Employee Postretirement Benefits - Schedule of Benefit Payments (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected Benefit Payments - 2013	$ 50.2
Expected Benefit Payments - 2014	48.2
Expected Benefit Payments - 2015	50.4
Expected Benefit Payments - 2016	54.4
Expected Benefit Payments - 2017	54.7
Expected Benefit Payments - 2018-2022	296.3
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected Benefit Payments - 2013	13.1
Expected Benefit Payments - 2014	13.8
Expected Benefit Payments - 2015	14.3
Expected Benefit Payments - 2016	14.9
Expected Benefit Payments - 2017	15.3
Expected Benefit Payments - 2018-2022	$ 80.5

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Amount of benefits expected to be paid in the five fiscal years after the fifth fiscal year following the latest fiscal year from a defined benefit plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (f)

-URI http://asc.fasb.org/extlink&oid=21915506&loc=d3e1928-114920

+ Details

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- Definition

Amount of benefits expected to be paid in the next fiscal year following the latest fiscal year from a defined benefit plan.

+ References

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- Definition

Amount of benefits expected to be paid in the fifth fiscal year following the latest fiscal year from a defined benefit plan.

+ References

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- Definition

Amount of benefits expected to be paid in the fourth fiscal year following the latest fiscal year from a defined benefit plan.

+ References

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Amount of benefits expected to be paid in the third fiscal year following the latest fiscal year from a defined benefit plan.

+ References

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Amount of benefits expected to be paid in the second fiscal year following the latest fiscal year from a defined benefit plan.

+ References

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