BANK LOANS, NET, Analysis of Payment Status of Loans Held for Investment (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Sep. 30, 2014
Analysis of payment status of loans held for investment [Abstract]
30-89 days and accruing	$ 4,948		$ 4,948		$ 1,829
90 days or more and accruing	0		0		0
Total past due and accruing	4,948		4,948		1,829
Nonaccrual	59,218		59,218		80,665
Current and accruing	12,091,446		12,091,446		11,020,924
Total loans held for investment	12,155,612		12,155,612		11,103,418
Performing nonaccrual loans	27,900		27,900		41,400
Impaired interest lost on nonaccrual loans	400	$ 900	1,100	$ 2,700
Impaired financing receivable, interest income recognized	300	$ 300	900	$ 1,100
Other real estate owned fair value	4,900		4,900		5,400
C&I loans
Analysis of payment status of loans held for investment [Abstract]
30-89 days and accruing	168		168		124
90 days or more and accruing	0		0		0
Total past due and accruing	168		168		124
Nonaccrual	0		0		0
Current and accruing	6,539,474		6,539,474		6,422,223
Total loans held for investment	6,539,642		6,539,642		6,422,347
CRE construction loans
Analysis of payment status of loans held for investment [Abstract]
30-89 days and accruing	0		0		0
90 days or more and accruing	0		0		0
Total past due and accruing	0		0		0
Nonaccrual	0		0		0
Current and accruing	120,267		120,267		94,195
Total loans held for investment	120,267		120,267		94,195
CRE loans
Analysis of payment status of loans held for investment [Abstract]
30-89 days and accruing	0		0		0
90 days or more and accruing	0		0		0
Total past due and accruing	0		0		0
Nonaccrual	11,108		11,108		18,876
Current and accruing	1,757,672		1,757,672		1,670,287
Total loans held for investment	1,768,780		1,768,780		1,689,163
Tax-exempt loans
Analysis of payment status of loans held for investment [Abstract]
30-89 days and accruing	0		0		0
90 days or more and accruing	0		0		0
Total past due and accruing	0		0		0
Nonaccrual	0		0		0
Current and accruing	385,234		385,234		122,218
Total loans held for investment	385,234		385,234		122,218
Residential mortgage - first mortgage loans
Analysis of payment status of loans held for investment [Abstract]
30-89 days and accruing	4,744		4,744		1,648
90 days or more and accruing	0		0		0
Total past due and accruing	4,744		4,744		1,648
Nonaccrual	47,826		47,826		61,391
Current and accruing	1,877,999		1,877,999		1,668,724
Total loans held for investment	1,930,569		1,930,569		1,731,763
Residential mortgage - home equity loans/lines
Analysis of payment status of loans held for investment [Abstract]
30-89 days and accruing	36		36		57
90 days or more and accruing	0		0		0
Total past due and accruing	36		36		57
Nonaccrual	284		284		398
Current and accruing	19,672		19,672		19,529
Total loans held for investment	19,992		19,992		19,984
SBL
Analysis of payment status of loans held for investment [Abstract]
30-89 days and accruing	0		0		0
90 days or more and accruing	0		0		0
Total past due and accruing	0		0		0
Nonaccrual	0		0		0
Current and accruing	1,391,128		1,391,128		1,023,748
Total loans held for investment	$ 1,391,128		$ 1,391,128		$ 1,023,748