CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 765,205	$ 397,697
Marketable investments	156,630	297,842
Accounts receivable, net of allowance of none for 2015 and 2014	179,642	162,287
Inventories, net	80,844	66,927
Other current assets	46,202	49,444
Total current assets	1,228,523	974,197
Marketable investments	91,706	122,658
Goodwill and other intangibles, net	28,533	29,465
Property, plant and equipment, net	474,770	478,421
Deferred tax assets, net	182,600	181,721
Other assets	153,101	97,948
Total assets	2,159,233	1,884,410
Current liabilities:
Accounts payable and accrued expenses	113,346	85,382
Convertible notes	30,017	126,414
Share tracking awards plan	214,017	282,101
Other current liabilities	199,962	10,413
Total current liabilities	557,342	504,310
Other liabilities	122,522	114,526
Total liabilities	$ 679,864	$ 618,836
Commitments and contingencies:
Temporary equity	$ 12,499	$ 23,218
Stockholders' equity:
Common stock, par value $.01, 245,000,000 shares authorized, 68,460,587 and 65,988,561 shares issued, and 45,583,017 and 47,107,709 shares outstanding at September 30, 2015 and December 31, 2014, respectively	685	660
Additional paid-in capital	1,723,888	1,376,141
Accumulated other comprehensive loss	(21,930)	(16,734)
Treasury stock, 22,877,570 and 18,880,852 shares at September 30, 2015 and December 31, 2014, respectively	(1,850,882)	(1,185,825)
Retained earnings	1,615,109	1,068,114
Total stockholders' equity	1,466,870	1,242,356
Total liabilities and stockholders' equity	$ 2,159,233	$ 1,884,410
Preferred stock
Stockholders' equity:
Preferred stock, par value $.01, no shares issued
Series A junior participating preferred stock
Stockholders' equity:
Preferred stock, par value $.01, no shares issued