Debt

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 June 30, 2014:


	June 30, 2014		December 31, 2013
U.S. revolving credit facility, maturing July 2018 (weighted average interest rate of 1.2% at June 30, 2014 and December 31, 2013)	$	105	$	420
Letter of credit facilities, maturing through December 2016		—		—
Canadian credit facility and term loan, maturing November 2017 (weighted average effective interest rate of 2.6% at June 30, 2014 and 2.7% at December 31, 2013)		351		414
Senior notes maturing through 2039, interest rates ranging from 2.60% to 7.75% (weighted average interest rate of 5.7% at June 30, 2014 and December 31, 2013)		6,279		6,287
Tax-exempt bonds, maturing through 2045, fixed and variable interest rates ranging from 0.04% to 5.7% (weighted average interest rate of 2.2% at June 30, 2014 and 2.3% at December 31, 2013)		2,649		2,664
Capital leases and other, maturing through 2055, interest rates up to 12%		413		441

		9,797		10,226
Current portion of long-term debt		786		726

	$	9,011	$	9,500

Debt Classification

As of June 30, 2014, we had (i) $517 million of debt maturing within the next 12 months, including $350 million of 6.375% senior notes that mature in March 2015 and $102 million of tax-exempt bonds; (ii) $105 million of short-term borrowings outstanding under the U.S. revolving credit facility (“$2.25 billion revolving credit facility”) and (iii) $905 million of tax-exempt borrowings subject to repricing within the next 12 months. Based on our intent and ability to refinance portions of our current obligations on a long-term basis as of June 30, 2014, including through use of forecasted available capacity under our $2.25 billion revolving credit facility, we have classified $741 million of this debt as long-term and the remaining $786 million as current obligations. The $741 million classified as long-term is less than our unused and available capacity under our $2.25 billion revolving credit facility of $1.3 billion discussed below due to expected decreases in such available capacity within the next 12 months.

Revolving Credit and Letter of Credit Facilities

As of June 30, 2014, we had an aggregate committed capacity of $2.65 billion for letters of credit under various U.S. credit facilities. Our $2.25 billion revolving credit facility expires in July 2018 and is our primary source of letter of credit capacity. Our remaining committed letter of credit capacity is provided under facilities with terms ending through December 2016. As of June 30, 2014, we had an aggregate of $1.3 billion of letters of credit outstanding under various credit facilities. Approximately $874 million of these letters of credit have been issued under our $2.25 billion revolving credit facility. As of June 30, 2014, we had outstanding borrowings under our $2.25 billion revolving credit facility of $105 million, leaving $1.3 billion of unused and available capacity.

We also have a Canadian credit agreement that matures in November 2017 and provides for C$150 million of revolving credit capacity. We have the ability to issue up to C$50 million of letters of credit under the Canadian revolving credit facility, which if utilized, reduces the amount of credit capacity available for borrowings. As of June 30, 2014, we had no letters of credit or borrowings outstanding under the credit facility.

Debt Borrowings and Repayments

$2.25 Billion Revolving Credit Facility — During the first half of 2014, we made net repayments of $315 million under our $2.25 billion revolving credit facility with available cash.

Canadian Credit Facility and Term Loan — We repaid C$65 million, or $60 million, of net advances under our Canadian credit facility and term loan during the six months ended June 30, 2014 with available cash.

Senior Notes — In March 2014, we repaid $350 million of 5.0% senior notes that matured in March 2014 with borrowings under our $2.25 billion revolving credit facility. In May 2014, we issued $350 million of 3.5% senior notes due May 15, 2024. The net proceeds from the debt issuance were $347 million, all of which were used to repay borrowings under our $2.25 billion revolving credit facility.

Tax-Exempt Bonds — During the six months ended June 30, 2014, we repaid $15 million of tax-exempt bonds with available cash.