Significant Accounting Policies - Additional Information (Detail) $ in Thousands	6 Months Ended
	Jun. 30, 2018 USD ($)
Maximum [Member]
Significant Accounting Policies [Line Items]
Percentage of increase on assets due to new accounting standard updates	1.00%
Percentage of increase on liabilities due to new accounting standard updates	1.00%
Retained Earnings [Member]
Significant Accounting Policies [Line Items]
Change in accounting principle for adoption of ASU 2016-01	$ 278
Accumulated Other Comprehensive Loss [Member]
Significant Accounting Policies [Line Items]
Change in accounting principle for adoption of ASU 2016-01	$ (278)