CONSOLIDATED BALANCE SHEETS (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Current assets:
Cash and cash equivalents	$ 343,550	$ 154,030
Marketable investments	353,041	325,175
Accounts receivable, net of allowance of none for 2013 and 2012	131,565	116,626
Other current assets	5,013	3,778
Prepaid expenses	11,147	17,053
Inventories, net	44,713	37,254
Deferred tax assets	14,554	14,554
Total current assets	903,583	668,470
Marketable investments	198,077	305,726
Marketable investments and cash-restricted	5,407	5,377
Goodwill and other intangibles, net	14,939	16,408
Property, plant and equipment, net	447,893	453,685
Deferred tax assets, net	149,813	150,147
Other assets	57,961	26,782
Total assets	1,777,673	1,626,595
Current liabilities:
Accounts payable	9,377	10,203
Accrued expenses	81,727	72,985
Convertible notes	210,166
Other current liabilities	110,955	93,567
Total current liabilities	412,225	176,755
Convertible notes		204,667
Mortgages payable-noncurrent	70,320	70,343
Other liabilities	78,989	79,967
Total liabilities	561,534	531,732
Commitments and contingencies:
Temporary equity	50,716	10,882
Stockholders' equity:
Common stock, par value $.01, 245,000,000 shares authorized, 62,465,829 and 62,082,007 shares issued, and 49,840,777 and 50,165,953 shares outstanding at June 30, 2013 and December 31, 2012, respectively	625	621
Additional paid-in capital	999,681	1,015,835
Accumulated other comprehensive loss	(17,115)	(14,957)
Treasury stock at cost, 12,625,052 and 11,916,054 shares at June 30, 2013 and December 31, 2012, respectively	(513,437)	(470,998)
Retained earnings	695,669	553,480
Total stockholders' equity	1,165,423	1,083,981
Total liabilities and stockholders' equity	1,777,673	1,626,595
Preferred stock
Stockholders' equity:
Preferred stock
Series A junior participating preferred stock
Stockholders' equity:
Preferred stock