Consolidated Statements of Changes in Stockholders' Equity (unaudited) - 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 Income (Loss) [Member]
Beginning balance at Dec. 31, 2015	$ 214,544	$ 3,601	$ 1,967	$ 12,292	$ 221,232			$ (24,548)
Net income	11,549				11,549
Other comprehensive income, net of tax:
Unrealized holding (losses) gains arising during period, net of taxes	(38)							(38)
Accretion of unrealized losses on securities transferred to held-to-maturity, net of taxes	1,747							1,747
Pension liability adjustment, net of taxes	485							485
Cash dividends						$ (866)	$ (235)
Ending balance at Jun. 30, 2016	227,186	3,601	1,967	12,292	231,680			(22,354)
Beginning balance at Dec. 31, 2016	240,041	3,601	1,967	12,292	243,565			(21,384)
Net income	14,253				14,253
Other comprehensive income, net of tax:
Unrealized holding (losses) gains arising during period, net of taxes	333							333
Accretion of unrealized losses on securities transferred to held-to-maturity, net of taxes	633							633
Pension liability adjustment, net of taxes	465							465
Conversion of Class B Common Stock to Class A Common Stock		3	(3)
Cash dividends						$ (865)	$ (235)
Ending balance at Jun. 30, 2017	$ 254,625	$ 3,604	$ 1,964	$ 12,292	$ 256,718			$ (19,953)