Annual report pursuant to Section 13 and 15(d)

Income Taxes - Summary of Changes in Liability Related to Unrecognized Tax Benefits (Parenthetical) (Detail)

v3.8.0.1
Income Taxes - Summary of Changes in Liability Related to Unrecognized Tax Benefits (Parenthetical) (Detail) - USD ($)
$ in Millions
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Schedule Of Unrecognized Tax Benefits [Line Items]        
Accrued interest and penalties $ 0.6 $ 0.8 $ 1.1 $ 1.2
State and Local Jurisdiction [Member]        
Schedule Of Unrecognized Tax Benefits [Line Items]        
Net operating losses $ 0.1 $ 0.3 $ 0.6