Securities - Summary of Securities with Unrealized Losses and Length of Time Continuous Loss Positions (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Available-for-sale securities, continuous unrealized loss position [Abstract]
Less than 12 months, Estimated fair value	$ 13,664	$ 34,154
Less than 12 months, Gross unrealized (losses)	(191)	(574)
12 months or more, Estimated fair value	117,279	117,753
12 months or more, Gross unrealized losses	(2,358)	(4,279)
Total, Estimated fair value	130,943	151,907
Total, Gross unrealized losses	(2,549)	(4,853)
U. S. government agency securities
Available-for-sale securities, continuous unrealized loss position [Abstract]
12 months or more, Estimated fair value	10,601	10,706
12 months or more, Gross unrealized losses	(184)	(347)
Total, Estimated fair value	10,601	10,706
Total, Gross unrealized losses	(184)	(347)
State and municipal securities
Available-for-sale securities, continuous unrealized loss position [Abstract]
Less than 12 months, Estimated fair value		13,455
Less than 12 months, Gross unrealized (losses)		(212)
12 months or more, Estimated fair value	15,888	17,376
12 months or more, Gross unrealized losses	(303)	(772)
Total, Estimated fair value	15,888	30,831
Total, Gross unrealized losses	(303)	(984)
Mortgage-backed securities
Available-for-sale securities, continuous unrealized loss position [Abstract]
Less than 12 months, Estimated fair value	2,931	7,075
Less than 12 months, Gross unrealized (losses)	(12)	(17)
12 months or more, Estimated fair value	85,318	87,232
12 months or more, Gross unrealized losses	(1,786)	(3,148)
Total, Estimated fair value	88,249	94,307
Total, Gross unrealized losses	(1,798)	(3,165)
Asset-backed securities
Available-for-sale securities, continuous unrealized loss position [Abstract]
Less than 12 months, Estimated fair value	9,748	8,262
Less than 12 months, Gross unrealized (losses)	(164)	(145)
12 months or more, Estimated fair value		2,439
12 months or more, Gross unrealized losses		(12)
Total, Estimated fair value	9,748	10,701
Total, Gross unrealized losses	(164)	(157)
Other debt securities
Available-for-sale securities, continuous unrealized loss position [Abstract]
Less than 12 months, Estimated fair value	985	5,362
Less than 12 months, Gross unrealized (losses)	(15)	(200)
12 months or more, Estimated fair value	5,472
12 months or more, Gross unrealized losses	(85)
Total, Estimated fair value	6,457	5,362
Total, Gross unrealized losses	$ (100)	$ (200)