CHANGE IN ACCUMULATED OTHER COMPREHENSIVE LOSS - Components of Other Comprehensive (Loss) Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income taxes	$ (23,035)	$ (22,425)	$ (43,976)	$ (24,162)
Salaries, benefits and other compensation	(72,367)	(68,189)	(145,216)	(139,119)
Income before taxes	91,630	83,327	175,233	89,031
Net income attributable to WSFS	68,678	60,740	131,082	64,544
Reclassification out of Accumulated Other Comprehensive Income (Loss)
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income attributable to WSFS	4,306	(39)	8,384	(191)
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 gains to income during the period	5,779	37	11,260	(74)
Income taxes	(1,386)	(9)	(2,702)	18
Net income attributable to WSFS	4,393	28	8,558	(56)
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)	38	38
Reclassification out of Accumulated Other Comprehensive Income (Loss) | Actuarial (gains) losses
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Salaries, benefits and other compensation	(43)	(17)	(86)	(34)
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	30	17
Income before taxes	(62)	(36)	(124)	(72)
Net income attributable to WSFS	(47)	(27)	(94)	(55)
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 gains to income during the period	(53)	(53)	(105)	(105)
Income taxes	13	13	25	25
Net income attributable to WSFS	$ (40)	$ (40)	$ (80)	$ (80)