Summary of Significant Accounting Policies - Schedule of Cumulative-Effect Adjustment to Retained Earnings (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017	Dec. 31, 2016
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
As of January 1, 2018, as originally presented	$ 92,969		$ 161,761	$ 149,834
Cumulative effect of ASU 2016-01			0
As of January 1, 2018, as adjusted			161,761
Retained Earnings [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
As of January 1, 2018, as originally presented	(30,355)	$ 38,348	38,348	45,443
Cumulative effect of ASU 2016-01		632	632
As of January 1, 2018, as adjusted		38,980	38,980
Accumulated Other Comprehensive Loss [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
As of January 1, 2018, as originally presented	$ (49,434)	(44,760)	(44,760)	$ (60,885)
Cumulative effect of ASU 2016-01		(632)	(632)
As of January 1, 2018, as adjusted		$ (45,392)	$ (45,392)