Segment Information - Details of Segment Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Interest income	$ 254,726	$ 216,578	$ 182,576
Noninterest income	124,644	105,061	90,256
Total revenue	379,370	321,639	272,832
Interest expense	33,455	22,833	15,776
Noninterest expenses	226,461	188,666	165,460
Provision for loan losses	10,964	12,986	7,790
Total expenses	270,880	224,485	189,026
Income before taxes	108,490	97,154	83,806
Provision for income taxes	58,246	33,074	30,273
Net income	50,244	64,080	53,533
Inter-Segment Eliminations
Segment Reporting Information [Line Items]
Interest income	18,579	12,113	10,185
Noninterest income	8,607	9,098	8,957
Total revenue	27,186	21,211	19,142
Interest expense	18,579	12,113	10,185
Noninterest expenses	8,607	9,098	8,957
Total expenses	27,186	21,211	19,142
External Customer
Segment Reporting Information [Line Items]
Total revenue	406,556	342,850	291,974
Total expenses	298,066	245,696	208,168
WSFS Bank
Segment Reporting Information [Line Items]
Interest income	245,932	208,525	174,636
Noninterest income	45,749	42,565	37,042
Total revenue	291,681	251,090	211,678
Interest expense	32,249	22,028	15,155
Noninterest expenses	158,942	146,526	129,138
Provision for loan losses	10,527	9,370	7,476
Total expenses	201,718	177,924	151,769
Income before taxes	97,213	78,171	63,757
WSFS Bank | Inter-Segment Eliminations
Segment Reporting Information [Line Items]
Interest income	9,567	4,963	3,507
Noninterest income	7,651	8,145	7,988
Total revenue	17,218	13,108	11,495
Interest expense	9,012	7,150	6,678
Noninterest expenses	956	953	969
Total expenses	9,968	8,103	7,647
WSFS Bank | External Customer
Segment Reporting Information [Line Items]
Total revenue	308,899	264,198	223,173
Total expenses	211,686	186,027	159,416
Cash Connect
Segment Reporting Information [Line Items]
Interest income	0	0	0
Noninterest income	42,641	35,776	30,421
Total revenue	42,641	35,776	30,421
Interest expense	0	0	0
Noninterest expenses	26,654	22,442	19,271
Provision for loan losses	0	0	0
Total expenses	26,654	22,442	19,271
Income before taxes	7,382	8,455	7,864
Cash Connect | Inter-Segment Eliminations
Segment Reporting Information [Line Items]
Interest income	0	0	0
Noninterest income	810	835	873
Total revenue	810	835	873
Interest expense	6,812	2,915	1,547
Noninterest expenses	2,603	2,799	2,612
Total expenses	9,415	5,714	4,159
Cash Connect | External Customer
Segment Reporting Information [Line Items]
Total revenue	43,451	36,611	31,294
Total expenses	36,069	28,156	23,430
Wealth Management
Segment Reporting Information [Line Items]
Interest income	8,794	8,053	7,940
Noninterest income	36,254	26,720	22,793
Total revenue	45,048	34,773	30,733
Interest expense	1,206	805	621
Noninterest expenses	40,865	19,698	17,051
Provision for loan losses	437	3,616	314
Total expenses	42,508	24,119	17,986
Income before taxes	3,895	10,528	12,185
Wealth Management | Inter-Segment Eliminations
Segment Reporting Information [Line Items]
Interest income	9,012	7,150	6,678
Noninterest income	146	118	96
Total revenue	9,158	7,268	6,774
Interest expense	2,755	2,048	1,960
Noninterest expenses	5,048	5,346	5,376
Total expenses	7,803	7,394	7,336
Wealth Management | External Customer
Segment Reporting Information [Line Items]
Total revenue	54,206	42,041	37,507
Total expenses	$ 50,311	$ 31,513	$ 25,322