Retirement Plans and Other Post-Retirement Benefits - Components of Amounts Recognized as Accumulated Other Comprehensive Income on Pre-Tax Basis (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2013	Dec. 31, 2012
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Prior service cost/(credit)	$ 14.8	$ 17.9
Net actuarial loss	131.9	237.6
Other Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Prior service cost/(credit)	(1.4)	(1.9)
Net actuarial loss	$ 1.4	$ 12.6

Retirement Plans and Other Post-Retirement Benefits - Components of Amounts Recognized as Accumulated Other Comprehensive Income on Pre-Tax Basis (Detail) (USD $)
In Millions, unless otherwise specified

12 Months Ended

Dec. 31, 2013

Dec. 31, 2012

Pension Benefits [Member]

Defined Benefit Plan Disclosure [Line Items]

Prior service cost/(credit)

$ 14.8

$ 17.9

Net actuarial loss

131.9

237.6

Other Benefits [Member]

Defined Benefit Plan Disclosure [Line Items]

Prior service cost/(credit)

(1.4)

(1.9)

Net actuarial loss

$ 1.4

$ 12.6