INVESTMENT SECURITIES - Schedule of Gross Unrealized Losses and Fair Value of Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Estimated Fair Value	$ 244,722	$ 480,324
Less Than 12 Months, Unrealized Losses	(1,738)	(7,009)
12 Months or More, Estimated Fair Value	69,559	12,284
12 Months or More, Unrealized Losses	(1,200)	(384)
Total Estimated Fair Value	314,281	492,608
Total Unrealized Losses	(2,938)	(7,393)
U.S. government sponsored agencies
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Estimated Fair Value	0	0
Less Than 12 Months, Unrealized Losses	0	0
12 Months or More, Estimated Fair Value	0	0
12 Months or More, Unrealized Losses	0	0
Total Estimated Fair Value	0	0
Total Unrealized Losses	0	0
State, county and municipal securities
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Estimated Fair Value	11,333	47,647
Less Than 12 Months, Unrealized Losses	(18)	(469)
12 Months or More, Estimated Fair Value	4,240	0
12 Months or More, Unrealized Losses	(56)	0
Total Estimated Fair Value	15,573	47,647
Total Unrealized Losses	(74)	(469)
Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Estimated Fair Value	8,131	18,377
Less Than 12 Months, Unrealized Losses	(35)	(363)
12 Months or More, Estimated Fair Value	10,854	493
12 Months or More, Unrealized Losses	(81)	(7)
Total Estimated Fair Value	18,985	18,870
Total Unrealized Losses	(116)	(370)
Mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Estimated Fair Value	225,258	414,300
Less Than 12 Months, Unrealized Losses	(1,685)	(6,177)
12 Months or More, Estimated Fair Value	54,465	11,791
12 Months or More, Unrealized Losses	(1,063)	(377)
Total Estimated Fair Value	279,723	426,091
Total Unrealized Losses	$ (2,748)	$ (6,554)