CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) shares in Thousands, $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Restricted cash and cash equivalents	$ 105,468	$ 160,967
Short-term restricted investments (in dollars)	350,060	363,840
Other current restricted assets (in dollars)	45,896	43,401
Long term restricted investments (in dollars)	$ 22,841	$ 2,854
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	54,063	53,536
Common stock, outstanding shares	24,401	23,935
Common stock in treasury, shares	29,662	29,601