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, 2015:


	September 30, 2015		December 31, 2014
U.S. revolving credit facility, maturing July 2020	$	—	$	—
Letter of credit facilities, maturing through December 2018		—		—
Canadian credit facility and term loan, maturing November 2017 (weighted average effective interest rate of 2.1% at September 30, 2015 and 2.6% at December 31, 2014)		114		232
Senior notes maturing through 2045, interest rates ranging from 2.60% to 7.75% (weighted average interest rate of 4.7% at September 30, 2015 and 5.7% at December 31, 2014)		6,083		6,273
Tax-exempt bonds, maturing through 2045, fixed and variable interest rates ranging from 0.02% to 5.7% (weighted average interest rate of 2.1% at September 30, 2015 and 2.2% at December 31, 2014)		2,493		2,541
Capital leases and other, maturing through 2055, interest rates up to 12%		360		389

		9,050		9,435
Current portion of long-term debt		215		1,090

	$	8,835	$	8,345