SECURITIES - Investment Securities Available for Sale in Continuous Unrealized Loss Position (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Available-for-sale securities in a continuous unrealized loss position, fair value [Abstract]
Less than 12 months	$ 129,637	$ 259,567
12 months or longer	57,919	225
Total	187,556	259,792
Available-for-sale securities in a continuous unrealized loss position, unrealized losses [Abstract]
Less than 12 months	1,078	7,804
12 months or longer	1,880	1
Total	2,958	7,805
Mortgage-backed securities, residential
Available-for-sale securities in a continuous unrealized loss position, fair value [Abstract]
Less than 12 months	121,345	233,843
12 months or longer	57,638	0
Total	178,983	233,843
Available-for-sale securities in a continuous unrealized loss position, unrealized losses [Abstract]
Less than 12 months	1,022	7,492
12 months or longer	1,871	0
Total	2,893	7,492
Obligations of states and political subdivisions
Available-for-sale securities in a continuous unrealized loss position, fair value [Abstract]
Less than 12 months	4,080	25,724
12 months or longer	281	0
Total	4,361	25,724
Available-for-sale securities in a continuous unrealized loss position, unrealized losses [Abstract]
Less than 12 months	19	312
12 months or longer	9	0
Total	28	312
Corporate bonds and notes
Available-for-sale securities in a continuous unrealized loss position, fair value [Abstract]
Less than 12 months	242
12 months or longer	0
Total	242
Available-for-sale securities in a continuous unrealized loss position, unrealized losses [Abstract]
Less than 12 months	7
12 months or longer	0
Total	7
SBA loan pools
Available-for-sale securities in a continuous unrealized loss position, fair value [Abstract]
Less than 12 months	3,970	0
12 months or longer	0	225
Total	3,970	225
Available-for-sale securities in a continuous unrealized loss position, unrealized losses [Abstract]
Less than 12 months	30	0
12 months or longer	0	1
Total	$ 30	$ 1