Schedule of Interest Expense on Note Payable to Related Party (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Related Party Transactions [Abstract]
Interest expense on note payable to related party (excluding amortization of debt premium and debt issuance costs)	$ 1,109	$ 1,040	$ 2,189	$ 2,160

Amount of interest expense incurred on a debt or other obligation to related party.

No definition available.

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