Short-Term Financing (Details) (USD $)	3 Months Ended		6 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Jun. 30, 2011
Short-term Debt [Line Items]
Maturities of commercial paper range			overnight to up to 364 days
Short-Term Commercial Paper Program [Member]
Short-term Debt [Line Items]
Average outstanding borrowings	$ 3,300,000,000	$ 2,300,000,000	$ 3,200,000,000	$ 2,300,000,000
Weighted average interest rates	0.10%	0.20%	0.10%	0.20%
Outstanding borrowings	0		0		0
Weighted average maturity of borrowings under the short-term commercial paper program	two days		two days
364-Day Credit Agreement [Member]
Short-term Debt [Line Items]
Maximum borrowing capacity under credit facilities	2,000,000,000		2,000,000,000
Expiration date of credit facilities			June 2012
Credit Facility Expiring In June 2015 [Member]
Short-term Debt [Line Items]
Maximum borrowing capacity under credit facilities	3,250,000,000		3,250,000,000
Credit facility, term (in years)			4
Expiration date of credit facilities			June 2015
Line of credit facility potentially available increase in maximum borrowing capacity			500,000,000
Credit Facility Expiring In June 2013 [Member]
Short-term Debt [Line Items]
Maximum borrowing capacity under credit facilities	1,500,000,000		1,500,000,000
Credit facility, term (in years)			3
Expiration date of credit facilities			June 2013
Line of credit facility potentially available increase in maximum borrowing capacity			500,000,000
Reverse Repurchase Agreements [Member]
Short-term Debt [Line Items]
Maximum borrowing capacity under credit facilities	2,000,000,000		2,000,000,000
Average outstanding borrowings	271,500,000	541,700,000	384,200,000	575,300,000
Weighted average interest rates	0.70%	0.50%	0.50%	0.40%
Outstanding borrowings	0		0		0
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