Condensed Financial Information Of Synovus Financial Corp. (Parent Company Only) (Condensed Statements of Comprehensive Income) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Condensed Financial Statements, Captions [Line Items]
Net income, Income Tax	$ (110,970)	$ (201,235)	$ (118,878)
Net income	373,695	563,780	428,476
Reclassification adjustment for net losses (gains) realized in net income on investment securities available for sale, Before-tax Amount	(78,931)	7,659	1,296
Reclassification adjustment for net losses (gains) realized in net income on investment securities available for sale, Income Tax	20,443	(1,984)	(336)
Reclassification adjustment for realized (gains) losses included in net income	(58,488)	5,675	960
Other comprehensive income (loss), Before-tax Amount	125,505	216,010	(43,447)
Other comprehensive income (loss), Income Tax	(32,511)	(55,949)	11,252
Net current period other comprehensive income (loss)	92,994	160,061	(32,195)
Comprehensive income	466,689	723,841	396,281
Parent Company
Condensed Financial Statements, Captions [Line Items]
Net income, Before-tax Amount	484,665	765,015	547,354
Net income, Income Tax	(110,970)	(201,235)	(118,878)
Net income	373,695	563,780	428,476
Reclassification adjustment for net losses (gains) realized in net income on investment securities available for sale, Before-tax Amount	0	(22)	0
Reclassification adjustment for net losses (gains) realized in net income on investment securities available for sale, Income Tax	0	6	0
Reclassification adjustment for realized (gains) losses included in net income	0	(16)	0
Other comprehensive (loss) gain of bank subsidiary, Before-tax Amount	125,505	216,032	(43,447)
Other comprehensive (loss) gain of bank subsidiary, Income Tax	(32,511)	(55,955)	11,252
Other comprehensive (loss) gain of bank subsidiary, Net of Tax Amount	92,994	160,077	(32,195)
Other comprehensive income (loss), Before-tax Amount	125,505	216,010	(43,447)
Other comprehensive income (loss), Income Tax	(32,511)	(55,949)	11,252
Net current period other comprehensive income (loss)	92,994	160,061	(32,195)
Comprehensive income	$ 466,689	$ 723,841	$ 396,281