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	26,288				26,288
Other comprehensive income, net of tax:
Unrealized holding gains arising during period, net of taxes	195							195
Accretion of net unrealized losses transferred during the period, net of taxes	872							872
Pension liability adjustment, net of taxes	877							877
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		(1,299)	(353)			$ (1,299)	$ (353)
Ending balance at Sep. 30, 2018	286,877	3,608	1,960	12,292	292,114			(23,097)
Beginning balance at Jun. 30, 2018	277,481	3,608	1,960	12,292	283,084			(23,463)
Net income	9,581				9,581
Other comprehensive income, net of tax:
Unrealized holding gains arising during period, net of taxes	(164)							(164)
Accretion of net unrealized losses transferred during the period, net of taxes	238							238
Pension liability adjustment, net of taxes	292							292
Cash dividends		(432)	(119)			(432)	(119)
Ending balance at Sep. 30, 2018	286,877	3,608	1,960	12,292	292,114			(23,097)
Beginning balance at Dec. 31, 2018	300,439	3,608	1,960	12,292	301,488			(18,909)
Net income	28,967				28,967
Other comprehensive income, net of tax:
Unrealized holding gains arising during period, net of taxes	(156)							(156)
Accretion of net unrealized losses transferred during the period, net of taxes	574							574
Pension liability adjustment, net of taxes	790							790
Conversion of Class B Common Stock to Class A Common Stock		42	(42)
Cash dividends		(1,304)	(350)			(1,304)	(350)
Ending balance at Sep. 30, 2019	328,960	3,650	1,918	12,292	328,801			(17,701)
Beginning balance at Jun. 30, 2019	318,937	3,620	1,948	12,292	319,270			(18,193)
Net income	10,084			0	10,084			0
Other comprehensive income, net of tax:
Unrealized holding gains arising during period, net of taxes	74							74
Accretion of net unrealized losses transferred during the period, net of taxes	155							155
Pension liability adjustment, net of taxes	263							263
Conversion of Class B Common Stock to Class A Common Stock		30	(30)
Cash dividends		(438)	(115)			$ (438)	$ (115)
Ending balance at Sep. 30, 2019	$ 328,960	$ 3,650	$ 1,918	$ 12,292	$ 328,801			$ (17,701)