Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Accounts receivable, allowance for doubtful accounts	$ 10,827	$ 12,341
Preferred Stock, par value per share	$ 5.0	$ 5.0
Preferred Stock, shares authorized	2,000,000	2,000,000
Preferred Stock, shares issued	0	0
Common Stock, shares outstanding	31,300,000	31,200,000
Treasury stock, shares	8,479,487	8,484,528
Common Class A [Member]
Common Stock, par value per share	$ 0.001	$ 0.001
Common Stock, shares authorized	100,000,000	100,000,000
Common Stock, shares issued	36,540,842	36,442,209
Common Class B [Member]
Common Stock, par value per share	$ 0.001	$ 0.001
Common Stock, shares authorized	25,000,000	25,000,000
Common Stock, shares issued	3,236,098	3,236,098
Common Stock, shares outstanding	3,236,098	3,236,098