INVESTMENT SECURITIES - Summary of Unrealized Losses - Available-for-Sale (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Securities with losses under 12 months, Fair Value	$ 232,776	$ 165,890
Securities with losses under 12 months, Gross Unrealized Loss	4,466	1,471
Securities with losses over 12 months, Fair Value	16,315	32,975
Securities with losses over 12 months, Gross Unrealized Loss	556	1,134
Total, Fair Value	249,091	198,865
Total, Gross Unrealized Loss	5,022	2,605
Obligations of state and political subdivisions
Schedule of Available-for-sale Securities [Line Items]
Securities with losses under 12 months, Fair Value	13,402	1,192
Securities with losses under 12 months, Gross Unrealized Loss	1,020	27
Securities with losses over 12 months, Fair Value	0	0
Securities with losses over 12 months, Gross Unrealized Loss	0	0
Total, Fair Value	13,402	1,192
Total, Gross Unrealized Loss	1,020	27
GSE mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Securities with losses under 12 months, Fair Value	29,119	21,607
Securities with losses under 12 months, Gross Unrealized Loss	302	229
Securities with losses over 12 months, Fair Value	0	0
Securities with losses over 12 months, Gross Unrealized Loss	0	0
Total, Fair Value	29,119	21,607
Total, Gross Unrealized Loss	302	229
Collateralized mortgage obligations: residential
Schedule of Available-for-sale Securities [Line Items]
Securities with losses under 12 months, Fair Value	187,235	140,999
Securities with losses under 12 months, Gross Unrealized Loss	3,099	1,207
Securities with losses over 12 months, Fair Value	14,194	30,029
Securities with losses over 12 months, Gross Unrealized Loss	507	1,069
Total, Fair Value	201,429	171,028
Total, Gross Unrealized Loss	3,606	2,276
Collateralized mortgage obligations: commercial
Schedule of Available-for-sale Securities [Line Items]
Securities with losses under 12 months, Fair Value	961	0
Securities with losses under 12 months, Gross Unrealized Loss	4	0
Securities with losses over 12 months, Fair Value	2,121	2,946
Securities with losses over 12 months, Gross Unrealized Loss	49	65
Total, Fair Value	3,082	2,946
Total, Gross Unrealized Loss	53	65
Mutual funds
Schedule of Available-for-sale Securities [Line Items]
Securities with losses under 12 months, Fair Value	2,059	2,092
Securities with losses under 12 months, Gross Unrealized Loss	41	8
Securities with losses over 12 months, Fair Value	0	0
Securities with losses over 12 months, Gross Unrealized Loss	0	0
Total, Fair Value	2,059	2,092
Total, Gross Unrealized Loss	$ 41	$ 8