Short-Term Financing (Details) (USD $)	3 Months Ended		6 Months Ended	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013	Jun. 30, 2013
Short-term Debt [Line Items]
Obligations under reverse repurchase agreements	$ 0		$ 0	$ 245,900,000
Credit agreement period			364 days
Line of credit facility potentially available increase in maximum borrowing capacity			500,000,000
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
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, 2014
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 2018 [Member]
Short-term Debt [Line Items]
Maximum borrowing capacity under credit facilities	2,000,000,000		2,000,000,000
Term of credit			5 years
Expiration date of credit facilities			Jun. 01, 2018
Short-Term Commercial Paper Program [Member]
Short-term Debt [Line Items]
Short-term Debt, Average Outstanding Amount	3,300,000,000	3,700,000,000	3,200,000,000	3,500,000,000
Weighted average interest rates	0.10%	0.20%	0.10%	0.20%
Commercial Paper Weight Average Maturity	2 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
Debt Instrument, Maturity Date				Jul. 02, 2013
Short-term Debt, Average Outstanding Amount	$ 402,000,000	$ 416,800,000	$ 465,700,000	$ 475,700,000
Weighted average interest rates	0.60%	0.70%	0.50%	0.70%