Debt, Bank Debt and Credit Facilities (Details)	6 Months Ended							6 Months Ended									6 Months Ended			1 Months Ended
	Jun. 30, 2012 USD ($)	Jun. 30, 2011 USD ($)	Jun. 30, 2012 U S Revolver [Member] USD ($)	Jun. 30, 2011 U S Revolver [Member] USD ($)	Dec. 31, 2011 U S Revolver [Member] USD ($)	Jun. 30, 2012 U S Revolver Letter of Credit [Member] USD ($)	Dec. 31, 2011 U S Revolver Letter of Credit [Member] USD ($)	Jun. 30, 2012 Canadian Revolver [Member] CAD	Jun. 30, 2011 Canadian Revolver [Member] CAD	Dec. 31, 2011 Canadian Revolver [Member] CAD	Jun. 30, 2012 Canadian Revolver Letter of Credit [Member] CAD	Dec. 31, 2011 Canadian Revolver Letter of Credit [Member] CAD	Jun. 30, 2012 Letter of Credit [Member] USD ($)	Dec. 31, 2011 Letter of Credit [Member] USD ($)	Jun. 30, 2012 Other Letter of Credit [Member] USD ($)	Dec. 31, 2011 Other Letter of Credit [Member] USD ($)	Jun. 30, 2012 Other Debt [Member] USD ($)	Jun. 30, 2011 Other Debt [Member] USD ($)	Jun. 30, 2012 Maximum [Member] U S Revolver [Member]	Jul. 31, 2012 Subsequent Event [Member] Letter of Credit [Member] USD ($)	Jul. 31, 2012 Subsequent Event [Member] Other Debt [Member] USD ($)
Line of Credit Facility
Line of credit facility, maximum borrowing capacity			$ 3,000,000,000					115,000,000												$ 550,000,000
Line of credit facility, expiration date (month, year)			December 2016					December 2012												June 2013
Line of credit facility, increase in maximum borrowing capacity																				50,000,000
Letters of credit outstanding			0		0	70,000,000	119,000,000	0		0	11,000,000	20,000,000	300,000,000	300,000,000	649,000,000	391,000,000
Accounts Receivable Sales Facility
Balance as of beginning of period																	250,000,000	100,000,000
Proceeds from the sale of receivables	1,300,000,000	0															1,300,000,000	0
Repayments	(1,450,000,000)	0															(1,450,000,000)	0
Balance as of end of period																	100,000,000	100,000,000
Credit Facilities (Textual)
Debt to capitalization ratios as per terms of revolver			0.26		0.29														0.60
Borrowings from long-term lines of credit	1,100,000,000	0	1,100,000,000	0				0	0
Repayments of long-term lines of credit	1,100,000,000	0	1,100,000,000	0				0	0
Accounts Receivable Sales Facility (Textual)
Maximum eligible trade receivables																	$ 1,000,000,000				$ 1,500,000,000
Extended term of accounts receivable sales facility																					July 2013