Asset Impairment - Additional Information (Detail) $ in Thousands	12 Months Ended
Dec. 31, 2016 USD ($)
Asset Impairment Charges [Line Items]
Impairment of assets	$ 3,464
HDC Assets [Member]
Asset Impairment Charges [Line Items]
Impairment of assets	$ 1,902

The amount of impairment loss recognized in the period resulting from the write-down of the carrying amount of a finite-lived intangible asset to fair value.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 3
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16373-109275

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