Fair Value Disclosures - Other Real Estate Owned (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Fair Value Disclosures [Abstract]
Carrying value of other real estate owned prior to re-measurement	$ 526	$ 88	$ 526	$ 88
Write-downs included in gain (loss) on sale of other real estate owned	(126)	(8)	(126)	(8)
Other real estate owned, fair value	$ 400	$ 80	$ 400	$ 80