Debt

Our debt consists of the following (in thousands):



	December 31,
	2013		2012
Debt payable to 2038 at 2.6% to 8.6% in 2013 and 2.6% to 8.8% in 2012	$	2,205,104	$	2,041,709
Unsecured notes payable under credit facilities	—		66,000
Debt service guaranty liability	73,740		74,075
Obligations under capital leases	21,000		21,000
Industrial revenue bonds payable at 2.4% in 2012	—		1,246
Total	$	2,299,844	$	2,204,030

The grouping of total debt between fixed and variable-rate as well as between secured and unsecured is summarized below (in thousands):



	December 31,
	2013		2012
As to interest rate (including the effects of interest rate contracts):
Fixed-rate debt	$	2,136,265	$	1,992,599
Variable-rate debt	163,579		211,431
Total	$	2,299,844	$	2,204,030
As to collateralization:
Unsecured debt	$	1,572,057	$	1,270,742
Secured debt	727,787		933,288
Total	$	2,299,844	$	2,204,030

We maintain a $500 million unsecured revolving credit facility, which was last amended and extended on April 18, 2013. This facility expires in April 2017, provides for two consecutive six-month extensions upon our request and borrowing rates that float at a margin over LIBOR plus a facility fee. At December 31, 2013, the borrowing margin and facility fee, which are priced off a grid that is tied to our senior unsecured credit ratings, are 115 and 20 basis points, respectively. The facility also contains a competitive bid feature that will allow us to request bids for up to $250 million. Additionally, an accordion feature allows us to increase the facility amount up to $700 million.

Effective May 2010, we entered into an agreement with a bank for an unsecured and uncommitted overnight facility totaling $99 million that we intend to maintain for cash management purposes. The facility provides for fixed interest rate loans at a 30 day LIBOR rate plus a borrowing margin based on market liquidity.

The following table discloses certain information regarding our unsecured notes payable under our credit facilities (in thousands, except percentages):



	December 31,
	2013			2012
Unsecured revolving credit facility:
Balance outstanding	$	—		$	30,000
Available balance	497,821			467,571
Letter of credit outstanding under facility	2,179			2,429
Variable interest rate (excluding facility fee)	—		%	1.1		%
Unsecured and uncommitted overnight facility:
Balance outstanding	$	—		$	36,000
Variable interest rate	—		%	1.5		%
Both facilities:
Maximum balance outstanding during the year	$	265,500		$	303,100
Weighted average balance	61,642			157,447
Year-to-date weighted average interest rate (excluding facility fee)	1.0		%	1.3		%

Related to a development project in Sheridan, Colorado, we have provided a guaranty for the payment of any debt service shortfalls until a coverage rate of 1.4 is met on tax increment revenue bonds issued in connection with the project. The bonds are to be repaid with incremental sales and property taxes and a PIF to be assessed on current and future retail sales and, to the extent necessary, any amounts we may have to provide under a guaranty. The incremental taxes and PIF are to remain intact until the earlier of the date the bond liability has been paid in full or 2040. Therefore, a debt service guaranty liability equal to the fair value of the amounts funded under the bonds was recorded. As of December 31, 2013 and 2012, we had $73.7 million and $74.1 million, respectively, outstanding for the debt service guaranty liability.

In October 2013, we issued $250 million of 4.45% senior unsecured notes maturing in 2024. The notes were issued at 99.58% of the principal amount with a yield to maturity of 4.50%. The net proceeds received of $247.3 million were used to reduce all amounts outstanding under our $500 million unsecured revolving credit facility, and net excess proceeds were invested in short-term instruments and will be used to pay down future debt maturities or for general business purposes.

In March 2013, we issued $300 million of 3.5% senior unsecured notes maturing in 2023. The notes were issued at 99.53% of the principal amount with a yield to maturity of 3.56%. The net proceeds received of $296.6 million were used to reduce amounts outstanding under our $500 million unsecured revolving credit facility, which included borrowings used to redeem $75 million of our 6.75% Series D Cumulative Redeemable Preferred Shares.

In addition, $173.6 million of fixed-rate medium term notes matured during 2013 at a weighted average interest rate of 5.4% and a $100 million 6% fixed-rate note payable was repaid prior to maturity.

In October 2012, we issued $300 million of 3.38% senior unsecured notes maturing in 2022. The notes were issued at 99.62% of the principal amount with a yield to maturity of 3.42%. The net proceeds received of $296.9 million were used to reduce amounts outstanding under our $500 million unsecured revolving credit facility and to repay our $54.1 million of 3.95% convertible senior unsecured notes.

Various leases and properties, and current and future rentals from those lease and properties, collateralize certain debt. At December 31, 2013 and 2012, the carrying value of such property aggregated $1.2 billion and $1.5 billion, respectively.

Scheduled principal payments on our debt (excluding $21.0 million of certain capital leases, $5.4 million fair value of interest rate contracts, $(3.3) million net premium/(discount) on debt, $6.5 million of non-cash debt-related items, and $73.7 million debt service guaranty liability) are due during the following years (in thousands):



2014	$	368,858
2015	276,346
2016	249,723
2017	142,332
2018	64,653
2019 ⁽¹⁾	153,907
2020	35,363
2021	2,278
2022	304,815
2023	301,937
Thereafter	296,327
Total	$	2,196,539

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(1)	Includes $100.0 million of our 8.1% senior unsecured notes due 2019 which may be redeemed by us at any time on or after September 2014 at our option.

Our various debt agreements contain restrictive covenants, including minimum interest and fixed charge coverage ratios, minimum unencumbered interest coverage ratios, minimum net worth requirements and maximum total debt levels. We are not aware of any non-compliance with our public debt and revolving credit facility covenants as of December 31, 2013.