Short-Term Financing (Details) - USD ($)	1 Months Ended	11 Months Ended	12 Months Ended
	Jun. 30, 2018	May 31, 2018	Jun. 30, 2018	Jun. 30, 2017
Short-term Debt [Line Items]
Credit borrowings	$ 0		$ 0	$ 0
Commercial Paper	0		$ 0	0
Maturities of short-term funding agreements			overnight to up to five business days
Obligations under reverse repurchase agreements	0		$ 0	$ 0
364-Day Credit Agreement [Member]
Short-term Debt [Line Items]
Maximum borrowing capacity under credit facilities	3,800,000,000		$ 3,800,000,000
Term of credit			364 days
Expiration date of credit facilities			Jun. 16, 2019
Debt Instrument, Extension Option Term			1 year
Short-Term Commercial Paper Program [Member]
Short-term Debt [Line Items]
Weighted average maturity of borrowings under the short-term commercial paper program			2 days	2 days
Reverse Repurchase Agreements [Member]
Short-term Debt [Line Items]
Short-term Debt, Average Outstanding Amount			$ 374,400,000	$ 274,800,000
Debt Instrument, Interest Rate During Period			1.30%	0.60%
Credit Facility Expiring In June Two Thousand Twenty Two [Member]
Short-term Debt [Line Items]
Maximum borrowing capacity under credit facilities	2,250,000,000		$ 2,250,000,000
Term of credit			5 years
Expiration date of credit facilities			Jun. 17, 2022
Line of credit facility potentially available increase in maximum borrowing capacity			$ 500,000,000
Credit Facility Expiring In June Two Thousand Twenty One [Member]
Short-term Debt [Line Items]
Maximum borrowing capacity under credit facilities	3,750,000,000		$ 3,750,000,000
Term of credit			5 years
Expiration date of credit facilities			Jun. 13, 2023
Line of credit facility potentially available increase in maximum borrowing capacity			$ 500,000,000
Commercial Paper [Member]
Short-term Debt [Line Items]
Aggregate amount of commercial paper issuable under the short-term commercial paper program	$ 9,800,000,000	$ 9,500,000,000
Maturities of commercial paper range			overnight to up to 364 days
Short-term Debt, Average Outstanding Amount			$ 2,800,000,000	$ 3,100,000,000
Debt Instrument, Interest Rate During Period			1.40%	0.60%