Annual report pursuant to Section 13 and 15(d)

Financial Instruments Financial Instruments (Details 2)

v3.8.0.1
Financial Instruments Financial Instruments (Details 2) - USD ($)
 12 Months Ended
Dec. 31, 2016
Dec. 31, 2017
Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Derivative Asset $ 0 $ 734,000.000 $ 0
Available-for-sale Securities, Amortized Cost Basis 93,129,000    
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax 0    
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax 39,000    
Available-for-sale Securities 93,090,000    
Money Market Funds [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Available-for-sale Securities, Amortized Cost Basis 39,181,000    
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax 0    
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax 0    
Available-for-sale Securities 39,181,000    
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Available-for-sale Securities 39,181,000    
Available-for-sale Securities, Debt Securities, Current 0    
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Contingent Consideration [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Available-for-sale Securities, Debt Securities, Current 0    
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | US Government Agencies Debt Securities [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Available-for-sale Securities 0    
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Corporate Debt Securities [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Available-for-sale Securities 0    
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Money Market Funds [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Available-for-sale Securities 39,181,000    
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Derivative Financial Instruments, Assets [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Derivative Asset   0.000  
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Available-for-sale Securities 53,909,000    
Available-for-sale Securities, Debt Securities, Current 0    
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Contingent Consideration [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Available-for-sale Securities, Debt Securities, Current 0    
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | US Government Agencies Debt Securities [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Available-for-sale Securities 27,993,000    
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Corporate Debt Securities [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Available-for-sale Securities 25,916,000    
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Money Market Funds [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Available-for-sale Securities 0    
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Derivative Financial Instruments, Assets [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Derivative Asset   734,000.000  
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Available-for-sale Securities 0    
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Contingent Consideration [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Available-for-sale Securities, Debt Securities, Current 375,000    
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | US Government Agencies Debt Securities [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Available-for-sale Securities 0    
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Corporate Debt Securities [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Available-for-sale Securities 0    
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Money Market Funds [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Available-for-sale Securities 0    
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Derivative Financial Instruments, Assets [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Derivative Asset   0.000  
Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Available-for-sale Securities 93,090,000    
Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member] | US Government Agencies Debt Securities [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Available-for-sale Securities 27,993,000    
Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Available-for-sale Securities 25,916,000    
Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member] | Money Market Funds [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Available-for-sale Securities 39,181,000    
Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member] | Derivative Financial Instruments, Assets [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Derivative Asset   734,000.000  
Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Contingent Consideration [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Business Combination, Contingent Consideration, Liability 375,000 $ 0  
Corporate Debt Securities [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Available-for-sale Securities, Amortized Cost Basis 25,923,000    
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax 0    
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax 7,000    
Available-for-sale Securities 25,916,000    
US Government Agencies Debt Securities [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Available-for-sale Securities, Amortized Cost Basis 28,025,000    
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax 0    
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax 32,000    
Available-for-sale Securities 27,993,000    
Cash and Cash Equivalents [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Available-for-sale Securities, Amortized Cost Basis 39,181,000    
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax 0    
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax 0    
Available-for-sale Securities 39,181,000    
Investments [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Available-for-sale Securities, Amortized Cost Basis 53,948,000    
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax 0    
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax 39,000    
Available-for-sale Securities $ 53,909,000    
Maximum [Member] | Fair Value, Inputs, Level 3 [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Fair Value Inputs, Discount Rate 1.00%