Debt (Tables)

3 Months Ended

Mar. 31, 2012

Debt (Tables) [Abstract]

Components of debt

	March 31, 2012		December 31, 2011
Revolving credit facility (interest rate of 1.4% at March 31, 2012 and 1.5% at December 31, 2011)	$	300	$	150
Letter of credit facilities		—		—
Canadian credit facility (weighted average effective interest rate of 1.6% at March 31, 2012 and 1.8% at December 31, 2011)		115		137
Senior notes and debentures, maturing through 2039, interest rates ranging from 2.60% to 7.75% (weighted average interest rate of 6.0% at March 31, 2012 and December 31, 2011)		6,223		6,228
Tax-exempt bonds, maturing through 2041, fixed and variable interest rates ranging from 0.2% to 7.4% (weighted average interest rate of 3.1% at March 31, 2012 and December 31, 2011)		2,736		2,771
Tax-exempt project bonds, maturing through 2029, fixed and variable interest rates ranging from 0.2% to 3.4% (weighted average interest rate of 1.4% at March 31, 2012 and 1.3% at December 31, 2011)		86		86
Capital leases and other, maturing through 2055, interest rates up to 12%		389		384
		9,849		9,756
Current portion of long-term debt		860		631
	$	8,989	$	9,125