Represents the age of employees to be eligible to participate in the defined contribution plan.

No definition available.

Name:	ssb_DefinedContributionPlanAgeOfEmployeesCovered
Namespace Prefix:	ssb_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents employee contributions to a defined contribution pension plan as a percentage of annual base compensation.

+ References

No definition available.

+ Details

Name:	ssb_DefinedContributionPlanEmployeeContributionAsPercentageOfAnnualBaseCompensation
Namespace Prefix:	ssb_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The percentage of the employee contribution for which the employer contributes a matching contribution to a defined contribution plan.

+ References

No definition available.

+ Details

Name:	ssb_DefinedContributionPlanEmployerContributionPercent
Namespace Prefix:	ssb_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- References

No definition available.

+ Details

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

- Definition

Amount of cost for defined contribution plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 70
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=49170846&loc=d3e28014-114942

+ Details

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

- Definition

Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan.

+ References

No definition available.

+ Details

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

- Definition

Percentage employer matches of the employee's percentage contribution matched.

+ References

No definition available.

+ Details

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

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Retirement Plans - Safe Harbor plan (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Employees' savings plan
Matching contribution by the company (as a percent)			100.00%
Expenses recognized under 401(K) plan	$ 3.7	$ 3.5	$ 11.8	$ 7.8
Minimum
Employees' savings plan
Age of employees to be eligible to participate in the defined contribution plan			21 years
Percentage of annual base compensation that participants may elect to contribute			1.00%
Maximum
Employees' savings plan
Percentage of annual base compensation that participants may elect to contribute			50.00%
Percentage of employees salary for which the company contributes a matching contribution			4.00%
Discretionary matching contribution (as a percent)			2.00%