Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Class A Common Stock [Member]	Class B Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Retained Earnings [Member] Class A Common Stock [Member]	Retained Earnings [Member] Class B Common Stock [Member]	Accumulated Other Comprehensive Loss [Member]
Beginning balance at Dec. 31, 2017	$ 260,297	$ 3,606	$ 1,962	$ 12,292	$ 263,666			$ (21,229)
Net income	7,709				7,709
Other comprehensive income, net of tax:
Unrealized holding gains arising during period, net of taxes	71							71
Accretion of net unrealized losses transferred during the period, net of taxes	381							381
Pension liability adjustment, net of taxes	293							293
Adoption of ASU 2018-2, Income Statement-Reporting Comprehensive Income (Topic 220)-Reclassification of Certain Tax Effects from AOCI					3,783			(3,783)
Adoption of ASU 2016-1, Financial Instruments-Overall (Subtopic 825-10) Recognition and Measurement of Financial Assets and Financial Liabilities					29			(29)
Conversion of Class B Common Stock to Class A Common Stock		2	(2)
Cash dividends						$ (434)	$ (117)
Ending balance at Mar. 31, 2018	268,200	3,608	1,960	12,292	274,636			(24,296)
Beginning balance at Dec. 31, 2018	300,439	3,608	1,960	12,292	301,488			(18,909)
Net income	9,418				9,418
Other comprehensive income, net of tax:
Unrealized holding gains arising during period, net of taxes	(462)							(462)
Accretion of net unrealized losses transferred during the period, net of taxes	216							216
Pension liability adjustment, net of taxes	263							263
Conversion of Class B Common Stock to Class A Common Stock		2	(2)
Cash dividends						$ (433)	$ (117)
Ending balance at Mar. 31, 2019	$ 309,324	$ 3,610	$ 1,958	$ 12,292	$ 310,356			$ (18,892)