Condensed Financial Information Of Synovus Financial Corp. (Parent Company Only) (Condensed Statements of Cash Flows) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Adjustments to reconcile net income to net cash provided by operating activities:
Net cash provided by operating activities	$ 641,626	$ 461,637	$ 444,986
Investing Activities
Proceeds from sales of investment securities available for sale	812,293	968,606	347,954
Net cash used in investing activities	(1,415,541)	(1,099,465)	(2,106,717)
Financing Activities
Repurchases of common stock	(175,079)	(263,084)	(199,221)
Repayments and redemption of long-term debt	(2,250,422)	(2,263,688)	(823,899)
Proceeds from issuance of long-term debt	1,771,866	1,875,000	871,644
Earnout payment	(892)	0	0
Net cash provided by financing activities	776,588	665,911	1,543,334
Increase (decrease) in cash and cash equivalents	2,673	28,083	(118,397)
Cash and cash equivalents at beginning of year	395,175	367,092	485,489
Cash and cash equivalents at end of year	397,848	395,175	367,092
Income tax payments, net	18,040	9,340	10,514
Interest paid	143,237	123,560	115,795
Parent Company
Operating Activities
Net income	275,474	246,784	226,082
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in undistributed loss (income) of subsidiaries	129,858	37,521	(30,847)
Deferred income tax expense (benefit)	60,931	17,989	(2,506)
Net (decrease) increase in other liabilities	(1,095)	7,746	(1,709)
Net (increase) decrease in other assets	(8)	(9,214)	1,045
Other, net	(3,330)	(1,648)	(178)
Net cash provided by operating activities	461,830	299,178	191,887
Investing Activities
Proceeds from sales of investment securities available for sale	4,305	0	0
Net cash received (used) in acquisitions/dispositions	0	(3,408)	0
Net decrease in short-term notes receivable from non-bank subsidiaries	35,200	31,800	10,000
Net cash used in investing activities	39,505	28,392	10,000
Financing Activities
Dividends paid to common and preferred shareholders	(64,908)	(69,663)	(65,592)
Repurchases of common stock	(175,079)	(263,084)	(199,221)
Repayments and redemption of long-term debt	(600,386)	(130,048)	(48,553)
Proceeds from issuance of long-term debt	296,866	0	246,644
Earnout payment	(892)	0	0
Net cash provided by financing activities	(544,399)	(462,795)	(66,722)
Increase (decrease) in cash and cash equivalents	(43,064)	(135,225)	135,165
Cash and cash equivalents at beginning of year	254,250	389,475	254,310
Cash and cash equivalents at end of year	211,186	254,250	389,475
Income tax payments, net	18,000	9,500	8,700
Interest paid	$ 51,000	$ 53,100	$ 46,900