Parent Company Financial Information - Condensed Statements of Financial Condition (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Sep. 01, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Assets:
Cash	$ 723,866		$ 821,923	$ 561,179	$ 508,039
Other assets	76,416		84,892
Total assets	6,999,540		6,765,270
Liabilities:
Trust preferred securities	67,011		67,011
Senior debt	98,171	$ 55,000	152,050
Interest payable	1,037		1,151
Other liabilities	88,748		70,898
Total liabilities	6,275,195		6,077,934
Stockholders’ Equity:
Common stock	563		580
Capital in excess of par value	336,271		329,457
Accumulated other comprehensive loss	(8,152)		(7,617)
Retained earnings	669,557		627,078
Treasury stock	(273,894)		(262,162)
Total stockholders’ equity	724,345		687,336	580,471	489,051
Total liabilities and stockholders’ equity	6,999,540		6,765,270
WSFS Financial Corporation
Assets:
Cash	37,344		103,018	$ 26,456	$ 54,331
Investment in subsidiaries	833,763		795,676
Investment in Capital Trust III	2,011		2,011
Other assets	17,465		6,480
Total assets	890,583		907,185
Liabilities:
Trust preferred securities	67,011		67,011
Senior debt	98,171		152,050
Interest payable	388		642
Other liabilities	668		146
Total liabilities	166,238		219,849
Stockholders’ Equity:
Common stock	563		580
Capital in excess of par value	336,271		329,457
Accumulated other comprehensive loss	(8,152)		(7,617)
Retained earnings	669,557		627,078
Treasury stock	(273,894)		(262,162)
Total stockholders’ equity	724,345		687,336
Total liabilities and stockholders’ equity	$ 890,583		$ 907,185