Leases - Lease cost and other information (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024
Lease Cost Components:
Amortization of ROU assets - finance leases	$ 117	$ 117	$ 348	$ 350
Interest on lease liabilities - finance leases	6	8	20	26
Operating lease cost (cost resulting from lease payments)	15,708	4,025	40,991	12,658
Short-term lease cost	528	144	1,308	467
Variable lease cost (cost excluded from lease payments)	898	704	3,213	2,457
Total lease cost	17,257	4,998	45,880	15,958
Supplemental Cash Flow and Other Information Related to Leases:
Finance lease - operating cash flows	6	8	20	26
Finance lease - financing cash flows	122	120	363	357
Operating lease - operating cash flows (fixed payments)	13,938	4,450	36,802	12,862
Operating lease - operating cash flows (net change asset/liability)	(6,330)	$ (3,436)	(17,752)	(10,103)
New ROU assets - operating leases	$ 2,646		$ 399,965	$ 9,093
Weighted - average remaining lease term (years) - finance leases	2 years 8 months 15 days	3 years 8 months 8 days	2 years 8 months 15 days	3 years 8 months 8 days
Weighted - average remaining lease term (years) - operating leases	12 years 5 months 26 days	8 years 7 months 17 days	12 years 5 months 26 days	8 years 7 months 17 days
Weighted - average discount rate - finance leases	1.80%	1.70%	1.80%	1.70%
Weighted - average discount rate - operating leases	6.40%	3.40%	6.40%	3.40%
Operating lease payments due:
2025 (excluding 9 months ended September 30, 2025)	$ 14,116		$ 14,116
2026	57,848		57,848
2027	56,862		56,862
2028	56,706		56,706
2029	55,848		55,848
Thereafter	536,093		536,093
Total undiscounted cash flows	777,473		777,473
Discount on cash flows	(285,869)		(285,869)
Total operating lease liabilities	$ 491,604		$ 491,604		$ 103,900
Operating Lease, Liability, Statement of Financial Position [Extensible List]	Other Liabilities.		Other Liabilities.		Other Liabilities.

The amount of increase (decrease) in operating cash flows due to change in assets and liabilities.

No definition available.

Name:	ssb_IncreaseDecreaseInOperatingCashFlowChangeInAssetAndLiability
Namespace Prefix:	ssb_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of lessee's undiscounted obligation for lease payment for operating lease due after fourth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

No definition available.