Stockholders' Equity and Regulatory Capital - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2005	Dec. 31, 2018
Capital Unit [Line Items]
Ratio of common equity Tier 1 capital to risk-weighted assets (as percent)	4.50%		4.50%
Ratio of Tier 1 capital to risk-weighted assets (as percent)	13.29%		12.04%
Ratio of total capital to risk-weighted assets (as percent)	13.78%		12.71%
Tier 1 leverage ratio (as percent)	11.54%		10.37%
Common stock outstanding, par value (in dollars per share)	$ 0.01		$ 0.01
Coupon rate (as percent)	3.68%
Cash remains at the holding company	$ 71.4
Minimum annual net income expected (as percent)	25.00%
Treasury Stock
Capital Unit [Line Items]
Stock repurchased (in shares)	2,132,390
Additional Stock Buyback Program
Capital Unit [Line Items]
Common stock average repurchase price (in dollars per share)	$ 42.83
Minimum
Capital Unit [Line Items]
Ratio of common equity Tier 1 capital to risk-weighted assets (as percent)	4.50%
Ratio of Tier 1 capital to risk-weighted assets (as percent)	6.00%
Ratio of total capital to risk-weighted assets (as percent)	8.00%
Tier 1 leverage ratio (as percent)	4.00%
WSFS Capital Trust III
Capital Unit [Line Items]
Pooled floating rate securities, par value		$ 2.0
Pooled floating rate securities issued		$ 67.0
LIBOR Rate | WSFS Capital Trust III
Capital Unit [Line Items]
Variable interest rate (as percent)		1.77%
Trust preferred borrowings | LIBOR Rate | WSFS Capital Trust III
Capital Unit [Line Items]
Variable interest rate (as percent)		1.77%