	June 30,			December 31,
	2020			2019
4.25% Convertible senior notes, due March 1, 2037	$	139,200		$	143,750
3.95% Promissory note, due through February 17, 2020		—			8,881
4% Promissory note, due through February 1, 2031		7,081			7,345
3.75% Callable promissory note, due through September 1, 2036		7,783			7,955
4.55% Promissory note, due through August 1, 2036		5,588			5,704
3.90% Promissory note, due through April 1, 2032		9,945			—
Finance lease liabilities, due through August 15, 2023		52			60
Total principal amount		169,649			173,695
Less: unamortized discount and issuance costs		(7,810	)		(10,000	)
Total long-term debt	$	161,839		$	163,695

The following table summarizes future maturities of long-term debt as of June 30, 2020, which takes into consideration the assumption that the 4.25% Convertible Senior Notes are repurchased at the earliest call date.

Due in 12 months following June 30,
2020	$	1,494
2021		140,755
2022		1,612
2023		1,668
2024		1,733
Thereafter		22,387
Total	$	169,649

Information with respect to interest expense related to long-term debt is as follows:

	Three Months Ended						Six Months Ended
	June 30,						June 30,
	2020			2019			2020			2019
Interest Expense:
Contractual interest	$	1,832		$	1,837		$	3,638		$	4,394
Non-cash expense (a)		1,068			999			2,120			2,789
Capitalized interest (b)		(42	)		(79	)		(83	)		(158	)
	$	2,858		$	2,757		$	5,675		$	7,025

4.25% Convertible Notes. The Company’s recent cash dividends on common stock have exceeded $0.35 per share, resulting in adjustments to the conversion rate of the 4.25% Convertible Notes. Accordingly, as of June 30, 2020, the conversion rate of the Company’s 4.25% Convertible Notes was 16.4039 shares of common stock for each $1 in principal amount, which was the equivalent of approximately $60.96 per share. In June 2020, the Company repurchased an aggregate of $4,550 in principal of the 4.25% Convertible Notes and recognized a $150 loss from the repurchases.

As of June 30, 2020, the remaining amortization period of the debt discount for 4.25% Convertible Notes was expected to be 1.7 years.

On February 28, 2020, the Company entered into a loan agreement with American Equity Investment Life Insurance Company for gross proceeds of $10,000. The agreement bears interest at a fixed rate of 3.90% and is secured by the Company’s shopping center property in Melbourne, Florida and the assignment of associated lease agreements. Approximately $60 of principal and interest is payable in 143 monthly installments beginning April 1, 2020 plus a final balloon payment of $5,007 including principal and unpaid interest payable on March 1, 2032. The promissory note may be repaid in full at any time as long as the Company provides at least 60 days’ written notice and pays a prepayment premium and processing fee. The proceeds were primarily used to repay the 3.95% Promissory Note due in February 2020.

On March 19, 2020, the loan agreement was modified to revise the due dates for the first and last installments to May 1, 2020 and April 1, 2032, respectively, while other terms and conditions remain intact.