Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Allowance for doubtful accounts receivable	$ 18,369	$ 19,140
Property and equipment, accumulated depreciation	262,470	242,111
Acquired intangible assets, accumulated amortization	150,347	131,095
Other assets, accumulated amortization	$ 36,984	$ 32,434
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	58,389,242	57,961,043
Treasury stock, shares	6,085,841	4,929,241