

	Effective	March 31	December 31	March 31
in thousands	Interest Rates	2020	2019	2019
Short-term Debt
Bank line of credit expires 2021 ¹		$ 0	$ 0	$ 178,500
Total short-term debt		$ 0	$ 0	$ 178,500
Long-term Debt
Bank line of credit expires 2021 ¹		$ 0	$ 0	$ 0
Floating-rate notes due 2020 ²	2.13%	250,000	250,000	250,000
Floating-rate notes due 2021 ²	2.51%	500,000	500,000	500,000
8.85% notes due 2021	8.88%	6,000	6,000	6,000
4.50% notes due 2025	4.65%	400,000	400,000	400,000
3.90% notes due 2027	4.00%	400,000	400,000	400,000
7.15% notes due 2037	8.05%	129,239	129,239	129,239
4.50% notes due 2047	4.59%	700,000	700,000	700,000
4.70% notes due 2048	5.42%	460,949	460,949	460,949
Other notes	6.46%	179	185	202
Total long-term debt - face value		$ 2,846,367	$ 2,846,373	$ 2,846,390
Unamortized discounts and debt issuance costs		(60,776)	(62,033)	(65,777)
Total long-term debt - book value		$ 2,785,591	$ 2,784,340	$ 2,780,613
Less current maturities		25	25	24
Total long-term debt - reported value		$ 2,785,566	$ 2,784,315	$ 2,780,589
Estimated fair value of long-term debt		$ 2,926,140	$ 3,073,693	$ 2,775,511

Discounts and debt issuance costs are amortized using the effective interest method over the terms of the respective notes resulting in $1,258,000 and $1,239,000 of net interest expense for these items for the three months ended March 31, 2020 and 2019, respectively.

Our unsecured $750,000,000 line of credit matures December 2021 and contains affirmative, negative and financial covenants customary for an unsecured investment-grade facility. The primary negative covenant limits our ability to incur secured debt. The financial covenants are: (1) a maximum ratio of debt to EBITDA of 3.5:1 (upon certain acquisitions, the maximum ratio can be 3.75:1 for three quarters), and (2) a minimum ratio of EBITDA to net cash interest expense of 3.0:1. As of March 31, 2020, we were in compliance with the line of credit covenants.

Borrowings on our line of credit are classified as short-term if we intend to repay within twelve months and as long-term if we have the intent and ability to extend repayment beyond twelve months. Borrowings bear interest, at our option, at either LIBOR plus a credit margin ranging from 1.00% to 1.75%, or Truist Bank’s base rate (generally, its prime rate) plus a credit margin ranging from 0.00% to 0.75%. The credit margin for both LIBOR and base rate borrowings is determined by our credit ratings. Standby letters of credit, which are issued under the line of credit and reduce availability, are charged a fee equal to the credit margin for LIBOR borrowings plus 0.175%. We also pay a commitment fee on the daily average unused amount of the line of credit that ranges from 0.10% to 0.25% determined by our credit ratings. As of March 31, 2020, the credit margin for LIBOR borrowings was 1.25%, the credit margin for base rate borrowings was 0.25%, and the commitment fee for the unused amount was 0.15%.

As of March 31, 2020, our available borrowing capacity was $695,871,000. Utilization of the borrowing capacity was as follows:

$54,129,000 was used to provide support for outstanding standby letters of credit

All of our $2,846,367,000 (face value) of term debt is unsecured. $2,846,188,000 of such debt is governed by three essentially identical indentures that contain customary investment-grade type covenants. The primary covenant in all three indentures limits the amount of secured debt we may incur without ratably securing such debt. As of March 31, 2020, we were in compliance with all term debt covenants.

Subsequent to quarter-end, we executed a $750,000,000 364-day delayed draw term loan with a subset of the banks that provide our line of credit. This facility provides for up to two draws through October 2020 and all borrowings are due April 2021. Borrowings may be repaid prior to maturity, but once repaid may not be borrowed again.

All terms and conditions of the delayed draw term loan are consistent with those of the line of credit except for the interest rate on borrowings and the commitment fee. Borrowings bear interest, at our option, at either LIBOR plus a credit margin ranging from 1.375% to 2.125%, or Truist Bank’s base rate (generally, its prime rate) plus a credit margin ranging from 0.375% to 1.125%. The credit margin for both LIBOR and base rate borrowings is determined by our credit ratings. The commitment fee, paid on the unused amount of the daily average unused amount of the facility, ranges from 0.125% to 0.25% and is determined by our credit ratings.

We provide, in the normal course of business, certain third-party beneficiaries with standby letters of credit to support our obligations to pay or perform according to the requirements of an underlying agreement. Such letters of credit typically have an initial term of one year, typically renew automatically, and can only be modified or canceled with the approval of the beneficiary. All of our standby letters of credit are issued by banks that participate in our $750,000,000 line of credit, and reduce the borrowing capacity thereunder. Our standby letters of credit as of March 31, 2020 are summarized by purpose in the table below: