DISCLOSURE OF OFFSETTING ASSETS AND LIABILITIES, COLLATERAL, ENCUMBERED ASSETS, AND REPURCHASE AGREEMENTS, Collateral (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Sep. 30, 2015
Collateral Received that Can be Resold or Repledged [Abstract]
Collateral we received that is available to be delivered or repledged	$ 2,076,066	$ 2,308,277
Collateral that we delivered or repledged	1,276,079	1,122,540
Value of margin securities pledged to clearing organizations	247,300	240,700
Securities reserve deposit required and made	$ 148,900	$ 147,600