Stockholders' Equity and Employee Stock Option Plans Stock option outstanding by exercise price range (Details) (USD $)
 12 Months Ended
Dec. 31, 2013
Mar. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]          
Options and SARS Outstanding, Weighted Average Remaining Contractual Term 7 years 0 months 29 days        
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value $ 4,640        
Options and SARS, Outstanding, Weighted Average Exercise Price $ 4.13   $ 6.08 $ 8.71 $ 8.55
Options and SARS, Outstanding, Number 4,104,849 5,505,404 3,939,315 3,103,472 4,275,648
Options, Vested and Expected to Vest, Outstanding, Number 3,918,854        
Options, Vested and Expected to Vest, Outstanding, Weighted Average Remaining Contractual Term 7 years 0 months 21 days        
Options, Vested and Expected to Vest, Outstanding, Weighted Average Exercise Price $ 4.20        
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Aggregate Intrinsic Value 4,212        
Options, Exercisable, Number 1,348,270        
Options, Exercisable, Weighted Average Remaining Contractual Term 3 years 7 months 20 days        
Options, Exercisable, Weighted Average Exercise Price $ 6.60        
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value 0        
Exercise Price Range One [Member]
          
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]          
Exercise Price Range, Lower Range Limit $ 2.11        
Exercise Price Range, Upper Range Limit $ 2.29        
Exercise Price Range, Number of Outstanding Options and SARS 419,600        
Options and SARS Outstanding, Weighted Average Remaining Contractual Term 9 years 8 months 4 days        
Exercise Price Range, Outstanding Options, Weighted Average Exercise Price $ 2.19        
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value 4,640        
Exercise Price Range Two [Member]
          
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]          
Exercise Price Range, Lower Range Limit $ 2.37        
Exercise Price Range, Upper Range Limit $ 2.37        
Exercise Price Range, Number of Outstanding Options and SARS 1,183,829        
Options and SARS Outstanding, Weighted Average Remaining Contractual Term 9 years 5 months 8 days        
Exercise Price Range, Outstanding Options, Weighted Average Exercise Price $ 2.37        
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value 0        
Exercise Price Range Three [Member]
          
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]          
Exercise Price Range, Lower Range Limit $ 2.51        
Exercise Price Range, Upper Range Limit $ 2.57        
Exercise Price Range, Number of Outstanding Options and SARS 92,500        
Options and SARS Outstanding, Weighted Average Remaining Contractual Term 9 years 3 months 18 days        
Exercise Price Range, Outstanding Options, Weighted Average Exercise Price $ 2.55        
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value 0        
Exercise Price Range Four [Member]
          
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]          
Exercise Price Range, Lower Range Limit $ 3.17        
Exercise Price Range, Upper Range Limit $ 3.17        
Exercise Price Range, Number of Outstanding Options and SARS 1,217,567        
Options and SARS Outstanding, Weighted Average Remaining Contractual Term 8 years 4 months 13 days        
Exercise Price Range, Outstanding Options, Weighted Average Exercise Price $ 3.17        
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value 0        
Exercise Price Range Five [Member]
          
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]          
Exercise Price Range, Lower Range Limit $ 3.40        
Exercise Price Range, Upper Range Limit $ 7.46        
Exercise Price Range, Number of Outstanding Options and SARS 513,725        
Options and SARS Outstanding, Weighted Average Remaining Contractual Term 4 years 2 months 23 days        
Exercise Price Range, Outstanding Options, Weighted Average Exercise Price $ 6.02        
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value 0        
Exercise Price Range Six [Member]
          
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]          
Exercise Price Range, Lower Range Limit $ 7.47        
Exercise Price Range, Upper Range Limit $ 8.20        
Exercise Price Range, Number of Outstanding Options and SARS 431,978        
Options and SARS Outstanding, Weighted Average Remaining Contractual Term 0 years 5 months 19 days        
Exercise Price Range, Outstanding Options, Weighted Average Exercise Price $ 7.55        
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value 0        
Exercise Price Range Seven [Member] [Member]
          
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]          
Exercise Price Range, Lower Range Limit $ 9.08        
Exercise Price Range, Upper Range Limit $ 10.62        
Exercise Price Range, Number of Outstanding Options and SARS 123,900        
Options and SARS Outstanding, Weighted Average Remaining Contractual Term 2 years 4 months 9 days        
Exercise Price Range, Outstanding Options, Weighted Average Exercise Price $ 9.99        
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value 0        
Exercise Price Range Eight [Member]
          
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]          
Exercise Price Range, Lower Range Limit $ 12.11        
Exercise Price Range, Upper Range Limit $ 12.11        
Exercise Price Range, Number of Outstanding Options and SARS 40,000        
Options and SARS Outstanding, Weighted Average Remaining Contractual Term 0 years 8 months 8 days        
Exercise Price Range, Outstanding Options, Weighted Average Exercise Price $ 12.11        
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value 0        
Exercise Price Range Nine [Member]
          
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]          
Exercise Price Range, Lower Range Limit $ 12.82        
Exercise Price Range, Upper Range Limit $ 12.82        
Exercise Price Range, Number of Outstanding Options and SARS 75,000        
Options and SARS Outstanding, Weighted Average Remaining Contractual Term 0 years 10 months 9 days        
Exercise Price Range, Outstanding Options, Weighted Average Exercise Price $ 12.82        
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value 0        
Exercise Price Range Ten [Member]
          
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]          
Exercise Price Range, Lower Range Limit $ 13.85        
Exercise Price Range, Upper Range Limit $ 13.85        
Exercise Price Range, Number of Outstanding Options and SARS 6,750        
Options and SARS Outstanding, Weighted Average Remaining Contractual Term 0 years 9 months 10 days        
Exercise Price Range, Outstanding Options, Weighted Average Exercise Price $ 13.85        
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value $ 0