SECURITIES - Amortized Cost and Fair Value of Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Schedule of Held-to-maturity Securities [Line Items]
Held for Investment, Amortized Cost, Total	$ 374,773	$ 372,498
Held for Investment, Fair Value, Total	374,961	369,881
Available for Sale, Amortized Cost, Total	997,155
Available for Sale, Fair Value, Total	996,799	950,503
Collateralized Loan Obligations [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held for Investment, Amortized Cost, Due in less than one year	0
Held for Investment, Fair Value, Due in less than one year	0
Available for Sale Amortized Cost, Due in less than one year	6,103
Available for Sale, Fair Value, Due in less than one year	6,108
Held for Investment, Amortized Cost, Due after one year through five years	3,600
Held for Investment, Fair Value, Due after one year through five years	3,614
Available for Sale, Amortized Cost, Due after one year through five years	79,463
Available for Sale, Fair Value, Due after one year through five years	80,338
Held for Investment, Amortized Cost, Due after five years through ten years	41,838
Held for Investment, Fair Value, Due after five years through ten years	42,052
Available for Sale, Amortized Cost, Due after five years through ten years	224,255
Available for Sale, Fair Value, Due after five years through ten years	225,737
Held for Investment, Amortized Cost, Due after ten years	0
Held for Investment, Fair Value, Due after ten years	0
Available for Sale, Amortized Cost, Due after ten years	26,525
Available for Sale, Fair Value, Due after ten years	26,635
Held for Investment, Amortized Cost, Total	45,438
Held for Investment, Fair Value, Total	45,666
Available for Sale, Amortized Cost, Total	336,346
Available for Sale, Fair Value, Total	338,818
Mortgage-backed securities of U.S. Government Sponsored Entities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held for Investment, Amortized Cost, Total	179,437
Held for Investment, Fair Value, Total	179,844	159,402
Available for Sale, Amortized Cost, Total	284,015
Available for Sale, Fair Value, Total	282,962	283,488
Collateralized Mortgage Obligations Of US Government Sponsored Entities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held for Investment, Amortized Cost, Total	126,849
Held for Investment, Fair Value, Total	125,805	144,964
Available for Sale, Amortized Cost, Total	232,278
Available for Sale, Fair Value, Total	228,802	234,054
Commercial mortgage backed securities of U.S. Government Sponsored Entities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held for Investment, Amortized Cost, Total	17,441
Held for Investment, Fair Value, Total	18,086	17,534
Available for Sale, Amortized Cost, Total	22,274
Available for Sale, Fair Value, Total	22,619	22,545
Private mortgage backed securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held for Investment, Amortized Cost, Total	0
Held for Investment, Fair Value, Total	0
Available for Sale, Amortized Cost, Total	32,928
Available for Sale, Fair Value, Total	33,853	31,989
Private collateralized mortgage obligations [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held for Investment, Amortized Cost, Total	5,608
Held for Investment, Fair Value, Total	5,560	6,318
Available for Sale, Amortized Cost, Total	50,725
Available for Sale, Fair Value, Total	51,105	67,289
Other debt securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held for Investment, Amortized Cost, Total	0
Held for Investment, Fair Value, Total	0
Available for Sale, Amortized Cost, Total	10,403
Available for Sale, Fair Value, Total	70,797	73,861
Private commercial mortgage backed securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held for Investment, Amortized Cost, Total	0
Held for Investment, Fair Value, Total	0
Available for Sale, Amortized Cost, Total	28,186
Available for Sale, Fair Value, Total	$ 28,219	$ 37,172