Parent Company Financial Information - Condensed Statements of Cash Flows (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating activities:
Net income attributable to WSFS	$ 45,704	$ 53,882	$ 36,200	$ 13,023	$ 29,718	$ 38,935	$ 28,740	$ 37,350	$ 148,809	$ 134,743	$ 50,244
Adjustments to reconcile net income to net cash provided by operating activities:
Unrealized gains on equity investments									(26,175)	(20,745)	0
Decrease in other assets									(4,676)	(6,297)	(2,517)
Increase (decrease) in accrued interest payable									1,203	863	(114)
Increase (decrease) in other liabilities									30,922	(2,931)	7,353
Net cash provided by operating activities									89,866	135,574	130,168
Investing activities:
Sale of Visa Class B shares									0	6,186	0
Payments To Acquire Non Marketable Securities									0	(1,568)	(10,072)
Net cash provided by (used for) investing activities									293,823	(359,910)	(388,786)
Financing activities:
Issuance of common stock and exercise of common stock options									7,755	11,253	3,421
Redemption of senior debt									0	0	(55,000)
Purchase of treasury stock									(97,186)	(31,202)	(11,752)
Dividends paid									(22,463)	(13,249)	(9,425)
Net cash (used for) provided by financing activities									(432,694)	121,227	160,561
(Decrease) increase in cash and cash equivalents									(49,005)	(103,109)	(98,057)
Cash and cash equivalents at beginning of period				620,757				723,866	620,757	723,866	821,923
Cash and cash equivalents at end of period	571,752				620,757				571,752	620,757	723,866
WSFS Financial Corporation
Operating activities:
Net income attributable to WSFS									148,809	134,743	50,244
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in undistributed (loss) income of subsidiaries									92,020	(97,626)	(35,722)
Equity Securities, FV-NI, Gain (Loss)									0	(3,757)	0
Unrealized gains on equity investments									(3,646)	(15,088)	0
Decrease in other assets									3,538	2,265	1,618
Increase (decrease) in other liabilities									6,012	(237)	1,422
Net cash provided by operating activities									246,733	20,300	17,562
Investing activities:
Payments for investment in and advances to subsidiaries									0	0	(1,360)
Sale or repayment of investments in and advances to subsidiaries									0	0	1,066
Sale of Visa Class B shares									0	6,186	0
Net cash for business combinations									(93,990)	0	0
Payments To Acquire Non Marketable Securities									0	(51)	(10,072)
Net cash provided by (used for) investing activities									(93,990)	6,135	(10,366)
Financing activities:
Issuance of common stock and exercise of common stock options									7,755	11,253	3,307
Redemption of senior debt									0	0	(55,000)
Purchase of treasury stock									(97,186)	(31,202)	(11,752)
Dividends paid									(22,463)	(13,249)	(9,425)
Net cash (used for) provided by financing activities									(111,894)	(33,198)	(72,870)
(Decrease) increase in cash and cash equivalents									40,849	(6,763)	(65,674)
Cash and cash equivalents at beginning of period				$ 30,581				$ 37,344	30,581	37,344	103,018
Cash and cash equivalents at end of period	$ 71,430				$ 30,581				$ 71,430	$ 30,581	$ 37,344