SECURITIES, Held to Maturity (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Sep. 30, 2015
Held-to-maturity Securities [Abstract]
Amortized cost	$ 485,768	$ 345,744
Gross unrealized gains	7,808	2,182
Gross unrealized (losses)	(226)	(1,079)
Fair value	493,350	346,847
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
LESS THAN 12 MONTHS, Fair Value	32,853	89,700
OVER 12 MONTHS, Fair Value	59,862	72,695
TOTAL, Fair Value	92,715	162,395
LESS THAN 12 MONTHS, Unrealized (Losses)	(82)	(442)
OVER 12 MONTHS, Unrealized (Losses)	(144)	(637)
TOTAL, Unrealized (Losses)	(226)	(1,079)
AMORTIZED COST [Abstract]
Due in one year or less	225	95
Due after one year through five years	11,721	8,411
Due after five years through ten years	143,869	140,145
Due after ten years	261,456	130,516
Total	417,271	279,167
Mortgage-backed securities	68,497	66,577
Amortized cost	485,768	345,744
FAIR VALUE [Abstract]
Due in one year or less	225	96
Due after one year through five years	11,885	8,430
Due after five years through ten years	147,574	140,505
Due after ten years	265,258	131,712
Total	424,942	280,743
Mortgage-backed securities	68,408	66,104
Total held to maturity securities	493,350	346,847
Non-bank Qualified Obligations of States and Political Subdivisions [Member]
Held-to-maturity Securities [Abstract]
Amortized cost	396,480	259,627
Gross unrealized gains	7,540	2,122
Gross unrealized (losses)	(61)	(419)
Fair value	403,959	261,330
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
LESS THAN 12 MONTHS, Fair Value	25,003	78,663
OVER 12 MONTHS, Fair Value	422	4,136
TOTAL, Fair Value	25,425	82,799
LESS THAN 12 MONTHS, Unrealized (Losses)	(56)	(365)
OVER 12 MONTHS, Unrealized (Losses)	(5)	(54)
TOTAL, Unrealized (Losses)	(61)	(419)
AMORTIZED COST [Abstract]
Amortized cost	396,480	259,627
FAIR VALUE [Abstract]
Total held to maturity securities	403,959	261,330
Mortgage-backed Securities [Member]
Held-to-maturity Securities [Abstract]
Amortized cost	68,497	66,577
Gross unrealized gains	30	0
Gross unrealized (losses)	(119)	(473)
Fair value	68,408	66,104
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
LESS THAN 12 MONTHS, Fair Value	2,945	5,509
OVER 12 MONTHS, Fair Value	56,954	60,595
TOTAL, Fair Value	59,899	66,104
LESS THAN 12 MONTHS, Unrealized (Losses)	(10)	(43)
OVER 12 MONTHS, Unrealized (Losses)	(109)	(430)
TOTAL, Unrealized (Losses)	(119)	(473)
AMORTIZED COST [Abstract]
Amortized cost	68,497	66,577
FAIR VALUE [Abstract]
Total held to maturity securities	68,408	66,104
Obligations of States and Political Subdivisions [Member]
Held-to-maturity Securities [Abstract]
Amortized cost	20,791	19,540
Gross unrealized gains	238	60
Gross unrealized (losses)	(46)	(187)
Fair value	20,983	19,413
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
LESS THAN 12 MONTHS, Fair Value	4,905	5,528
OVER 12 MONTHS, Fair Value	2,486	7,964
TOTAL, Fair Value	7,391	13,492
LESS THAN 12 MONTHS, Unrealized (Losses)	(16)	(34)
OVER 12 MONTHS, Unrealized (Losses)	(30)	(153)
TOTAL, Unrealized (Losses)	(46)	(187)
AMORTIZED COST [Abstract]
Amortized cost	20,791	19,540
FAIR VALUE [Abstract]
Total held to maturity securities	$ 20,983	$ 19,413

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