DEBT

A summary of long-term debt is as follows:



(In thousands)	December 31, 2015		September 30, 2015
6.5% Senior Notes due 2020 ("Senior Notes")	$	648,399	$	648,268
Revolving Credit Facility	960,000		1,030,000
Total long-term debt	$	1,608,399	$	1,678,268

Senior Notes

As of December 31, 2015, our Senior Notes had an aggregate principal amount of $650 million and is presented in the table above net of unamortized debt issuance costs and the unamortized premium from their issuance. Our Senior Notes are unsecured obligations and are not guaranteed by any of our subsidiaries.

Revolving Credit Facility

As of December 31, 2015, our senior secured revolving credit facility (the "Credit Facility") had $1.547 billion of total commitments and there were $960 million of outstanding borrowings. The outstanding borrowings are presented net of unamortized debt issuance costs in the table above. As of December 31, 2015, we had approximately $587 million available for borrowings under the Credit Facility. Borrowings under the Credit Facility bear interest at the Eurodollar rate plus a margin ranging from 1.75% to 2.00% and the commitment fee on the unused portion of the underlying commitment ranges from 0.30% to 0.40% per annum, in each case based on our corporate credit ratings. Approximately $305 million of the commitments mature in May 2018 and approximately $1.242 billion of the commitments under the Credit Facility mature in May 2019.

Obligations under the Credit Facility are secured primarily by first preferred mortgages on eight of our drilling units (Atwood Aurora, Atwood Beacon, Atwood Condor, Atwood Eagle, Atwood Falcon, Atwood Mako, Atwood Manta and Atwood Osprey), as well as liens on the equity interests of our subsidiaries that own, directly or indirectly, such drilling units. Our Credit Facility contains various financial covenants. We were in compliance with all financial covenants under the Credit Facility at December 31, 2015 and we anticipate that we will continue to be in compliance for the remainder of fiscal year 2016.

The weighted-average effective interest rate on our long-term debt was approximately 4.10% per annum at December 31, 2015. The effective rate was determined after giving consideration to the effect of our interest rate swaps accounted for as hedges and the amortization of premiums or discount. Interest capitalized for the three months ended December 31, 2015 was approximately $5 million and interest capitalized for the three months ended December 31, 2014 was approximately $4 million.