Fair Value of Assets and Liabilities - Schedule of Trust Preferred Securities Measured at Fair Value on a Recurring Basis (Detail) - Trust Preferred Securities [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Balance at beginning of period	$ 1,685	$ 1,817
Accretion included in net income	4	16
Unrealized gain (loss) included in comprehensive income	294	(148)
Call of security at book value	(1,658)
Realized gain on call of security	$ (325)
Balance at end of period		$ 1,685