Business and Basis of Presentation (Details) $ / shares in Units, $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2019 $ / shares	Dec. 31, 2018 USD ($) Subsidiary Office	Dec. 31, 2017 USD ($)
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Number of office locations		76
Number of unconsolidated subsidiary | Subsidiary		1
Forecast
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Shares issued	0.3013
Cash paid per share (USD per share) | $ / shares	$ 2.93
Cypress
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Assets under management | $		$ 948.8	$ 901.5
West Capital
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Assets under management | $		695.5	$ 861.2
WSFS Capital Trust III
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Amount of aggregate principal issued | $		67.0
Trust preferred securities redeemed | $		$ 51.5
WSFS Financial Corporation
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Number of wholly-owned subsidiaries | Subsidiary		3
Delaware
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Number of office locations		45
Pennsylvania
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Number of office locations		29
Virginia
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Number of office locations		1
Nevada
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Number of office locations		1