Short-Term Borrowings (Selected Data) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Short Term Borrowings Selected Data [Abstract]
Maximum outstanding at any month-end during the year	$ 5,196	$ 4,385	$ 10,473
Balance outstanding at end of year	4,138	2,864	3,566
Average outstanding during the year	$ 4,459	$ 3,408	$ 5,189
Average interest rate during the year	0.13%	0.20%	0.21%
Average interest rate at end of year	0.12%	0.22%	0.20%