Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 831,798	$ 397,697
Marketable investments	121,974	297,842
Accounts receivable, net of allowance of none for 2015 and 2014	192,827	162,287
Inventories, net	81,334	66,927
Other current assets	47,402	32,836
Total current assets	1,275,335	957,589
Marketable investments	38,002	122,658
Goodwill and other intangible assets, net	28,378	29,465
Property, plant and equipment, net	495,774	478,421
Deferred tax assets, net	192,676	198,329
Other assets	154,280	97,948
Total assets	2,184,445	1,884,410
Current liabilities:
Accounts payable and accrued expenses	103,433	85,382
Convertible notes	5,387	126,414
Share tracking awards plan	274,542	282,101
Other current liabilities	57,462	10,413
Total current liabilities	440,824	504,310
Non-current liabilities:
Other liabilities	143,974	114,526
Total liabilities	$ 584,798	$ 618,836
Commitments and contingencies - Note 9
Temporary equity	$ 11,095	$ 23,218
Stockholders' equity:
Common stock, par value $.01, 245,000,000 shares authorized, 68,987,919 and 65,988,561 shares issued, and 45,760,845 and 47,107,709 shares outstanding at December 31, 2015 and 2014, respectively	690	660
Additional paid-in capital	1,790,620	1,376,141
Accumulated other comprehensive loss	(20,401)	(16,734)
Treasury stock, 23,227,074 and 18,880,852 shares at December 31, 2015 and 2014, respectively	(1,902,110)	(1,185,825)
Retained earnings	1,719,753	1,068,114
Total stockholders' equity	1,588,552	1,242,356
Total liabilities and stockholders' equity	$ 2,184,445	$ 1,884,410
Preferred stock
Stockholders' equity:
Preferred stock, par value $.01, 10,000,000 shares authorized, no shares issued
Series A junior participating preferred stock
Stockholders' equity:
Preferred stock, par value $.01, 10,000,000 shares authorized, no shares issued