Other Short-term Borrowings and Long-term Debt - Schedule of Long-term Debt Instruments (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Long-term debt	$ 1,932,534,000	$ 4,109,597,000
Synovus Bank
Debt Instrument [Line Items]
Long-term debt	$ 1,379,831,000	3,465,107,000
4.00% Subordinated Notes, Due October 29, 2030 | Synovus Bank
Debt Instrument [Line Items]
Stated percentage	4.00%
Debt, face amount	$ 200,000,000.0
Interest rate period	5 years
Subordinated notes	$ 192,732,000	$ 190,107,000
4.00% Subordinated Notes, Due October 29, 2030 | US Treasury Rate | Synovus Bank
Debt Instrument [Line Items]
Basis spread on variable rate	3.625%
Federal Home Loan Bank Advance | Synovus Bank
Debt Instrument [Line Items]
Weighted average interest rate	5.57%	4.56%
Other long-term debt	$ 700,000,000	$ 3,275,000,000
Senior Notes | 5.625% Senior Bank Notes due February 15, 2028 | Synovus Bank
Debt Instrument [Line Items]
Stated percentage	5.625%
Debt, face amount	$ 500,000,000.0
Long-term debt, gross	487,099,000	0
Parent Company
Debt Instrument [Line Items]
Long-term debt	$ 552,703,000	644,490,000
Parent Company | 5.90% Subordinated Notes, due February 7, 2029
Debt Instrument [Line Items]
Stated percentage	5.90%
Debt, face amount	$ 300,000,000.0
Interest rate period	5 years
Subordinated notes	$ 201,925,000	298,158,000
Parent Company | 5.90% Subordinated Notes, due February 7, 2029 | Five-Year Mid Swap Rate
Debt Instrument [Line Items]
Basis spread on variable rate	3.379%
Parent Company | SOFR Plus Spread of 2.06% Debentures, due June 15, 2035
Debt Instrument [Line Items]
Stated percentage	2.06%
Debt, face amount		$ 10,000,000
Interest rate at period end	7.45%	6.57%
Unsecured debt	$ 10,000,000	$ 10,000,000
Parent Company | Senior Notes | 5.200% Senior Notes due August 11, 2025
Debt Instrument [Line Items]
Stated percentage	5.20%
Debt, face amount	$ 350,000,000.0
Long-term debt, gross	$ 340,778,000	$ 336,332,000