Annual report pursuant to Section 13 and 15(d)

Financial Instruments Financial Instruments - Additional Information (Details 4)

v3.3.1.900
Financial Instruments Financial Instruments - Additional Information (Details 4)
 9 Months Ended 12 Months Ended
Sep. 30, 2015
Dec. 31, 2015
USD ($)
debt_security
Dec. 31, 2014
USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Fair Value, Assets, Level 1 to Level 2 Transfers, Amount   $ 0  
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | debt_security   36  
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value   $ 52,800,000  
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax   114,000 $ 50,000
Fair Value, Assets, Level 2 to Level 1 Transfers, Amount   0  
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net   $ 0  
Minimum [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Available For Sale Securities Non Current Maturity Period 1 year    
Minimum [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   0.85% 0.54%
Maximum [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Period Of Unrealized Loss Position   12 months  
Available For Sale Securities Non Current Maturity Period 2 years    
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   0.41% 0.33%
Investments [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax   $ 114,000 $ 50,000