Debt (Tables)

9 Months Ended

Sep. 30, 2011

Debt [Abstract]

Outstanding letters of credit under committed lines of credit

We had outstanding letters of credit under our committed lines of credit as follows (in millions):

			Amounts Outstanding
	Borrowing Capacity	Expiration	September 30, 2011	December 31, 2010
Letter of credit facility	$200	June 2012	$—	$—
Letter of credit facility	$300	June 2012	$300	$100
Revolver	$2,400	November 2012	$74	$399
Canadian revolving credit facility	C$115	December 2012	C$20	C$20