Condensed Financial Information of Synovus Financial Corp. (Parent Company only) - Condensed Statements of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Operating Activities
Net income (loss)	$ 543,705	$ 757,902	$ 760,467
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Other	(7,329)	677	0
Net cash provided by (used in) operating activities	1,282,623	1,191,489	794,016
Investing Activities
Net cash provided by (used in) investing activities	323,966	(4,855,482)	(4,384,166)
Financing Activities
Repurchase of common stock	0	(12,987)	(199,932)
Repayments and redemption of long-term debt	(5,404,731)	(700,000)	0
Proceeds from long-term debt, net	3,220,912	3,622,892	0
Other	0	0	(1,104)
Net cash provided by (used in) financing activities	(1,132,943)	2,631,920	2,347,086
Increase (decrease) in cash and cash equivalents including restricted cash	473,646	(1,032,073)	(1,243,064)
Cash, cash equivalents, and restricted cash at beginning of year	1,977,780	3,009,853	4,252,917
Cash, cash equivalents, and restricted cash at end of year	2,451,426	1,977,780	3,009,853
Parent Company
Operating Activities
Net income (loss)	543,705	757,902	760,467
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Equity in undistributed (income) loss of subsidiaries	(141,994)	(448,555)	(368,702)
Deferred income tax expense (benefit)	433	143	(7,296)
Net increase (decrease) in other liabilities	4,849	3,233	(2,082)
Net (increase) decrease in other assets	(4,676)	8,022	5,280
Other	1,616	825	928
Net cash provided by (used in) operating activities	403,933	321,570	388,595
Investing Activities
Increase in other investments	(774)	(1,027)	(10,000)
Net cash provided by (used in) investing activities	(774)	(1,027)	(10,000)
Financing Activities
Dividends paid to common and preferred shareholders	(252,011)	(229,311)	(227,840)
Repurchase of common stock	0	(12,987)	(199,932)
Repayments and redemption of long-term debt	(97,033)	(300,000)	0
Proceeds from long-term debt, net	0	347,892	0
Other	0	0	(1,104)
Net cash provided by (used in) financing activities	(349,044)	(194,406)	(428,876)
Increase (decrease) in cash and cash equivalents including restricted cash	54,115	126,137	(50,281)
Cash, cash equivalents, and restricted cash at beginning of year	524,485	398,348	448,629
Cash, cash equivalents, and restricted cash at end of year	$ 578,600	$ 524,485	$ 398,348