Summary of Significant Accounting Policies - Reconciliation of the Captions in the Consolidated Balance Sheet to the Consolidated Statements of Cash Flows (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accounting Policies [Abstract]
Cash and cash equivalents	$ 56,992	$ 81,146
Restricted cash	2,396	2,383
Cash, cash equivalents and restricted cash in Consolidated Statements of Cash Flows	$ 59,388	$ 83,529	$ 201,153