Change in Accumulated Other Comprehensive Income (Loss) - Components of Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Realized gains on securities transactions	$ 331	$ 9,076	$ 333
Income taxes	(86,095)	(31,636)	(46,452)
Income before taxes	357,700	144,956	194,370
Net income attributable to WSFS	271,442	114,774	148,809
Reclassification out of Accumulated Other Comprehensive Income (Loss)
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income attributable to WSFS	(796)	(7,453)	(668)
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	20	75	33
Prior service (credits) costs	(85)	(266)	(76)
Actuarial gains	0	(47)	(63)
Income before taxes	(85)	(313)	(139)
Net income attributable to WSFS	(65)	(238)	(106)
Reclassification out of Accumulated Other Comprehensive Income (Loss) | Defined benefit pension plan settlement:
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income taxes	0	(67)	0
Actuarial gains	0	279	0
Net income attributable to WSFS	0	212	0
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	(497)	(444)	0
Income taxes	119	107	0
Net income attributable to WSFS	(378)	(337)	0
Reclassification out of Accumulated Other Comprehensive Income (Loss) | Securities available-for-sale: | Net change in investment securities available for sale
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Realized gains on securities transactions	(331)	(9,076)	(333)
Income taxes	79	2,178	80
Net income attributable to WSFS	(252)	(6,898)	(253)
Reclassification out of Accumulated Other Comprehensive Income (Loss) | Net unrealized holding gains on securities transferred between available-for-sale and held-to-maturity: | 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	(133)	(251)	(407)
Income taxes	32	59	98
Net income attributable to WSFS	$ (101)	$ (192)	$ (309)