Long-Term Debt and Short-Term Borrowings (Details) (USD $)		1 Months Ended
	Sep. 30, 2011 Medium-term notes program	Sep. 30, 2011 Fixed rate medium term notes due 2016	Jun. 30, 2012 Fixed rate medium term notes due 2017	Jun. 30, 2012 Fixed rate medium term notes due 2022	Sep. 30, 2012 Five-year credit facility agreement	Aug. 31, 2012 One-year credit facility agreement with HSBC Bank USA	Aug. 31, 2011 One-year credit facility agreement with HSBC Bank USA	Sep. 30, 2012 Stand alone letters of credit
Debt instrument
Medium-term notes program established in connection with a prior "well-known seasoned issuer" shelf registration	$ 3,000,000,000
Principal amount		1,000,000,000	650,000,000	600,000,000
Interest rate		1.375%	1.00%	2.00%
Term of debt instrument		5 years	5 years	10 years	5 years	1 year	1 year
Current borrowing capacity					1,500,000,000	150,000,000	200,000,000
Maximum increase available subject to lender approval					500,000,000
Maximum borrowing capacity including portion subject to lender approval					2,000,000,000
Required minimum EBITDA to Interest Ratio					3	3
Actual EBITDA to Interest Ratio					44	44
Number of consecutive quarters over which the ratio of required EBITDA to Interest Ratio is calculated					4	4
Amount of letters of credit outstanding utilized in connection with normal business activities						$ 120,000,000		$ 100,000,000