Debt

Our debt consists of the following (in thousands):



	December 31,
	2017		2016
Debt payable, net to 2038 ⁽¹⁾	$	1,996,007	$	2,023,403
Unsecured notes payable under credit facilities	—		245,000
Debt service guaranty liability	64,145		67,125
Obligations under capital leases	21,000		21,000
Total	$	2,081,152	$	2,356,528

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(1)	At December 31, 2017, interest rates ranged from 2.6% to 7.9% at a weighted average rate of 4.0%. At December 31, 2016, interest rates ranged from 1.7% to 7.9% at a weighted average rate of 4.0%.

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



	December 31,
	2017		2016
As to interest rate (including the effects of interest rate contracts):
Fixed-rate debt	$	2,063,263	$	2,089,769
Variable-rate debt	17,889		266,759
Total	$	2,081,152	$	2,356,528
As to collateralization:
Unsecured debt	$	1,667,462	$	1,913,399
Secured debt	413,690		443,129
Total	$	2,081,152	$	2,356,528

We maintain a $500 million unsecured revolving credit facility, which was amended and extended on March 30, 2016. This facility expires in March 2020, 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 both December 31, 2017 and 2016, the borrowing margin and facility fee, which are priced off a grid that is tied to our senior unsecured credit ratings, were 90 and 15 basis points, respectively. The facility also contains a competitive bid feature that allows us to request bids for up to $250 million. Additionally, an accordion feature allows us to increase the facility amount up to $850 million.

Additionally, we have a $10 million unsecured short-term facility, which was amended and extended on March 27, 2017, that we maintain for cash management purposes, which matures in March 2018. At December 31, 2017, the facility provided for fixed interest rate loans at a 30-day LIBOR rate plus a borrowing margin, facility fee and an unused facility fee of 125, 10, and 5 basis points, respectively. At December 31, 2016, the borrowing margin, facility fee and an unused facility fee was 125, 10, and 10 basis points, respectively.

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



	December 31,
	2017			2016
Unsecured revolving credit facility:
Balance outstanding	$	—		$	245,000
Available balance	493,610			250,140
Letter of credit outstanding under facility	6,390			4,860
Variable interest rate (excluding facility fee) at end date	—		%	1.5		%
Unsecured short-term facility:
Balance outstanding	$	—		$	—
Variable interest rate at end date	—		%	—		%
Both facilities:
Maximum balance outstanding during the year	$	245,000		$	372,000
Weighted average balance	133,386			141,017
Year-to-date weighted average interest rate (excluding facility fee)	1.8		%	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 1.4x 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, 2017 and 2016, we had $64.1 million and $67.1 million outstanding for the debt service guaranty liability, respectively.

In December 2016, we repaid $75 million of fixed-rate unsecured medium term notes upon maturity at a weighted average interest rate of 5.5%.

In August 2016, we issued $250 million of 3.25% senior unsecured notes maturing in 2026. The notes were issued at 99.16% of the principal amount with a yield to maturity of 3.35%. The net proceeds received of $246.3 million were used to reduce the amount outstanding under our $500 million unsecured revolving credit facility.

In June 2016, we amended an existing $90 million secured note to extend the maturity to 2028 and reduce the interest rate from 7.5% to 4.5% per annum. In connection with this transaction, we have recorded a $2.0 million gain on extinguishment of debt that has been classified as net interest expense in our Consolidated Statements of Operations.

Various leases and properties, and current and future rentals from those leases and properties, collateralize certain debt. At both December 31, 2017 and 2016, the carrying value of such assets aggregated $.7 billion.

Scheduled principal payments on our debt (excluding $21.0 million of certain capital leases, $(5.4) million net premium/(discount) on debt, $(8.9) million of deferred debt costs, $4.0 million of non-cash debt-related items, and $64.1 million debt service guaranty liability) are due during the following years (in thousands):



2018	$	113,427
2019	56,245
2020	237,779
2021	17,667
2022	307,614
2023	305,694
2024	255,954
2025	303,302
2026	277,291
2027	38,288
Thereafter	93,024
Total	$	2,006,285

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, 2017.