DEBT	12 Months Ended
Dec. 31, 2017
DEBT
DEBT	4. DEBT As of December 31, 2017, outstanding debt balances totaled $148.9 million, net of unamortized discount and debt issuance costs, all of which were our long-term senior notes. On October 2, 2013, we completed a public debt offering, issuing $150.0 million in senior notes maturing September 15, 2023, and paying interest semi-annually at the rate of 4.875 percent. The notes were issued at a discount resulting in proceeds, net of discount and commission, of $148.6 million. The amount of the discount is being charged to income over the life of the debt on an effective-yield basis. On December 12, 2013, a portion of the proceeds were used to redeem the $100.0 million in senior notes that were to mature on January 15, 2014, and the remaining proceeds were made available for general corporate purposes. The estimated fair value for the senior note was $160.3 million as of December 31, 2017. The fair value of our long-term debt is based on the limited observable prices that reflect thinly traded securities and is therefore classified as a level 2 liability within the fair value hierarchy. We incurred $7.4 million of interest expense on our senior notes in each of the last three years. The average rate on debt was 4.91 percent in 2017, 2016 and 2015. We maintain a revolving line of credit with JP Morgan Chase Bank N.A., which permits us to borrow up to an aggregate principal amount of $40.0 million. This facility was entered into during the second quarter of 2014 and replaced the previous $25.0 million facility which expired on May 31, 2014. Under certain conditions, the line may be increased up to an aggregate principal amount of $65.0 million. This facility has a four-year term that expires on May 28, 2018. As of and during the years ended December 31, 2017, 2016 and 2015, no amounts were outstanding on these facilities.

4. DEBT

As of December 31, 2017, outstanding debt balances totaled $148.9 million, net of unamortized discount and debt issuance costs, all of which were our long-term senior notes.

On October 2, 2013, we completed a public debt offering, issuing $150.0 million in senior notes maturing September 15, 2023, and paying interest semi-annually at the rate of 4.875 percent. The notes were issued at a discount resulting in proceeds, net of discount and commission, of $148.6 million. The amount of the discount is being charged to income over the life of the debt on an effective-yield basis. On December 12, 2013, a portion of the proceeds were used to redeem the $100.0 million in senior notes that were to mature on January 15, 2014, and the remaining proceeds were made available for general corporate purposes. The estimated fair value for the senior note was $160.3 million as of December 31, 2017. The fair value of our long-term debt is based on the limited observable prices that reflect thinly traded securities and is therefore classified as a level 2 liability within the fair value hierarchy.

We incurred $7.4 million of interest expense on our senior notes in each of the last three years. The average rate on debt was 4.91 percent in 2017, 2016 and 2015.

We maintain a revolving line of credit with JP Morgan Chase Bank N.A., which permits us to borrow up to an aggregate principal amount of $40.0 million. This facility was entered into during the second quarter of 2014 and replaced the previous $25.0 million facility which expired on May 31, 2014. Under certain conditions, the line may be increased up to an aggregate principal amount of $65.0 million. This facility has a four-year term that expires on May 28, 2018. As of and during the years ended December 31, 2017, 2016 and 2015, no amounts were outstanding on these facilities.