Consolidated Balance Sheets (Parentheticals) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Allowance for doubtful accounts receivable	$ 21,512	$ 14,787
Property and equipment, accumulated depreciation	207,282	175,875
Aquired intangible assets, accumulated amortization	140,829	129,119
Other assets, accumulated amortization	$ 24,247	$ 19,529
Preferred stock, par value per share	$ 0.02	$ 0.02
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Common stock, par value per share	$ 0.02	$ 0.02
Common stock, shares authorized	90,000,000	90,000,000
Common stock, shares, issued	52,976,558	51,982,227
Treasury stock, shares	3,653,958	1,543,441