The following table summarizes the Company’s total outstanding balance on its revolving credit facility, Senior Secured Notes net of unamortized discount and deferred financing costs, and Senior Unsecured Notes net of unamortized deferred financing costs, as of September 30, 2021, and December 31, 2020:

The Company’s Credit Agreement, which is scheduled to mature on September 28, 2023, provides for a senior secured revolving credit facility with a maximum loan amount of $2.5 billion. On June 8, 2021, the Company entered into a sixth amendment to the Credit Agreement to amend certain definitions and covenants relating to the Company's ability to issue permitted refinancing debt and to repurchase or redeem outstanding indebtedness to facilitate the Tender Offer and the 2022 Senior Notes Redemption, each as defined below. As of September 30, 2021, the borrowing base and aggregate lender commitments under the Credit Agreement were $1.1 billion. Subsequent to September 30, 2021, the fall semi-annual borrowing base redetermination was completed, which reaffirmed both the Company’s borrowing base and aggregate lender commitments at $1.1 billion. The next scheduled borrowing base redetermination date is April 1, 2022.

Interest and commitment fees associated with the revolving credit facility are accrued based on a borrowing base utilization grid set forth in the Credit Agreement as presented in Note 5 - Long-Term Debt in the 2020 Form 10-K. At the Company’s election, borrowings under the Credit Agreement may be in the form of Eurodollar, Alternate Base Rate (“ABR”), or Swingline loans. Eurodollar loans accrue interest at LIBOR, plus the applicable margin from the utilization grid, and ABR and Swingline loans accrue interest at a market-based floating rate, plus the applicable margin from the utilization grid. Commitment fees are accrued on the unused portion of the aggregate lender commitment amount at rates from the utilization grid and are included in the interest expense line item on the accompanying statements of operations.

The Credit Agreement specifies that if LIBOR is no longer a widely used benchmark rate, or if it is no longer used for determining interest rates for loans in the United States, a replacement interest rate that fairly reflects the cost to the lenders of funding loans shall be established by the Administrative Agent, as defined in the Credit Agreement, in consultation with the Company. Please refer to Note 1 - Summary of Significant Accounting Policies for discussion of FASB ASU 2020-04 and ASU 2021-01, which provides guidance related to reference rate reform.


	As of October 21, 2021		As of September 30, 2021		As of December 31, 2020

	(in thousands)
Revolving credit facility (1)	$	—	$	—	$	93,000
Letters of credit (2)	2,500		2,500		42,000
Available borrowing capacity	1,097,500		1,097,500		965,000
Total aggregate lender commitment amount	$	1,100,000	$	1,100,000	$	1,100,000

(1) Unamortized deferred financing costs attributable to the revolving credit facility are presented as a component of the other noncurrent assets line item on the accompanying balance sheets and totaled $3.1 million and $4.3 million as of September 30, 2021, and December 31, 2020, respectively. These costs are being amortized over the term of the revolving credit facility on a straight-line basis.

Senior Secured Notes. Senior Secured Notes, net of unamortized discount and deferred financing costs, included within the Senior Notes, net line item on the accompanying balance sheets as of September 30, 2021, and December 31, 2020, consisted of the following (collectively referred to as “Senior Secured Notes”):


	As of September 30, 2021
	Principal Amount		Unamortized Debt Discount		Unamortized Deferred Financing Costs		Net

	(in thousands)

10.0% Senior Secured Notes due 2025	$	446,675	$	32,232	$	9,436	$	405,007


	As of December 31, 2020
	Principal Amount		Unamortized Debt Discount		Unamortized Deferred Financing Costs		Net

	(in thousands)
1.50% Senior Secured Convertible Notes due 2021	$	65,485	$	1,828	$	175	$	63,482
10.0% Senior Secured Notes due 2025	446,675		37,943		11,558		397,174
Total	$	512,160	$	39,771	$	11,733	$	460,656

The Senior Secured Notes listed above are senior obligations of the Company, secured on a second-priority basis, ranking junior to the Company’s obligations under the Credit Agreement and equal in priority to one another. The Senior Secured Notes rank senior in right of payment with all of the Company’s existing and any future unsecured senior or subordinated debt.

The 1.50% Senior Secured Convertible Notes due 2021 (“2021 Senior Secured Convertible Notes”) matured on July 1, 2021, and on that day, the Company used borrowings under its revolving credit facility to retire at par the outstanding principal amount of $65.5 million. Interest expense recognized on the 2021 Senior Secured Convertible Notes related to the stated interest rate and amortization of the debt discount. No interest expense was recognized for the three months ended September 30, 2021, $1.1 million was recognized for the three months ended September 30, 2020, and $2.3 million and $6.6 million was recognized for the nine months ended September 30, 2021, and 2020, respectively.

The Company may redeem some or all of its 10.0% Senior Secured Notes due 2025 (“2025 Senior Secured Notes”) prior to their maturity at redemption prices based on a premium, plus accrued and unpaid interest, as described in the indenture governing the 2025 Senior Secured Notes.

Senior Unsecured Notes. Senior Unsecured Notes, net of unamortized deferred financing costs, included within the Senior Notes, net line item on the accompanying balance sheets as of September 30, 2021, and December 31, 2020, consisted of the following (collectively referred to as “Senior Unsecured Notes,” and together with the Senior Secured Notes, “Senior Notes”):


	As of September 30, 2021						As of December 31, 2020
	Principal Amount		Unamortized Deferred Financing Costs		Principal Amount, Net		Principal Amount		Unamortized Deferred Financing Costs		Principal Amount, Net

	(in thousands)
6.125% Senior Notes due 2022	$	—	$	—	$	—	$	212,403	$	855	$	211,548
5.0% Senior Notes due 2024	104,769		451		104,318		277,034		1,576		275,458
5.625% Senior Notes due 2025	349,118		2,318		346,800		349,118		2,792		346,326
6.75% Senior Notes due 2026	419,235		3,445		415,790		419,235		3,970		415,265
6.625% Senior Notes due 2027	416,791		4,143		412,648		416,791		4,725		412,066
6.5% Senior Notes due 2028	400,000		6,933		393,067		—		—		—
Total	$	1,689,913	$	17,290	$	1,672,623	$	1,674,581	$	13,918	$	1,660,663

Second Quarter 2021 Senior Notes Transactions. On June 23, 2021, the Company issued $400.0 million in aggregate principal amount of its 6.5% Senior Notes at par with a maturity date of July 15, 2028 (“2028 Senior Notes”). The Company received net proceeds of $392.8 million after deducting fees of $7.2 million, which are being amortized as deferred financing costs over the life of the 2028 Senior Notes. The net proceeds were used to repurchase $193.1 million and $172.3 million of outstanding principal amount of the Company’s 6.125% Senior Notes due 2022 (“2022 Senior Notes”) and 5.0% Senior Notes due 2024 (“2024 Senior Notes”), respectively, through a cash tender offer (“Tender Offer”), and to redeem the remaining $19.3 million of 2022 Senior Notes not repurchased as part of the Tender Offer (“2022 Senior Notes Redemption”). The Company paid total consideration, excluding accrued interest, of $385.3 million, and recorded a net loss on extinguishment of debt of $2.1 million for the three months ended June 30, 2021, which included $1.5 million of accelerated unamortized deferred financing costs and $0.6 million of net premiums. The Company canceled all repurchased and redeemed 2022 Senior Notes and 2024 Senior Notes upon settlement.

Second Quarter 2020 Senior Notes Transactions. During the second quarter of 2020, the Company initiated an offer to exchange certain of its then outstanding Senior Unsecured Notes, other than its 1.50% Senior Unsecured Convertible Notes due 2021 (“2021 Senior Unsecured Convertible Notes,” and together with the Senior Unsecured Notes, “Old Notes”), and entered into a private exchange of certain of its then outstanding 2021 Senior Unsecured Convertible Notes and portions of its then outstanding Senior Unsecured Notes (“Private Exchange”), in each case, for newly issued 2025 Senior Secured Notes, referred to together as “Exchange Offers.”

On June 17, 2020, the Company exchanged $611.9 million in aggregate principal amount of Senior Unsecured Notes and $107.0 million in aggregate principal amount of 2021 Senior Unsecured Convertible Notes for $446.7 million in aggregate principal amount of 2025 Senior Secured Notes. Further, in connection with the Private Exchange, the Company tendered $53.5 million in cash to certain holders of the 2021 Senior Unsecured Convertible Notes and issued the Warrants. Please refer to Note 3 - Equity for more information regarding the Warrants. Upon the closing of the Exchange Offers, the Company recorded a net gain on extinguishment of debt of $227.3 million which included the recognition of $6.1 million and $5.6 million of previously unamortized debt discount and deferred financing costs, respectively. The Company canceled all Senior Unsecured Notes and 2021 Senior Unsecured Convertible Notes that were retired upon closing of the Exchange Offers. Pursuant to the indenture governing its 2021 Senior Unsecured Convertible Notes, the Company’s remaining outstanding 2021 Senior Unsecured Convertible Notes became secured. Please refer to Note 5 - Long-Term Debt in the 2020 Form 10-K for additional information regarding the debt transactions that occurred during the second quarter of 2020.

First Quarter and Third Quarter 2020 Senior Notes Transactions. During the nine months ended September 30, 2020, the Company repurchased $103.2 million in aggregate principal amount of its 2022 Senior Notes and $29.0 million in aggregate principal amount of its 2024 Senior Notes in open market transactions at a discount, for a total settlement amount, excluding accrued interest, of $94.2 million. In connection with the repurchases, the Company recorded a net gain on extinguishment of debt of $25.1 million and $37.3 million for the three and nine months ended September 30, 2020, respectively. The net gain on extinguishment of debt includes discounts realized upon repurchase of $25.5 million and $37.9 million for the three and nine months ended September 30, 2020, respectively, partially offset by accelerated unamortized deferred financing costs of $0.5 million and $0.7 million for the three and nine months ended September 30, 2020, respectively. The Company canceled all repurchased 2022 Senior Notes and 2024 Senior Notes upon settlement.

The Company is subject to certain financial and non-financial covenants under the Credit Agreement and the indentures governing the Senior Notes that, among other terms, limit the Company’s ability to incur additional indebtedness, make restricted payments including dividends, sell assets, create liens that secure debt, enter into transactions with affiliates, merge or consolidate with another company, and with respect to the Company’s restricted subsidiaries, permit the consensual restriction on the ability of such restricted subsidiaries to pay dividends or indebtedness owing to the Company or to any other restricted subsidiaries. The Company was in compliance with all covenants under the Credit Agreement and the indentures governing the Senior Notes as of September 30, 2021, and through the filing of this report. Please refer to Note 5 - Long-Term Debt in the 2020 Form 10-K for additional detail on the Company’s covenants under the Credit Agreement and indentures governing the Senior Notes.

Capitalized interest costs for the three months ended September 30, 2021, and 2020, totaled $3.5 million and $4.8 million, respectively, and totaled $12.5 million and $11.6 million for the nine months ended September 30, 2021, and 2020, respectively. The amount of interest the Company capitalizes generally fluctuates based on the amount borrowed, the Company’s capital program, and