XML 62 R51.htm IDEA: XBRL DOCUMENT v3.10.0.1
Income Taxes - Roll-Forward of Unrecognized Tax Benefits (Detail) - USD ($)
$ in Millions
9 Months Ended 12 Months Ended
Sep. 30, 2018
Dec. 31, 2017
Income Tax Disclosure [Abstract]    
Opening balance at January 1 $ 2.2 $ 2.2
Additions for tax positions of prior periods 0.9 0.5
Reductions due to lapsed statute of limitations (0.5) (0.5)
Closing balance $ 2.6 $ 2.2