SECURITIES (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Sep. 30, 2016
Available-for-sale debt securities [Abstract]
Mortgage-back securities	$ 586,454	$ 558,940
Available-for-sale equity securities [Abstract]
Fair value	1,106,977	910,309
Available-for-sale securities [Abstract]
Amortized cost	1,680,307	1,435,272
Gross unrealized gains	19,884	37,257
Gross unrealized (losses)	(6,760)	(3,280)
Total securities	1,693,431	1,469,249
Amortized Cost	1,680,307	1,435,272
Fair Value	1,693,431	1,469,249
Available-for-sale securities in a continuous unrealized loss position [Abstract]
LESS THAN 12 MONTHS, Fair Value	518,797	151,949
OVER 12 MONTHS, Fair Value	106,140	52,770
TOTAL, Fair Value	624,937	204,719
LESS THAN 12 MONTHS, Unrealized (Losses)	(4,512)	(1,033)
OVER 12 MONTHS, Unrealized (Losses)	(2,248)	(2,247)
TOTAL, Unrealized (Losses)	(6,760)	(3,280)
AMORTIZED COST [Abstract]
Due in one year or less	0	0
Due after one year through five years	36,586	17,370
Due after five years through ten years	347,831	426,034
Due after ten years	705,963	436,077
Total Amortized Cost	1,090,380	879,481
Mortgage-backed securities	588,918	555,036
Common equities and mutual funds	1,009	755
Amortized cost	1,680,307	1,435,272
FAIR VALUE [Abstract]
Due in one year or less	0	0
Due after one year through five years	37,674	17,897
Due after five years through ten years	358,198	446,771
Due after ten years	709,660	444,516
Total Fair Value	1,105,532	909,184
Mortgage-back securities	586,454	558,940
Common equities and mutual funds	1,445	1,125
Total securities	1,693,431	1,469,249
Held To Maturity
Amortized cost	563,529	619,853
Gross unrealized gains	4,901	12,807
Gross unrealized (losses)	(4,245)	(86)
Fair value	564,185	632,574
Held-to-maturity securities in a continuous unrealized loss position [Abstract]
LESS THAN 12 MONTHS, Fair Value	315,838	24,264
OVER 12 MONTHS, Fair Value	10,295	2,256
TOTAL, Fair Value	326,133	26,520
LESS THAN 12 MONTHS, Unrealized (Losses)	(4,022)	(55)
OVER 12 MONTHS, Unrealized (Losses)	(223)	(31)
TOTAL, Unrealized (Losses)	(4,245)	(86)
AMORTIZED COST [Abstract]
Due in one year or less	1,483	472
Due after one year through five years	17,926	12,502
Due after five years through ten years	144,996	157,944
Due after ten years	285,435	315,177
Total Amortized Cost	449,840	486,095
Mortgage-backed securities	113,689	133,758
Amortized cost	563,529	619,853
FAIR VALUE [Abstract]
Due in one year or less	1,480	471
Due after one year through five years	18,160	12,696
Due after five years through ten years	147,832	163,806
Due after ten years	284,257	321,166
Total Fair Value	451,729	498,139
Mortgage-backed securities	112,456	134,435
Total securities	564,185	632,574
Trust Preferred Securities [Member]
Available-for-sale securities [Abstract]
Amortized cost		14,936
Total securities		12,978
Amortized Cost		14,936
Fair Value		12,978
Unrealized Gain (Loss)		(1,958)
AMORTIZED COST [Abstract]
Amortized cost		14,936
FAIR VALUE [Abstract]
Total securities		12,978
S&P Credit Rating, BB+ [Member] | Moody's Credit Rating, Baa2 [Member] | Key Corp Capital I [Member] | Trust Preferred Securities [Member]
Available-for-sale securities [Abstract]
Amortized cost		4,987
Total securities		4,189
Amortized Cost		4,987
Fair Value		4,189
Unrealized Gain (Loss)		(798)
AMORTIZED COST [Abstract]
Amortized cost		4,987
FAIR VALUE [Abstract]
Total securities		4,189
S&P Credit Rating, BB [Member] | Moody's Credit Rating, Baa2 [Member] | Huntington Capital Trust II SE [Member] | Trust Preferred Securities [Member]
Available-for-sale securities [Abstract]
Amortized cost		4,981
Total securities		4,077
Amortized Cost		4,981
Fair Value		4,077
Unrealized Gain (Loss)		(904)
AMORTIZED COST [Abstract]
Amortized cost		4,981
FAIR VALUE [Abstract]
Total securities		4,077
Standard & Poor's, BBB- Rating [Member] | Moody's Credit Rating, Baa1 [Member] | PNC Capital Trust [Member] | Trust Preferred Securities [Member]
Available-for-sale securities [Abstract]
Amortized cost		4,968
Total securities		4,712
Amortized Cost		4,968
Fair Value		4,712
Unrealized Gain (Loss)		(256)
AMORTIZED COST [Abstract]
Amortized cost		4,968
FAIR VALUE [Abstract]
Total securities		4,712
Trust preferred and corporate securities [Member]
Available-for-sale debt securities [Abstract]
Amortized cost		14,935
Gross unrealized gains		0
Gross unrealized (losses)		(1,957)
Mortgage-back securities		12,978
Available-for-sale securities in a continuous unrealized loss position [Abstract]
LESS THAN 12 MONTHS, Fair Value		0
OVER 12 MONTHS, Fair Value		12,978
TOTAL, Fair Value		12,978
LESS THAN 12 MONTHS, Unrealized (Losses)		0
OVER 12 MONTHS, Unrealized (Losses)		(1,957)
TOTAL, Unrealized (Losses)		(1,957)
FAIR VALUE [Abstract]
Mortgage-back securities		12,978
Small Business Administration Securities [Member]
Available-for-sale debt securities [Abstract]
Amortized cost	57,046	78,431
Gross unrealized gains	825	2,288
Gross unrealized (losses)	0	0
Mortgage-back securities	57,871	80,719
Available-for-sale securities in a continuous unrealized loss position [Abstract]
LESS THAN 12 MONTHS, Fair Value		8,481
OVER 12 MONTHS, Fair Value		2,688
TOTAL, Fair Value		11,169
LESS THAN 12 MONTHS, Unrealized (Losses)		(58)
OVER 12 MONTHS, Unrealized (Losses)		(39)
TOTAL, Unrealized (Losses)		(97)
FAIR VALUE [Abstract]
Mortgage-back securities	57,871	80,719
Non-Bank Qualified Obligation of States And Political Subdivisions [Member]
Available-for-sale debt securities [Abstract]
Amortized cost	938,883	668,628
Gross unrealized gains	14,983	30,141
Gross unrealized (losses)	(3,037)	(97)
Mortgage-back securities	950,829	698,672
Available-for-sale securities in a continuous unrealized loss position [Abstract]
LESS THAN 12 MONTHS, Fair Value	280,900	89,403
OVER 12 MONTHS, Fair Value	5,853	0
TOTAL, Fair Value	286,753	89,403
LESS THAN 12 MONTHS, Unrealized (Losses)	(2,887)	(745)
OVER 12 MONTHS, Unrealized (Losses)	(150)	0
TOTAL, Unrealized (Losses)	(3,037)	(745)
FAIR VALUE [Abstract]
Mortgage-back securities	950,829	698,672
Asset-backed Securities [Member]
Available-for-sale debt securities [Abstract]
Amortized cost	94,451	117,487
Gross unrealized gains	2,381	73
Gross unrealized (losses)	0	(745)
Mortgage-back securities	96,832	116,815
FAIR VALUE [Abstract]
Mortgage-back securities	96,832	116,815
Collateralized Mortgage Backed Securities [Member]
Available-for-sale debt securities [Abstract]
Amortized cost	588,918	555,036
Gross unrealized gains	1,259	4,382
Gross unrealized (losses)	(3,723)	(478)
Mortgage-back securities	586,454	558,940
Available-for-sale securities in a continuous unrealized loss position [Abstract]
LESS THAN 12 MONTHS, Fair Value	237,897	54,065
OVER 12 MONTHS, Fair Value	100,287	36,979
TOTAL, Fair Value	338,184	91,044
LESS THAN 12 MONTHS, Unrealized (Losses)	(1,625)	(230)
OVER 12 MONTHS, Unrealized (Losses)	(2,098)	(248)
TOTAL, Unrealized (Losses)	(3,723)	(478)
FAIR VALUE [Abstract]
Mortgage-back securities	586,454	558,940
Debt Securities [Member]
Available-for-sale debt securities [Abstract]
Amortized cost	1,679,298	1,434,517
Gross unrealized gains	19,448	36,884
Gross unrealized (losses)	(6,760)	(3,277)
Mortgage-back securities	1,691,986	1,468,124
Available-for-sale securities in a continuous unrealized loss position [Abstract]
LESS THAN 12 MONTHS, Fair Value	518,797	151,949
OVER 12 MONTHS, Fair Value	106,140	52,645
TOTAL, Fair Value	624,937	204,594
LESS THAN 12 MONTHS, Unrealized (Losses)	(4,512)	(1,033)
OVER 12 MONTHS, Unrealized (Losses)	(2,248)	(2,244)
TOTAL, Unrealized (Losses)	(6,760)	(3,277)
FAIR VALUE [Abstract]
Mortgage-back securities	1,691,986	1,468,124
Common Equities And Mutual Funds [Member]
Available-for-sale equity securities [Abstract]
Amortized cost	1,009	755
Gross unrealized gains	436	373
Gross unrealized (losses)	0	(3)
Fair value	1,445	1,125
Available-for-sale securities in a continuous unrealized loss position [Abstract]
LESS THAN 12 MONTHS, Fair Value		0
OVER 12 MONTHS, Fair Value		125
TOTAL, Fair Value		125
LESS THAN 12 MONTHS, Unrealized (Losses)		0
OVER 12 MONTHS, Unrealized (Losses)		(3)
TOTAL, Unrealized (Losses)		(3)
US States and Political Subdivisions Debt Securities [Member]
Held To Maturity
Amortized cost	19,247	20,626
Gross unrealized gains	157	355
Gross unrealized (losses)	(36)	(44)
Fair value	19,368	20,937
Held-to-maturity securities in a continuous unrealized loss position [Abstract]
LESS THAN 12 MONTHS, Fair Value	1,364	2,909
OVER 12 MONTHS, Fair Value	4,089	2,256
TOTAL, Fair Value	5,453	5,165
LESS THAN 12 MONTHS, Unrealized (Losses)	(6)	(13)
OVER 12 MONTHS, Unrealized (Losses)	(30)	(31)
TOTAL, Unrealized (Losses)	(36)	(44)
AMORTIZED COST [Abstract]
Amortized cost	19,247	20,626
FAIR VALUE [Abstract]
Total securities	19,368	20,937
Non-Bank Qualified Obligation of States And Political Subdivisions [Member]
Held To Maturity
Amortized cost	430,593	465,469
Gross unrealized gains	4,744	11,744
Gross unrealized (losses)	(2,976)	(11)
Fair value	432,361	477,202
Held-to-maturity securities in a continuous unrealized loss position [Abstract]
LESS THAN 12 MONTHS, Fair Value	202,018	1,294
OVER 12 MONTHS, Fair Value	6,206	0
TOTAL, Fair Value	208,224	1,294
LESS THAN 12 MONTHS, Unrealized (Losses)	(2,783)	(11)
OVER 12 MONTHS, Unrealized (Losses)	(193)	0
TOTAL, Unrealized (Losses)	(2,976)	(11)
AMORTIZED COST [Abstract]
Amortized cost	430,593	465,469
FAIR VALUE [Abstract]
Total securities	432,361	477,202
Collateralized Mortgage Backed Securities [Member]
Held To Maturity
Amortized cost	113,689	133,758
Gross unrealized gains	0	708
Gross unrealized (losses)	(1,233)	(31)
Fair value	112,456	134,435
Held-to-maturity securities in a continuous unrealized loss position [Abstract]
LESS THAN 12 MONTHS, Fair Value	112,456	20,061
OVER 12 MONTHS, Fair Value	0	0
TOTAL, Fair Value	112,456	20,061
LESS THAN 12 MONTHS, Unrealized (Losses)	(1,233)	(31)
OVER 12 MONTHS, Unrealized (Losses)	0	0
TOTAL, Unrealized (Losses)	(1,233)	(31)
AMORTIZED COST [Abstract]
Amortized cost	113,689	133,758
FAIR VALUE [Abstract]
Total securities	$ 112,456	$ 134,435