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	16,707				16,707
Other comprehensive income, net of tax:
Unrealized holding gains arising during period, net of taxes	359							359
Accretion of net unrealized losses transferred during the period, net of taxes	634							634
Pension liability adjustment, net of taxes	585							585
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		(866)	(235)			$ (866)	$ (235)
Ending balance at Jun. 30, 2018	277,481	3,608	1,960	12,292	283,084			(23,463)
Beginning balance at Mar. 31, 2018	268,200	3,608	1,960	12,292	274,636			(24,296)
Net income	8,998				8,998
Other comprehensive income, net of tax:
Unrealized holding gains arising during period, net of taxes	288							288
Accretion of net unrealized losses transferred during the period, net of taxes	253							253
Pension liability adjustment, net of taxes	292							292
Cash dividends		(433)	(117)			(433)	(117)
Ending balance at Jun. 30, 2018	277,481	3,608	1,960	12,292	283,084			(23,463)
Beginning balance at Dec. 31, 2018	300,439	3,608	1,960	12,292	301,488			(18,909)
Net income	18,884				18,884
Other comprehensive income, net of tax:
Unrealized holding gains arising during period, net of taxes	(230)							(230)
Accretion of net unrealized losses transferred during the period, net of taxes	419							419
Pension liability adjustment, net of taxes	527							527
Conversion of Class B Common Stock to Class A Common Stock		12	(12)
Cash dividends		(867)	(235)			(867)	(235)
Ending balance at Jun. 30, 2019	318,937	3,622	1,948	12,292	319,270			(18,193)
Beginning balance at Mar. 31, 2019	309,324	3,610	1,958	12,292	310,356			(18,892)
Net income	9,466				9,466			0
Other comprehensive income, net of tax:
Unrealized holding gains arising during period, net of taxes	232							232
Accretion of net unrealized losses transferred during the period, net of taxes	203							203
Pension liability adjustment, net of taxes	264							264
Conversion of Class B Common Stock to Class A Common Stock		12	(12)
Cash dividends		(435)	(117)			$ (435)	$ (117)
Ending balance at Jun. 30, 2019	$ 318,937	$ 3,622	$ 1,948	$ 12,292	$ 319,270			$ (18,193)