CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Thousands, except Per Share data	Jun. 30, 2011	Dec. 31, 2010
Accounts receivable, allowance for doubtful accounts (in dollars)	$ 2,393	$ 1,985
Short-term restricted investments (in dollars)	98,438	114,903
Other current assets, restricted deposits (in dollars)	24,880	21,302
Long-term restricted investments (in dollars)	$ 17,338	$ 84,950
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, Authorized shares	10,000	10,000
Preferred stock, Issued shares	0	0
Preferred stock, outstanding shares	0	0
Ordinary common stock in treasury, shares	14,133	9,905
Ordinary common stock
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, Authorized shares	100,000	100,000
Common stock, Issued shares	44,940	43,687
Common stock, outstanding shares	30,807	33,782
Multi-Vote common stock
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, Authorized shares	40,000	40,000
Common stock, Issued shares	0	0
Common stock, outstanding shares	0	0