CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Thousands, except Per Share data	Jun. 30, 2011	Dec. 31, 2010
CONSOLIDATED BALANCE SHEETS
Accounts receivable, allowance for doubtful accounts (in dollars)	$ 2,150	$ 2,175
Class A common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Class A common stock, shares authorized	199,300	199,300
Class A common stock, shares issued	97,863	97,474
Class A common stock, shares outstanding	92,114	91,725
Treasury stock, at cost, shares held	5,749	5,749