Debt

Total debt as of December 31 consisted of the following:



(millions)	2015		2014
5.5% senior notes due 2025	$	350	$	—
5.875% senior notes due 2021	350		350
6.3% senior notes due 2016	500		500
7.75% senior notes due 2018	500		500
7.875% senior notes due 2020 (net of discount: 2015 - $1; 2014 - $1)	249		249
8.375% senior notes due 2018	—		350
Ship mortgage facility (includes current portion of long-term debt: 2015 - $0; 2014 - $4)	—		21
Industrial revenue bonds (due 2028 through 2034)	239		239
Total	$	2,188	$	2,209
Less unamortized debt issuance costs ^(a)	$	13	$	14
Total	$	2,175	$	2,195


(a)	Reflects the change in presentation of unamortized debt issuance costs from other assets to a reduction in debt. See Note 2.

Repurchase of 8.375% Senior Notes and Issuance of 5.5% Senior Notes

In the first quarter of 2015, we repurchased $350 million of our 8.375% senior notes due in 2018 through both a cash tender offer and a subsequent notice of redemption. On February 24, 2015, we completed a cash tender offer pursuant to which we repurchased $126 million of the 8.375% senior notes for aggregate consideration, including tender offer premium and accrued and unpaid interest, of $135 million. On March 26, 2015, we repurchased the remaining $224 million of the 8.375% senior notes for aggregate consideration, including premiums and accrued and unpaid interest, of $242 million. As a result of the repurchases, we recorded a loss on early extinguishment of debt of $19 million including the write-off of unamortized debt issuance costs. Also on February 24, 2015, we issued $350 million of 5.5% senior notes due March 1, 2025. The net proceeds from the issuance of these notes and cash on hand were used to fund the repurchases of the 8.375% senior notes and all related costs and expenses. We deferred approximately $6 million of debt issuance costs that are being amortized to interest expense over the term of the notes. As of December 31, 2015, these notes were recorded on the accompanying consolidated balance sheet at $344 million.

Senior Notes

All of the senior notes are senior unsecured obligations and rank equally with all of our other existing and future unsecured senior indebtedness. The indentures governing the notes contain events of default, covenants and restrictions that are customary for similar transactions, including a limitation on our ability and the ability of certain of our subsidiaries to create or incur secured indebtedness.



Interest rate ^(a)	6.30%	7.75%	5.500%	7.875%	5.875%
Principal net of discount (in millions) ^(b)	$500	$500	$350	$249	$350
Maturity	November 15, 2016	January 15, 2018	March 1, 2025	March 30, 2020	November 1, 2021
Call date	Any time ^(c)	Any time ^(c)	March 1, 2020 ^(d)	March 30, 2016 ^(d)	November 1, 2016 ^(d)
Mandatory redemption	at 101% plus accrued and unpaid interest in the event of a change in control and a related downgrade below investment grade by both Moody’s Investors Service and Standard & Poor’s Financial Services LLC		at 101% plus accrued and unpaid interest in the event of a change in control


(a)	The 7.75% senior notes currently have an effective interest rate of 9.75%. The rate is subject to an adjustment of up to 2% if the debt rating is downgraded or subsequently upgraded by Moody's Investors Service and Standard & Poor's Financial Services LLC.


(b)	Principal amounts do not include unamortized debt issuance costs that have been reclassified from other assets to a reduction in debt. See Note 2.

(c)

Callable at any time at a price equal to the greater of (1) 100% of the principal and (2) the sum of the present value of the remaining scheduled payments of principal and interest discounted to the redemption date on a semi-annual basis at the applicable U.S. Treasury rate plus a spread (as outlined in the respective indentures), plus any accrued and unpaid interest on the principal amount being called.


(d)	Callable at any time prior to the call date at a price equal to 100% of the principal plus a premium (as outlined in the respective indentures), plus any accrued and unpaid interest on the principal amount being called. Callable after the call date at stated redemption prices (as outlined in the respective indentures), plus any accrued and unpaid interest on the principal amount being called.

Credit Facility

Our credit facility allows for a maximum borrowing limit under the credit agreement of $450 million (including a $50 million borrowing sublimit for CGC, Inc.). The agreement allows for the borrowing of revolving loans and issuance of letters of credit (up to a maximum of $200 million at any time outstanding, in aggregate) to USG and its subsidiaries. The maximum allowable borrowings may be increased at our request with the agreement of the lenders providing increased or new lending commitments, provided that the maximum allowable borrowings after giving effect to the increase may not exceed $650 million.

Our obligations under the credit facility are guaranteed by USG and its significant domestic subsidiaries and secured by trade receivables and inventory. The credit facility matures on October 22, 2019 unless terminated earlier in accordance with its terms. The credit facility is available to fund working capital needs and for other general corporate purposes.

The credit agreement contains a financial covenant that would require us to maintain a minimum fixed charge coverage ratio. Because we currently satisfy the required fixed charge coverage ratio, we are not required to maintain a minimum borrowing availability under the credit facility. The credit agreement contains other covenants and events of default that are customary for similar agreements and may limit our ability to take various actions including our ability to pay a dividend or repurchase our stock.

Taking into account the most recent borrowing base calculation delivered under the credit facility, which reflects trade receivables and inventory as of December 31, 2015, and outstanding letters of credit, borrowings available under the credit facility were approximately $295 million, including $50 million for CGC. As of December 31, 2015 and during the year then-ended, there were no borrowings under the facility. Had there been any borrowings as of that date, the applicable interest rate would have been 1.86% for loans in the US and 2.12% for loans in Canada. Outstanding letters of credit totaled $49 million, including $1 million for CGC, as of December 31, 2015.

Ship Mortgage Facility

Our subsidiary, Gypsum Transportation Limited, or GTL, had a secured loan facility agreement with DVB Bank SE, as lender, agent and security trustee which was repaid during 2015 in connection with the sale of two self-unloading vessels. See Note 13 for discussion of GTL.

Industrial Revenue Bonds

Our $239 million of industrial revenue bonds have fixed interest rates ranging from 5.5% to 6.4%. The weighted average rate of interest on our industrial revenue bonds is 5.875%. These bonds mature during the years 2028 through 2034.

OTHER INFORMATION

The fair value of our debt was $2.295 billion and $2.338 billion as of December 31, 2015 and 2014, respectively, and was determined using the fair value hierarchy of inputs described in Note 1. The fair values were based on quoted prices for identical or similar liabilities in markets that are not active or valuation models in which all significant inputs and value drivers are observable and, as a result, are classified as Level 2.

Interest accrued on our debt as of December 31, 2015 and December 31, 2014 was $45 million for both periods.

As of December 31, 2015, we were in compliance with the financial covenants contained in our credit facility.

As of December 31, 2015, the amounts of total debt outstanding maturing in each of the next five years and beyond were as follows:



(millions)	2016		2017		2018		2019		2020		After 2020
Debt maturities (principal amounts)	$	500	$	—	$	500	$	—	$	250	$	939