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Fair Value - Fair Value Hierarchy (Details) - USD ($)
Sep. 30, 2019
Dec. 31, 2018
Assets:    
Government bonds and notes $ 4,880,876 $ 7,173,037
Assets, Fair Value Disclosure 11,144,490 14,504,042
Money Market Funds And Corporate Bonds [Member]    
Assets:    
Cash equivalents - money market funds and corporate bonds 6,263,614 7,331,005
Government [Member]    
Assets:    
Government bonds and notes 849,923 897,381
Corporate Bonds, Notes and Commercial Paper [Member]    
Assets:    
Government bonds and notes 4,030,953 6,275,656
Level 1 inputs [Member]    
Assets:    
Assets, Fair Value Disclosure 6,314,837 5,732,814
Level 1 inputs [Member] | Money Market Funds And Corporate Bonds [Member]    
Assets:    
Cash equivalents - money market funds and corporate bonds 5,464,914 4,835,433
Level 1 inputs [Member] | Government [Member]    
Assets:    
Government bonds and notes 849,923 897,381
Level 1 inputs [Member] | Corporate Bonds, Notes and Commercial Paper [Member]    
Assets:    
Government bonds and notes 0 0
Level 2 inputs [Member]    
Assets:    
Assets, Fair Value Disclosure 4,829,653 8,771,228
Level 2 inputs [Member] | Money Market Funds And Corporate Bonds [Member]    
Assets:    
Cash equivalents - money market funds and corporate bonds 798,700 2,495,572
Level 2 inputs [Member] | Government [Member]    
Assets:    
Government bonds and notes 0 0
Level 2 inputs [Member] | Corporate Bonds, Notes and Commercial Paper [Member]    
Assets:    
Government bonds and notes 4,030,953 6,275,656
Level 3 inputs [Member]    
Assets:    
Assets, Fair Value Disclosure 0 0
Level 3 inputs [Member] | Money Market Funds And Corporate Bonds [Member]    
Assets:    
Cash equivalents - money market funds and corporate bonds 0 0
Level 3 inputs [Member] | Government [Member]    
Assets:    
Government bonds and notes 0 0
Level 3 inputs [Member] | Corporate Bonds, Notes and Commercial Paper [Member]    
Assets:    
Government bonds and notes $ 0 $ 0