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Summary of Significant Accounting Policies - Additional Information (Details)
shares in Millions
12 Months Ended
Dec. 31, 2018
Derivative
Segment
shares
Dec. 31, 2017
Derivative
Summary Of Significant Accounting Policies [Line Items]    
Maximum period of investments with original maturities from date of acquisition to be cash equivalents 3 months  
Pre-funded penny warrants outstanding | shares 0.1  
Number of business segments | Segment 1  
Designated as Hedges [Member]    
Summary Of Significant Accounting Policies [Line Items]    
Number of derivative instruments | Derivative 0 0
Minimum [Member]    
Summary Of Significant Accounting Policies [Line Items]    
Property, plant and equipment, estimated useful life 3 years  
Maximum [Member]    
Summary Of Significant Accounting Policies [Line Items]    
Property, plant and equipment, estimated useful life 7 years