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, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Condensed Financial Statements, Captions [Line Items]
Net income, Before-tax Amount									$ 480,138	$ 388,451	$ 358,573
Net income, Tax (Expense) Benefit	$ (74,361)	$ (54,668)	$ (41,788)	$ (33,847)	$ (39,519)	$ (37,375)	$ (33,574)	$ (31,199)	(204,664)	(141,667)	(132,491)
Net income	$ 29,605	$ 98,007	$ 76,003	$ 71,857	$ 68,549	$ 65,245	$ 60,457	$ 52,531	275,474	246,784	226,082
Reclassification adjustment for losses realized in net income, Before-tax Amount									130	467	521
Reclassification adjustment for losses realized in net income, Tax (Expense) Benefit									(50)	(180)	(201)
Reclassification adjustment for losses realized in net income, Net of Tax Amount									80	287	320
Reclassification adjustment for net losses (gains) realized in net income on investment securities available for sale, Before-tax Amount									289	(6,011)	(2,769)
Reclassification adjustment for net losses (gains) realized in net income on investment securities available for sale, Tax (Expense) Benefit									(111)	2,314	1,066
Reclassification adjustment for net losses (gains) realized in net income on investment securities available for sale, Net of Tax Amount									178	(3,697)	(1,703)
Net unrealized gains (losses) arising during the period, Before-tax Amount									1,038	(36,432)	(25,707)
Net unrealized gains (losses) arising during the period, Tax (Expense) Benefit									(362)	14,027	9,901
Net unrealized gains (losses) arising during the period, Net of Tax Amount									676	(22,405)	(15,806)
Other comprehensive income (loss), Before-tax Amount									1,408	(42,018)	(27,991)
Other comprehensive income (loss), Tax (Expense) Benefit									(503)	16,178	10,777
Net current period other comprehensive income (loss)									905	(25,840)	(17,214)
Comprehensive income, Net of Tax Amount									276,379	220,944	208,868
Parent Company
Condensed Financial Statements, Captions [Line Items]
Net income, Before-tax Amount									480,138	388,451	358,573
Net income, Tax (Expense) Benefit									(204,664)	(141,667)	(132,491)
Net income									275,474	246,784	226,082
Reclassification adjustment for losses realized in net income, Before-tax Amount									130	467	521
Reclassification adjustment for losses realized in net income, Tax (Expense) Benefit									(50)	(180)	(201)
Reclassification adjustment for losses realized in net income, Net of Tax Amount									80	287	320
Reclassification adjustment for net losses (gains) realized in net income on investment securities available for sale, Before-tax Amount									(5,506)	(5,763)	0
Reclassification adjustment for net losses (gains) realized in net income on investment securities available for sale, Tax (Expense) Benefit									2,120	2,219	0
Reclassification adjustment for net losses (gains) realized in net income on investment securities available for sale, Net of Tax Amount									(3,386)	(3,544)	0
Net unrealized gains (losses) arising during the period, Before-tax Amount									0	2,358	2,908
Net unrealized gains (losses) arising during the period, Tax (Expense) Benefit									0	(908)	(1,120)
Net unrealized gains (losses) arising during the period, Net of Tax Amount									0	1,450	1,788
Other comprehensive gain (loss) of bank subsidiary, Before-tax Amount									6,784	(39,080)	(31,420)
Other comprehensive gain (loss) of bank subsidiary, Tax (expense) Benefit									(2,573)	15,047	12,098
Other comprehensive gain (loss) of bank subsidiary, Net of Tax Amount									4,211	(24,033)	(19,322)
Other comprehensive income (loss), Before-tax Amount									1,408	(42,018)	(27,991)
Other comprehensive income (loss), Tax (Expense) Benefit									(503)	16,178	10,777
Net current period other comprehensive income (loss)									905	(25,840)	(17,214)
Comprehensive income, Net of Tax Amount									$ 276,379	$ 220,944	$ 208,868