Long-Term Obligations (Details) (USD $)			1 Months Ended	12 Months Ended			1 Months Ended	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Jan. 31, 2008 Convertible Subordinated Notes	Dec. 31, 2011 Convertible Subordinated Notes D	Dec. 31, 2010 Convertible Subordinated Notes	Dec. 31, 2009 Convertible Subordinated Notes	Jul. 31, 2002 Note Payable	Dec. 31, 2011 Note Payable	Dec. 31, 2011 Capital Lease	Dec. 31, 2010 Capital Lease
Information related to long-term obligations
Carrying value of convertible subordinated notes	$ 172,500,000	$ 172,500,000
Estimated fair value of convertible subordinated notes	189,588,000	202,391,000
Carrying value of note payable to lessor		42,000
Estimated fair value of note payable to lessor		42,000
Debt disclosures
Loan amount			172,500,000				900,000
Proceeds from issuance of debt, net of issuance costs			166,700,000
Interest rate (as a percent)				3.00%
Conversion rate, number of shares to be issued per $1000 of principal amount of notes				38.6548
Principal amount used for debt instrument conversion ratio				1,000
Initial conversion price of convertible notes into common stock (in dollars per share)				$ 25.87
Unamortized debt issuance costs				2,500,000
Amortization expense				800,000	800,000	800,000
Percentage of principal amount at which the entity may redeem some or all notes				100.00%
Percentage of closing sales price of the entity's common stock the conversion price must exceed in order for the notes to be convertible				130.00%
Number of days within 30 consecutive trading days in which the closing price of the entity's common stock must exceed the conversion price for the notes to be redeemable				20
Number of consecutive trading days during which the closing price of the entity's common stock must exceed the conversion price for at least 20 days in order for the notes to be redeemable				30
Interest rate (as a percent)								14.50%
Aggregate maturities of note payable								42,000
Capital lease agreement
Obligation of lease arrangement									79,000	130,000
Minimum lease payments less interest									(52,000)	(51,000)
Present value of future payments									27,000	79,000
Less current portion									(27,000)	(52,000)
Long-term portion										27,000
Cost of equipment financed under capital leases									200,000
Accumulated amortization									$ 72,000	$ 41,000