DEBT

Long-term debt consisted of the following:



($ in millions)	September 30 2017			December 31 2016
Senior notes due December 15, 2021, 5.000%	$	600		$	600
Senior notes due November 15, 2025, 5.000%	600			600
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	(23		)	(27		)
Total long-term debt	$	1,282		$	1,278

Credit Facility - In July 2015, the Company entered into a Second Amended and Restated Credit Agreement (the “Amended Credit Facility”) with third-party lenders. The Amended Credit Facility includes a revolving credit facility of $1,250 million, which may be drawn upon during a period of five years from July 2015. The revolving credit facility includes a letter of credit subfacility of $500 million. 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 leverage ratio, which may vary between 1.25% and 2.0%. The revolving credit facility also has a commitment fee rate on the unutilized balance based on the Company’s leverage ratio. The commitment fee rate as of September 30, 2017, was 0.25% and may vary between 0.25% and 0.35%.

The Amended Credit Facility contains customary affirmative and negative covenants, as well as a financial covenant based on a maximum leverage ratio, which could limit the amount of dividends the Company may pay and shares the Company may repurchase. 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 Amended Credit Facility. Substantially all tangible and intangible material assets of the Company and domestic subsidiaries are pledged as collateral under the Amended Credit Facility.

As of September 30, 2017, approximately $15 million in standby letters of credit were issued but undrawn, and the remaining $1,235 million of the revolving credit facility was unutilized. The Company had unamortized debt issuance costs associated with its credit facilities of $6 million and $8 million as of September 30, 2017, and December 31, 2016, respectively.

Senior Notes - In December 2014, the Company issued $600 million aggregate principal amount of unregistered 5.000% senior notes due December 2021. In November 2015, the Company issued $600 million aggregate principal amount of unregistered 5.000% senior notes due November 2025. Interest on the Company's senior notes is payable semi-annually.

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 the senior notes of $17 million and $19 million as of September 30, 2017, and December 31, 2016, respectively.

Mississippi Economic Development Revenue Bonds - As of each of September 30, 2017, and December 31, 2016, the Company had $84 million outstanding under Industrial Revenue Bonds issued by the Mississippi Business Finance Corporation. These bonds accrue interest at a fixed rate of 7.81% per annum (payable semi-annually) and mature in 2024.

Gulf Opportunity Zone Industrial Development Revenue Bonds - As of each of September 30, 2017, and December 31, 2016, the Company had $21 million outstanding under Gulf Opportunity Zone Industrial Development Revenue Bonds issued by the Mississippi Business Finance Corporation. These bonds accrue interest at a fixed rate of 4.55% per annum (payable semi-annually) and mature in 2028.

The Company's debt arrangements contain customary affirmative and negative covenants, including a maximum leverage ratio. The Company was in compliance with all debt covenants during the nine months ended September 30, 2017.

The estimated fair values of the Company's total long-term debt as of September 30, 2017, and December 31, 2016, were $1,385 million and $1,372 million, respectively. The fair values of the Company's long-term debt were calculated based on either recent trades of the Company's debt instruments in inactive markets or yields available on debt with substantially similar risks, terms and maturities, which fall within Level 2 under the fair value hierarchy.

The Company has $600 million in principal payments due on long-term debt in 2021.