Fair Value Of Financial Instruments (Details) (USD $)	6 Months Ended
	Jun. 30, 2011	Dec. 31, 2010	Jun. 30, 2010	Dec. 31, 2009
Cash and cash equivalents, carrying amount	$ 198,648,000	$ 44,791,000	$ 69,107,000	$ 108,172,000
Short-term investments (held-to-maturity), carrying amount	41,698,000	13,870,000
Total short-term investments, carrying amount	41,698,000	20,070,000
Long-term investments (held-to-maturity), carrying amount	1,280,000	1,280,000
Total cash and cash equivalents and investments, carrying amount	241,626,000
Total cash and cash equivalents and investments, estimated fair value	241,626,000
Assets and liabilities measured at fair value	197,341,000
Carrying amount of the convertible notes	173,300,000
Accretion of discount on convertible notes	3,587,000
4.75% Convertible Senior Notes Due On 2018 [Member] | Level 3 [Member]
Convertible notes at fair value	169,800,000
Cash And Cash Equivalents [Member]
Cash and cash equivalents, carrying amount	198,648,000
Cash and cash equivalents, estimated fair value	198,648,000
Assets and liabilities measured at fair value	197,341,000
Cash And Cash Equivalents [Member] | Level 1 [Member]
Assets and liabilities measured at fair value	197,341,000
Cash And Cash Equivalents [Member] | Level 1 [Member] | Cash [Member]
Assets and liabilities measured at fair value	4,315,000
Cash And Cash Equivalents [Member] | Level 1 [Member] | Money Market Funds [Member]
Assets and liabilities measured at fair value	193,026,000
Cash And Cash Equivalents [Member] | Cash [Member]
Cash and cash equivalents, carrying amount	4,315,000
Cash and cash equivalents, estimated fair value	4,315,000
Assets and liabilities measured at fair value	4,315,000
Cash And Cash Equivalents [Member] | Certificates Of Deposit [Member]
Cash and cash equivalents, carrying amount	1,307,000
Cash and cash equivalents, estimated fair value	1,307,000
Cash And Cash Equivalents [Member] | Money Market Funds [Member]
Cash and cash equivalents, carrying amount	193,026,000
Cash and cash equivalents, estimated fair value	193,026,000
Assets and liabilities measured at fair value	193,026,000
Short-Term Investments (Held-To-Maturity) [Member] | Certificates Of Deposit [Member]
Short-term investments (held-to-maturity), carrying amount	41,698,000
Short-term investments (held-to-maturity), estimated fair value	41,698,000
Total Short-Term Investments [Member]
Total short-term investments, carrying amount	41,698,000
Short-term investments (held-to-maturity), estimated fair value	41,698,000
Total Cash And Cash Equivalents And Short-Term Investments [Member]
Total cash and cash equivalents and short-term investments, carrying amount	240,346,000
Total cash and cash equivalents and short term investments, estimated fair value	240,346,000
Assets and liabilities measured at fair value	197,341,000
Total Cash And Cash Equivalents And Short-Term Investments [Member] | Level 1 [Member]
Assets and liabilities measured at fair value	197,341,000
Long-Term Investments (Held-To-Maturity) [Member]
Long-term investments (held-to-maturity), carrying amount	1,280,000
Long-term investments (held-to-maturity), estimated fair value	1,280,000
Long-Term Investments (Held-To-Maturity) [Member] | Certificates Of Deposit [Member]
Long-term investments (held-to-maturity), carrying amount	1,280,000
Long-term investments (held-to-maturity), estimated fair value	1,280,000
Level 1 [Member]
Assets and liabilities measured at fair value	$ 197,341,000