8.Debt

At December 31, 2015 and September 30, 2015, we had the following unsecured long-term debt outstanding:

					Unamortized Discount and
	Principal				Debt Issuance Costs
	December 31,		September 30,		December 31,			September 30,
	2015		2015		2015			2015
	(in thousands)

Unsecured senior notes issued July 21, 2009:
Due July 21, 2016	$	40,000	$	40,000	$	(441	)	$	(498	)

Unsecured senior notes issued March 19, 2015:
Due March 19, 2025	500,000		500,000		(7,799		)	(7,965		)

	540,000		540,000		(8,240		)	(8,463		)
Less long-term debt due within one year	40,000		40,000		(908		)	(906		)

Long-term debt	$	500,000	$	500,000	$	(7,332	)	$	(7,557	)

We have $40 million senior unsecured fixed-rate notes outstanding at December 31, 2015 that mature July 2016. Interest on the notes is paid semi-annually based on an annual rate of 6.10 percent. A final annual principal repayment of $40 million is due July 2016. We have complied with our financial covenants which require us to maintain a funded leverage ratio of less than 55 percent and an interest coverage ratio (as defined) of not less than 2.50 to 1.00.

On March 19, 2015, we issued $500 million of 4.65 percent 10-year unsecured senior notes. The net proceeds, after discount and issuance cost, have been or will be used for general corporate purposes, including capital expenditures associated with our rig construction program. Interest is payable semi-annually on March 15 and September 15. The debt discount is being amortized to interest expense using the effective interest method. The debt issuance costs are amortized straight-line over the stated life of the obligation, which approximates the effective yield method.

We have a $300 million unsecured revolving credit facility that will mature May 25, 2017. The credit facility has $100 million available to use for letters of credit. The majority of borrowings under the facility would accrue interest at a spread over the London Interbank Offered Rate (LIBOR). We also pay a commitment fee based on the unused balance of the facility. Borrowing spreads as well as commitment fees are determined according to a scale based on a ratio of our total debt to total capitalization. The spread over LIBOR ranges from 1.125 percent to 1.75 percent per annum and commitment fees range from .15 percent to .35 percent per annum. Based on our debt to total capitalization on December 31, 2015, the spread over LIBOR and commitment fees would be 1.125 percent and .15 percent, respectively. Financial covenants in the facility require us to maintain a funded leverage ratio (as defined) of less than 50 percent and an interest coverage ratio (as defined) of not less than 3.00 to 1.00. The credit facility contains additional terms, conditions, restrictions, and covenants that we believe are usual and customary in unsecured debt arrangements for companies of similar size and credit quality. As of December 31, 2015, there were no borrowings, but there were three letters of credit outstanding in the amount of $40.3 million. At December 31, 2015, we had $259.7 million available to borrow under our $300 million unsecured credit facility.

At December 31, 2015, we had two letters of credit outstanding, totaling $12 million that were issued to support international operations. These letters of credit were issued separately from the $300 million credit facility so they do not reduce the available borrowing capacity discussed in the previous paragraph.