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, 2011:


	September 30,		December 31,
	2011		2010

Revolving credit facility	$	—	$	—
Letter of credit facilities		—		—
Canadian credit facility (weighted average effective interest rate of 2.3% at September 30, 2011 and 2.2% at December 31, 2010)		133		212
Senior notes and debentures, maturing through 2039, interest rates ranging from 2.60% to 7.75% (weighted average interest rate of 6.0% at September 30, 2011 and 6.5% at December 31, 2010)		6,233		5,452
Tax-exempt bonds, maturing through 2041, fixed and variable interest rates ranging from 0.2% to 7.4% (weighted average interest rate of 3.0% at September 30, 2011 and 3.1% at December 31, 2010)		2,751		2,696
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, 2011 and 2.5% at December 31, 2010)		86		116
Capital leases and other, maturing through 2050, interest rates up to 12%		410		431

		9,613		8,907
Current portion of long-term debt		225		233

	$	9,388	$	8,674