Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Statement of Comprehensive Income [Abstract]
Income before income taxes and equity in undistributed income of subsidiaries	$ 696,162	$ 964,177	$ 989,360
Net income, income tax	(154,021)	(206,275)	(228,893)
Net income	542,141	757,902	760,467
Before-tax Amount
Net unrealized gains (losses) arising during the period	215,914	(1,522,047)	(234,550)
Reclassification adjustment for realized (gains) losses included in net income	76,718	0	799
Net change	292,632	(1,522,047)	(233,751)
Income Tax
Net unrealized gains (losses) arising during the period	(52,101)	369,764	60,304
Reclassification adjustment for realized (gains) losses included in net income	(18,527)	0	(202)
Net change	(70,628)	369,764	60,102
Net of Tax Amount
Net unrealized gains (losses) arising during the period	163,813	(1,152,283)	(174,246)
Reclassification adjustment for realized (gains) losses included in net income	58,191	0	597
Net change	222,004	(1,152,283)	(173,649)
Before-tax Amount
Net unrealized gains (losses) arising during the period	(40,606)	(298,289)	(77,948)
Reclassification adjustment for realized (gains) losses included in net income	176,442	24,057	(12,862)
Net change	135,836	(274,232)	(90,810)
Income Tax
Net unrealized gains (losses) arising during the period	9,815	72,574	20,243
Reclassification adjustment for realized (gains) losses included in net income	(42,611)	(5,855)	3,260
Net change	(32,796)	66,719	23,503
Net of Tax Amount
Net unrealized gains (losses) arising during the period	(30,791)	(225,715)	(57,705)
Reclassification adjustment for realized (gains) losses included in net income	133,831	18,202	(9,602)
Net change	103,040	(207,513)	(67,307)
Total other comprehensive income (loss)	428,468	(1,796,279)	(324,561)
Other comprehensive income (loss), income tax	(103,424)	436,483	83,605
Other comprehensive income (loss)	325,044	(1,359,796)	(240,956)
Comprehensive income (loss)	867,185	(601,894)	519,511
Less: comprehensive income (loss) attributable to noncontrolling interest	(1,564)	0	0
Comprehensive income (loss) attributable to Synovus Financial Corp.	$ 868,749	$ (601,894)	$ 519,511