BANK LOANS, NET, Changes in the Allowance for Loan Losses (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2015	Mar. 31, 2014
Changes in the allowance for loan losses [Roll Forward]
Balance at beginning of period	$ 156,767	$ 138,124	$ 147,574	$ 136,501
Provision (benefit) for loan losses	3,937	1,979	13,302	3,615
Net (charge-offs)/recoveries:
Charge-offs	(411)	(2,475)	(876)	(2,724)
Recoveries	542	643	1,127	1,183
Net (charge-offs)/recoveries	131	(1,832)	251	(1,541)
Foreign exchange translation adjustment	(827)	(331)	(1,119)	(635)
Balance at end of period	160,008	137,940	160,008	137,940
Loans held for investment | C&I
Changes in the allowance for loan losses [Roll Forward]
Balance at beginning of period	109,582	96,629	103,179	95,994
Provision (benefit) for loan losses	1,530	1,113	8,364	2,015
Net (charge-offs)/recoveries:
Charge-offs	0	(1,805)	(238)	(1,845)
Recoveries	536	12	536	16
Net (charge-offs)/recoveries	536	(1,793)	298	(1,829)
Foreign exchange translation adjustment	(523)	(247)	(716)	(478)
Balance at end of period	111,125	95,702	111,125	95,702
Loans held for investment | CRE construction
Changes in the allowance for loan losses [Roll Forward]
Balance at beginning of period	1,709	1,647	1,594	1,000
Provision (benefit) for loan losses	(8)	169	117	824
Net (charge-offs)/recoveries:
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Net (charge-offs)/recoveries	0	0	0	0
Foreign exchange translation adjustment	(26)	(17)	(36)	(25)
Balance at end of period	1,675	1,799	1,675	1,799
Loans held for investment | CRE
Changes in the allowance for loan losses [Roll Forward]
Balance at beginning of period	25,095	20,210	25,022	19,266
Provision (benefit) for loan losses	900	2,133	1,062	3,062
Net (charge-offs)/recoveries:
Charge-offs	0	0	0	0
Recoveries	0	0	0	80
Net (charge-offs)/recoveries	0	0	0	80
Foreign exchange translation adjustment	(278)	(67)	(367)	(132)
Balance at end of period	25,717	22,276	25,717	22,276
Loans held for investment | Tax-exempt loans
Changes in the allowance for loan losses [Roll Forward]
Balance at beginning of period	2,738	0	1,380	0
Provision (benefit) for loan losses	1,171	0	2,529	0
Net (charge-offs)/recoveries:
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Net (charge-offs)/recoveries	0	0	0	0
Foreign exchange translation adjustment	0	0	0	0
Balance at end of period	3,909	0	3,909	0
Loans held for investment | Residential mortgage
Changes in the allowance for loan losses [Roll Forward]
Balance at beginning of period	15,319	18,300	14,350	19,126
Provision (benefit) for loan losses	168	(1,641)	787	(2,702)
Net (charge-offs)/recoveries:
Charge-offs	(411)	(670)	(638)	(879)
Recoveries	0	625	577	1,069
Net (charge-offs)/recoveries	(411)	(45)	(61)	190
Foreign exchange translation adjustment	0	0	0	0
Balance at end of period	15,076	16,614	15,076	16,614
Loans held for investment | SBL and other consumer
Changes in the allowance for loan losses [Roll Forward]
Balance at beginning of period	2,324	1,338	2,049	1,115
Provision (benefit) for loan losses	176	205	443	416
Net (charge-offs)/recoveries:
Charge-offs	0	0	0	0
Recoveries	6	6	14	18
Net (charge-offs)/recoveries	6	6	14	18
Foreign exchange translation adjustment	0	0	0	0
Balance at end of period	$ 2,506	$ 1,549	$ 2,506	$ 1,549