Income Taxes - Summary of Changes in Unrecognized Tax Benefit (Including Interest and Penalties) (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($)
Income Tax Disclosure [Abstract]
UTB, Beginning Balance	$ 114
UTB, Lapse of the applicable statute of limitations	(54)
UTB, Ending Balance	60
Interest/Penalties, Beginning Balance	7
Interest/Penalties, Lapse of the applicable statute of limitations	(5)
Interest/Penalties, Ending Balance	2
Total, Beginning Balance	121
Total, Lapse of the applicable statute of limitations	(59)
Total, Ending Balance	$ 62