Investments - Cash Flows from Consolidated Investing Activities by Security (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Mar. 31, 2013	Apr. 01, 2012
Gain (Loss) on Investments [Line Items]
Proceeds from investments sold, matured or repaid	$ 6,016.3	$ 3,223.2
Cost of investments acquired	(5,916.2)	(2,194.3)
Available-for-sale Securities [Member]
Gain (Loss) on Investments [Line Items]
Proceeds from investments sold, matured or repaid	5,769.7	3,059.7
Cost of investments acquired	(5,839.0)	(2,022.0)
Held-to-maturity Securities [Member]
Gain (Loss) on Investments [Line Items]
Proceeds from investments sold, matured or repaid		74.9
Cost of investments acquired		(34.0)
Trading (acquired for holding) [Member]
Gain (Loss) on Investments [Line Items]
Proceeds from investments sold, matured or repaid	91.8	9.2
Cost of investments acquired	(0.9)	(70.4)
Derivative and other [Member]
Gain (Loss) on Investments [Line Items]
Proceeds from investments sold, matured or repaid	154.8	79.4
Cost of investments acquired	$ (76.3)	$ (67.9)