Short-Term Financing (Details) (USD $)	3 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Jun. 30, 2012
Short-term Debt [Line Items]
Credit agreement period	364 days
Maturities of commercial paper range	overnight to up to 364 days
Obligations under reverse repurchase agreements	$ 442,700,000		$ 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, 2013
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 Two Thousand Seventeen [Member]
Short-term Debt [Line Items]
Maximum borrowing capacity under credit facilities	1,500,000,000
Term of credit	5 years
Expiration date of credit facilities	Jun. 01, 2017
Credit Facility Expiring In June 2013 [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]
Outstanding borrowings	0		0
Average outstanding borrowings	3,200,000,000	3,000,000,000
Weighted average interest rates	0.20%	0.10%
Weighted average maturity of borrowings under the short-term commercial paper program	2 days
Reverse Repurchase Agreements [Member]
Short-term Debt [Line Items]
Maximum borrowing capacity under credit facilities	3,000,000,000
Outstanding borrowings			0
Debt Instrument, Maturity Date	Oct. 03, 2012
Average outstanding borrowings	534,500,000	496,800,000
Weighted average interest rates	0.70%	0.50%
Issuance Of Debt [Member]
Short-term Debt [Line Items]
Aggregate amount of commercial paper issuable under the short-term commercial paper program	$ 6,750,000,000