CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) shares in Thousands, $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
CONSOLIDATED BALANCE SHEETS
Restricted Cash and Cash Equivalents, Current	$ 83,061	$ 81,776
Accounts receivable, allowance for doubtful accounts (in dollars)	7,402	5,644
Short-term restricted investments (in dollars)	225,443	227,795
Other current assets, restricted deposits (in dollars)	32,997	38,785
Long term restricted investments (in dollars)	$ 8,395	$ 6,306
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
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, Authorized shares	100,000	100,000
Common stock, Issued shares	52,235	51,993
Common stock, outstanding shares	23,683	23,517
Ordinary common stock in treasury, shares	28,552	28,476