Short-Term Borrowings And Borrowing Arrangements (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Short-term Debt [Line Items]
Aggregate principal borrowings available	$ 3,000,000,000
5-Year Agreement [Member]
Short-term Debt [Line Items]
Short-term Debt	0	0
Expiration date	Jun. 30, 2016
Terms of senior unsecured revolving credit agreement	5 years
Aggregate principal borrowings available	$ 3,000,000,000
Ratio of debt to consolidated EBITDA, maximum, numerator	3.0
Ratio of consolidated EBITDA to consolidated interest expense, minimum, numerator	4.0
Ratio of debt to consolidated EBITDA, numerator	1.8
Ratio of consolidated EBITDA to consolidated interest expense, numerator	7.0
5-Year Agreement [Member] | Minimum [Member]
Short-term Debt [Line Items]
Marginal interest rate spread	0.75%
5-Year Agreement [Member] | Maximum [Member]
Short-term Debt [Line Items]
Marginal interest rate spread	1.75%