Summary of Significant Accounting Policies - Loans (Details) $ in Millions	Jun. 30, 2025 USD ($)
Summary of Significant Accounting Policies
Net book balance	$ 1
Net book balance, purchased credit deteriorated loans	$ 1

Represents the net book balance for purchased credit deteriorated loans to be individually evaluated for loss.

No definition available.

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