The following table summarizes the major components of debt at each balance sheet date (in millions) and provides the maturities and interest rate ranges of each major category as of September 30, 2012:


	September 30, 2012		December 31, 2011
Revolving credit facility (weighted average interest rate of 1.5% at December 31, 2011)	$	—	$	150
Letter of credit facilities		—		—
Canadian credit facility (weighted average effective interest rate of 2.0% at September 30, 2012 and 1.8% at December 31, 2011)		117		137
Senior notes and debentures, maturing through 2039, interest rates ranging from 2.6% to 7.75% (weighted average interest rate of 5.8% at September 30, 2012 and 6.0% at December 31, 2011)		6,711		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 2.9% at September 30, 2012 and 3.1% at December 31, 2011)		2,680		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 September 30, 2012 and 1.3% at December 31, 2011)		86		86
Capital leases and other, maturing through 2055, interest rates up to 12%		398		384

		9,992		9,756
Current portion of long-term debt		826		631

	$	9,166	$	9,125