Stockholders' Equity and Regulatory Capital - Schedule of Capital Position (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Capital Unit [Line Items]
Total Capital (to risk-weighted assets), Consolidated Bank Capital Amount	$ 659,376	$ 624,440
Tier 1 Capital (to risk-weighted assets), Consolidated Bank Capital Amount	617,945	583,715
Common Equity Tier 1 Capital (to risk-weighted assets), Consolidated Bank Capital Amount	552,982	518,856
Tier 1 Capital (to adjusted tangible assets), Consolidated Bank Capital Amount	$ 617,945	$ 583,715
Total Capital (to risk-weighted assets), Consolidated Bank Capital Percent	11.41%	11.20%
Tier 1 Capital (to risk-weighted assets), Consolidated Bank Capital Percent	10.70%	10.47%
Common Equity Tier 1 Capital (to risk-weighted assets), Consolidated Bank Capital Percent	9.57%	9.31%
Tier 1 Leverage Capital (to adjusted tangible assets), Consolidated Bank Capital Percent	9.15%	9.02%
Total Capital (to risk-weighted assets), For Capital Adequacy Purposes Amount	$ 462,195	$ 446,001
Tier 1 Capital (to risk-weighted assets), For Capital Adequacy Purposes Amount	346,646	334,501
Common Equity Tier 1 Capital (to risk-weighted assets), For Capital Adequacy Purposes Amount	259,984	250,875
Tier 1 Leverage Capital (to adjusted tangible assets), For Capital Adequacy Purposes Amount	$ 270,249	$ 258,767
Total Capital (to risk-weighted assets), For Capital Adequacy Purposes Percentage	8.00%	8.00%
Tier 1 Capital (to risk-weighted assets), For Capital Adequacy Purposes Percentage	6.00%	6.00%
Common Equity Tier 1 Capital (to risk-weighted assets), For Capital Adequacy Purposes Percentage	4.50%	4.50%
Tier 1 Leverage Capital (to adjusted tangible assets), For Capital Adequacy Purposes Percentage	4.00%	4.00%
Total Capital (to risk-weighted assets), To Be Well-Capitalized Under Prompt Corrective Action Provisions Amount	$ 577,743	$ 557,501
Tier 1 Capital (to risk-weighted assets), To Be Well-Capitalized Under Prompt Corrective Action Provisions Amount	462,195	446,001
Common Equity Tier 1 Capital (to risk-weighted assets), To Be Well-Capitalized Under Prompt Corrective Action Provisions Amount	375,533	362,376
Tier 1 Leverage Capital (to adjusted tangible assets), To Be Well-Capitalized Under Prompt Corrective Action Provisions Amount	$ 337,812	$ 323,459
Total Capital (to risk-weighted assets), To Be Well-Capitalized Under Prompt Corrective Action Provisions Percentage	10.00%	10.00%
Tier 1 Capital (to risk-weighted assets), To Be Well-Capitalized Under Prompt Corrective Action Provisions Percentage	8.00%	8.00%
Common Equity Tier 1 Capital (to risk-weighted assets), To Be Well-Capitalized Under Prompt Corrective Action Provisions Percentage	6.50%	6.50%
Tier 1 Leverage Capital (to adjusted tangible assets), To Be Well-Capitalized Under Prompt Corrective Action Provisions Percentage	5.00%	5.00%
WSFS Bank
Capital Unit [Line Items]
Total Capital (to risk-weighted assets), Consolidated Bank Capital Amount	$ 695,739	$ 663,892
Tier 1 Capital (to risk-weighted assets), Consolidated Bank Capital Amount	654,308	623,167
Common Equity Tier 1 Capital (to risk-weighted assets), Consolidated Bank Capital Amount	654,308	623,167
Tier 1 Capital (to adjusted tangible assets), Consolidated Bank Capital Amount	$ 654,308	$ 623,167
Total Capital (to risk-weighted assets), Consolidated Bank Capital Percent	12.08%	11.93%
Tier 1 Capital (to risk-weighted assets), Consolidated Bank Capital Percent	11.36%	11.19%
Common Equity Tier 1 Capital (to risk-weighted assets), Consolidated Bank Capital Percent	11.36%	11.19%
Tier 1 Leverage Capital (to adjusted tangible assets), Consolidated Bank Capital Percent	9.73%	9.66%
Total Capital (to risk-weighted assets), For Capital Adequacy Purposes Amount	$ 460,639	$ 445,376
Tier 1 Capital (to risk-weighted assets), For Capital Adequacy Purposes Amount	345,480	334,032
Common Equity Tier 1 Capital (to risk-weighted assets), For Capital Adequacy Purposes Amount	259,110	250,524
Tier 1 Leverage Capital (to adjusted tangible assets), For Capital Adequacy Purposes Amount	$ 269,008	$ 257,957
Total Capital (to risk-weighted assets), For Capital Adequacy Purposes Percentage	8.00%	8.00%
Tier 1 Capital (to risk-weighted assets), For Capital Adequacy Purposes Percentage	6.00%	6.00%
Common Equity Tier 1 Capital (to risk-weighted assets), For Capital Adequacy Purposes Percentage	4.50%	4.50%
Tier 1 Leverage Capital (to adjusted tangible assets), For Capital Adequacy Purposes Percentage	4.00%	4.00%
Total Capital (to risk-weighted assets), To Be Well-Capitalized Under Prompt Corrective Action Provisions Amount	$ 575,799	$ 556,720
Tier 1 Capital (to risk-weighted assets), To Be Well-Capitalized Under Prompt Corrective Action Provisions Amount	460,639	445,376
Common Equity Tier 1 Capital (to risk-weighted assets), To Be Well-Capitalized Under Prompt Corrective Action Provisions Amount	374,270	361,868
Tier 1 Leverage Capital (to adjusted tangible assets), To Be Well-Capitalized Under Prompt Corrective Action Provisions Amount	$ 336,260	$ 322,446
Total Capital (to risk-weighted assets), To Be Well-Capitalized Under Prompt Corrective Action Provisions Percentage	10.00%	10.00%
Tier 1 Capital (to risk-weighted assets), To Be Well-Capitalized Under Prompt Corrective Action Provisions Percentage	8.00%	8.00%
Common Equity Tier 1 Capital (to risk-weighted assets), To Be Well-Capitalized Under Prompt Corrective Action Provisions Percentage	6.50%	6.50%
Tier 1 Leverage Capital (to adjusted tangible assets), To Be Well-Capitalized Under Prompt Corrective Action Provisions Percentage	5.00%	5.00%