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	8,579	6,702	1,877		8,579
Other comprehensive income, net of tax:
Unrealized holding (losses) gains arising during period, net of taxes and realized net gains	2,118							2,118
Pension liability adjustment, net of taxes	324							324
Conversion of class B common stock to class A common stock		2	(2)
Stock options exercised	130	6		124
Cash dividends paid		(852)	(240)			(852)	(240)
Ending balance at Jun. 30, 2012	170,708	3,556	1,992	11,711	153,526			(77)
Beginning balance at Mar. 31, 2012
Net income	4,771	3,727	1,044
Other comprehensive income, net of tax:
Unrealized holding (losses) gains arising during period, net of taxes and realized net gains	382
Pension liability adjustment, net of taxes	162
Ending balance at Jun. 30, 2012	170,708	3,556	1,992
Beginning balance at Dec. 31, 2012	179,990	3,568	1,986	11,891	162,892			(347)
Net income	9,502	7,437	2,065		9,502
Other comprehensive income, net of tax:
Unrealized holding (losses) gains arising during period, net of taxes and realized net gains	(22,553)							(22,553)
Pension liability adjustment, net of taxes	347							347
Conversion of class B common stock to class A common stock		4	(4)
Stock options exercised	42	2		40
Cash dividends paid		(857)	(238)			(857)	(238)
Ending balance at Jun. 30, 2013	166,233	3,574	1,982	11,931	171,299			(22,553)
Beginning balance at Mar. 31, 2013
Net income	5,026	3,935	1,091
Other comprehensive income, net of tax:
Unrealized holding (losses) gains arising during period, net of taxes and realized net gains	(19,437)
Pension liability adjustment, net of taxes	174
Ending balance at Jun. 30, 2013	$ 166,233	$ 3,574	$ 1,982