Regulatory Capital (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Capital conservation buffer	1.90%	1.30%
CET1 capital
CET1 capital, Actual	$ 2,897,997	$ 2,763,168
CET1 capital, For Capital Adequacy Purposes	1,310,460	1,250,488
Tier 1 risk-based capital
Tier I risk-based capital, Actual	3,090,416	2,872,001
Tier I risk-based capital, For Capital Adequacy Purposes	1,747,280	1,660,074
Total risk-based capital
Total risk-based capital, Actual	3,601,376	3,383,081
Total risk-based capital, For Capital Adequacy Purposes	$ 2,329,706	$ 2,213,432
CET1 capital ratio
CET1 capital ratio, Actual	9.95%	9.99%
CET1 capital ratio, For Capital Adequacy Purposes	4.50%	4.50%
Tier 1 risk-based capital ratio
Tier I risk-based capital ratio, Actual	10.61%	10.38%
Tier I risk-based capital ratio, For Capital Adequacy Purposes	6.00%	6.00%
Total risk-based capital ratio
Total risk-based capital ratio, Actual	12.37%	12.23%
Total risk-based capital ratio, For Capital Adequacy Purposes	8.00%	8.00%
Leverage ratio
Leverage ratio, Actual	9.60%	9.19%
Leverage ratio, For Capital Adequacy Purposes	4.00%	4.00%
Synovus Bank Reporting Unit
CET1 capital
CET1 capital, Actual	$ 3,382,497	$ 3,155,163
CET1 capital, For Capital Adequacy Purposes	1,309,527	1,247,462
CET1 capital, To Be Well Capitalized Under Prompt Corrective Action Provisions	1,891,538	1,795,004
Tier 1 risk-based capital
Tier I risk-based capital, Actual	3,382,497	3,155,163
Tier I risk-based capital, For Capital Adequacy Purposes	1,746,035	1,656,927
Tier I risk-based capital, To Be Well Capitalized Under Prompt Corrective Action Provisions	2,328,047	2,209,236
Total risk-based capital
Total risk-based capital, Actual	3,633,457	3,406,243
Total risk-based capital, For Capital Adequacy Purposes	2,328,047	2,209,236
Total risk-based capital, To Be Well Capitalized Under Prompt Corrective Action Provisions	$ 2,910,059	$ 2,761,545
CET1 capital ratio
CET1 capital ratio, Actual	11.62%	11.43%
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	11.62%	11.43%
Tier I risk-based capital ratio, For Capital Adequacy Purposes	6.00%	6.00%
Tier I risk-based capital ratio, To Be Well Capitalized Under Prompt Corrective Action Provisions	8.00%	8.00%
Total risk-based capital ratio
Total risk-based capital ratio, Actual	12.49%	12.33%
Total risk-based capital ratio, For Capital Adequacy Purposes	8.00%	8.00%
Total risk-based capital ratio, To Be Well Capitalized Under Prompt Corrective Action Provisions	10.00%	10.00%
Leverage ratio
Leverage ratio, Actual	10.51%	10.12%
Leverage ratio, For Capital Adequacy Purposes	4.00%	4.00%
Leverage ratio, To Be Well Capitalized Under Prompt Corrective Action Provisions	5.00%	5.00%
When fully phased-in on January 1, 2019
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Capital conservation buffer	2.50%