Consolidated Balance Sheets (Unaudited) (Parentheticals) (USD $) In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Allowance for doubtful accounts (in Dollars)	$ 141	$ 336
Accumulated depreciation (in Dollars)	$ 98,328	$ 97,883
Preferred stock, par value (in Dollars per share) (in Dollars per share)	$ 0	$ 0
Preferred stock, shares authorized (in Shares)	15,000	15,000
Preferred stock, shares outstanding (in Shares)	0	0
Common Class A [Member]
Common stock, par value (in Dollars per share)	$ 0	$ 0
Common stock, shares authorized (in Shares)	100,000	100,000
Common stock, shares issued (in Shares)	22,950	22,916
Common stock, shares outstanding (in Shares)	22,950	22,916
Common Class B [Member]
Common stock, par value (in Dollars per share)	$ 0	$ 0
Common stock, shares authorized (in Shares)	25,000	25,000
Common stock, shares issued (in Shares)	2,693	2,762
Common stock, shares outstanding (in Shares)	2,693	2,762