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 March 31, 2014:


	March 31, 2014		December 31, 2013
U.S. revolving credit facility, maturing July 2018 (weighted average interest rate of 1.2% at March 31, 2014 and December 31, 2013)	$	790	$	420
Letter of credit facilities, maturing through December 2016		—		—
Canadian credit facility and term loan, maturing November 2017 (weighted average effective interest rate of 2.5% at March 31, 2014 and 2.7% at December 31, 2013)		375		414
Senior notes maturing through 2039, interest rates ranging from 2.60% to 7.75% (weighted average interest rate of 5.8% at March 31, 2014 and 5.7% at December 31, 2013)		5,933		6,287
Tax-exempt bonds, maturing through 2045, fixed and variable interest rates ranging from 0.06% to 5.7% (weighted average interest rate of 2.3% at March 31, 2014 and December 31, 2013)		2,664		2,664
Capital leases and other, maturing through 2055, interest rates up to 12%		432		441

		10,194		10,226
Current portion of long-term debt		1,216		726

	$	8,978	$	9,500

Debt Classification

As of March 31, 2014, we had (i) $498 million of debt maturing within the next 12 months, including $350 million of 6.375% senior notes that mature in March 2015 and $82 million of tax-exempt bonds; (ii) $790 million of borrowings and advances outstanding under the U.S. revolving credit facility (“$2.25 billion revolving credit facility”) and (iii) $874 million of tax-exempt borrowings subject to repricing within the next 12 months. Of the $790 million of borrowings outstanding under our $2.25 billion revolving credit facility, we have classified $370 million of these borrowings as long-term because we intend and have the ability to refinance or maintain these borrowings on a long-term basis. Based on our intent and ability to refinance other portions of our current obligations on a long-term basis as of March 31, 2014, including through use of forecasted available capacity under our $2.25 billion revolving credit facility, we have classified an additional $576 million of debt as long-term. The remaining $1.2 billion, including $420 million of outstanding borrowings under our $2.25 billion revolving credit facility, is classified as current obligations.

Revolving Credit and Letter of Credit Facilities

As of March 31, 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 March 31, 2014, we had an aggregate of $1.3 billion of letters of credit outstanding under various credit facilities. Approximately $884 million of these letters of credit have been issued under our $2.25 billion revolving credit facility. As of March 31, 2014, we had outstanding borrowings under our $2.25 billion revolving credit facility of $790 million, leaving $576 million of unused and available capacity.

We also have a Canadian credit agreement that matures in November 2017 and provides for C$500 million of term credit and 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. The C$500 million of term credit was established specifically to fund the acquisition of the assets of RCI Environnement, Inc. and was fully drawn in July 2013. The term credit is non-revolving credit and principal amounts repaid may not be re-borrowed. As of March 31, 2014 and December 31, 2013, we had no letters of credit outstanding under the credit facility. We had outstanding borrowings of C$10 million at December 31, 2013 that were repaid with available cash during the first quarter of 2014.

Debt Borrowings and Repayments

$2.25 Billion Revolving Credit Facility — During the first quarter of 2014, we incurred $370 million of net borrowings under our $2.25 billion revolving credit facility principally to repay the $350 million of 5.0% senior notes that matured in March 2014.

Canadian Credit Facility and Term Loan — We repaid C$25 million, or $23 million, of net advances under our Canadian credit facility and term loan during the three months ended March 31, 2014 with available cash.

Senior Notes — We repaid $350 million of 5.0% senior notes that matured in March 2014 with proceeds from borrowings under our $2.25 billion revolving credit facility.