BANK LOANS, NET, Credit Quality of Held for Investment Loan Portfolio (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Sep. 30, 2015
Financing Receivable, Recorded Investment [Line Items]
Total loans held for investment	$ 14,409,920	$ 13,073,183
Performing residential first mortgage loans	1,848,847
LTV less than 50%
Financing Receivable, Recorded Investment [Line Items]
Performing residential first mortgage loans	658,860
LTV greater than 50% but less than 80%
Financing Receivable, Recorded Investment [Line Items]
Performing residential first mortgage loans	1,085,978
LTV greater than 80% but less than 100%
Financing Receivable, Recorded Investment [Line Items]
Performing residential first mortgage loans	88,862
LTV greater than 100%, but less than 120%
Financing Receivable, Recorded Investment [Line Items]
Performing residential first mortgage loans	13,466
LTV greater than 120%
Financing Receivable, Recorded Investment [Line Items]
Performing residential first mortgage loans	1,681
C&I loans
Financing Receivable, Recorded Investment [Line Items]
Total loans held for investment	7,283,214	6,928,018
CRE construction loans
Financing Receivable, Recorded Investment [Line Items]
Total loans held for investment	145,905	162,356
CRE loans
Financing Receivable, Recorded Investment [Line Items]
Total loans held for investment	2,448,268	2,054,154
Tax-exempt loans
Financing Receivable, Recorded Investment [Line Items]
Total loans held for investment	610,274	484,537
Residential – first mortgage loans
Financing Receivable, Recorded Investment [Line Items]
Total loans held for investment	2,198,370	1,941,794
Home equity loans/lines
Financing Receivable, Recorded Investment [Line Items]
Total loans held for investment	19,214	20,820
SBL
Financing Receivable, Recorded Investment [Line Items]
Total loans held for investment	1,704,675	1,481,504
Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans held for investment	14,100,253	12,790,684
Pass | C&I loans
Financing Receivable, Recorded Investment [Line Items]
Total loans held for investment	7,046,244	6,739,179
Pass | CRE construction loans
Financing Receivable, Recorded Investment [Line Items]
Total loans held for investment	145,905	162,356
Pass | CRE loans
Financing Receivable, Recorded Investment [Line Items]
Total loans held for investment	2,443,599	2,034,692
Pass | Tax-exempt loans
Financing Receivable, Recorded Investment [Line Items]
Total loans held for investment	610,274	484,537
Pass | Residential – first mortgage loans
Financing Receivable, Recorded Investment [Line Items]
Total loans held for investment	2,130,729	1,868,044
Pass | Home equity loans/lines
Financing Receivable, Recorded Investment [Line Items]
Total loans held for investment	18,827	20,372
Pass | SBL
Financing Receivable, Recorded Investment [Line Items]
Total loans held for investment	1,704,675	1,481,504
Special mention
Financing Receivable, Recorded Investment [Line Items]
Total loans held for investment	108,667	112,680
Special mention | C&I loans
Financing Receivable, Recorded Investment [Line Items]
Total loans held for investment	95,379	97,623
Special mention | CRE construction loans
Financing Receivable, Recorded Investment [Line Items]
Total loans held for investment	0	0
Special mention | CRE loans
Financing Receivable, Recorded Investment [Line Items]
Total loans held for investment	0	39
Special mention | Tax-exempt loans
Financing Receivable, Recorded Investment [Line Items]
Total loans held for investment	0	0
Special mention | Residential – first mortgage loans
Financing Receivable, Recorded Investment [Line Items]
Total loans held for investment	13,073	14,890
Special mention | Home equity loans/lines
Financing Receivable, Recorded Investment [Line Items]
Total loans held for investment	215	128
Special mention | SBL
Financing Receivable, Recorded Investment [Line Items]
Total loans held for investment	0	0
Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans held for investment	201,000	169,819
Substandard | C&I loans
Financing Receivable, Recorded Investment [Line Items]
Total loans held for investment	141,591	91,216
Substandard | CRE construction loans
Financing Receivable, Recorded Investment [Line Items]
Total loans held for investment	0	0
Substandard | CRE loans
Financing Receivable, Recorded Investment [Line Items]
Total loans held for investment	4,669	19,423
Substandard | Tax-exempt loans
Financing Receivable, Recorded Investment [Line Items]
Total loans held for investment	0	0
Substandard | Residential – first mortgage loans
Financing Receivable, Recorded Investment [Line Items]
Total loans held for investment	54,568	58,860
Substandard | Home equity loans/lines
Financing Receivable, Recorded Investment [Line Items]
Total loans held for investment	172	320
Substandard | SBL
Financing Receivable, Recorded Investment [Line Items]
Total loans held for investment	0	0
Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans held for investment	0	0
Doubtful | C&I loans
Financing Receivable, Recorded Investment [Line Items]
Total loans held for investment	0	0
Doubtful | CRE construction loans
Financing Receivable, Recorded Investment [Line Items]
Total loans held for investment	0	0
Doubtful | CRE loans
Financing Receivable, Recorded Investment [Line Items]
Total loans held for investment	0	0
Doubtful | Tax-exempt loans
Financing Receivable, Recorded Investment [Line Items]
Total loans held for investment	0	0
Doubtful | Residential – first mortgage loans
Financing Receivable, Recorded Investment [Line Items]
Total loans held for investment	0	0
Doubtful | Home equity loans/lines
Financing Receivable, Recorded Investment [Line Items]
Total loans held for investment	0	0
Doubtful | SBL
Financing Receivable, Recorded Investment [Line Items]
Total loans held for investment	$ 0	$ 0