Investment Securities - Summary of Unrealized Losses of Available-for-Sale Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale, Securities with losses under 12 months, Fair Value	$ 137,529	$ 232,776
Available-for-sale, Securities with losses under 12 months, Gross Unrealized Loss	1,341	4,466
Available-for-sale, Securities with losses over 12 months, Fair Value	53,140	16,315
Available-for-sale, Securities with losses over 12 months, Gross Unrealized Loss	1,043	556
Available-for-sale, Total, Fair Value	190,669	249,091
Available-for-sale, Total, Gross Unrealized Loss	2,384	5,022
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	8,092	13,402
Available-for-sale, Securities with losses under 12 months, Gross Unrealized Loss	141	1,020
Available-for-sale, Securities with losses over 12 months, Fair Value	5,324	0
Available-for-sale, Securities with losses over 12 months, Gross Unrealized Loss	211	0
Available-for-sale, Total, Fair Value	13,416	13,402
Available-for-sale, Total, Gross Unrealized Loss	352	1,020
GSE mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale, Securities with losses under 12 months, Fair Value	6,168	29,119
Available-for-sale, Securities with losses under 12 months, Gross Unrealized Loss	22	302
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	6,168	29,119
Available-for-sale, Total, Gross Unrealized Loss	22	302
Collateralized mortgage obligations: residential
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale, Securities with losses under 12 months, Fair Value	118,195	187,235
Available-for-sale, Securities with losses under 12 months, Gross Unrealized Loss	1,153	3,099
Available-for-sale, Securities with losses over 12 months, Fair Value	45,344	14,194
Available-for-sale, Securities with losses over 12 months, Gross Unrealized Loss	805	507
Available-for-sale, Total, Fair Value	163,539	201,429
Available-for-sale, Total, Gross Unrealized Loss	1,958	3,606
Collateralized mortgage obligations: commercial
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale, Securities with losses under 12 months, Fair Value	0	961
Available-for-sale, Securities with losses under 12 months, Gross Unrealized Loss	0	4
Available-for-sale, Securities with losses over 12 months, Fair Value	2,472	2,121
Available-for-sale, Securities with losses over 12 months, Gross Unrealized Loss	27	49
Available-for-sale, Total, Fair Value	2,472	3,082
Available-for-sale, Total, Gross Unrealized Loss	27	53
Mutual funds
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale, Securities with losses under 12 months, Fair Value	2,079	2,059
Available-for-sale, Securities with losses under 12 months, Gross Unrealized Loss	21	41
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	2,079	2,059
Available-for-sale, Total, Gross Unrealized Loss	21	$ 41
Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale, Securities with losses under 12 months, Fair Value	2,995
Available-for-sale, Securities with losses under 12 months, Gross Unrealized Loss	4
Available-for-sale, Securities with losses over 12 months, Fair Value	0
Available-for-sale, Securities with losses over 12 months, Gross Unrealized Loss	0
Available-for-sale, Total, Fair Value	2,995
Available-for-sale, Total, Gross Unrealized Loss	$ 4