Property and Equipment - Property and Equipment Impairment Charges (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Continuing Operations [Member]
Property Plant And Equipment [Line Items]
Property and equipment impairment charges	$ 4,894	$ 8,063	$ 12,210

The charge against earnings resulting from the aggregate write down of tangible assets from their carrying value to their fair value.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84176398&loc=d3e2921-110230

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=64827811&loc=d3e1361-107760

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