Annual report pursuant to Section 13 and 15(d)

Accounting Policies - Additional Information (Detail)

v3.19.1
Accounting Policies - Additional Information (Detail)
$ in Millions
12 Months Ended
Dec. 31, 2018
segment
Jan. 01, 2019
USD ($)
Accounting Policies [Line Items]    
Maturity period of liquid investments 3 months  
Maturity period of financial instruments Greater than three months and less than one year  
Number of operating segments | segment 1  
ASU 2016-02 [Member] | Subsequent Event [Member]    
Accounting Policies [Line Items]    
Operating lease, right-of-use asset   $ 0.5
Operating lease, liability   $ 0.5
Restricted Stock Unit Awards [Member]    
Accounting Policies [Line Items]    
Award vesting period 4 years