CHANGE IN ACCUMULATED OTHER COMPREHENSIVE LOSS - Schedule of Components of Other Comprehensive (Loss) Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income taxes	$ (22,904)	$ (25,767)	$ (66,880)	$ (49,929)
Salaries, benefits and other compensation	(74,453)	(72,294)	(219,669)	(211,413)
Income before taxes	97,167	99,111	272,400	188,142
Net income attributable to WSFS	74,166	73,382	205,248	137,926
Reclassification out of Accumulated Other Comprehensive Income (Loss)
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income attributable to WSFS	4,290	5,899	12,675	5,709
Reclassification out of Accumulated Other Comprehensive Income (Loss) | Net change in investment securities available-for-sale
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of net unrealized losses to income during the period	5,745	7,851	17,005	7,777
Income taxes	(1,379)	(1,884)	(4,081)	(1,866)
Net income attributable to WSFS	4,366	5,967	12,924	5,911
Reclassification out of Accumulated Other Comprehensive Income (Loss) | Prior service credits
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Salaries, benefits and other compensation	(19)	(19)	57	57
Reclassification out of Accumulated Other Comprehensive Income (Loss) | Actuarial gains
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Salaries, benefits and other compensation	(44)	(17)	(130)	(51)
Reclassification out of Accumulated Other Comprehensive Income (Loss) | Amortization of defined benefit pension plan-related items:
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income taxes	15	9	45	26
Income before taxes	(63)	(36)	(187)	(108)
Net income attributable to WSFS	(48)	(27)	(142)	(82)
Reclassification out of Accumulated Other Comprehensive Income (Loss) | Net unrealized gains on terminated cash flow hedges:
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of net unrealized losses to income during the period	(37)	(54)	(141)	(158)
Income taxes	9	13	34	38
Net income attributable to WSFS	$ (28)	$ (41)	$ (107)	$ (120)