SEGMENT INFORMATION - Details of Segment Information - Statement of Financial Condition (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Cash and cash equivalents	$ 711,372	$ 723,866	$ 733,365	$ 821,923
Goodwill	166,007	166,007
Other segment assets	6,282,463	6,109,667
Total assets	7,159,842	6,999,540
Capital expenditures	4,908	8,994
WSFS Bank
Segment Reporting Information [Line Items]
Cash and cash equivalents	132,857	104,530
Goodwill	145,808	145,808
Other segment assets	6,053,095	5,882,910
Total assets	6,331,760	6,133,248
Capital expenditures	4,252	8,197
Cash Connect
Segment Reporting Information [Line Items]
Cash and cash equivalents	564,915	611,385
Goodwill	0	0
Other segment assets	8,098	6,078
Total assets	573,013	617,463
Capital expenditures	340	184
Wealth Management
Segment Reporting Information [Line Items]
Cash and cash equivalents	13,600	7,951
Goodwill	20,199	20,199
Other segment assets	221,270	220,679
Total assets	255,069	248,829
Capital expenditures	$ 316	$ 613