New Financial Accounting Pronouncements - Schedule of Reconciliation of Cash, Cash Equivalents and Restricted Cash Reported within Condensed Consolidated Statements of Cash Flows (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Cash and cash equivalents	$ 30,718	$ 29,902
Total cash, cash equivalents and restricted cash	32,710	$ 30,659	$ 25,871	$ 48,006
ASU 2016-18 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Cash and cash equivalents	30,718		24,567
Restricted cash	774		873
Cash and cash equivalents included in assets held for sale	1,218
Restricted cash included within deferred charges and other assets			431
Total cash, cash equivalents and restricted cash	$ 32,710		$ 25,871