Property and Equipment - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property Plant And Equipment [Abstract]
Depreciation and amortization expense	$ 148.3	$ 147.0	$ 166.4

Depreciation of property, plant and equipment directly related to services rendered by an entity during the reporting period.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.2(d))
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

Name:	us-gaap_CostOfServicesDepreciationAndAmortization
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration