Debt

6 Months Ended

Jun. 30, 2020

DEBT

Long-term debt consisted of the following:


($ in millions)	June 30, 2020		December 31, 2019
Senior notes due November 15, 2025, 5.000%	600		600
Senior notes due December 1, 2027, 3.483%	600		600
Senior notes due May 1, 2025, 3.844%	500		—
Senior notes due May 1, 2030, 4.200%	500		—
Mississippi economic development revenue bonds due May 1, 2024, 7.81%	84		84
Gulf opportunity zone industrial development revenue bonds due December 1, 2028, 4.55%	21		21

Less unamortized debt issuance costs	(29)		(19)
Total long-term debt	$	2,276	$	1,286

Credit Facility - The Company's credit facility with third-party lenders (the "Credit Facility") includes a revolving credit facility of $1,250 million, which may be drawn upon during a period of five years from November 22, 2017. The revolving credit facility includes a letter of credit subfacility of $500 million.

The Credit Facility contains customary affirmative and negative covenants, as well as a financial covenant based on a maximum total leverage ratio. Each of the Company's existing and future material wholly owned domestic subsidiaries, except those that are specifically designated as unrestricted subsidiaries, are and will be guarantors under the Credit Facility. See Note 19: Subsidiary Guarantors.

As of June 30, 2020, the Company had $16 million in issued but undrawn letters of credit and $1,234 million unutilized under the Credit Facility. The Company had unamortized debt issuance costs associated with its credit facilities of $7 million as of each of June 30, 2020, and December 31, 2019.

In the second quarter of 2020, the Company entered into a 364-day revolving credit agreement (the "364-Day Facility") with third-party lenders. The 364-Day Facility includes a revolving credit facility of $500 million, which may be drawn upon during a period of 364 days from April 3, 2020. The revolving credit facility has a variable interest rate on outstanding borrowings based on the London Interbank Offered Rate ("LIBOR") plus a spread based upon the Company's credit rating, which may vary between 2.000% and 2.375%. The revolving credit facility also has a commitment fee rate of 0.50%.

The 364-Day Facility contains customary affirmative and negative covenants, as well as a financial covenant based on a maximum total leverage ratio. Each of the Company's existing and future material wholly owned domestic subsidiaries, except those that are specifically designated as unrestricted subsidiaries, are and will be guarantors under the 364-Day Facility.

Under the Company's unsecured commercial paper program, the Company may issue up to $1 billion of unsecured commercial paper notes.

Senior Notes - In the second quarter of 2020, the Company issued $500 million aggregate principal amount of unregistered 3.844% senior notes due 2025 and $500 million aggregate principal amount of unregistered 4.200% senior notes due 2030, both with registration rights. The net proceeds are intended to be used for general corporate purposes, which may include debt repayments and working capital. Interest on these senior notes is payable semiannually.

The terms of the senior notes limit the Company’s ability and the ability of certain of its subsidiaries to create liens, enter into sale and leaseback transactions, sell assets, and effect consolidations or mergers.

The Company had unamortized debt issuance costs associated with its senior notes of $22 million and $12 million as of June 30, 2020, and December 31, 2019, respectively.

The Company's debt arrangements contain customary affirmative and negative covenants. The Company was in compliance with all debt covenants during the six months ended June 30, 2020.

The estimated fair values of the Company's total long-term debt as of June 30, 2020, and December 31, 2019, were $2,492 million and $1,379 million, respectively. The fair values of the Company's long-term debt were calculated based on recent trades of the Company's debt instruments in inactive markets, which fall within Level 2 under the fair value hierarchy.

As of June 30, 2020, the aggregate amounts of principal payments due on long-term debt within the next five years consisted of $84 million due in 2024 and $500 million due in 2025.