Employee Benefits (Schedule of plan's funded status and amounts recognized in consolidated statement of financial condition) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Employee Benefits
Projected and accumulated benefit obligation	$ (22,160)	$ (20,953)
Plan assets at fair value	21,835	20,628
Funded status included in accrued expenses and other liabilities	$ (325)	$ (325)