Condensed Financial Information Of Synovus Financial Corp. (Parent Company Only) (Condensed Statements of Comprehensive Income) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Condensed Financial Statements, Captions [Line Items]
Net income, Before-tax Amount									$ 547,354	$ 480,138	$ 388,451
Net income, Tax (Expense) Benefit	$ (38,784)	$ (18,949)	$ (30,936)	$ (30,209)	$ (74,361)	$ (54,668)	$ (41,788)	$ (33,847)	(118,878)	(204,664)	(141,667)
Net income	$ 105,070	$ 109,059	$ 111,181	$ 103,166	$ 29,605	$ 98,007	$ 76,003	$ 71,857	428,476	275,474	246,784
Reclassification adjustment for losses realized in net income on cash flow hedges, Before-tax Amount									0	130	467
Reclassification adjustment for losses realized in net income on cash flow hedges, Tax (Expense) Benefit									0	(50)	(180)
Reclassification adjustment for losses realized in net income, Net of Tax Amount									0	80	287
Reclassification adjustment for net losses (gains) realized in net income on investment securities available for sale, Before-tax Amount									1,296	289	(6,011)
Reclassification adjustment for net losses (gains) realized in net income on investment securities available for sale, Tax (Expense) Benefit									(336)	(111)	2,314
Reclassification adjustment for net losses (gains) realized in net income on investment securities available for sale, Net of Tax Amount									960	178	(3,697)
Net unrealized (losses) gains arising during the period, Before-tax Amount									(44,565)	1,038	(36,432)
Net unrealized gains (losses) arising during the period, Tax (Expense) Benefit									11,542	(362)	14,027
Net unrealized gains (losses) arising during the period, Net of Tax Amount									(33,023)	676	(22,405)
Other comprehensive (loss) income, Before-tax Amount									(43,447)	1,408	(42,018)
Other comprehensive (loss) income, Tax (Expense) Benefit									11,252	(503)	16,178
Net current period other comprehensive income (loss)									(32,195)	905	(25,840)
Comprehensive income, Net of Tax Amount									396,281	276,379	220,944
Parent Company
Condensed Financial Statements, Captions [Line Items]
Net income, Before-tax Amount									547,354	480,138	388,451
Net income, Tax (Expense) Benefit									(118,878)	(204,664)	(141,667)
Net income									428,476	275,474	246,784
Reclassification adjustment for losses realized in net income on cash flow hedges, Before-tax Amount									0	130	467
Reclassification adjustment for losses realized in net income on cash flow hedges, Tax (Expense) Benefit									0	(50)	(180)
Reclassification adjustment for losses realized in net income, Net of Tax Amount									0	80	287
Reclassification adjustment for net losses (gains) realized in net income on investment securities available for sale, Before-tax Amount									0	(5,506)	(5,763)
Reclassification adjustment for net losses (gains) realized in net income on investment securities available for sale, Tax (Expense) Benefit									0	2,120	2,219
Reclassification adjustment for net losses (gains) realized in net income on investment securities available for sale, Net of Tax Amount									0	(3,386)	(3,544)
Net unrealized (losses) gains arising during the period, Before-tax Amount									0	0	2,358
Net unrealized gains (losses) arising during the period, Tax (Expense) Benefit									0	0	(908)
Net unrealized gains (losses) arising during the period, Net of Tax Amount									0	0	1,450
Other comprehensive (loss) gain of bank subsidiary, Before-tax Amount									(43,447)	6,784	(39,080)
Other comprehensive (loss) gain of bank subsidiary, Tax (expense) Benefit									11,252	(2,573)	15,047
Other comprehensive (loss) gain of bank subsidiary, Net of Tax Amount									(32,195)	4,211	(24,033)
Other comprehensive (loss) income, Before-tax Amount									(43,447)	1,408	(42,018)
Other comprehensive (loss) income, Tax (Expense) Benefit									11,252	(503)	16,178
Net current period other comprehensive income (loss)									(32,195)	905	(25,840)
Comprehensive income, Net of Tax Amount									$ 396,281	$ 276,379	$ 220,944