SECURITIES - Held to Maturity (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Sep. 30, 2016
Held-to-maturity Securities [Abstract]
Amortized cost	$ 604,976	$ 619,853
Gross unrealized gains	1,371	12,807
Gross unrealized (losses)	(7,246)	(86)
Securities held to maturity	599,101	632,574
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
LESS THAN 12 MONTHS, Fair Value	495,052	24,264
LESS THAN 12 MONTHS, Unrealized (Losses)	(7,198)	(55)
OVER 12 MONTHS, Fair Value	2,236	2,256
OVER 12 MONTHS, Unrealized (Losses)	(48)	(31)
TOTAL, Fair Value	497,288	26,520
TOTAL, Unrealized (Losses)	(7,246)	(86)
AMORTIZED COST
Due in one year or less	341	472
Due after one year through five years	12,648	12,502
Due after five years through ten years	157,174	157,944
Due after ten years	308,448	315,177
Total	478,611	486,095
Mortgage-backed securities	126,365	133,758
Amortized cost	604,976	619,853
FAIR VALUE
Due in one year or less	341	471
Due after one year through five years	12,618	12,696
Due after five years through ten years	156,228	163,806
Due after ten years	305,445	321,166
Total	474,632	498,139
Mortgage-backed securities	124,469	134,435
Securities held to maturity	599,101	632,574
Non-bank Qualified Obligations of States and Political Subdivisions [Member]
Held-to-maturity Securities [Abstract]
Amortized cost	458,259	465,469
Gross unrealized gains	1,326	11,744
Gross unrealized (losses)	(5,072)	(11)
Securities held to maturity	454,513	477,202
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
LESS THAN 12 MONTHS, Fair Value	356,031	1,294
LESS THAN 12 MONTHS, Unrealized (Losses)	(5,072)	(11)
OVER 12 MONTHS, Fair Value	0	0
OVER 12 MONTHS, Unrealized (Losses)	0	0
TOTAL, Fair Value	356,031	1,294
TOTAL, Unrealized (Losses)	(5,072)	(11)
AMORTIZED COST
Amortized cost	458,259	465,469
FAIR VALUE
Securities held to maturity	454,513	477,202
Mortgage-backed Securities [Member]
Held-to-maturity Securities [Abstract]
Amortized cost	126,365	133,758
Gross unrealized gains	0	708
Gross unrealized (losses)	(1,896)	(31)
Securities held to maturity	124,469	134,435
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
LESS THAN 12 MONTHS, Fair Value	124,469	20,061
LESS THAN 12 MONTHS, Unrealized (Losses)	(1,896)	(31)
OVER 12 MONTHS, Fair Value	0	0
OVER 12 MONTHS, Unrealized (Losses)	0	0
TOTAL, Fair Value	124,469	20,061
TOTAL, Unrealized (Losses)	(1,896)	(31)
AMORTIZED COST
Amortized cost	126,365	133,758
FAIR VALUE
Securities held to maturity	124,469	134,435
Obligations of States and Political Subdivisions [Member]
Held-to-maturity Securities [Abstract]
Amortized cost	20,352	20,626
Gross unrealized gains	45	355
Gross unrealized (losses)	(278)	(44)
Securities held to maturity	20,119	20,937
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
LESS THAN 12 MONTHS, Fair Value	14,552	2,909
LESS THAN 12 MONTHS, Unrealized (Losses)	(230)	(13)
OVER 12 MONTHS, Fair Value	2,236	2,256
OVER 12 MONTHS, Unrealized (Losses)	(48)	(31)
TOTAL, Fair Value	16,788	5,165
TOTAL, Unrealized (Losses)	(278)	(44)
AMORTIZED COST
Amortized cost	20,352	20,626
FAIR VALUE
Securities held to maturity	$ 20,119	$ 20,937

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Amount of accumulated unrealized loss on investments in debt securities classified as held-to-maturity that have been in a continuous loss position for twelve months or longer.

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Fair value of held-to-maturity debt securities maturing in the sixth fiscal year through the tenth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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