Balance Sheet Parenthetical (Parentheticals) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Allowance for doubtful accounts receivable	$ 18,352	$ 19,140
Accumulated depreciation of property and equipment	256,131	242,111
Accumulated amortization of intangible assets	142,921	131,095
Accumulated amortization of other assets	$ 35,632	$ 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	58,180,273	57,961,043
Treasury Stock, shares	6,086,853	4,929,241