(In thousands)	March 31, 2019		December 31, 2018
Senior notes	$	45,000	$	45,000
Revolving credit facility		—		—
Total long-term debt		45,000		45,000
Less: Current maturities		—		—
Total maturities due after one year	$	45,000	$	45,000

We have one unsecured senior note agreement with an amount outstanding of $45.0 million at each of March 31, 2019 and December 31, 2018. Our unsecured senior note agreement calls for a scheduled principal payment of $45.0 million due on January 3, 2021. The interest rate on the January 3, 2021 scheduled principal payment is 4.79%.

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.

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%. 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.

For periods covered under the Credit Agreement, the applicable margin on LIBOR loans and letter of credit fees were 1.0% and commitment fees were 0.125%. There were $58.9 million and $61.5 million of outstanding letters of credit at March 31, 2019 and December 31, 2018, respectively.