SECURITIES - Securities in a Continuous Unrealized Loss Position (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Securities in a Continuous Unrealized Loss Position, Less than 12 months, Estimated Fair Value	$ 75,287	$ 216,025
Securities in a Continuous Unrealized Loss Position, Less than 12 Months, Unrealized Losses	(781)	(6,170)
Securities in a Continuous Unrealized Loss Position, More than 12 Months, Estimated Fair Value	59,887	2,803
Securities in a Continuous Unrealized Loss Position, More than 12 Months Unrealized Losses	(1,520)	(90)
Securities in a Continuous Unrealized Loss Position, Total Estimated Fair Value	135,174	218,828
Securities in a Continuous Unrealized Loss Position, Total Unrealized Losses	(2,301)	(6,260)
U.S. Government and agency securities
Schedule of Available-for-sale Securities [Line Items]
Securities in a Continuous Unrealized Loss Position, Less than 12 months, Estimated Fair Value	1,153	0
Securities in a Continuous Unrealized Loss Position, Less than 12 Months, Unrealized Losses	(18)	0
Securities in a Continuous Unrealized Loss Position, More than 12 Months, Estimated Fair Value	0	0
Securities in a Continuous Unrealized Loss Position, More than 12 Months Unrealized Losses	0	0
Securities in a Continuous Unrealized Loss Position, Total Estimated Fair Value	1,153	0
Securities in a Continuous Unrealized Loss Position, Total Unrealized Losses	(18)	0
Municipal securities
Schedule of Available-for-sale Securities [Line Items]
Securities in a Continuous Unrealized Loss Position, Less than 12 months, Estimated Fair Value	51,739	178,876
Securities in a Continuous Unrealized Loss Position, Less than 12 Months, Unrealized Losses	(554)	(5,655)
Securities in a Continuous Unrealized Loss Position, More than 12 Months, Estimated Fair Value	56,306	0
Securities in a Continuous Unrealized Loss Position, More than 12 Months Unrealized Losses	(1,415)	0
Securities in a Continuous Unrealized Loss Position, Total Estimated Fair Value	108,045	178,876
Securities in a Continuous Unrealized Loss Position, Total Unrealized Losses	(1,969)	(5,655)
Agency mortgage-backed pass-through securities
Schedule of Available-for-sale Securities [Line Items]
Securities in a Continuous Unrealized Loss Position, Less than 12 months, Estimated Fair Value	13,173	12,520
Securities in a Continuous Unrealized Loss Position, Less than 12 Months, Unrealized Losses	(168)	(347)
Securities in a Continuous Unrealized Loss Position, More than 12 Months, Estimated Fair Value	3,581	2,803
Securities in a Continuous Unrealized Loss Position, More than 12 Months Unrealized Losses	(105)	(90)
Securities in a Continuous Unrealized Loss Position, Total Estimated Fair Value	16,754	15,323
Securities in a Continuous Unrealized Loss Position, Total Unrealized Losses	(273)	(437)
Corporate bonds and other
Schedule of Available-for-sale Securities [Line Items]
Securities in a Continuous Unrealized Loss Position, Less than 12 months, Estimated Fair Value	9,222	24,629
Securities in a Continuous Unrealized Loss Position, Less than 12 Months, Unrealized Losses	(41)	(168)
Securities in a Continuous Unrealized Loss Position, More than 12 Months, Estimated Fair Value	0	0
Securities in a Continuous Unrealized Loss Position, More than 12 Months Unrealized Losses	0	0
Securities in a Continuous Unrealized Loss Position, Total Estimated Fair Value	9,222	24,629
Securities in a Continuous Unrealized Loss Position, Total Unrealized Losses	$ (41)	$ (168)