Short-Term Financing (Details) (USD $)	3 Months Ended		6 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Jun. 30, 2012
Short-term Debt [Line Items]
Obligations under reverse repurchase agreements	$ 13,500,000		$ 13,500,000		$ 0
Credit agreement period			364 days
Maturities of commercial paper range			overnight to up to 364 days
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		2,000,000,000
Expiration date of credit facilities			Jun. 01, 2013
Outstanding borrowings	0		0
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
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 2017 [Member]
Short-term Debt [Line Items]
Maximum borrowing capacity under credit facilities	1,500,000,000		1,500,000,000
Term of credit			5 years
Expiration date of credit facilities			Jun. 01, 2017
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]
Outstanding borrowings	0		0		0
Average outstanding borrowings	3,700,000,000	3,300,000,000	3,500,000,000	3,200,000,000
Weighted average interest rates	0.20%	0.10%	0.20%	0.10%
Weighted average maturity of borrowings under the short-term commercial paper program	3 days		2 days
Reverse Repurchase Agreements [Member]
Short-term Debt [Line Items]
Maximum borrowing capacity under credit facilities	3,000,000,000		3,000,000,000
Outstanding borrowings					0
Debt Instrument, Maturity Date	Jan. 02, 2013
Average outstanding borrowings	416,800,000	271,500,000	475,700,000	384,200,000
Weighted average interest rates	0.70%	0.70%	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