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Fair Value Of Financial Instruments (Details) (USD $)
9 Months Ended
Sep. 30, 2011
Dec. 31, 2010
Sep. 30, 2010
Dec. 31, 2009
Derivatives, Fair Value [Line Items]    
Cash and cash equivalents, Carrying Amount$ 154,773,000$ 44,791,000$ 63,307,000$ 108,172,000
Short-term investments (held-to-maturity), Carrying Amount47,935,00013,870,000  
Total short-term investments, Carrying Amount47,935,00020,070,000  
Long-term investments (held-to-maturity), Carrying Amount1,280,0001,280,000  
Total cash and cash equivalents and investments, Carrying Amount203,988,000   
Total cash and cash equivalents and investments, Estimated Fair Value203,988,000   
Assets and Liabilities Measured at Fair Value154,773,000   
Carrying amount of the convertible notes173,800,000   
Accretion of discount on convertible notes4,109,000   
4.75% Convertible Senior Notes Due On 2018 [Member] | Level 3 [Member]
    
Derivatives, Fair Value [Line Items]    
Convertible notes at fair value169,700,000   
Cash And Cash Equivalents [Member]
    
Derivatives, Fair Value [Line Items]    
Cash and cash equivalents, Carrying Amount154,773,000   
Cash and cash equivalents, Estimated Fair Value154,773,000   
Assets and Liabilities Measured at Fair Value154,773,000   
Cash And Cash Equivalents [Member] | Level 1 [Member]
    
Derivatives, Fair Value [Line Items]    
Assets and Liabilities Measured at Fair Value154,773,000   
Cash And Cash Equivalents [Member] | Level 1 [Member] | Cash [Member]
    
Derivatives, Fair Value [Line Items]    
Assets and Liabilities Measured at Fair Value6,640,000   
Cash And Cash Equivalents [Member] | Level 1 [Member] | Money Market Funds [Member]
    
Derivatives, Fair Value [Line Items]    
Assets and Liabilities Measured at Fair Value148,133,000   
Cash And Cash Equivalents [Member] | Cash [Member]
    
Derivatives, Fair Value [Line Items]    
Cash and cash equivalents, Carrying Amount6,640,000   
Cash and cash equivalents, Estimated Fair Value6,640,000   
Assets and Liabilities Measured at Fair Value6,640,000   
Cash And Cash Equivalents [Member] | Money Market Funds [Member]
    
Derivatives, Fair Value [Line Items]    
Cash and cash equivalents, Carrying Amount148,133,000   
Cash and cash equivalents, Estimated Fair Value148,133,000   
Assets and Liabilities Measured at Fair Value148,133,000   
Short-Term Investments (Held-To-Maturity) [Member] | Certificates Of Deposit [Member]
    
Derivatives, Fair Value [Line Items]    
Short-term investments (held-to-maturity), Carrying Amount47,935,000   
Short-term investments (held-to-maturity), Estimated Fair Value47,935,000   
Total Short-Term Investments [Member]
    
Derivatives, Fair Value [Line Items]    
Total short-term investments, Carrying Amount47,935,000   
Short-term investments (held-to-maturity), Estimated Fair Value47,935,000   
Total Cash And Cash Equivalents And Short-Term Investments [Member]
    
Derivatives, Fair Value [Line Items]    
Total cash and cash equivalents and short-term investments, Carrying Amount202,708,000   
Total cash and cash equivalents and short term investments, Estimated Fair Value202,708,000   
Assets and Liabilities Measured at Fair Value154,773,000   
Total Cash And Cash Equivalents And Short-Term Investments [Member] | Level 1 [Member]
    
Derivatives, Fair Value [Line Items]    
Assets and Liabilities Measured at Fair Value154,773,000   
Long-Term Investments (Held-To-Maturity) [Member]
    
Derivatives, Fair Value [Line Items]    
Long-term investments (held-to-maturity), Carrying Amount1,280,000   
Long-term investments (held-to-maturity), Estimated Fair Value1,280,000   
Long-Term Investments (Held-To-Maturity) [Member] | Certificates Of Deposit [Member]
    
Derivatives, Fair Value [Line Items]    
Long-term investments (held-to-maturity), Carrying Amount1,280,000   
Long-term investments (held-to-maturity), Estimated Fair Value1,280,000   
Level 1 [Member]
    
Derivatives, Fair Value [Line Items]    
Assets and Liabilities Measured at Fair Value$ 154,773,000