Income Taxes - Deferred Taxes in Consolidated Balance Sheets (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Deferred income taxes	$ 138.1	$ 164.5
Other non-current liabilities	(2.1)	(1.6)
Net deferred tax assets	$ 136.0	$ 162.9

Amount after allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and carryforwards classified as noncurrent.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant