Commitments and Contingencies - Rent Expense (Detail) - USD ($)	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Litigation [Abstract]
Right-of-use Asset Amortization Expense	$ 40,000
Rent expense	$ 66,000	$ 65,000

Rental expense for the reporting period incurred under operating leases, including minimum and any contingent rent expense, net of related sublease income.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=77902758&loc=d3e41499-112717

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