Stockholders' Equity (Details) (USD $)	3 Months Ended								12 Months Ended												12 Months Ended				12 Months Ended					12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 Common Stock	Dec. 31, 2011 Common Stock	Dec. 31, 2010 Common Stock	Dec. 31, 2010 Common Stock Restatement	Dec. 31, 2012 Class A common stock	Dec. 31, 2011 Class A common stock	Dec. 31, 2010 Class A common stock	Dec. 31, 2009 Class A common stock	Dec. 31, 2010 Class A common stock Restatement	Dec. 31, 2012 Additional Paid-in Capital	Dec. 31, 2011 Additional Paid-in Capital	Dec. 31, 2010 Additional Paid-in Capital	Dec. 31, 2010 Additional Paid-in Capital Restatement	Dec. 31, 2012 Retained Earnings	Dec. 31, 2011 Retained Earnings	Dec. 31, 2010 Retained Earnings	Dec. 31, 2010 Retained Earnings Restatement	Dec. 31, 2010 Retained Earnings Cumulative effect of accounting change for adoption of ASU 2010-16	Dec. 31, 2012 Accumulated Other Comprehensive Loss	Dec. 31, 2011 Accumulated Other Comprehensive Loss	Dec. 31, 2010 Accumulated Other Comprehensive Loss	Dec. 31, 2010 Accumulated Other Comprehensive Loss Restatement
Changes in the components of stockholders' equity
Balance at the beginning of the period												$ 1,576,000	$ 1,564,000	$ 1,546,000	$ 1,564,000	$ 1,660,000	$ 1,660,000	$ 1,660,000	$ 1,660,000	$ 1,660,000	$ 3,464,000	$ 2,721,000	$ 1,664,000	$ 2,721,000	$ 108,090,000	$ 106,432,000	$ 103,559,000	$ 106,619,000	$ 187,000	$ (2,284,000)	$ (1,626,000)	$ (1,190,000)	$ (1,626,000)
Net earnings	(528,000)	1,147,000	1,817,000	2,371,000	2,120,000	2,039,000	1,238,000	(38,000)	4,807,000	5,359,000	6,743,000														4,807,000	5,359,000	6,743,000
Dividends paid, $.12 per share																									(3,575,000)	(3,888,000)	(3,870,000)
Issuance of nonvested stock awards, net of forfeitures												19,000	16,000	21,000							(19,000)	(16,000)	(21,000)
Stock-based compensation																					793,000	905,000	1,192,000
Unrealized gain (loss) on interest rate swap, net of income tax expense (benefit)									83,000	272,000	(245,000)																			83,000	272,000	(245,000)
Change in net actuarial loss and prior service cost, net of income tax expense										(1,994,000)																				(1,059,000)	(925,000)	(194,000)
Unrealized gain on available-for-sale securities, net of income tax expense									12,000	(5,000)	3,000																			12,000	(5,000)	3,000
Repurchase and retirement of common stock									(107,000)	(150,000)	(117,000)	(5,000)	(4,000)	(3,000)							(102,000)	(146,000)	(114,000)
Balance at the end of the period												1,590,000	1,576,000	1,564,000	1,564,000	1,660,000	1,660,000	1,660,000	1,660,000	1,660,000	4,136,000	3,464,000	2,721,000	2,721,000	109,322,000	108,090,000	106,432,000	106,619,000	187,000	(3,248,000)	(2,284,000)	(1,626,000)	(1,626,000)
Dividend paid (in dollars per share)									$ 0.11	$ 0.12	$ 0.12
Income tax expense on unrealized gain (loss) on interest rate swap									64,000	179,000	(167,000)
Income tax expense on change in pension net actuarial loss and prior service cost									699,000	609,000	133,000
Income tax expense on unrealized gain on available-for-sale securities									8,000	4,000	2,000
Accumulated other comprehensive loss
Net actuarial loss and prior service cost not yet recognized in net periodic benefit cost, net of income tax benefit	(3,265,000)				(2,206,000)				(3,265,000)	(2,206,000)
Unrealized loss on interest rate swap, net of income tax benefit					(83,000)					(83,000)
Accumulated unrealized gain on available-for-sale securities, net of income tax expense	17,000				5,000				17,000	5,000
Accumulated other comprehensive loss	(3,248,000)				(2,284,000)				(3,248,000)	(2,284,000)
Income tax benefit of net actuarial loss and prior service cost not yet recognized in net periodic benefit cost	2,158,000				1,486,000				2,158,000	1,486,000
Income tax benefit of unrealized loss on interest rate swap					64,000					64,000
Income tax benefit of accumulated unrealized gain on available-for-sale securities	$ 12,000				$ 4,000				$ 12,000	$ 4,000