The following table summarizes the major components of debt as of each balance sheet date (in millions) and provides the maturities and interest rate ranges of each major category as of September 30, 2017:


	September 30,		December 31,
	2017		2016
$2.25 billion revolving credit facility, maturing July 2020 (weighted average interest rate of 1.9% as of December 31, 2016)	$	—	$	426
Commercial paper program (weighted average interest rate of 1.4% as of September 30, 2017)		502		—
Other letter of credit facilities, maturing through December 2018		—		—
Canadian term loan and revolving credit facility, maturing March 2019 (weighted average effective interest rate of 2.5% as of September 30, 2017 and 2.1% as of December 31, 2016)		143		239
Senior notes maturing through 2045, interest rates ranging from 2.4% to 7.75% (weighted average interest rate of 4.6% as of September 30, 2017 and December 31, 2016)		6,033		6,033
Tax-exempt bonds, maturing through 2045, fixed and variable interest rates ranging from 1.0% to 5.7% (weighted average interest rate of 1.9% as of September 30, 2017 and 1.8% as of December 31, 2016)		2,339		2,304
Capital leases and other, maturing through 2055, interest rates up to 12%		328		308
		9,345		9,310
Current portion of long-term debt		850		417
	$	8,495	$	8,893