	As of December 31, 2020			As of December 31, 2019
Revolving credit facility(A)	$	165,407		$	—
Term loan		200,000			200,000
British pound sterling term loan(B)		956,900			—
Australian term loan facility(B)		923,280			842,520
4.000% Senior Unsecured Notes due 2022(B)		610,800			560,650
2.550% Senior Unsecured Notes due 2023(B)		546,800			530,280
5.500% Senior Unsecured Notes due 2024		—			300,000
6.375% Senior Unsecured Notes due 2024		—			500,000
3.325% Senior Unsecured Notes due 2025(B)		610,800			560,650
5.250% Senior Unsecured Notes due 2026		500,000			500,000
5.000% Senior Unsecured Notes due 2027		1,400,000			1,400,000
3.692% Senior Unsecured Notes due 2028(B)		820,200			795,420
4.625% Senior Unsecured Notes due 2029		900,000			900,000
3.500% Senior Unsecured Notes due 2031		1,300,000			—
	$	8,934,187		$	7,089,520
Debt issue costs and discount, net		(68,729	)		(65,841	)
	$	8,865,458		$	7,023,679

As of December 31, 2020, principal payments due on our debt (which exclude the effects of any discounts, premiums, or debt issue costs recorded) are as follows ($ amounts in thousands):

2021	$	165,407
2022		810,800
2023		546,800
2024		923,280
2025		1,567,700
Thereafter		4,920,200
Total	$	8,934,187

Our current unsecured credit facility (“Credit Facility”) includes a $1.3 billion unsecured revolving loan facility and a $200 million unsecured term loan facility. At December 31, 2020, the maturity date of our unsecured revolving loan facility was in February 2021, while our term loan’s maturity date was February 1, 2022. The term loan and/or revolving loan commitments could be increased in an aggregate amount not to exceed $500 million.

At our election, loans under the Credit Facility could be made as either ABR Loans or Eurodollar Loans. The applicable margin for term loans that are ABR Loans was adjustable on a sliding scale from 0.00% to 0.95% based on our current credit rating. The applicable margin for term loans that are Eurodollar Loans was adjustable on a sliding scale from 0.90% to 1.95% based on our current credit rating. The applicable margin for revolving loans that are ABR Loans was adjustable on a sliding scale from 0.00% to 0.65% based on our current credit rating. The applicable margin for revolving loans that are Eurodollar Loans was adjustable on a sliding scale from 0.875% to 1.65% based on our current credit rating. The commitment fee was adjustable on a sliding scale from 0.125% to 0.30% based on our current credit rating and was payable on the revolving loan facility.

At December 31, 2020, we had $165.4 million outstanding on the revolving credit facility, whereas, we had no outstanding borrowings on our revolving credit facility at December 31, 2019. At December 31, 2020 and 2019, our availability under our revolving credit facility was $1.1 billion and $1.3 billion, respectively. The weighted-average interest rate on the revolving facility was 1.4% and 2.0% during 2020 and 2019, respectively.

At December 31, 2020 and 2019, the interest rate in effect on our term loan was 1.65% and 3.30%, respectively.

Our Credit Facility was amended in January 2021 – see Note 13 for details of this amendment.

On January 6, 2020, we entered into a £700 million unsecured sterling-denominated term loan with Bank of America, N.A., as administrative agent, and several lenders from time-to-time are parties thereto. The term loan matures on January 15, 2025. The applicable margin under the term loan is adjustable based on a pricing grid from 0.85% to 1.65% dependent on our current credit rating. On March 4, 2020, we entered into an interest rate swap transaction (effective March 6, 2020) to fix the interest rate to approximately 0.70% for the duration of the loan. The current applicable margin for the pricing grid (which can vary based on our credit rating) is 1.25% for an all-in fixed rate of 1.95%.

On May 23, 2019, we entered into an A$1.2 billion term loan with Bank of America, N.A., as administrative agent, and several lenders from time-to-time are parties thereto. The term loan matures on May 23, 2024. The interest rate under the term loan is adjustable based on a pricing grid from 0.85% to 1.65%, dependent on our current senior unsecured credit rating. On June 27, 2019, we entered into an interest rate swap transaction (effective July 3, 2019) to fix the interest rate to approximately 1.20% for the duration of the loan as long as the reference rate stays above 0.00%. The current applicable margin for the pricing grid (which can vary based on our credit rating) is 1.25% for an all-in fixed rate of 2.45%.

At December 31, 2020 and 2019, we had a derivative liability of approximately $51.3 million and $5.6 million, respectively, included in "Accounts payable and accrued expenses" in our consolidated balance sheets associated with these interest rate swaps.

The following are the basic terms of our senior unsecured notes. Typically, we may redeem some or all of the notes at any time, but may require a redemption premium that will decrease over time. In the event of a change of control, each holder of the notes may

require us to repurchase some or all of our notes at a repurchase price equal to 101% of the aggregate principal amount of the notes plus accrued and unpaid interest to the date of purchase.

On August 19, 2015, we completed a €500 million senior unsecured notes offering. Interest on the notes is payable annually on August 19 of each year. The notes pay interest in cash at a rate of 4.000% per year. The notes mature on August 19, 2022.

On December 5, 2019, we completed a £400 million senior unsecured notes offering. Interest on the notes is payable annually on December 5 of each year. The notes pay interest in cash at a rate of 2.550% per year. The notes mature on December 5, 2023.

On April 17, 2014, we completed a $300 million senior unsecured notes offering. Interest on the notes was payable semi-annually on May 1 and November 1 of each year. The notes paid interest in cash at a rate of 5.500% per year. The notes were to mature on May 1, 2024; however, we redeemed the notes on December 19, 2020.

On February 22, 2016, we completed a $500 million senior unsecured notes offering. Interest on the notes was payable on March 1 and September 1 of each year. Interest on the notes was paid in cash at a rate of 6.375% per year. The notes were to mature on March 1, 2024; however, we redeemed the notes on December 19, 2020.

On March 24, 2017, we completed a €500 million senior unsecured notes offering. Interest on the notes is payable annually on March 24 of each year. The notes pay interest in cash at a rate of 3.325% per year. The notes mature on March 24, 2025.

On July 22, 2016, we completed a $500 million senior unsecured notes offering. Interest on the notes is payable on February 1 and August 1 of each year. Interest on the notes is to be paid in cash at a rate of 5.250% per year. The notes mature on August 1, 2026.

On September 7, 2017, we completed a $1.4 billion senior unsecured notes offering. Interest on the notes is payable on April 15 and October 15 of each year. The notes pay interest in cash at a rate of 5.000% per year. The notes mature on October 15, 2027.

On December 5, 2019, we completed a £600 million senior unsecured notes offering. The notes were issued at 99.998% of par value. Interest on the notes is payable on June 5 of each year. The notes pay interest in cash at a rate of 3.692% per year. The notes mature on June 5, 2028.

On July 26, 2019, we completed a $900 million senior unsecured notes offering. Interest on the notes is payable on February 1 and August 1 of each year, commencing on February 1, 2020. The notes were issued at 99.5% of par value, pay interest at a rate of 4.625% per year and mature on August 1, 2029.

On December 4, 2020, we completed a $1.3 billion senior unsecured notes offering. Interest on the notes is payable semi-annually on March 15 and September 15 of each year. The notes pay interest in cash at a rate of 3.500% per year. The notes mature on March 15, 2031.

In preparation of the joint venture with Primotop described under “2018 Activity” in Note 3, we issued secured debt on August 3, 2018, resulting in gross proceeds of €655 million. Provisions of the secured debt included a term of seven years and a swapped fixed rate of approximately 2.3%. Subsequently, on August 31, 2018, the secured debt was contributed along with the related real estate of 71 properties to form the joint venture.

With proceeds from our $1.3 billion, 3.500% Senior Unsecured Notes due 2031 offering completed on December 4, 2020, we redeemed all of our outstanding $500.0 million aggregate principal amount of 6.375% Senior Unsecured Notes due 2024 and $300.0 million aggregate principal amount of 5.500% Senior Unsecured Notes due 2024, including accrued and unpaid interest. As a result of these redemptions, we incurred a charge of approximately $28 million (including redemption premiums and accelerated amortization of deferred debt issuance costs).

On July 10, 2019, we received a commitment to provide a senior unsecured bridge loan facility to fund our investment in Prospect. With this commitment, we paid approximately $4 million of underwriting and other fees. However, this commitment was cancelled with the completion of the debt and equity offerings in July 2019 (as more fully described above and in Note 9), which resulted in fully expensing the total amount of underwriting and other fees that were paid.

In anticipation of funding our Australian acquisition in June 2019 and the Circle transaction in January 2020, we entered into term loans on the date these deals were signed that had a delayed draw feature. This feature allowed for us to not draw on the term loans until needed to fund these transactions. However, with this type of structure, we incurred approximately $2.0 million in accelerated debt issue cost amortization expense during 2019.

Our debt facilities impose certain restrictions on us, including restrictions on our ability to: incur debts; create or incur liens; provide guarantees in respect of obligations of any other entity; make redemptions and repurchases of our capital stock; prepay, redeem, or repurchase debt; engage in mergers or consolidations; enter into affiliated transactions; dispose of real estate or other assets; and change our business. In addition, the credit agreements governing our Credit Facility limit the amount of dividends we can pay as a percentage of normalized adjusted funds from operations (“NAFFO”), as defined in the agreements, on a rolling four quarter basis. Through 2020, the dividend restriction was 95% of NAFFO. The indentures governing our senior unsecured notes also limit the amount of dividends we can pay based on the sum of 95% of NAFFO, proceeds of equity issuances and certain other net cash proceeds. Finally, our senior unsecured notes require us to maintain total unencumbered assets (as defined in the related indenture) of not less than 150% of our unsecured indebtedness.

In addition to these restrictions, the Credit Facility contains customary financial and operating covenants, including covenants relating to our total leverage ratio, fixed charge coverage ratio, secured leverage ratio, consolidated adjusted net worth, unsecured leverage ratio, and unsecured interest coverage ratio. The Credit Facility also contains customary events of default, including among others, nonpayment of principal or interest, material inaccuracy of representations, and failure to comply with our covenants. If an event of default occurs and is continuing under the Credit Facility, the entire outstanding balance may become immediately due and payable. At December 31, 2020, we were in compliance with all such financial and operating covenants.