Securities - Amortized Cost of Securities and their Estimated Fair Values (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
FHLB stock	$ 4,428	$ 4,428
FHLB stock	4,428	4,428
Amortized Cost	172,777	184,940
Gross Unrealized Gains	584	1,414
Gross Unrealized Losses	(2,557)	(1,563)
Estimated Fair Value	170,804	184,791
Estimated Fair Value, Less than 12 months	1,465	87,323
Unrealized Losses, Less than 12 months	(8)	(772)
Estimated Fair Value, 12 months or longer	115,115	32,325
Unrealized Losses, 12 months or longer	(2,549)	(791)
Estimated Fair Value	116,580	119,648
Unrealized Losses	(2,557)	(1,563)
U.S. Agency Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	81,158	84,210
Gross Unrealized Gains	345	536
Gross Unrealized Losses	(1,154)	(653)
Estimated Fair Value	80,349	84,093
U.S. Agency Securities [Member] | Temporarily Impaired Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value, Less than 12 months		41,501
Unrealized Losses, Less than 12 months		(431)
Estimated Fair Value, 12 months or longer	54,441	9,846
Unrealized Losses, 12 months or longer	(1,154)	(222)
Estimated Fair Value	54,441	51,347
Unrealized Losses	(1,154)	(653)
Tax Free Municipal Bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	25,753	26,412
Gross Unrealized Gains	181	637
Gross Unrealized Losses	(152)	(83)
Estimated Fair Value	25,782	26,966
Tax Free Municipal Bonds [Member] | Temporarily Impaired Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value, Less than 12 months	1,465	4,860
Unrealized Losses, Less than 12 months	(8)	(51)
Estimated Fair Value, 12 months or longer	5,619	913
Unrealized Losses, 12 months or longer	(144)	(32)
Estimated Fair Value	7,084	5,773
Unrealized Losses	(152)	(83)
Taxable Municipals Bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	957	1,279
Gross Unrealized Gains	2	5
Gross Unrealized Losses	(5)	(1)
Estimated Fair Value	954	1,283
Taxable Municipals Bonds [Member] | Temporarily Impaired Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value, Less than 12 months		521
Unrealized Losses, Less than 12 months		(1)
Estimated Fair Value, 12 months or longer	507
Unrealized Losses, 12 months or longer	(5)
Estimated Fair Value	507	521
Unrealized Losses	(5)	(1)
Mortgage-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	64,909	71,389
Gross Unrealized Gains	56	201
Gross Unrealized Losses	(1,246)	(826)
Estimated Fair Value	63,719	70,764
Mortgage-Backed Securities [Member] | Temporarily Impaired Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value, Less than 12 months		40,441
Unrealized Losses, Less than 12 months		(289)
Estimated Fair Value, 12 months or longer	54,548	21,566
Unrealized Losses, 12 months or longer	(1,246)	(537)
Estimated Fair Value	54,548	62,007
Unrealized Losses	$ (1,246)	(826)
Trust Preferred Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost		1,650
Gross Unrealized Gains		35
Estimated Fair Value		$ 1,685