Quarterly report pursuant to Section 13 or 15(d)

Financial Instruments - Additional Information (Details Textuals)

v3.7.0.1
Financial Instruments - Additional Information (Details Textuals)
 12 Months Ended
Dec. 31, 2016
USD ($)
Mar. 31, 2016
Mar. 31, 2017
USD ($)
debt_security
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | debt_security     22
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value     $ 44,500,000
Fair Value, Assets, Level 2 to Level 1 Transfers, Amount $ 0    
Fair Value, Assets, Level 1 to Level 2 Transfers, Amount     $ 0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net $ 0    
Maximum [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Period Of Unrealized Loss Position   12 months  
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 100.00%