SEGMENT INFORMATION - Details of Segment Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Segment Reporting Information [Line Items]
Interest income	$ 67,613	$ 60,826
Noninterest income	47,467	28,092
Total revenue	115,080	88,918
Interest expense	9,899	7,723
Noninterest expenses	53,412	51,506
Provision for loan losses	3,650	2,162
Total expenses	66,961	61,391
Income before taxes	48,119	27,527
Income tax provision	10,769	8,590
Net income	37,350	18,937
Inter-Segment Eliminations
Segment Reporting Information [Line Items]
Interest income	5,331	4,061
Noninterest income	2,323	2,391
Total revenue	7,654	6,452
Interest expense	5,331	4,061
Noninterest expenses	2,323	2,391
Total expenses	7,654	6,452
Operating Segments
Segment Reporting Information [Line Items]
Total revenue	122,734	95,370
Total expenses	74,615	67,843
WSFS Bank
Segment Reporting Information [Line Items]
Interest income	65,290	58,688
Noninterest income	26,606	10,167
Total revenue	91,896	68,855
Interest expense	9,503	7,463
Noninterest expenses	39,435	38,960
Provision for loan losses	3,661	1,716
Total expenses	52,599	48,139
Income before taxes	41,795	22,584
WSFS Bank | Inter-Segment Eliminations
Segment Reporting Information [Line Items]
Interest income	2,968	1,996
Noninterest income	2,108	2,164
Total revenue	5,076	4,160
Interest expense	2,363	2,065
Noninterest expenses	215	227
Total expenses	2,578	2,292
WSFS Bank | Operating Segments
Segment Reporting Information [Line Items]
Total revenue	96,972	73,015
Total expenses	55,177	50,431
Cash Connect
Segment Reporting Information [Line Items]
Interest income	0	0
Noninterest income	11,353	9,677
Total revenue	11,353	9,677
Interest expense	0	0
Noninterest expenses	7,319	6,135
Provision for loan losses	0	0
Total expenses	7,319	6,135
Income before taxes	1,484	1,613
Cash Connect | Inter-Segment Eliminations
Segment Reporting Information [Line Items]
Interest income	0	0
Noninterest income	181	191
Total revenue	181	191
Interest expense	2,059	1,405
Noninterest expenses	672	715
Total expenses	2,731	2,120
Cash Connect | Operating Segments
Segment Reporting Information [Line Items]
Total revenue	11,534	9,868
Total expenses	10,050	8,255
Wealth Management
Segment Reporting Information [Line Items]
Interest income	2,323	2,138
Noninterest income	9,508	8,248
Total revenue	11,831	10,386
Interest expense	396	260
Noninterest expenses	6,658	6,411
Provision for loan losses	(11)	446
Total expenses	7,043	7,117
Income before taxes	4,840	3,330
Wealth Management | Inter-Segment Eliminations
Segment Reporting Information [Line Items]
Interest income	2,363	2,065
Noninterest income	34	36
Total revenue	2,397	2,101
Interest expense	909	591
Noninterest expenses	1,436	1,449
Total expenses	2,345	2,040
Wealth Management | Operating Segments
Segment Reporting Information [Line Items]
Total revenue	14,228	12,487
Total expenses	$ 9,388	$ 9,157