Annual report pursuant to Section 13 and 15(d)

Fair Value Remeasurement Based on Significant Inputs Not Observable (Parenthetical) (Detail)

v3.8.0.1
Fair Value Remeasurement Based on Significant Inputs Not Observable (Parenthetical) (Detail) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Fair value of liabilities settlements [1] $ 1.5 $ 7.6
Common Stock    
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Fair value of liabilities settlements $ 1.2 $ 6.6
[1] Acquisition liabilities settled in common stock totaled $1.2 million and $6.6 million during 2017 and 2016, respectively.