Fair Value - Information About our Fixed Rate Financial instruments not Measured at Fair Value (Detail) - Level 2 - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Reported Value Measurement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed rate debt	$ (109,197)	$ (111,506)
Estimate of Fair Value Measurement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed rate debt	$ (109,114)	$ (109,789)

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

No definition available.

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