Accumulated Other Comprehensive (Loss) Income - Reclassifications Out of Accumulated Other Comprehensive (Loss) Income (Parenthetical) (Detail) $ in Millions	3 Months Ended
Mar. 31, 2018 USD ($)
Statement of Comprehensive Income [Abstract]
Gain on sale of discontinued operations, tax	$ 3.6

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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=84228862&loc=d3e640-108580

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration