Debt (Tables)

12 Months Ended

Dec. 31, 2016

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 December 31, 2016:


	2016		2015
$2.25 billion revolving credit facility, maturing July 2020 (weighted average interest rate of 1.9% at December 31, 2016)	$	426	$	20
Commercial paper program		—		—
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 2.1% at December 31, 2016 and 2.2% at December 31, 2015)		239		84
Senior notes maturing through 2045, interest rates ranging from 2.40% to 7.75% (weighted average interest rate of 4.6% at December 31, 2016 and 4.7% at December 31, 2015)		6,033		6,050
Tax-exempt bonds maturing through 2045, fixed and variable interest rates ranging from 0.7% to 5.7% (weighted average interest rate of 1.8% at December 31, 2016 and 1.9% at December 31, 2015)		2,304		2,447
Capital leases and other, maturing through 2055, interest rates up to 12%		308		328

	$	9,310	$	8,929
Current portion of long-term debt		417		253

	$	8,893	$	8,676

Summary of Requirements of Financial Covenants Contained in Revolving Credit Facilities

The following table summarizes the most restrictive requirements of these financial covenants (all terms used to measure these ratios are defined by the facilities):


Interest coverage ratio		> 2.75 to 1
Total debt to EBITDA		< 3.50 to 1