CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
CONSOLIDATED BALANCE SHEETS
Accounts receivable, allowance for doubtful accounts (in dollars)	$ 4,782	$ 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	98,181	97,474
Class A common stock, shares outstanding	92,433	91,725
Treasury stock, at cost, shares held	5,749	5,749