Borrowings (Details Numeric) (USD $)	6 Months Ended
	Jun. 30, 2014
Borrowings [Abstract]
Weighted-average effective rate	4.40%
Maturities of borrowings at par value [Abstract]
Maturities of borrowings in 2014	$ 35,000,000
Maturities of borrowings in 2015	500,000,000
Maturities of borrowings in 2016	1,000,000,000
Maturities of borrowings in 2017	500,000,000
Maturities of borrowings in 2018	400,000,000
Maturities of borrowings thereafter	1,300,000,000
Commercial paper [Member]
Borrowings [Abstract]
Maximum issuance, reduced by borrowings in excess of amount	150,000,000
Weighted-average effective rate	0.30%
Weighted-average term (in days)	4 days
Maximum [Member] | Commercial paper [Member]
Borrowings [Abstract]
Commercial paper program, maximum amount of issuance	$ 1,500,000,000
Commercial paper program, maximum days to maturity	397 days