Stockholders' equity, Share-based Compensation Arrangements by Share-based Payment Award (Details) (USD $)
12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Stock-based compensation expense $ 11,238,000 $ 11,115,000 $ 10,739,000
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]      
Total stock-based compensation expense 11,110,000 11,115,000 10,739,000
Cost of Product Sales [Member]
     
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]      
Total stock-based compensation expense 575,000 513,000 466,000
Research and Development [Member]
     
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]      
Total stock-based compensation expense 3,283,000 3,451,000 3,203,000
Selling, General and Administrative [Member]
     
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]      
Total stock-based compensation expense 7,252,000 7,151,000 7,070,000
Stock Options [Member]
     
Aggregate Intrinsic Value [Abstract]      
Outstanding, beginning of period 4,801,378    
Exercisable, beginning of period 4,476,830    
Outstanding, end of period 23,148,738 4,801,378  
Exercisable, end of period 12,685,394 4,476,830  
Options expected to vest, end of period 7,820,256    
Aggregate intrinsic value [Abstract]      
Weighted average remaining contractual term of options outstanding 4 years 1 month 6 days 4 years 2 months 12 days  
Weighted average remaining contractual term of options exercisable 3 years 4 months 24 days 3 years 6 months  
Weighted average grant date fair value of options granted (in dollars per share) $ 5.38 $ 5.16 $ 10.09
Total intrinsic value of options exercised 6,900,000 589,000 10,200,000
Total fair value of awards vested 9,100,000 10,300,000 7,900,000
2006 Plan [Member] | Stock Options [Member]
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Common stock authorized for issuance under the plan (in shares) 11,178,826    
Options outstanding [Roll Forward]      
Outstanding, beginning of period (in shares) 3,549,842    
Exercisable, beginning of period (in shares) 2,144,732    
Granted (in shares) 993,544    
Exercised (in shares) (481,549)    
Forfeited (in shares) (419,742)    
Outstanding, end of period (in shares) 3,642,095    
Exercisable, end of period (in shares) 2,074,772    
Options expected to vest, end of period (in shares) 1,171,171    
Weighted-Average Exercise Price [Roll Forward]      
Outstanding, beginning of period (in dollars per share) $ 17.08    
Exercisable, beginning of period (in dollars per share) $ 16.25    
Granted (in dollars per share) $ 15.21    
Exercised (in dollars per share) $ 12.61    
Forfeited (in dollars per share) $ 18.34    
Outstanding, end of period (in dollars per share) $ 17.01    
Exercisable, end of period (in dollars per share) $ 17.44    
Options expected to vest, end of period (in dollars per share) $ 16.44    
2006 Plan [Member] | Stock Options [Member] | Maximum [Member]
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Maximum number of shares that may be granted per year to a single participant (in shares) 287,700    
2006 Plan [Member] | Restricted Stock Units (RSUs) [Member]
     
Restricted stock unit award activity [Roll Forward]      
Outstanding, beginning of period (in shares) 715,276    
Granted (in shares) 496,771    
Vested (in shares) (337,498)    
Forfeited (in shares) (80,873)    
Outstanding, end of period (in shares) 793,676    
Weighted-Average Grant Price [Roll Forward]      
Outstanding, beginning of period (in dollars per share) $ 18.41    
Granted (in dollars per share) $ 15.21    
Vested (in dollars per share) $ 14.91    
Forfeited (in dollars per share) $ 16.72    
Outstanding, end of period (in dollars per share) $ 16.52    
Aggregate intrinsic value [Abstract]      
Outstanding, beginning of period 11,473,027    
Outstanding, end of period 18,246,611    
2004 Plan [Member] | Stock Options [Member]
     
Options outstanding [Roll Forward]      
Outstanding, beginning of period (in shares) 53,156    
Exercisable, beginning of period (in shares) 53,156    
Granted (in shares) 0    
Exercised (in shares) 0    
Forfeited (in shares) 0    
Outstanding, end of period (in shares) 53,156    
Exercisable, end of period (in shares) 53,156    
Options expected to vest, end of period (in shares) 0    
Weighted-Average Exercise Price [Roll Forward]      
Outstanding, beginning of period (in dollars per share) $ 8.86    
Exercisable, beginning of period (in dollars per share) $ 8.86    
Granted (in dollars per share) $ 0    
Exercised (in dollars per share) $ 0    
Forfeited (in dollars per share) $ 0    
Outstanding, end of period (in dollars per share) $ 8.86    
Exercisable, end of period (in dollars per share) $ 8.86    
Options expected to vest, end of period (in dollars per share) $ 0    
Employee Stock Purchase Plan [Member]
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Threshold limit for common stock ownership to be ineligible to participate in ESPP (in hundredths) 5.00%    
Common stock authorized for issuance under the plan (in shares) 1,000,000    
Number of plan periods 2    
Discount from market price (in hundredths) 15.00%    
Maximum number of shares that may be granted per year to a single participant (in shares) 800    
Stock-based compensation expense $ 128,000    
Employee Stock Purchase Plan [Member] | Minimum [Member]
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Employee subscription rate (in hundredths) 1.00%    
Employee Stock Purchase Plan [Member] | Maximum [Member]
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Employee subscription rate (in hundredths) 10.00%