Fair Value of Financial Instruments - Additional Information (Detail) - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Transfers between fair value measurement levels	$ 0	$ 0
Recurring Basis [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Liabilities measured at fair value	$ 0

Fair value of financial and nonfinancial obligations.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258

Name:	us-gaap_LiabilitiesFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant