Investments - Cash Flows from Consolidated Investing Activities by Security (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Jun. 30, 2013	Jul. 01, 2012
Gain (Loss) on Investments [Line Items]
Document Period End Date	Jun. 30, 2013
Proceeds from investments sold, matured or repaid	$ 7,396.3	$ 4,386.3
Cost of investments acquired	(7,271.4)	(3,860.6)
Available-for-sale Securities [Member]
Gain (Loss) on Investments [Line Items]
Proceeds from investments sold, matured or repaid	7,052.1	4,208.6
Cost of investments acquired	(7,148.7)	(3,697.0)
Held-to-maturity Securities [Member]
Gain (Loss) on Investments [Line Items]
Proceeds from investments sold, matured or repaid		75.7
Cost of investments acquired		(34.7)
Trading (acquired for holding) [Member]
Gain (Loss) on Investments [Line Items]
Proceeds from investments sold, matured or repaid	91.8	12.0
Cost of investments acquired	(10.2)	(22.9)
Derivative and other [Member]
Gain (Loss) on Investments [Line Items]
Proceeds from investments sold, matured or repaid	252.4	90.0
Cost of investments acquired	$ (112.5)	$ (106.0)