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Stock-Based Compensation Plans - Fair Value of Liability Cash-Settled Long-Term Incentives (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Balance at January 1	$ 1.0	$ 0.1
Compensation (credit)/charge for the period	(0.7)	0.1
Balance at March 31	$ 0.3	$ 0.2

X

- Definition

Change in fair value of liability cash-settled stock appreciation rights.

+ References

No definition available.

+ Details

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X

- Definition

Fair value of liability cash-settled stock appreciation rights.

+ References

No definition available.

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Data Type:	xbrli:monetaryItemType
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- References

No definition available.

+ Details

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