Stockholders' Equity and Regulatory Capital - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2005	Dec. 31, 2019	Dec. 31, 2017	Dec. 31, 2015
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)	12.04%			10.70%
Ratio of total capital to risk-weighted assets (as percent)	12.71%			11.41%
Tier 1 leverage ratio (as percent)	10.37%			9.15%
Common stock outstanding, par value (in dollars per share)	$ 0.01			$ 0.01
Coupon rate (as percent)	4.51%
Cash remains at the holding company	$ 30.6
Authorized repurchase amount (as percent)					5.00%
Minimum annual net income expected (as percent)	25.00%
Additional Stock Buyback Program
Capital Unit [Line Items]
Shares authorized to repurchase of common stock (in shares)	691,742
Common stock average repurchase price (in dollars per share)	$ 45.06
Additional Stock Buyback Program | Forecast
Capital Unit [Line Items]
Authorized amount			$ 15.4
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%