(In thousands)	Maturity Dates	December 31, 2019		December 31, 2018
Unsecured private placement notes
3.95% (net of unamortized debt issuance cost of $316 and $360 for 2019 and 2018, respectively)	2021-2027	$	99,684	$	99,640
3.86% (net of unamortized debt issuance cost of $291 and $347 for 2019 and 2018, respectively)	2020-2025		85,423		99,653
4.86% (net of unamortized debt issuance cost of $147 and $186 for 2019 and 2018, respectively)	2020-2023		36,996		46,243
5.88% (net of unamortized debt issuance cost of $0 and $85 for 2019 and 2018, respectively)	2019		—		22,772
Debt of foreign subsidiaries
Unsecured bank debt, foreign currency	2019		—		7,772
Total debt		$	222,103	$	276,080
Less current maturities			23,571		37,058
Long-term debt		$	198,532	$	239,022

The Company’s long-term debt financing is currently composed of unsecured private placement notes issued to insurance companies, totaling $222,857,000 as of December 31, 2019. These notes are denominated in U.S. dollars and have fixed interest rates ranging from 3.86 percent to 4.86 percent. The notes had original maturities of 12 years with mandatory amortization of principal beginning six years after issuance. The Company will be required to make amortization payments on the currently outstanding notes from 2020 to 2027.

The Company has a committed $350,000,000 multi-currency revolving credit agreement that expires on January 30, 2023. The Company maintains standby letters of credit under its workers’ compensation insurance agreements and for other purposes, as needed from time to time, which are issued under the revolving credit agreement. As of December 31, 2019, the Company had outstanding letters of credit of $4,929,000 and no borrowings under the revolving credit agreement. There was $345,071,000 available under the revolving credit agreement as of December 31, 2019.

Loans under the credit agreement may be incurred, at the discretion of the Company, with terms to maturity of one to six months. The Company may choose from two interest rate options: (1) LIBOR applicable to each currency plus spreads ranging from 1.25 percent to 1.875 percent, depending on the Company’s net leverage ratio, or (2) the prime rate plus 0.25 percent to 0.875 percent, depending on the Company’s net leverage ratio. The credit agreement requires the Company to pay a commitment fee ranging from 0.15 percent to 0.325 percent per annum, which also depends on the Company’s net leverage ratio. The credit agreement requires the maintenance of certain financial ratios and compliance with certain other covenants that are similar to the Company’s existing debt agreements, including net worth, interest coverage and leverage financial covenants and limitations on restricted payments, indebtedness and liens.

On June 12, 2019, the Company prepaid the $17,100,000 outstanding principal balance of its 5.88 percent Series 2010-A Senior Notes due June 1, 2022 (Notes) and the related make-whole amount of $1,173,000. The make-whole amount primarily reflected the net present value of the remaining scheduled interest payments on the Notes, calculated in accordance with the applicable note purchase agreement. The prepayment was made with cash on hand. The Company also expensed remaining unamortized debt issuance costs of $74,000.

The Company’s foreign subsidiaries had no unsecured debt at December 31, 2019.

The Company’s loan agreements contain provisions, which, among others, require maintenance of certain financial ratios and place limitations on additional debt, investments and payment of dividends. Based on the loan agreement provisions that place limitations on dividend payments, unrestricted retained earnings (i.e., retained earnings available for dividend distribution) were $283,956,000 and $190,442,000 at December 31, 2019 and 2018, respectively.

Debt at December 31, 2019, matures as follows: $23,571,000 in 2020; $37,858,000 in 2021; $37,858,000 in 2022; $37,857,000 in 2023; $28,572,000 in 2024 and $57,141,000 after 2024. Debt maturing in 2020 includes $23,571,000 of scheduled repayments under long-term debt agreements. Although the Company’s foreign subsidiaries currently have no short-term working capital loans, these type of loans routinely exist. These short-term loan agreements could be supplemented, if necessary, by the Company’s $350,000,000 revolving credit agreement entered into on January 30, 2018.

Net interest expense for the years ended December 31, 2019, 2018 and 2017, comprised the following:

(In thousands)	2019			2018			2017
Interest expense	$	12,744		$	13,360		$	14,428
Interest income		(5,717	)		(1,829	)		(2,075	)
		7,027			11,531			12,353
Capitalized interest		(1,095	)		(760	)		(909	)
Interest expense, net	$	5,932		$	10,771		$	11,444