Accumulated Other Comprehensive Loss - Schedule of Income Tax (Provision) Benefit Allocated to Components of OCI (Detail) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Equity [Abstract]
Foreign currency translation adjustments	$ (0.3)	$ (0.1)	$ (0.4)	$ (0.6)
Unrecognized pension and postretirement costs	3.9	3.9	11.4	11.9
Derivative financial instruments	(1.2)	(3.8)	1.0	(13.8)
Income tax (provision) benefit related to AOCL	$ 2.4	$ 0.0	$ 12.0	$ (2.5)

Other Comprehensive Income (Loss), Derivative Financial Instruments, Tax

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Amount of tax expense (benefit), after reclassification adjustments of gain (loss) on foreign currency translation adjustments, foreign currency transactions designated and effective as economic hedges of a net investment in a foreign entity and intra-entity foreign currency transactions that are of a long-term-investment nature.

+ References

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Amount of tax (expense) benefit for reclassification adjustment from accumulated other comprehensive (income) loss of defined benefit plan.

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Amount of tax expense (benefit) allocated to other comprehensive income (loss).

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