Unsecured Credit Facility
On September 3, 2020, we entered into a $1.5 billion unsecured five-year Amended and Restated Credit Agreement (“Credit Agreement”) that amended and restated our then existing $1.5 billion unsecured revolving credit facility. As of September 30, 2021, borrowings under the Credit Agreement were available at variable rates based on LIBOR plus 1.25% or the bank prime rate plus 0.25% and we currently pay a commitment fee at an annual rate of 0.20% on the unused portion of the revolving credit facility. The applicable margins over LIBOR and base rate borrowings, along with commitment fees, are subject to adjustment every quarter based on our total net leverage ratio, as defined in the Credit Agreement. All borrowings under the Credit Agreement may be prepaid without penalty. Our Credit Agreement includes provisions to change the reference rate to the then-prevailing market convention for similar agreements if a replacement rate for LIBOR is necessary during its term.
As of September 30, 2021 and December 31, 2020, we had 0 outstanding borrowings on the revolving credit facility. As of September 30, 2021, we had $16.0 million of letters of credit issued on the revolving credit facility.
Senior Unsecured Notes
On November 20, 2006, we entered into an indenture (the “2006 Indenture”) for the issuance of $600.0 million of unsecured debt securities. The total issuance was comprised of (a) $350.0 million aggregate principal amount of senior unsecured notes bearing interest at the rate of 6.20% per annum, which matured and were repaid on November 15, 2016 and (b) $250.0 million aggregate principal amount of senior unsecured notes bearing interest at the rate of 6.85% per annum, maturing on November 15, 2036.
On April 12, 2013, we entered into an indenture (the “2013 Indenture”) for the issuance of $500.0 million aggregate principal amount of senior unsecured notes at the rate of 4.50% per annum, maturing on April 15, 2023.
On August 3, 2020, we entered into an indenture (the “2020 Indenture” and, together with the 2013 Indenture and 2006 Indenture, the “Indentures”) for the issuance of $900.0 million of unsecured debt securities. The total issuance was comprised of (a) $400.0 million aggregate principal amount of senior unsecured notes bearing interest at the rate of 1.30% per annum, maturing on August 15, 2025 and (b) $500.0 million aggregate principal amount of senior unsecured notes bearing interest at the rate of 2.15% per annum, maturing on August 15, 2030.
Under the Indentures, the notes are senior unsecured obligations and rank equally in right of payment with all of our existing and future unsecured and unsubordinated obligations. If we experience a change in control accompanied by a downgrade in our credit rating, we will be required to make an offer to repurchase each series of the notes at a price equal to 101% of their principal amount plus accrued and unpaid interest.
Other Notes, Revolving Credit and Letter of Credit/Letters of Guarantee Facilities
Revolving credit facilities with a combined credit limit of $13.4 million are in place for operations in Asia with combined outstanding balances of $4.6 million and $5.4 million as of September 30, 2021 and December 31, 2020, respectively.
Various industrial revenue bonds had combined outstanding balances of $8.0 million and $8.3 million as of September 30, 2021 and December 31, 2020, respectively, and have maturities through 2027.
A standby letters of credit/letters of guarantee agreement with one of the lenders under our Credit Agreement provides letters of credit or letters of guarantee in an amount not to exceed $50.0 million in the aggregate. As of September 30, 2021, a total of $23.0 million of letters of credit/guarantee were issued on the facility.
Covenants
The Credit Agreement and the Indentures include customary representations, warranties, covenants and events of default provisions. The covenants under the Credit Agreement include, among other things, 2 financial maintenance