CONDENSED CONSOLIDATED BALANCE SHEETS (unaudited) (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Current assets:
Trade accounts receivable, allowances for doubtful accounts	$ 7,751	$ 7,204
Accumulated amortization	$ 34,341	$ 31,699
Shareholders' equity:
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Common stock shares issued (in shares)	14,141,780	14,118,348
Treasury stock (in shares)	141,471	141,471
Series A Preferred Stock [Member]
Shareholders' equity:
Preferred stock, par value (in dollars per share)	$ 1.00	$ 1.00
Preferred stock, voting rights	1/10th vote per share	1/10th vote per share
Preferred stock, liquidation preference (in dollars per share)	$ 100	$ 100
Preferred stock, authorized (in shares)	1,000,000	1,000,000
Preferred stock, issued (in shares)	1,122	1,122
Preferred stock, outstanding (in shares)	1,122	1,122
Series B Convertible Preferred Stock [Member]
Shareholders' equity:
Preferred stock, par value (in dollars per share)	$ 1.00	$ 1.00
Preferred stock, voting rights	1/10th vote per share	1/10th vote per share
Preferred stock, liquidation preference (in dollars per share)	$ 1,500	$ 1,500
Preferred stock, Stated value (in dollars per share)	$ 100	$ 100
Preferred stock, authorized (in shares)	1,000,000	1,000,000
Preferred stock, issued (in shares)	15,000	15,000
Preferred stock, outstanding (in shares)	15,000	15,000