Maturity (Dollars in Millions)	Effective Rate			Coupon Rate			Outstanding
Maturity (Dollars in Millions)	Effective Rate			Coupon Rate			January 30, 2021			February 1, 2020
2023		3.25	%		3.25	%	$	350		$	350
2023		4.78	%		4.75	%		184			184
2025		9.50	%		9.50	%		600		—
2025		4.25	%		4.25	%		650			650
2029		7.36	%		7.25	%		42			42
2033		6.05	%		6.00	%		113			113
2037		6.89	%		6.88	%		101			101
2045		5.57	%		5.55	%		427			427
Outstanding unsecured senior debt								2,467			1,867
Unamortized debt discounts and deferred financing costs								(16	)		(11	)
Unsecured senior debt							$	2,451		$	1,856
Effective interest rate								5.90	%		4.74	%

Our unsecured senior long-term debt is classified as Level 1, financial instruments with unadjusted, quoted prices listed on active market exchanges. The estimated fair value of our unsecured senior debt was $2.8 billion at January 30, 2021 and $2.0 billion at February 1, 2020.

In March 2020, we fully drew down our $1.0 billion senior unsecured revolver. In April 2020, we replaced and upsized the unsecured credit facility with a $1.5 billion senior secured, asset based revolving credit facility maturing in July 2024. The revolver is secured by substantially all of our assets other than real estate, and contains customary events of default and financial, affirmative, and negative covenants, including but not limited to, a springing financial covenant related to our fixed charge coverage ratio and restrictions on indebtedness, liens, investments, asset dispositions, and restricted payments. Outstanding borrowings under the credit facility bear interest at a variable rate based on LIBOR plus the applicable margin. In October 2020, we fully repaid the $1.0 billion outstanding borrowings on our revolver. As of January 30, 2021 we had $31 million of standby and trade letters of credit under the credit facility, which reduces the available borrowing capacity. No borrowings were outstanding on the credit facility as of January 30, 2021 or February 1, 2020.

In April 2020, we issued $600 million of 9.50% notes with semi-annual interest payments beginning in November 2020. The notes include coupon rate step ups if our long-term debt is downgraded to below a BBB- credit rating by S&P Global Ratings or Baa3 by Moody’s Investors Service, Inc. The notes mature in May 2025. We used part of the net proceeds from this offering to repay $500 million of the borrowings under our senior secured, asset based revolving credit facility with the remaining net proceeds available for general corporate purposes.

Our various debt agreements contain covenants including limitations on additional indebtedness and certain financial tests. As of January 30, 2021, we were in compliance with all covenants of the various debt agreements.

We also have additional outstanding trade letters of credit outside of the credit facility totaling approximately $8 million at January 30, 2021.