Composition of Domestic Pension Plan Assets (Detail) (Pension Benefits, Domestic, USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 268.5	$ 270.0	$ 256.5
Equity Securities And Funds, Domestic
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	39.2	39.2
Equity Securities And Funds, International
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	40.4	50.2
Fixed Income Securities And Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	104.1	87.1
Alternative investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	83.5	89.6
Cash And Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1.3	3.9
Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	127.3	135.0
Level 1 | Equity Securities And Funds, Domestic
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	29.0	39.2
Level 1 | Fixed Income Securities And Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	73.6	66.8
Level 1 | Alternative investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	24.5	26.2
Level 1 | Cash And Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.2	2.8
Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	129.9	121.2
Level 2 | Equity Securities And Funds, Domestic
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	10.2
Level 2 | Equity Securities And Funds, International
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	40.4	50.2
Level 2 | Fixed Income Securities And Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	30.5	20.3
Level 2 | Alternative investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	48.8	50.7
Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	11.3	13.8	14.1
Level 3 | Alternative investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	10.2	12.7
Level 3 | Cash And Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 1.1	$ 1.1