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 Loss [Member]
Beginning balance at Dec. 31, 2014	$ 192,500	$ 3,601	$ 1,967	$ 12,292	$ 200,411			$ (25,771)
Net income	17,050	13,392	3,658		17,050
Other comprehensive income, net of tax:
Unrealized holding (losses) gains arising during period, net of taxes	(104)							(104)
Accretion of unrealized losses on securities transferred to held-to-maturity net of taxes	2,697							2,697
Pension liability adjustment, net of taxes	639							639
Cash dividends	(1,296)					$ (1,296)	$ (354)
Ending balance at Sep. 30, 2015	211,132	3,601	1,967	12,292	215,811			(22,539)
Beginning balance at Dec. 31, 2015	214,544	3,601	1,967	12,292	221,232			(24,548)
Net income	18,034	14,165	3,869		18,034
Other comprehensive income, net of tax:
Unrealized holding (losses) gains arising during period, net of taxes	(148)							(148)
Accretion of unrealized losses on securities transferred to held-to-maturity net of taxes	2,274							2,274
Pension liability adjustment, net of taxes	727							727
Cash dividends	(1,296)					$ (1,296)	$ (354)
Ending balance at Sep. 30, 2016	$ 233,781	$ 3,601	$ 1,967	$ 12,292	$ 237,616			$ (21,695)