8.Debt

At December 31, 2016 and September 30, 2016, we had the following unsecured long-term debt outstanding:

	Principal				Unamortized Discount and Debt Issuance Costs
	December 31,		September 30,		December 31,			September 30,
	2016		2016		2016			2016
	(in thousands)

Unsecured senior notes issued March 19, 2015:
Due March 19, 2025	500,000		500,000		(7,890		)	(8,153		)

	500,000		500,000		(7,890		)	(8,153		)
Less long-term debt due within one year	—		—		—			—

Long-term debt	$	500,000	$	500,000	$	(7,890	)	$	(8,153	)

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 interest method.

We have a $300 million unsecured revolving credit facility which will mature on July 13, 2021. The credit facility has $75 million available to use as letters of credit. The majority of any 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 .30 percent per annum. Based on our debt to total capitalization on December 31, 2016, the spread over LIBOR and commitment fees would be 1.125 percent and .15 percent, respectively. There is one financial covenant in the facility which requires us to maintain a funded leverage ratio (as defined) of less than 50 percent. 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 including a limitation that priority debt (as defined in the agreement) may not exceed 17.5% of the net worth of the Company. As of December 31, 2016, there were no borrowings, but there were four letters of credit outstanding in the amount of $40.3 million. At December 31, 2016, we had $259.7 million available to borrow under our $300 million unsecured credit facility.

The applicable agreements for all unsecured debt contain additional terms, conditions and restrictions that we believe are usual and customary in unsecured debt arrangements for companies that are similar in size and credit quality. At December 31, 2016, we were in compliance with all debt covenants.