Annual report pursuant to Section 13 and 15(d)

Severance Charges - Additional Information (Detail)

v3.8.0.1
Severance Charges - Additional Information (Detail)
Dec. 31, 2017
USD ($)
Aug. 01, 2017
USD ($)
SeniorExecutive
Restructuring Cost and Reserve [Line Items]    
Number of terminated senior executives | SeniorExecutive   1
Senior Executive [Member]    
Restructuring Cost and Reserve [Line Items]    
Severance payable | $ $ 0 $ 1,200,000