Short-Term Financing (Details) (USD $)	3 Months Ended	12 Months Ended
	Sep. 30, 2013	Jun. 30, 2013
Short-term Debt [Line Items]
Obligations under reverse repurchase agreements	$ 340,900,000	$ 245,900,000
Credit agreement period	364 days
Aggregate amount of commercial paper issuable under the short-term commercial paper program	7,250,000,000
Maturities of commercial paper range	overnight to up to 364 days
Obligation under commercial paper borrowing	2,477,000,000	0
Maturities of short-term funding agreements	overnight to up to five business days
364-Day Credit Agreement [Member]
Short-term Debt [Line Items]
Maximum borrowing capacity under credit facilities	2,000,000,000
Expiration date of credit facilities	Jun. 01, 2014
Outstanding borrowings	0
Credit Facility Expiring In June 2015 [Member]
Short-term Debt [Line Items]
Maximum borrowing capacity under credit facilities	3,250,000,000
Term of credit	4 years
Expiration date of credit facilities	Jun. 01, 2015
Line of credit facility potentially available increase in maximum borrowing capacity	500,000,000
Credit Facility Expiring In June 2018 [Member]
Short-term Debt [Line Items]
Maximum borrowing capacity under credit facilities	2,000,000,000
Term of credit	5 years
Expiration date of credit facilities	Jun. 01, 2018
Credit Facility Expiring In June 2017 [Member]
Short-term Debt [Line Items]
Line of credit facility potentially available increase in maximum borrowing capacity	500,000,000
Short-Term Commercial Paper Program [Member]
Short-term Debt [Line Items]
Short-term Debt, Average Outstanding Amount	3,100,000,000	3,200,000,000
Weighted average interest rates	0.10%	0.20%
Commercial Paper Weight Average Maturity	2 days
Reverse Repurchase Agreements [Member]
Short-term Debt [Line Items]
Maximum borrowing capacity under credit facilities	3,000,000,000
Debt Instrument, Maturity Date		Jul. 02, 2013
Short-term Debt, Average Outstanding Amount	$ 529,400,000	$ 534,500,000
Weighted average interest rates	0.50%	0.70%
Subsequent Event [Member] | Commercial Paper [Member]
Short-term Debt [Line Items]
Debt Instrument, Maturity Date	Oct. 02, 2013
Subsequent Event [Member] | Reverse Repurchase Agreements [Member]
Short-term Debt [Line Items]
Debt Instrument, Maturity Date	Oct. 01, 2013