Annual report pursuant to Section 13 and 15(d)

Financial Instruments Financial Instruments (Details 1)

v3.8.0.1
Financial Instruments Financial Instruments (Details 1) - USD ($)
$ in Thousands
Dec. 31, 2017
Nov. 03, 2017
Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Derivative, Fixed Interest Rate 4.25% 1.74685%  
Available-for-sale Securities, Amortized Cost Basis     $ 93,129
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax     0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax     39
Available-for-sale Securities     93,090
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
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
Investments [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Available-for-sale Securities, Amortized Cost Basis     53,948
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax     0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax     39
Available-for-sale Securities     53,909
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
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax     0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax     32
Available-for-sale Securities     27,993
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
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax     0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax     7
Available-for-sale Securities     25,916
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
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
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
Estimate of Fair Value Measurement [Member] | Money Market Funds [Member] | Fair Value, Measurements, Recurring [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Available-for-sale Securities     $ 39,181