observable Inputs (Level 2) \| Residential mortgage pass-through securities issued or guaranteed by U.S. government agencies or sponsored enterprises
Assets
Securities available for sale	1,558,306	1,698,353
Recurring basis \| Significant Other Observable Inputs (Level 2) \| Residential Collateralized Mortgage-Obligations Issued By U.S. Government Agencies Or Sponsored Enterprises
Assets
Securities available for sale	527,422	601,045
Recurring basis \| Significant Other Observable Inputs (Level 2) \| Commercial mortgage-backed securities issued by U.S. government agencies or sponsored enterprises
Assets
Securities available for sale	1,024,170	1,000,398
Recurring basis \| Significant Other Observable Inputs (Level 2) \| State and municipal obligations
Assets
Securities available for sale	977,461	1,064,852
Recurring basis \| Significant Other Observable Inputs (Level 2) \| Small Business Administration loan-backed securities
Assets
Securities available for sale		444,810
Recurring basis \| Significant Other Observable Inputs (Level 2) \| Mortgage-backed securities
Assets
Securities available for sale	371,686
Recurring basis \| Significant Other Observable Inputs (Level 2) \| Corporate securities.
Assets
Securities available for sale	26,747	32,638
Recurring basis \| Significant Unobservable Inputs (Level 3)
Assets
Mortgage servicing rights	85,164	86,610
SBA servicing asset	5,952	6,068
Fair value of Assets, Total	$ 91,116	$ 92,678
Changes in fair value of assets
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Revenue from Contract with Customer, Excluding Assessed Tax	Revenue from Contract with Customer, Excluding Assessed Tax
Unrealized losses included in accumulated other comprehensive (loss) income related to Level 3 financial assets and liabilities	$ 0	$ 0
Recurring basis \| Significant Unobservable Inputs (Level 3) \| Mortgage Servicing Rights
Changes in fair value of assets
Fair value of assets at the beginning of the period	86,610	65,620
Servicing assets that resulted from transfers of financial assets	8,444	16,002
Changes in fair value assets due to valuation inputs or assumptions	(1,350)	14,886
Changes in fair value due to decay	(8,540)	(9,898)
Fair value of assets at the end of the period	85,164	86,610
Recurring basis \| Significant Unobservable Inputs (Level 3) \| SBA servicing asset
Changes in fair value of assets
Fair value of assets at the beginning of the period	6,068	7,369
Servicing assets that resulted from transfers of financial assets	1,621	1,273
Changes in fair value assets due to valuation inputs or assumptions	507	(729)
Changes in fair value due to decay	(2,244)	(1,845)
Fair value of assets at the end of the period	$ 5,952	$ 6,068

Represents the amount of servicing assets that resulted from transfers of financial assets.

No definition available.

Name:	ssb_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetServicingAssetsResultingFromTransfers
Namespace Prefix:	ssb_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, the element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. The item represents residential mortgage servicing rights as presented on the statement of financial position which are due to the entity as of the balance sheet date.

+ References

No definition available.