Quarterly report pursuant to Section 13 or 15(d)

Basis of Presentation and Principles of Consolidation - Additional Information (Detail)

v3.10.0.1
Basis of Presentation and Principles of Consolidation - Additional Information (Detail)
$ in Millions
6 Months Ended
Jun. 30, 2018
Segment
Dec. 31, 2017
USD ($)
Dec. 31, 2016
USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]      
New accounting pronouncement or change in accounting principle, effect of adoption, quantification     $ 0.0
Number of reportable segments | Segment 3    
Operating leases, future minimum payments   $ 9.9  
Additional Paid-in Capital [Member]      
New Accounting Pronouncements or Change in Accounting Principle [Line Items]      
New accounting pronouncement or change in accounting principle, effect of adoption, quantification     0.5
Retained Earnings [Member]      
New Accounting Pronouncements or Change in Accounting Principle [Line Items]      
New accounting pronouncement or change in accounting principle, effect of adoption, quantification     $ (0.5)