SECURITIES (Securities Debt Maturities) (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Investments, Debt and Equity Securities [Abstract]
Trading Securities, Amortized Cost, Maturing in one year or less	$ 1,741
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	8,262
Trading Securities, Amortized Cost, Maturing after twenty years	18,740
Trading Securities, Amortized Cost, Total with contractual maturity	30,173
Trading Securities, Amortized Cost, Equity securities	14
Trading Securities, Amortized Cost	30,187	$ 30,154
Trading Securities, Fair Value, Maturing in one year or less	1,750
Trading Securities, Fair Value, Maturing after one year through five years	231
Trading Securities, Fair Value, Maturing after five years through ten years	1,291
Trading Securities, Fair Value, Maturing after ten years through twenty years	7,974
Trading Securities, Fair Value, Maturing after twenty years	13,388
Trading Securities, Fair Value, Total with contractual maturity	24,634
Trading Securities, Fair Value, Equity securities	119
Trading Securities, Fair Value	24,753	24,568
Available-for-sale Securities, Amortized Cost, Maturing in one year or less	23,099
Available-for-sale Securities, Amortized Cost, Maturing after one year through five years	115,084
Available-for-sale Securities, Amortized Cost, Maturing after five years through ten years	215,933
Available-for-sale Securities, Amortized Cost, Maturing after ten years through twenty years	293,580
Available-for-sale Securities, Amortized Cost, Maturing after twenty years	578,963
Available-for-sale Securities, Amortized Cost, Total with contractual maturity	1,226,659
Available-for-sale Securities, Amortized Cost, Equity securities	88
Available-for-sale Securities, Amortized Cost	1,226,747	806,336
Available-for-sale Securities, Fair Value, Maturing in one year or less	23,082
Available-for-sale Securities, Fair Value, Maturing after one year through five years	115,031
Available-for-sale Securities, Fair Value, Maturing after five years through ten years	214,541
Available-for-sale Securities, Fair Value, Maturing after ten years through twenty years	293,840
Available-for-sale Securities, Fair Value, Maturing after twenty years	577,172
Available-for-sale Securities, Fair Value, Total with contractual maturity	1,223,666
Available-for-sale Securities, Fair Value, Equity securities	98
Available-for-sale Securities, Fair Value	1,223,764	800,917
Held-to-maturity Securities, Amortized Cost, Maturing in one year or less	1,957
Held-to-maturity Securities, Amortized Cost, Maturing after one year through five years	19,868
Held-to-maturity Securities, Amortized Cost, Maturing after five years through ten years	112,229
Held-to-maturity Securities, Amortized Cost, Maturing after ten years through twenty years	88,077
Held-to-maturity Securities, Amortized Cost, Maturing after twenty years	44,260
Held-to-maturity Securities, Amortized Cost	266,391	267,873
Held-to-maturity Securities, Fair Value, Maturing in one year or less	1,964
Held-to-maturity Securities, Fair Value, Maturing after one year through five years	19,989
Held-to-maturity Securities, Fair Value, Maturing after five years through ten years	113,151
Held-to-maturity Securities, Fair Value, Maturing after ten years through twenty years	90,802
Held-to-maturity Securities, Fair Value, Maturing after twenty years	43,496
Held-to-maturity Securities, Fair Value	$ 269,402	$ 270,528