Retirement Plans and Other Post-Retirement Benefits - Schedule of Fair Value of Benefit Plan Assets (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 0	$ 0
Large Cap [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	187.6	204.6
Small and Mid Cap [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	61.1	68.1
International Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	104.5	114.3
Real Estate Investment Trusts (REIT) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	31.6	25.9
Fixed Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	235.0	171.6
Cash and Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	18.2	16.7
Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	372.7	412.7
Level 1 [Member] | Large Cap [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	187.6	204.6
Level 1 [Member] | Small and Mid Cap [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	61.1	68.1
Level 1 [Member] | International Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	65.1	73.7
Level 1 [Member] | Real Estate Investment Trusts (REIT) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	31.6	25.9
Level 1 [Member] | Fixed Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	27.3	40.4
Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	265.3	188.5
Level 2 [Member] | International Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	39.4	40.6
Level 2 [Member] | Fixed Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	207.7	131.2
Level 2 [Member] | Cash and Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 18.2	$ 16.7