CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Statement of Comprehensive Income [Abstract]
Net income, before-tax amount	$ 161,013	$ 259,871
Net income, tax	(36,943)	(57,712)
Net income	124,070	202,159
Before-tax Amount
Net unrealized gains (losses) arising during the period	(155,636)	153,081
Reclassification adjustment for realized (gains) losses included in net income	0	(1,030)
Net change	(155,636)	152,051
Income Tax
Net unrealized gains (losses) arising during the period	37,586	(37,260)
Reclassification adjustment for realized (gains) losses included in net income	0	251
Net change	37,586	(37,009)
Net of Tax Amount
Net unrealized gains (losses) arising during the period	(118,050)	115,821
Reclassification adjustment for realized (gains) losses included in net income	0	(779)
Net change	(118,050)	115,042
Before-tax Amount
Net unrealized gains (losses) arising during the period	(57,056)	10,000
Reclassification adjustment for realized (gains) losses included in net income	39,823	39,892
Net change	(17,233)	49,892
Income Tax
Net unrealized gains (losses) arising during the period	13,779	(2,434)
Reclassification adjustment for realized (gains) losses included in net income	(9,617)	(9,710)
Net change	4,162	(12,144)
Net of Tax Amount
Net unrealized gains (losses) arising during the period	(43,277)	7,566
Reclassification adjustment for realized (gains) losses included in net income	30,206	30,182
Net change	(13,071)	37,748
Total other comprehensive income (loss)	(172,869)	201,943
Total other comprehensive income (loss), income tax	41,748	(49,153)
Total other comprehensive income (loss), net of tax amount	(131,121)	152,790
Comprehensive income (loss)	(7,051)	354,949
Less: comprehensive income (loss) attributable to noncontrolling interest	(437)	0
Comprehensive income (loss) attributable to Synovus Financial Corp.	$ (6,614)	$ 354,949