Regulatory Capital (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Capital conservation buffer	2.50%
CET1 capital
CET1 capital, Actual	$ 4,034,865	$ 3,743,459
CET1 capital, For Capital Adequacy Purposes	1,879,551	1,882,424
Tier 1 risk-based capital
Tier I risk-based capital, Actual	4,572,010	4,280,604
Tier I risk-based capital, For Capital Adequacy Purposes	2,506,068	2,509,899
Total risk-based capital
Total risk-based capital, Actual	5,604,230	5,123,381
Total risk-based capital, For Capital Adequacy Purposes	$ 3,341,425	$ 3,346,531
CET1 capital ratio
CET1 capital ratio, Actual	9.66%	8.95%
CET1 capital ratio, For Capital Adequacy Purposes	4.50%	4.50%
Tier 1 risk-based capital ratio
Tier I risk-based capital ratio, Actual	0.1095	0.1023
Tier I risk-based capital ratio, For Capital Adequacy Purposes	0.0600	0.0600
Total risk-based capital ratio
Total risk-based capital ratio, Actual	0.1342	0.1225
Total risk-based capital ratio, For Capital Adequacy Purposes	0.0800	0.0800
Leverage ratio
Leverage ratio, Actual	0.0850	0.0916
Leverage ratio, For Capital Adequacy Purposes	0.0400	0.0400
Synovus Bank Reporting Unit
CET1 capital
CET1 capital, Actual	$ 4,641,711	$ 4,640,501
CET1 capital, For Capital Adequacy Purposes	1,880,757	1,881,199
CET1 capital, To Be Well Capitalized Under Prompt Corrective Action Provisions	2,716,650	2,717,287
Tier 1 risk-based capital
Tier I risk-based capital, Actual	4,641,711	4,640,501
Tier I risk-based capital, For Capital Adequacy Purposes	2,507,677	2,508,265
Tier I risk-based capital, To Be Well Capitalized Under Prompt Corrective Action Provisions	3,343,569	3,344,354
Total risk-based capital
Total risk-based capital, Actual	5,361,611	4,923,279
Total risk-based capital, For Capital Adequacy Purposes	3,343,569	3,344,354
Total risk-based capital, To Be Well Capitalized Under Prompt Corrective Action Provisions	$ 4,179,461	$ 4,180,442
CET1 capital ratio
CET1 capital ratio, Actual	11.11%	11.10%
CET1 capital ratio, For Capital Adequacy Purposes	4.50%	4.50%
CET1 capital ratio, To Be Well Capitalized Under Prompt Corrective Action Provisions	6.50%	6.50%
Tier 1 risk-based capital ratio
Tier I risk-based capital ratio, Actual	0.1111	0.1110
Tier I risk-based capital ratio, For Capital Adequacy Purposes	0.0600	0.0600
Tier I risk-based capital ratio, To Be Well Capitalized Under Prompt Corrective Action Provisions	0.0800	0.0800
Total risk-based capital ratio
Total risk-based capital ratio, Actual	0.1283	0.1178
Total risk-based capital ratio, For Capital Adequacy Purposes	0.0800	0.0800
Total risk-based capital ratio, To Be Well Capitalized Under Prompt Corrective Action Provisions	0.1000	0.1000
Leverage ratio
Leverage ratio, Actual	0.0873	0.0994
Leverage ratio, For Capital Adequacy Purposes	0.0400	0.0400
Leverage ratio, To Be Well Capitalized Under Prompt Corrective Action Provisions	0.0500	0.0500