	June 30, 2020			December 31, 2019
Senior Notes	$	150,000		$	150,000
Credit Facility		138,000			157,000
Total long-term debt		288,000			307,000
Less: Debt issuance costs		(1,390	)		(1,717	)
Long-term debt, net	$	286,610		$	305,283

We have two series of senior notes outstanding with an aggregate principal amount of $150 million ("Senior Notes") issued in a private placement transaction. Series A consists of $75 million in aggregate principal amount of notes that bear interest at a fixed rate of 4.01% and are due in full on September 30, 2021. Series B consists of $75 million in aggregate principal amount of notes that bear interest at a fixed rate of 4.11% and are due in full on September 30, 2023. Interest on each series of the Senior Notes is payable semi-annually on March 30 and September 30.

On June 22, 2020, we entered into Amendment No. 1 (the “Amendment”) to the Seventh Amended and Restated Credit Agreement, dated June 19, 2018 (as amended, the “Credit Facility”). The Amendment increases the maximum leverage ratio permitted under the Credit Facility for certain periods. Pursuant to the terms of the Amendment, the maximum leverage ratio permitted under the Credit Facility is equal to (a) 3.00 to 1.00 from the fiscal quarter ending June 30, 2020 through and including the fiscal quarter ending June 30, 2021; (b) 2.75 to 1.00 for the fiscal quarter ending September 30, 2021; and (c) 2.50 to 1.00 for the fiscal quarter ending December 31, 2021 and thereafter. Moreover, the Amendment modified the range of variable interest rates that the Credit Facility may bear to be a range from LIBOR plus 1.500% to LIBOR plus 2.875%, and included the addition of a LIBOR floor of 0.50%. In addition, pursuant to the Amendment, the aggregate borrowing commitment under the Credit Facility was reduced to $225 million and the amount by which we may elect to increase the facility size was reduced from $100 million to $50 million, subject to the satisfaction of certain conditions. Any outstanding balance under the Credit Facility is due on maturity on June 19, 2023. Our available capacity at any point in time is reduced by borrowings outstanding at the time and outstanding letters of credit which totaled $14.2 million at June 30, 2020, resulting in an available borrowing capacity under the Credit Facility of $72.8 million. In addition to indebtedness under the Credit Facility, we had $5.8 million of outstanding letters of credit and performance guarantees and bonds from other sources as of June 30, 2020.

The Credit Facility remains unsecured, and contains customary representations, warranties, terms and conditions for similar types of facilities.

During the three months ended June 30, 2020, in connection with our entry into the Amendment, we recorded an additional expense of $0.3 million associated with unamortized debt issuance cost.

The terms of the Credit Facility and Senior Notes require us to meet certain covenants, including, but not limited to, an interest coverage ratio (calculated as consolidated EBITDA divided by interest expense) and a leverage ratio (calculated as consolidated net indebtedness divided by consolidated EBITDA), where consolidated EBITDA (as defined in each agreement) and interest expense are calculated using the most recent four fiscal quarters. The Credit Facility and Senior Notes include a cross-default provision, which means that a default under one agreement may result in the default of the other agreement. The Credit Facility has more restrictive covenants with a minimum interest coverage ratio of 3.0 to 1.0 and permits a maximum leverage ratio as described above. The Credit Facility agreement allows non-cash charges such as impairment of assets, stock compensation and other non-cash charges to be added back in the calculation of EBITDA. The terms of our Credit Facility also allow us to negotiate in good faith to amend any ratio or requirement to preserve the original intent of the agreement if any change in accounting principles would affect the computation of any financial ratio or requirement of the Credit Facility. Pursuant to the terms of our Credit Facility, our leverage ratio is 2.21, and our interest coverage ratio is 6.74 for the period ended June 30, 2020. We believe that we are in compliance with all covenants contained in our credit agreements. Certain of our material, wholly-owned subsidiaries are guarantors or co-borrowers under the Credit Facility and Senior Notes.

We entered into two interest rate swap agreements for a total notional amount of $50 million, including one of which was entered during the six months ended June 30, 2020. See Note 16 - Derivative Instruments and Hedging Activities.

The estimated fair value of total debt at June 30, 2020 and December 31, 2019 approximated the book value of total debt. The fair value was estimated using Level 2 inputs by calculating the sum of the discounted future interest and principal payments through the date of maturity.