Note 8. Debt

A summary of total debt is as follows:

	March 31,		December 31,
(all dollar amounts in thousands)	2013		2012

Unsecured private placement notes	$	150,000	$	150,000
Revolving-credit agreement with financial institutions	59,000		5,500
Commercial paper placement agreement	11,500		40,700
Total long-term debt	$	220,500	$	196,200

On March 31, 2010, we entered into a note purchase and private-shelf agreement. This agreement provided for the April 9, 2010, issuance of $50 million of unsecured senior notes having an interest rate of 5.69% that mature on April 9, 2017, and also established a three-year private shelf facility under which up to $125 million of additional promissory notes may be issued at terms agreed upon by the parties at the time of issuance. On April 4, 2011, we issued an additional aggregate principal amount of $50 million of our senior notes under the terms of this note purchase and private-shelf agreement. The notes bear interest at 4.68% and mature on April 4, 2018. On August 22, 2011, the private-shelf agreement was amended to expand the total amount available under the private-shelf agreement to $150 million. On April 9, 2012, we issued an additional aggregate principal amount of $50 million of our senior notes under this note purchase and private-shelf agreement. The notes bear interest at 4.00% and mature on June 30, 2016. At March 31, 2013, the total availability of unsecured private placement notes was $200 million, with $150 million of unsecured private placement notes currently outstanding.

We have estimated the fair value of our long-term debt in accordance with FASB authoritative guidance. The FASB defines fair value as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between participants at the measurement date. Fair value information for long-term debt is within Level 2 of the fair value hierarchy and is based on current market interest rates and estimates of current market conditions for instruments with similar terms and maturities. At March 31, 2013, the estimated fair value of long-term debt is approximately $233 million which compares to the carrying value of $221 million. At December 31, 2012, the estimated fair value of long-term debt was approximately $209 million which compares to the carrying value of $196 million.

On June 23, 2010, we entered into a $125 million revolving-credit agreement with five financial institutions that will expire on June 23, 2014. At March 31, 2013 and December 31, 2012, there was $59.0 million and $5.5 million, respectively, outstanding under the revolving-credit agreement.

In addition, at March 31, 2013, we had $11.5 million of commercial paper outstanding under an existing unrated commercial paper placement agreement with a bank. The agreement requires unused credit availability under our revolving-credit agreement equal to the amount of outstanding commercial paper. At March 31, 2013, the amount of commercial paper outstanding has been classified as long-term on our Condensed Consolidated Balance Sheets as we have the ability and intent to refinance the obligations under our revolving-credit agreement.

We are subject to certain financial and other covenants under the revolving-credit agreement and the note purchase and private-shelf agreement. At March 31, 2013, we were in compliance with all required covenants and expect to remain in full compliance throughout the remainder of 2013.