BANK LOANS, NET, Held for Sale and Held for Investment (Details) $ in Thousands	Mar. 31, 2016 USD ($) segment	Sep. 30, 2015 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loan portfolio segments | segment	6
Loans Receivable Held-for-sale, Net [Abstract]
Loans receivable held-for-sale, net	$ 172,222	$ 119,519
Loans held for investment:
Total loans held for investment	14,409,920	13,073,183
Net unearned income and deferred expenses	(39,441)	(32,424)
Total loans held for investment, net	14,370,479	13,040,759
Total loans held for sale and investment	14,542,701	13,160,278
Allowance for loan losses	(194,220)	(172,257)
Bank loans, net	$ 14,348,481	$ 12,988,021
Associated percentage of each major loan category in loan portfolios [Abstract]
Loans held for sale, net (in hundredths)	1.00%	1.00%
Total loans held for sale and investment (in hundredths)	100.00%	100.00%
Domestic
Loans held for investment:
C&I loans	$ 6,236,413	$ 5,893,631
CRE construction loans	143,437	126,402
CRE loans	2,035,699	1,679,332
Tax-exempt loans	610,274	484,537
Residential mortgage loans	$ 2,215,264	$ 1,959,786
Associated percentage of each major loan category in loan portfolios [Abstract]
C&I loans (in hundredths)	43.00%	44.00%
CRE construction loans (in hundredths)	1.00%	1.00%
CRE loans (in hundredths)	14.00%	13.00%
Tax-exempt loans (in hundredths)	4.00%	4.00%
Residential mortgage loans (in hundredths)	15.00%	15.00%
SBL (in hundredths)	12.00%	11.00%
Foreign
Loans held for investment:
C&I loans	$ 1,046,801	$ 1,034,387
CRE construction loans	2,468	35,954
CRE loans	412,569	374,822
Residential mortgage loans	$ 2,320	$ 2,828
Associated percentage of each major loan category in loan portfolios [Abstract]
C&I loans (in hundredths)	7.00%	8.00%
CRE construction loans (in hundredths)	0.00%	0.00%
CRE loans (in hundredths)	3.00%	3.00%
Residential mortgage loans (in hundredths)	0.00%	0.00%
SBL (in hundredths)	0.00%	0.00%
SBL
Loans held for investment:
Total loans held for investment	$ 1,704,675	$ 1,481,504
SBL | Domestic
Loans held for investment:
SBL	1,702,766	1,479,562
SBL | Foreign
Loans held for investment:
SBL	$ 1,909	$ 1,942