Derivative Instruments and Hedging Activities Derivative Instruments and Hedging Activities - Offsetting Assets and Liabilities (Details) - USD ($) $ in Millions	Jun. 30, 2015	Sep. 30, 2014	Jun. 30, 2014
Offsetting Derivative Assets and Liabilities [Abstract]
Gross amount recognized, derivative assets	$ 258	$ 243	$ 250
Gross amount recognized, derivative liabilities	1,708	1,813	1,793
Gross amount eligible for offsetting, derivative assets	(8)	(11)	(6)
Gross amount eligible for offsetting, derivative liabilities	(8)	(11)	(6)
Net derivative amount, derivative assets	250	232	244
Net derivative amount, derivative liabilities	$ 1,700	$ 1,802	$ 1,787