Stockholders' Equity (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Changes in the components of stockholders' equity
Balance at the beginning of the period			$ 112,349,000
Net earnings (loss)	$ 631,000	$ 164,000	279,000	$ (889,000)
Unrealized gain on available-for-sale securities, net of income tax expense of $1	(2,000)	$ 4,000	2,000	6,000
Repurchase and retirement of common stock			(65,000)	$ (104,000)
Balance at the end of the period	112,805,000		112,805,000
Common Stock | Common stock.
Changes in the components of stockholders' equity
Balance at the beginning of the period			1,788,000
Issuance of nonvested stock awards, net of forfeitures			18,000
Repurchase and retirement of common stock			(7,000)
Balance at the end of the period	1,799,000		1,799,000
Common Stock | Class A common stock
Changes in the components of stockholders' equity
Balance at the beginning of the period			1,487,000
Balance at the end of the period	1,487,000		1,487,000
Additional Paid-in Capital
Changes in the components of stockholders' equity
Balance at the beginning of the period			5,125,000
Issuance of nonvested stock awards, net of forfeitures			(18,000)
Stock-based compensation			195,000
Repurchase and retirement of common stock			(58,000)
Balance at the end of the period	5,244,000		5,244,000
Retained Earnings
Changes in the components of stockholders' equity
Balance at the beginning of the period			108,629,000
Net earnings (loss)			279,000
Balance at the end of the period	108,908,000		108,908,000
Accumulated Other Comprehensive Loss
Changes in the components of stockholders' equity
Balance at the beginning of the period			(4,680,000)
Change in net actuarial loss and prior service cost, net of income tax expense of $30			45,000
Unrealized gain on available-for-sale securities, net of income tax expense of $1			2,000
Balance at the end of the period	$ (4,633,000)		(4,633,000)
Income tax expense on change in pension net actuarial loss and prior service cost			30,000
Income tax expense on unrealized gain on available-for-sale securities			$ 1,000