XML 128 R97.htm IDEA: XBRL DOCUMENT v3.10.0.1
Employee Benefit Plans - Schedule of fair values of defined benefit plan's assets (Detail) - Defined Benefit Pension Plan [Member] - USD ($)
$ in Millions
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]      
Fair value of defined benefit plan assets $ 438.6 $ 416.4 $ 410.1
Partnerships [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of defined benefit plan assets 35.3 32.7  
Derivative [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of defined benefit plan assets 14.8 19.0  
US Government Debt Securities [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of defined benefit plan assets 88.1 88.9  
Corporate Debt Securities [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of defined benefit plan assets 18.3 25.5  
Domestic Equity [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of defined benefit plan assets 144.4 66.7  
Foreign Equity [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of defined benefit plan assets 57.5 86.0  
Foreign Bond [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of defined benefit plan assets 41.8 33.3  
Hedge Funds [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of defined benefit plan assets 1.6 30.3  
Short-term Investments [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of defined benefit plan assets 36.8 34.0  
Fair Value, Inputs, Level 1 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of defined benefit plan assets 36.8 34.0  
Fair Value, Inputs, Level 1 [Member] | Short-term Investments [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of defined benefit plan assets 36.8 34.0  
Fair Value, Inputs, Level 2 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of defined benefit plan assets 401.8 382.4  
Fair Value, Inputs, Level 2 [Member] | Partnerships [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of defined benefit plan assets 35.3 32.7  
Fair Value, Inputs, Level 2 [Member] | Derivative [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of defined benefit plan assets 14.8 19.0  
Fair Value, Inputs, Level 2 [Member] | US Government Debt Securities [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of defined benefit plan assets 88.1 88.9  
Fair Value, Inputs, Level 2 [Member] | Corporate Debt Securities [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of defined benefit plan assets 18.3 25.5  
Fair Value, Inputs, Level 2 [Member] | Domestic Equity [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of defined benefit plan assets 144.4 66.7  
Fair Value, Inputs, Level 2 [Member] | Foreign Equity [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of defined benefit plan assets 57.5 86.0  
Fair Value, Inputs, Level 2 [Member] | Foreign Bond [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of defined benefit plan assets 41.8 33.3  
Fair Value, Inputs, Level 2 [Member] | Hedge Funds [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of defined benefit plan assets $ 1.6 $ 30.3