Quarterly report pursuant to Section 13 or 15(d)

Summary of Significant Accounting Policies - Additional Information (Detail)

v3.10.0.1
Summary of Significant Accounting Policies - Additional Information (Detail)
6 Months Ended 12 Months Ended
Jun. 30, 2018
Dec. 31, 2017
Product Information [Line Items]    
Cash and cash equivalents, maturity description 90 days or less  
US federal corporate tax rate 21.00% 35.00%
Limitation of the deduction for net operating losses 80.00%  
Provisional amounts measurement period 1 year  
Maximum [Member]    
Product Information [Line Items]    
Short-term contractual maturities 1 year  
Minimum [Member]    
Product Information [Line Items]    
Long-term contractual maturities 1 year