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Assets, usually stocks, bonds, and other investments, that have been segregated and restricted (usually in a trust) to provide benefits, at their fair value as of the measurement date. Plan assets include amounts contributed by the employer (and by employees for a contributory plan) and amounts earned from investing the contributions, less benefits paid. If a plan has liabilities other than for benefits, those non-benefit obligations may be considered as reductions of plan assets.

+ 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 (b)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 30

-Section 35

-Paragraph 50

-URI http://asc.fasb.org/extlink&oid=29635418&loc=d3e12355-114930

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- Definition

Target allocation maximum percentage of investments of this type to total plan assets presented on a weighted average basis.

+ 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 (d)(i)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

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-Name Accounting Standards Codification

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-Section 50

-Paragraph 5

-Subparagraph (c)(i)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e2446-114920

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Target allocation minimum percentage of investments of this type to total plan assets presented on a weighted average basis.

+ 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 (d)(i)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

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Allocation of Plan Assets by Investments (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Schedule of Defined Benefit Plan Asset Allocation Targets [Line Items]
Plan assets	$ 2,309.4	$ 2,108.4	$ 1,901.0
Equity Funds
Schedule of Defined Benefit Plan Asset Allocation Targets [Line Items]
Equity funds, target minimum	50.00%	50.00%
Equity funds, target maximum	70.00%	70.00%
Plan assets	1,357.7	1,247.2
Equity Funds \| United States
Schedule of Defined Benefit Plan Asset Allocation Targets [Line Items]
Plan assets	666.4	585.5
Equity Funds \| Global
Schedule of Defined Benefit Plan Asset Allocation Targets [Line Items]
Plan assets	691.3	661.7
Fixed Income Funds
Schedule of Defined Benefit Plan Asset Allocation Targets [Line Items]
Equity funds, target minimum	30.00%	30.00%
Equity funds, target maximum	50.00%	50.00%
Plan assets	895.1	812.4
Fixed Income Funds \| United States
Schedule of Defined Benefit Plan Asset Allocation Targets [Line Items]
Plan assets	608.6	552.1
Fixed Income Funds \| Non U.S.
Schedule of Defined Benefit Plan Asset Allocation Targets [Line Items]
Plan assets	286.5	260.3
Cash and other
Schedule of Defined Benefit Plan Asset Allocation Targets [Line Items]
Plan assets	56.6	48.8
Level 1
Schedule of Defined Benefit Plan Asset Allocation Targets [Line Items]
Plan assets	277.1	253.7
Level 1 \| Fixed Income Funds
Schedule of Defined Benefit Plan Asset Allocation Targets [Line Items]
Plan assets	269.4	252.5
Level 1 \| Fixed Income Funds \| United States
Schedule of Defined Benefit Plan Asset Allocation Targets [Line Items]
Plan assets	269.4	252.5
Level 1 \| Cash and other
Schedule of Defined Benefit Plan Asset Allocation Targets [Line Items]
Plan assets	7.7	1.2
Level 2
Schedule of Defined Benefit Plan Asset Allocation Targets [Line Items]
Plan assets	2,032.3	1,854.7
Level 2 \| Equity Funds
Schedule of Defined Benefit Plan Asset Allocation Targets [Line Items]
Plan assets	1,357.7	1,247.2
Level 2 \| Equity Funds \| United States
Schedule of Defined Benefit Plan Asset Allocation Targets [Line Items]
Plan assets	666.4	585.5
Level 2 \| Equity Funds \| Global
Schedule of Defined Benefit Plan Asset Allocation Targets [Line Items]
Plan assets	691.3	661.7
Level 2 \| Fixed Income Funds
Schedule of Defined Benefit Plan Asset Allocation Targets [Line Items]
Plan assets	625.7	559.9
Level 2 \| Fixed Income Funds \| United States
Schedule of Defined Benefit Plan Asset Allocation Targets [Line Items]
Plan assets	339.2	299.6
Level 2 \| Fixed Income Funds \| Non U.S.
Schedule of Defined Benefit Plan Asset Allocation Targets [Line Items]
Plan assets	286.5	260.3
Level 2 \| Cash and other
Schedule of Defined Benefit Plan Asset Allocation Targets [Line Items]
Plan assets	$ 48.9	$ 47.6