Investment Securities - Summary of Unrealized Losses of Available-for-Sale Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale, Securities with losses under 12 months, Fair Value	$ 98,958	$ 93,037
Available-for-sale, Securities with losses under 12 months, Gross Unrealized Loss	2,195	826
Available-for-sale, Securities with losses over 12 months, Fair Value	150,493	158,412
Available-for-sale, Securities with losses over 12 months, Gross Unrealized Loss	6,564	4,528
Available-for-sale, Total, Fair Value	249,451	251,449
Available-for-sale, Total, Gross Unrealized Loss	8,759	5,354
Obligations of state and political subdivisions
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale, Securities with losses under 12 months, Fair Value	1,622	596
Available-for-sale, Securities with losses under 12 months, Gross Unrealized Loss	28	5
Available-for-sale, Securities with losses over 12 months, Fair Value	12,343	12,716
Available-for-sale, Securities with losses over 12 months, Gross Unrealized Loss	797	437
Available-for-sale, Total, Fair Value	13,965	13,312
Available-for-sale, Total, Gross Unrealized Loss	825	442
GSE mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale, Securities with losses under 12 months, Fair Value	35,985	29,725
Available-for-sale, Securities with losses under 12 months, Gross Unrealized Loss	791	224
Available-for-sale, Securities with losses over 12 months, Fair Value	5,568	5,858
Available-for-sale, Securities with losses over 12 months, Gross Unrealized Loss	185	97
Available-for-sale, Total, Fair Value	41,553	35,583
Available-for-sale, Total, Gross Unrealized Loss	976	321
Collateralized mortgage obligations: residential
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale, Securities with losses under 12 months, Fair Value	54,829	57,665
Available-for-sale, Securities with losses under 12 months, Gross Unrealized Loss	1,208	548
Available-for-sale, Securities with losses over 12 months, Fair Value	130,399	137,598
Available-for-sale, Securities with losses over 12 months, Gross Unrealized Loss	5,535	3,960
Available-for-sale, Total, Fair Value	185,228	195,263
Available-for-sale, Total, Gross Unrealized Loss	6,743	4,508
Collateralized mortgage obligations: commercial
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale, Securities with losses under 12 months, Fair Value	0	0
Available-for-sale, Securities with losses under 12 months, Gross Unrealized Loss	0	0
Available-for-sale, Securities with losses over 12 months, Fair Value	2,183	2,240
Available-for-sale, Securities with losses over 12 months, Gross Unrealized Loss	47	34
Available-for-sale, Total, Fair Value	2,183	2,240
Available-for-sale, Total, Gross Unrealized Loss	47	34
Mutual funds
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale, Securities with losses under 12 months, Fair Value	2,026	2,061
Available-for-sale, Securities with losses under 12 months, Gross Unrealized Loss	74	39
Available-for-sale, Securities with losses over 12 months, Fair Value	0	0
Available-for-sale, Securities with losses over 12 months, Gross Unrealized Loss	0	0
Available-for-sale, Total, Fair Value	2,026	2,061
Available-for-sale, Total, Gross Unrealized Loss	74	39
Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale, Securities with losses under 12 months, Fair Value	4,496	2,990
Available-for-sale, Securities with losses under 12 months, Gross Unrealized Loss	94	10
Available-for-sale, Securities with losses over 12 months, Fair Value	0	0
Available-for-sale, Securities with losses over 12 months, Gross Unrealized Loss	0	0
Available-for-sale, Total, Fair Value	4,496	2,990
Available-for-sale, Total, Gross Unrealized Loss	$ 94	$ 10