Long-term debt, net of unamortized debt issuance costs, consisted of the following:

(In thousands)	June 30, 2021		December 31, 2020
Senior notes	$	99,939	$	99,931
Revolving credit facility		—		—
Total long-term debt		99,939		99,931
Less: Current maturities		—		—
Total maturities due after one year	$	99,939	$	99,931

On May 4, 2020, we entered into a Note Purchase and Private Shelf Agreement with PGIM, Inc. (“Prudential”) and certain affiliates and managed accounts of Prudential (the “Note Agreement”). The Note Agreement, which is uncommitted and subject to Prudential’s sole discretion, provides for the issuance of senior promissory notes with an aggregate principal amount of up to $350.0 million through May 4, 2023. Pursuant to the Note Agreement, we issued $100.0 million aggregate principal amount of senior promissory notes (the “Series B Notes”), the proceeds of which are available for capital expenditures, share repurchases, dividends, acquisitions, or general corporate purposes. Borrowing availability under the Note Agreement is reduced by the outstanding amount of the existing Series B Notes, and all other senior promissory notes issued pursuant to the Note Agreement.

The Series B Notes bear interest at 3.10% per annum and mature on May 4, 2027, unless prepaid. Principal payments are required annually beginning on May 4, 2023 in equal installments of $20.0 million through May 4, 2027. The Series B Notes are senior unsecured obligations and rank pari passu with borrowings under our Credit Agreement or Note Agreement.

On November 21, 2019, we entered into a second amended and restated credit agreement with Wells Fargo Bank, National Association serving as administrative agent for the lenders (the “Credit Agreement”). The Credit Agreement provides for a five-year, $250.0 million senior unsecured revolving line of credit and a $150.0 million accordion feature, which if fully exercised and approved, would expand the total borrowing capacity up to an aggregate of $400.0 million. Of the $250.0 million line of credit commitments under the Credit Agreement, 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 (including applicable successor provisions) plus an applicable margin (based on our ratio of net debt-to-total capitalization) that ranges from 1.000% to 1.375%; or (ii) a Base Rate, as defined in the Credit Agreement, plus an applicable margin (based on our ratio of net debt-to-total capitalization) that ranges from 0.000% to 0.375%. 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 0.100% to 0.175% (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 1.000% and commitment fees were 0.100%.

There were $39.2 million and $42.1 million of outstanding letters of credit at June 30, 2021 and December 31, 2020, respectively.

The Credit Agreement and Note Agreement contain customary covenants, including financial covenants that require us to observe a maximum ratio of debt to total capital and a minimum fixed charge coverage ratio. The Credit Agreement and Note Agreement also include a provision limiting our ability to make restricted payments, including dividends and payments for share repurchases, unless, among other conditions, no defaults or events of default are ongoing (or would be caused by such restricted payment).