Note 4. Long-Term Debt

Long-term debt consisted of the following:



(In thousands)	June 30, 2017			December 31, 2016
Senior notes	$	95,000		$	95,000
Revolving credit facility	—			9,975
Total long-term debt	95,000			104,975
Less: Current maturities	(50,000		)	—
Total maturities due after one year	$	45,000		$	104,975

We had one unsecured senior note agreement with an amount outstanding of $95.0 million at each of June 30, 2017 and December 31, 2016. Our unsecured senior note agreement calls for two scheduled principal payments of $50.0 million and $45.0 million on January 3, 2018 and January 3, 2021, respectively. Interest rates on the January 3, 2018 and January 3, 2021 scheduled principal payments are 4.00% and 4.79%, respectively. The effective average interest rate on our outstanding senior note agreement was 4.37% at each of June 30, 2017 and December 31, 2016.

On December 15, 2015, we entered into an amended and restated credit agreement with Wells Fargo Bank, National Association ("Wells Fargo") serving as administrative agent for the lenders (the "Credit Agreement"). The Credit Agreement originally provided for a five-year, $250.0 million senior unsecured revolving line of credit and a $100.0 million accordion feature, which if fully exercised and approved, would expand the total borrowing capacity up to an aggregate of $350.0 million.

On September 9, 2016, we exercised a portion of the accordion feature and entered into an amendment to the Credit Agreement to increase the aggregate commitments from existing lenders by $50.0 million to an aggregate of $300.0 million. Of the $300.0 million line of credit commitments under the Credit Agreement, as amended, up to $100.0 million may be used for letters of credit and $30.0 million may be used for borrowings under the Wells Fargo Sweep Plus Loan Program (the "Sweep Program"). We utilize the Sweep Program to manage our daily cash needs, as it automatically initiates borrowings to cover overnight cash requirements primarily for working capital needs.

At our option, borrowings under the Credit Agreement bear interest at either: (i) LIBOR plus an applicable margin (based on our ratio of net debt-to-total capitalization) that ranges from 1.0% to 1.50%; or (ii) a Base Rate plus an applicable margin (based on our ratio of net debt-to-total capitalization) that ranges from 0.0% to 0.5%. Loans under the Sweep Program bear interest at the LIBOR plus applicable margin rate. Letter of credit fees equal to the applicable margin for LIBOR loans are charged quarterly in arrears on the daily average aggregate stated amount of all letters of credit outstanding during the quarter. Commitment fees ranging from 0.125% to 0.2% (based upon the ratio of net debt-to-total capitalization) are charged quarterly in arrears on the aggregate unutilized portion of the Credit Agreement. Wells Fargo, as administrative agent, also receives an annual fee for providing administrative services.

For each of the three and six-month periods ended June 30, 2017 and 2016, the applicable margin on LIBOR loans was 1.0% and commitment fees were 0.125% under the Credit Agreement. There were $71.4 million and $74.6 million of outstanding letters of credit at June 30, 2017 and December 31, 2016, respectively. Letter of credit fees remained at 1.0% during each of the three and six-month periods ended June 30, 2017 and 2016.