UK Pension Assets, Fair Value Inputs (Detail) (Pension Benefits, Non U.S. Plans, USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Defined Benefit Plan Disclosure [Line Items]
Diversified Growth fund	$ 123.7	$ 106.6
Fixed Interest and Index-linked Securities	63.5	61.1
Index-linked Bonds		8.1
Cash Equivalents	0.8	0.2
Total	188.0	176.0
Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Diversified Growth fund	0	0
Fixed Interest and Index-linked Securities	0	0
Index-linked Bonds		0
Cash Equivalents	0.8	0.2
Total	0.8	0.2
Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Diversified Growth fund	123.7	106.6
Fixed Interest and Index-linked Securities	63.5	61.1
Index-linked Bonds		8.1
Cash Equivalents	0	0
Total	187.2	175.8
Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Diversified Growth fund	0	0
Fixed Interest and Index-linked Securities	0	0
Index-linked Bonds		0
Cash Equivalents	0	0
Total	$ 0	$ 0

Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid investments that are both readily convertible to known amounts of cash, and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months. Compensating balance arrangements that do not legally restrict the withdrawal or usage of cash equivalents may be reported as cash equivalents, while legally restricted equivalents held as compensating balances against borrowing arrangements, contracts entered into with others, or company statements of intention with regard to particular equivalents are not generally reported as part of unrestricted cash equivalents.

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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.

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