Available-for-Sale Securities - Company's Securities' Gross Unrealized Losses and Fair Values, Aggregated by Length of Time Individual Securities Have Been in a Continuous Unrealized Loss Position (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Schedule Of Available For Sale Securities [Line Items]
Securities With Gross Unrealized Losses Less Than 12 Months, Fair Value	$ 29,956	$ 4,995
Securities With Gross Unrealized Losses Less Than 12 Months, Unrealized Losses	(4)	(2)
Securities With Gross Unrealized Losses 12 Months or More, Fair Value	21,415	21,274
Securities With Gross Unrealized Losses 12 Months or More, Unrealized Losses	(79)	(428)
Securities With Gross Unrealized Losses, Total Fair Value	51,371	26,269
Securities With Gross Unrealized Losses, Total Unrealized Losses	(83)	(430)
U.S. Government and Federal Agencies
Schedule Of Available For Sale Securities [Line Items]
Securities With Gross Unrealized Losses 12 Months or More, Fair Value	20,852	20,515
Securities With Gross Unrealized Losses 12 Months or More, Unrealized Losses	(75)	(409)
Securities With Gross Unrealized Losses, Total Fair Value	20,852	20,515
Securities With Gross Unrealized Losses, Total Unrealized Losses	(75)	(409)
FNMA Certificates
Schedule Of Available For Sale Securities [Line Items]
Securities With Gross Unrealized Losses 12 Months or More, Fair Value	563	759
Securities With Gross Unrealized Losses 12 Months or More, Unrealized Losses	(4)	(19)
Securities With Gross Unrealized Losses, Total Fair Value	563	759
Securities With Gross Unrealized Losses, Total Unrealized Losses	(4)	(19)
US Treasury
Schedule Of Available For Sale Securities [Line Items]
Securities With Gross Unrealized Losses Less Than 12 Months, Fair Value	29,956	4,995
Securities With Gross Unrealized Losses Less Than 12 Months, Unrealized Losses	(4)	(2)
Securities With Gross Unrealized Losses, Total Fair Value	29,956	4,995
Securities With Gross Unrealized Losses, Total Unrealized Losses	$ (4)	$ (2)