CONSOLIDATED BALANCE SHEETS (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Current assets:
Cash and cash equivalents	$ 413,794	$ 278,889
Marketable investments	346,698	409,645
Accounts receivable, net of allowance of none for 2014 and 2013	131,771	126,297
Inventories, net	51,717	47,758
Other current assets	46,288	46,424
Total current assets	990,268	909,013
Marketable investments	384,140	448,134
Marketable investments and cash-restricted	5,393	5,369
Goodwill and other intangibles, net	13,737	14,115
Property, plant and equipment, net	474,410	464,950
Deferred tax assets, net	193,910	192,718
Other assets	53,076	53,268
Total assets	2,114,934	2,087,567
Current liabilities:
Accounts payable and accrued expenses	104,015	92,244
Convertible notes	218,739	215,845
Share tracking awards plan	207,786	287,956
Mortgages payable-current	66,614	66,614
Other current liabilities	61,381	25,015
Total current liabilities	658,535	687,674
Mortgages payable-noncurrent	3,700	3,724
Other liabilities	95,009	91,858
Total liabilities	757,244	783,256
Commitments and contingencies:
Temporary equity	42,143	45,037
Stockholders' equity:
Common stock, par value $.01, 245,000,000 shares authorized, 63,310,968 and 63,013,192 shares issued, and 49,658,547 and 50,388,140 shares outstanding at March 31, 2014 and December 31, 2013, respectively	633	630
Additional paid-in capital	1,076,061	1,057,224
Accumulated other comprehensive loss	(15,641)	(13,183)
Treasury stock at cost, 13,652,421 and 12,625,052 shares at March 31, 2014 and December 31, 2013, respectively	(611,070)	(513,437)
Retained earnings	865,564	728,040
Total stockholders' equity	1,315,547	1,259,274
Total liabilities and stockholders' equity	2,114,934	2,087,567
Preferred stock
Stockholders' equity:
Preferred stock
Series A junior participating preferred stock
Stockholders' equity:
Preferred stock