Consolidated Statements of Changes in Shareholders' Equity (USD $) In Thousands, unless otherwise specified	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, 2011	$ 160,649	$ 3,548	$ 1,994	$ 11,587	$ 146,039			$ (2,519)
Net income	19,039	14,877	4,162		19,039
Other comprehensive income, net of tax:
Unrealized holding (losses) gains arising during period, net of taxes and realized net gains	4,011							4,011
Pension liability adjustment, net of taxes	(1,839)							(1,839)
Conversion of Class B Common Stock to Class A Common Stock		8	(8)
Stock options exercised	304	12		292
Cashless stock options exercised	12			12
Cash dividends		(1,708)	(478)			(1,708)	(478)
Ending balance at Dec. 31, 2012	179,990	3,568	1,986	11,891	162,892			(347)
Net income	20,046	15,698	4,348		20,046
Other comprehensive income, net of tax:
Unrealized holding (losses) gains arising during period, net of taxes and realized net gains	(13,375)							(13,375)
Unrealized losses on securities transferred to held-to-maturity net of taxes	(15,553)							(15,553)
Accretion of net unrealized losses transferred during the period, net of taxes	1,886							1,886
Pension liability adjustment, net of taxes	5,626							5,626
Conversion of Class B Common Stock to Class A Common Stock		10	(10)
Stock options exercised	43	2		41
Cash dividends		(1,716)	(475)			(1,716)	(475)
Ending balance at Dec. 31, 2013	176,472	3,580	1,976	11,932	180,747			(21,763)
Net income	21,860	17,157	4,703		21,860
Other comprehensive income, net of tax:
Unrealized holding (losses) gains arising during period, net of taxes and realized net gains	1,122							1,122
Accretion of net unrealized losses transferred during the period, net of taxes	3,188							3,188
Pension liability adjustment, net of taxes	(8,318)							(8,318)
Conversion of Class B Common Stock to Class A Common Stock		9	(9)
Stock options exercised	361	12		349
Cashless stock options exercised	11			11
Cash dividends		(1,723)	(473)			(1,723)	(473)
Ending balance at Dec. 31, 2014	$ 192,500	$ 3,601	$ 1,967	$ 12,292	$ 200,411			$ (25,771)