Recent Accounting Pronouncements - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2017	Sep. 30, 2017
ASU 2017-07
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net periodic benefit credits, other than service cost components, reclassified to other income—net	$ (0.8)	$ (0.2)

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

Name:	us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration