Long-Term Obligations and Commitments (Details) (USD $) Share data in Millions, except Per Share data, unless otherwise specified	12 Months Ended			1 Months Ended	12 Months Ended		12 Months Ended			1 Months Ended		12 Months Ended		12 Months Ended				1 Months Ended	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Aug. 31, 2012 2 3/4 percent convertible senior notes	Dec. 31, 2013 2 3/4 percent convertible senior notes	Dec. 31, 2012 2 3/4 percent convertible senior notes	Dec. 31, 2013 2 3/4 percent convertible senior notes On or after October 5, 2016 D	Dec. 31, 2013 Long-term financing liability for leased research and development facility	Dec. 31, 2012 Long-term financing liability for leased research and development facility	Jun. 30, 2013 Equipment Financing Arrangement	Jun. 30, 2012 Equipment Financing Arrangement	Dec. 31, 2013 Equipment Financing Arrangement	Dec. 31, 2012 Equipment Financing Arrangement	Dec. 31, 2013 Equipment Financing Arrangement Minimum	Dec. 31, 2013 Equipment Financing Arrangement Maximum	Dec. 31, 2013 Leases and other obligations	Dec. 31, 2012 Leases and other obligations	Sep. 30, 2012 2 5/8 percent convertible subordinated notes	Dec. 31, 2013 2 5/8 percent convertible subordinated notes
Long-term obligations
Total	$ 232,572,000	$ 226,821,000			$ 150,334,000	$ 143,990,000		$ 71,288,000	$ 70,550,000			$ 7,461,000	$ 9,993,000			$ 3,489,000	$ 2,288,000
Less: current portion	(4,408,000)	(4,879,000)
Total Long-Term Obligations	228,164,000	221,942,000
Interest rate on convertible debt (as a percent)					2.75%													2.625%
Proceeds raised net of issuance cost		194,697,000		194,700,000
Issuance costs				6,600,000
Amount of debt redeemed																		162,500,000
Amount of debt redeemed including accrued interest																		164,000,000
Loss on redemption of debt		4,770,000																4,800,000
Write-off of unamortized debt discount and debt issuance cost																		3,600,000
Early redemption premium																		1,200,000
Number of shares to be issued upon debt conversion					12.1
Conversion price (in dollars per share)					$ 16.63
Within 30 consecutive trading days, number of days with closing price of the entity's common stock at least 130% of the conversion price to trigger the redemption option							20
Period of consecutive trading days within which a closing price of the entity's common stock of at least 130% of the conversion price for at least 20 days triggers the redemption option							30 days
Threshold closing price of the entity's common stock as percentage of conversion price, to trigger the redemption option							130.00%
Ratio of additional redemption price of debt instrument to principal amount							0.09
Redemption price as a percentage of principal							100.00%
If-converted value of notes in excess of principal					281,000,000
Debt issuance costs, amortization period					7 years														7 years
Nonconvertible debt borrowing rate (as a percent)					8.00%													9.30%
Principal and accrued interest payable					202,600,000
Fair value of convertible notes					505,100,000
Non-cash interest expense related to the amortization of the debt discount and debt issuance costs	6,300,000	8,400,000	8,600,000
Summary of equity and liability components of the 2 3/4 percent notes
Principal amount of convertible notes outstanding				201,300,000	201,250,000	201,250,000
Unamortized portion of liability component					(50,916,000)	(57,260,000)
Long-term debt	232,572,000	226,821,000			150,334,000	143,990,000		71,288,000	70,550,000			7,461,000	9,993,000			3,489,000	2,288,000
Carrying value of equity component					59,528,000	59,528,000
Draw down period												3 years
Interest rate swap period, used to calculate interest												3 years
Basis for variable interest rate												three year interest rate swap
Percentage added to variable rate basis														3.50%	4.00%
Additional principal amount drawn during the period										2,500,000	9,100,000
Interest rate on new draw down (as a percent)										4.39%	4.12%
Weighted average interest rate (as a percent)												4.28%
Maximum borrowing capacity for equipment purchases												$ 3,400,000