Debt (Details) (USD $)	1 Months Ended		6 Months Ended		6 Months Ended		6 Months Ended
	Jul. 31, 2011	Jun. 30, 2011	Jun. 30, 2011 Senior Notes Due July 15, 2016 [Member]	Jul. 31, 2011 Senior Notes Due July 15, 2016 [Member]	Jun. 30, 2011 Senior Notes Due July 15, 2021 [Member]	Jul. 31, 2011 Senior Notes Due July 15, 2021 [Member]	Jun. 30, 2011 Senior Notes Due July 15, 2041 [Member]	Jul. 31, 2011 Senior Notes Due July 15, 2041 [Member]	Jun. 30, 2011 Minimum [Member]	Jun. 30, 2011 Maximum [Member]	Jun. 30, 2011 Maximum [Member] Commercial Paper General Maturity Maximum [Member]	Mar. 31, 2011 Previous Borrowing Capacity [Member]	Jun. 30, 2011 Current Borrowing Capacity [Member]
Senior credit facility, borrowing capacity		$ 2,700,000,000
Outstanding senior credit facility borrowings		0
Ratio of total funded debt to total capitalization to be less than		65.00%
Debt-to-capitalization ratio, current percentage		19.3
Commercial paper program, borrowing capacity												2,200,000,000	5,000,000,000
Commercial paper maturity (days)									1	365	90
Cash and short-term investments		6,700,000,000
Outstanding commercial paper borrowings		2,300,000,000
Average borrowing rate on commercial paper borrowings		0.27%
Proceeds from issuance of debt	2,224,000,000
Debt instrument, face amount				500,000,000		500,000,000		1,250,000,000
Debt instrument, interest rate, stated percentage				2.40%		4.00%		5.60%
Debt instrument, maturity date			Jul. 15, 2016		Jul. 15, 2021		Jul. 15, 2041
Long-term outstanding commercial paper	$ 2,224,000,000