Composition of Domestic Pension Plan Assets (Detail) - Pension Benefits, Domestic - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 517.5	$ 268.5	$ 270.0
Equity Securities And Funds, Domestic
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	120.0	39.2
Equity Securities And Funds, International
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	88.3	40.4
Fixed Income Securities And Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	148.6	104.1
Alternative investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	154.4	83.5
Cash And Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6.2	1.3
Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	320.1	127.3
Level 1 | Equity Securities And Funds, Domestic
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	115.1	29.0
Level 1 | Equity Securities And Funds, International
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	59.3
Level 1 | Fixed Income Securities And Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	119.9	73.6
Level 1 | Alternative investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	20.7	24.5
Level 1 | Cash And Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5.1	0.2
Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	158.5	129.9
Level 2 | Equity Securities And Funds, Domestic
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4.9	10.2
Level 2 | Equity Securities And Funds, International
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	29.0	40.4
Level 2 | Fixed Income Securities And Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	28.7	30.5
Level 2 | Alternative investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	95.9	48.8
Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	38.9	11.3	$ 13.8
Level 3 | Alternative investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	37.8	10.2
Level 3 | Cash And Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 1.1	$ 1.1