SECURITIES (Securities Debt Maturities) (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Investments, Debt and Equity Securities [Abstract]
Trading Securities, Amortized Cost, Maturing in one year or less	$ 130
Trading Securities, Amortized Cost, Maturing after one year through five years	230
Trading Securities, Amortized Cost, Maturing after five years through ten years	1,200
Trading Securities, Amortized Cost, Maturing after ten years through twenty years	17,089
Trading Securities, Amortized Cost, Maturing after twenty years	10,000
Trading Securities, Amortized Cost, Total with contractual maturity	28,649
Trading Securities, Amortized Cost, Equity securities	14
Trading Securities, Amortized Cost	28,663	$ 30,154
Trading Securities, Fair Value, Maturing in one year or less	131
Trading Securities, Fair Value, Maturing after one year through five years	231
Trading Securities, Fair Value, Maturing after five years through ten years	1,274
Trading Securities, Fair Value, Maturing after ten years through twenty years	14,248
Trading Securities, Fair Value, Maturing after twenty years	7,427
Trading Securities, Fair Value, Total with contractual maturity	23,311
Trading Securities, Fair Value, Equity securities	155
Trading Securities, Fair Value	23,466	24,568
Available-for-sale Securities, Amortized Cost, Maturing in one year or less	26,951
Available-for-sale Securities, Amortized Cost, Maturing after one year through five years	110,023
Available-for-sale Securities, Amortized Cost, Maturing after five years through ten years	265,137
Available-for-sale Securities, Amortized Cost, Maturing after ten years through twenty years	255,076
Available-for-sale Securities, Amortized Cost, Maturing after twenty years	675,990
Available-for-sale Securities, Amortized Cost, Total with contractual maturity	1,333,177
Available-for-sale Securities, Amortized Cost, Equity securities	5,686
Available-for-sale Securities, Amortized Cost	1,338,863	806,336
Available-for-sale Securities, Fair Value, Maturing in one year or less	26,911
Available-for-sale Securities, Fair Value, Maturing after one year through five years	110,293
Available-for-sale Securities, Fair Value, Maturing after five years through ten years	264,366
Available-for-sale Securities, Fair Value, Maturing after ten years through twenty years	256,319
Available-for-sale Securities, Fair Value, Maturing after twenty years	675,583
Available-for-sale Securities, Fair Value, Total with contractual maturity	1,333,472
Available-for-sale Securities, Fair Value, Equity securities	5,585
Available-for-sale Securities, Fair Value	1,339,057	800,917
Held-to-maturity Securities, Amortized Cost, Maturing in one year or less	1,226
Held-to-maturity Securities, Amortized Cost, Maturing after one year through five years	24,269
Held-to-maturity Securities, Amortized Cost, Maturing after five years through ten years	108,739
Held-to-maturity Securities, Amortized Cost, Maturing after ten years through twenty years	88,407
Held-to-maturity Securities, Amortized Cost, Maturing after twenty years	42,111
Held-to-maturity Securities, Amortized Cost	264,752	267,873
Held-to-maturity Securities, Fair Value, Maturing in one year or less	1,226
Held-to-maturity Securities, Fair Value, Maturing after one year through five years	24,432
Held-to-maturity Securities, Fair Value, Maturing after five years through ten years	110,368
Held-to-maturity Securities, Fair Value, Maturing after ten years through twenty years	91,280
Held-to-maturity Securities, Fair Value, Maturing after twenty years	41,357
Held-to-maturity Securities, Fair Value	$ 268,663	$ 270,528