CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) shares in Thousands, $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Accounts receivable, allowance for doubtful accounts (in dollars)	$ 3,246	$ 4,047
Short-term restricted investments (in dollars)	277,556	132,808
Other current assets, restricted deposits (in dollars)	$ 27,752	$ 30,620
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	26,648	23,150
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	51,340	50,085
Common stock, outstanding shares	24,692	26,935
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