Consolidated Balance Sheets (Parentheticals) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Allowance for doubtful accounts receivable	$ 22,079	$ 21,512
Property and equipment, accumulated depreciation	231,327	207,282
Acquired intangible assets, accumulated amortization	132,927	140,829
Other assets, accumulated amortization	$ 25,363	$ 24,247
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	54,276,761	52,976,558
Treasury stock, shares	3,650,519	3,653,958