Consolidated Balance Sheets (Parentheticals) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Allowance for doubtful accounts (in Dollars)	$ 2,191	$ 173
Accumulated depreciation (in Dollars)	$ 117,679	$ 106,871
Preferred stock, par value (in Dollars per share)
Preferred stock, shares authorized	15,000us-gaap_PreferredStockSharesAuthorized	15,000us-gaap_PreferredStockSharesAuthorized
Preferred stock, shares outstanding	0us-gaap_PreferredStockSharesOutstanding	0us-gaap_PreferredStockSharesOutstanding
Common Class A [Member]
Common stock, par value (in Dollars per share)
Common stock, shares authorized	100,000	100,000
Common stock, shares issued	23,671	23,329
Common stock, shares outstanding	23,671	23,329
Common Class B [Member]
Common stock, par value (in Dollars per share)
Common stock, shares authorized	25,000	25,000
Common stock, shares issued	2,562	2,562
Common stock, shares outstanding	2,562	2,562

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

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