CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Thousands, except Per Share data, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Accounts receivable, allowance	$ 10,819	$ 11,627
Accumulated amortization	$ 463,551	$ 424,705
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	1,000,000	1,000,000
Common stock, shares issued	492,883	490,650
Common stock, shares outstanding	492,148	490,271
Treasury stock, shares	735	379