Significant Accounting Policies - Property Plant and Equipment Estimated Useful Lives (Details)	12 Months Ended
	Dec. 31, 2018
Research Equipment [Member]
Property Plant And Equipment [Line Items]
Property, Plant and Equipment, Useful Life	5 years
Office Furniture and Equipment [Member]
Property Plant And Equipment [Line Items]
Property, Plant and Equipment, Useful Life	5 years
Computer Equipment [Member]
Property Plant And Equipment [Line Items]
Property, Plant and Equipment, Useful Life	3 years
Leasehold Improvements [Member]
Property Plant And Equipment [Line Items]
Property, Plant and Equipment, Estimated Useful Lives	Over the lesser of lease term or estimated useful life