Capital Ratios (Details) $ in Thousands		Sep. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)	Jan. 01, 2020 USD ($)		Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Jan. 01, 2019	Dec. 31, 2018 USD ($)
Capital ratios
Capital conversion buffer common equity Tier 1 of risk-weighted assets (as a percent)									2.50%
Additional allowance for credit losses for loans		$ 440,159	$ 434,608			$ 56,927	$ 60,255	$ 58,213		$ 55,798
Deferred tax assets		107,500				31,316	27,844
Additional reserve for unfunded commitments		43,200
Retained earnings		$ 604,564				$ 679,895	$ 646,325
Tier One Risk Based Capital to Risk Weighted Assets		11.48				12.25	12.19
Capital to Risk Weighted Assets (as a percent)		13.86				12.78	12.71
Tier One Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets (as a percent)		8.00				8.00	8.00
Common equity Tier 1 to risk-weighted assets
Actual, Capital Amount		$ 2,940,041				$ 1,326,725	$ 1,302,034
Actual, Ratio (as a percent)		11.48%				11.30%	11.22%
Minimum capital required, Ratio (as a percent)		4.50%
Required to be considered well capitalized, Capital Amount		$ 1,664,927				$ 763,495	$ 754,257
Required to be considered well capitalized, Ratio (as a percent)		6.50%				6.50%	6.50%
Tier I capital to risk-weighted assets
Actual, Capital Amount		$ 2,940,041				$ 1,438,995	$ 1,414,138
Actual, Ratio (as a percent)		11.48				12.25	12.19
Minimum capital required, Ratio (as a percent)		4				6
Required to be considered well capitalized, Capital Amount		$ 2,049,141				$ 939,686	$ 928,316
Required to be considered well capitalized, Ratio (as a percent)		8.00				8.00	8.00
Total capital to risk-weighted assets
Actual, Capital Amount		$ 3,550,019				$ 1,501,321	$ 1,474,728
Actual, Ratio (as a percent)		13.86				12.78	12.71
Required to be considered well capitalized, Capital Amount		$ 2,561,427				$ 1,174,607	$ 1,160,395
Required to be considered well capitalized, Ratio (as a percent)		10.00				10.00	10.00
Tier I capital to average assets (leverage ratio)
Actual, Capital Amount		$ 2,940,041				$ 1,438,995	$ 1,414,138
Actual, Ratio (as a percent)		8.12				9.73	9.72
Minimum capital required, Ratio (as a percent)		8
Required to be considered well capitalized, Capital Amount		$ 1,809,663				$ 739,664	$ 727,232
Required to be considered well capitalized, Ratio (as a percent)		5.00				5.00	5.00
ASU 2016-13
Capital ratios
Additional allowance for credit losses for loans	[1]			$ 54,438
Deferred tax assets	[2]			12,639
Additional reserve for unfunded commitments				6,400
Retained earnings				$ (44,820)	[3]	$ 44,800
ASU 2016-13 | Cumulative Effect of Adoption of ASU
Capital ratios
Retained earnings						44,800
Fully Phased-In
Common equity Tier 1 to risk-weighted assets
Minimum capital required, Capital Amount		$ 1,792,999				$ 822,225	$ 812,276
Minimum capital required, Ratio (as a percent)		7.00%				7.00%	7.00%
Tier I capital to risk-weighted assets
Minimum capital required, Capital Amount		$ 2,177,213				$ 998,416	$ 986,336
Minimum capital required, Ratio (as a percent)		8.50				8.50	8.50
Total capital to risk-weighted assets
Minimum capital required, Capital Amount		$ 2,689,498				$ 1,233,338	$ 1,218,415
Minimum capital required, Ratio (as a percent)		10.50				10.50	10.50
Tier I capital to average assets (leverage ratio)
Minimum capital required, Capital Amount		$ 1,447,730				$ 591,731	$ 581,786
Minimum capital required, Ratio (as a percent)		4.00				4.00	4.00
South State Bank (the Bank)
Capital ratios
Tier One Risk Based Capital to Risk Weighted Assets		11.95				12.07	12.00
Capital to Risk Weighted Assets (as a percent)		12.80				12.60	12.52
Tier One Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets (as a percent)		8.00				8.00	8.00
Common equity Tier 1 to risk-weighted assets
Actual, Capital Amount		$ 3,052,492				$ 1,417,616	$ 1,392,599
Actual, Ratio (as a percent)		11.95%				12.07%	12.00%
Required to be considered well capitalized, Capital Amount		$ 1,660,445				$ 763,488	$ 754,263
Required to be considered well capitalized, Ratio (as a percent)		6.50%				6.50%	6.50%
Tier I capital to risk-weighted assets
Actual, Capital Amount		$ 3,052,492				$ 1,417,616	$ 1,392,599
Actual, Ratio (as a percent)		11.95				12.07	12.00
Required to be considered well capitalized, Capital Amount		$ 2,043,625				$ 939,677	$ 928,324
Required to be considered well capitalized, Ratio (as a percent)		8.00				8.00	8.00
Total capital to risk-weighted assets
Actual, Capital Amount		$ 3,270,970				$ 1,479,942	$ 1,453,189
Actual, Ratio (as a percent)		12.80				12.60	12.52
Required to be considered well capitalized, Capital Amount		$ 2,554,531				$ 1,174,597	$ 1,160,405
Required to be considered well capitalized, Ratio (as a percent)		10.00				10.00	10.00
Tier I capital to average assets (leverage ratio)
Actual, Capital Amount		$ 3,052,492				$ 1,417,616	$ 1,392,599
Actual, Ratio (as a percent)		8.46				9.59	9.58
Required to be considered well capitalized, Capital Amount		$ 1,803,670				$ 739,490	$ 727,060
Required to be considered well capitalized, Ratio (as a percent)		5.00				5.00	5.00
South State Bank (the Bank) | Fully Phased-In
Common equity Tier 1 to risk-weighted assets
Minimum capital required, Capital Amount		$ 1,788,172				$ 822,218	$ 812,284
Minimum capital required, Ratio (as a percent)		7.00%				7.00%	7.00%
Tier I capital to risk-weighted assets
Minimum capital required, Capital Amount		$ 2,171,352				$ 998,407	$ 986,345
Minimum capital required, Ratio (as a percent)		8.50				8.50	8.50
Total capital to risk-weighted assets
Minimum capital required, Capital Amount		$ 2,682,258				$ 1,233,327	$ 1,218,426
Minimum capital required, Ratio (as a percent)		10.50				10.50	10.50
Tier I capital to average assets (leverage ratio)
Minimum capital required, Capital Amount		$ 1,442,936				$ 591,592	$ 581,648
Minimum capital required, Ratio (as a percent)		4.00				4.00	4.00

[1] This is the calculated adjustment to the ACL related to the adoption of ASC 326. Additional reserve related to non-acquired loans was $34,049, to acquired loans was $16,981 and to purchased credit deteriorated loans was $3,408.

[2] This is the effect of deferred tax assets related to the adjustment to the ACL from the adoption of ASC 326 using a 22% tax rate.

[3] This is the net adjustment to retained earnings related to the adoption of ASC 326.