XML 113 R99.htm IDEA: XBRL DOCUMENT v3.10.0.1
Defined Benefit Plans - Reconciliation of Level Three Measurements (Detail) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]    
Beginning balance $ 656.6  
Ending balance 599.6 $ 656.6
Group annuity/insurance contracts (Level 3)    
Defined Benefit Plan Disclosure [Line Items]    
Beginning balance 23.3 22.8
Actual return on assets related to assets still held 0.3 0.5
Ending balance $ 23.6 $ 23.3