Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Statement [Abstract]
Loans, including fees	$ 2,684,762	$ 1,806,060	$ 1,482,567
Investment securities available for sale	248,294	209,951	140,077
Loans held for sale	30,092	34,037	23,809
Federal Reserve Bank balances	68,289	18,117	3,777
Other earning assets	18,921	7,622	3,113
Total interest income	3,050,358	2,075,787	1,653,343
Interest expense:
Deposits	1,026,755	187,232	74,919
Long-term debt	180,670	79,402	45,349
Federal funds purchased, securities sold under repurchase agreements, and other borrowings	26,278	12,253	128
Total interest expense	1,233,703	278,887	120,396
Net interest income	1,816,655	1,796,900	1,532,947
Provision for (reversal of) credit losses	189,079	84,553	(106,251)
Net interest income after provision for credit losses	1,627,576	1,712,347	1,639,198
Non-interest revenue:
Service charges on deposit accounts	90,096	93,067	86,310
Fiduciary and asset management fees	78,077	78,414	77,147
Card fees	72,357	61,833	51,399
Brokerage revenue	83,431	67,034	56,439
Mortgage banking income	15,157	17,476	54,371
Capital markets income	32,181	26,702	26,118
Income from bank-owned life insurance	31,429	29,720	38,019
Investment securities gains (losses), net	(76,718)	0	(799)
Recovery of NPA	13,126	0	0
Other non-interest revenue	64,874	35,090	61,062
Total non-interest revenue	404,010	409,336	450,066
Non-interest expense:
Salaries and other personnel expense	728,378	681,710	649,426
Net occupancy, equipment, and software expense	179,581	174,730	169,222
Third-party processing and other services	86,649	88,617	86,688
Professional fees	39,854	37,189	32,785
FDIC insurance and other regulatory fees	94,737	29,083	22,355
Restructuring charges (reversals)	17,707	(9,690)	7,223
Loss on other loans held for sale	50,064	0	0
Other operating expense	138,454	155,867	132,205
Non-interest expense	1,335,424	1,157,506	1,099,904
Income before income taxes	696,162	964,177	989,360
Income tax expense	154,021	206,275	228,893
Net income	542,141	757,902	760,467
Less: Net income (loss) attributable to noncontrolling interest	(1,564)	0	0
Net income attributable to Synovus Financial Corp.	543,705	757,902	760,467
Less: Preferred stock dividends	35,950	33,163	33,163
Net income available to common shareholders	$ 507,755	$ 724,739	$ 727,304
Net income per common share, basic (in dollars per share)	$ 3.48	$ 4.99	$ 4.95
Net income per common share, diluted (in dollars per share)	$ 3.46	$ 4.95	$ 4.90
Weighted average common shares outstanding, basic (in shares)	146,115	145,364	147,041
Weighted average common shares outstanding, diluted (in shares)	146,734	146,481	148,495