NOTES PAYABLE (Details) (USD $) In Thousands, except Share data, unless otherwise specified	0 Months Ended	12 Months Ended						0 Months Ended	12 Months Ended				12 Months Ended		12 Months Ended
	Feb. 04, 2011	Dec. 31, 2012		Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Oct. 13, 2008	Feb. 04, 2011 Corporate 7.50 % Senior Convertible Notes [Member]	Dec. 31, 2012 Corporate 7.50 % Senior Convertible Notes [Member]	Feb. 15, 2014 Corporate 7.50 % Senior Convertible Notes [Member] Tradingdays	Dec. 31, 2011 Corporate 7.50 % Senior Convertible Notes [Member]	Jan. 31, 2011 Corporate 7.50 % Senior Convertible Notes [Member]	Dec. 31, 2012 7.5% Senior Exchange Convertible Notes [Member]	Dec. 31, 2011 7.5% Senior Exchange Convertible Notes [Member]	Dec. 31, 2012 4.50 % Convertible Senior Notes [Member]	Dec. 31, 2011 4.50 % Convertible Senior Notes [Member]	Mar. 30, 2004 4.50 % Convertible Senior Notes [Member]
Debt Instrument [Line Items]
Outstanding debt									$ 55,500		$ 100,000		$ 44,500	$ 0	$ 5,402	$ 5,402
Total		105,402		105,402
Aggregate principal amount												100,000				41,637	120,000
Stated interest rate (in hundredths)		7.50%		4.50%			4.50%		7.50%		7.50%				4.50%	4.50%
Proceeds from convertible debt		0		100,000	0			95,373
Underwriter's discount (in hundredths)								4.25%
Debt issuance costs		1,683		4,627	0			377
Principal amount of debt retired	17,765												44,500
Cash used to repurchase debt								18,171
Convertible, number of equity instruments (in shares)									33.3333				55.5555
Principal conversion standard base unit									$ 1				$ 1
Convertible conversion price (in dollars per share)									$ 30.00				$ 18
Financial covenants [Abstract]
Minimum cash and cash equivalents		79,815		124,316	115,502	217,132					20,000
Maximum total consolidated indebtedness									150,000
Maximum total consolidated indebtedness for specific covenants									50,000
Debt instrument repurchase date									Feb. 15, 2014
Redemption right [Abstract]
Number of trading days out of 30 trading days needed to compute the redemption percentage										20
Number of consecutive trading days used as denominator for redemption calculation										30
Percentage of conversion price, minimum (in hundredths)										130.00%			130.00%
Percentage of face value the notes were sold to the public (in hundredths)												100.00%
Debt instrument redemption date									Feb. 15, 2014
Maturity date of debt									Dec. 31, 2016				Feb. 15, 2016		Dec. 31, 2024
Fiscal Year Maturity [Abstract]
2013		0
2014		0
2015		0
2016		100,000	[1],[2]
2017		0
Therafter		5,402	[3]
Total long-term debt		105,402
Interest incurred		9,236		9,955	5,681
Interest capitalized		(1,263)		(439)	(150)
Interest expense		7,973		9,516	5,531
Interest payments		$ 7,587		$ 6,136	$ 3,572

[1] Holders may require us to repurchase the 7.50% Notes for cash on February 15, 2014; or upon the occurrence of a breach of any of the financial covenants, a "fundamental change" or in an event of default (as defined in the indenture for the 7.50% Notes); or we may call the 7.50% Notes at any time on or after February 15, 2014, according to restrictions defined in the Indenture.

[2] Holders may require us to repurchase the 7.50% Exchange notes upon the occurrence of a breach of any of the financial covenants, a "fundamental change" or in an event of default (as defined in the indenture for the 7.5% Exchange Notes); or we may call the 7.5% Exchange Notes at any time on or after February 15, 2014, according to restrictions defined in the indenture.

[3] Holders may require us to repurchase the 4.50% Notes for cash on April 1, 2014 and April 1, 2019; or in certain circumstances involving a designated event, as defined in the indenture for the 4.50% Notes; or we may call the 4.50% Notes at any time on or after April 5, 2011.