The aggregate principal amount of debt outstanding as of June 30, 2019 and December 31, 2018 consisted of the following:

	June 30,		December 31,
	2019		2018
Term loans	$	292,500	$	294,000
Mortgage loan		6,802		6,958
Total principal amount of debt outstanding	$	299,302	$	300,958

Current and non-current debt obligations reflected in the condensed consolidated balance sheets as of June 30, 2019 and December 31, 2018 consisted of the following:

	June 30,			December 31,
	2019			2018
Current liabilities:
Term loans	$	3,000		$	3,000
Mortgage loan		319			314
Current portion of principal payment obligations		3,319			3,314
Unamortized debt issuance costs, current portion		(1,130	)		(1,135	)
Current portion of long-term debt, net of unamortized debt issuance costs	$	2,189		$	2,179
Non-current liabilities:
Term loans	$	289,500		$	291,000
Mortgage loan		6,483			6,644
Non-current portion of principal payment obligations		295,983			297,644
Unamortized debt issuance costs, non-current portion		(3,804	)		(4,364	)
Long-term debt, net of current portion and unamortized debt issuance costs	$	292,179		$	293,280

On December 20, 2016, the Company entered into a credit agreement with JPMorgan Chase Bank, N.A., as administrative agent, various lenders and JPMorgan Chase Bank, N.A. and Barclays Bank PLC providing for (i) a term loan facility of $300,000 and (ii) a revolving credit facility of up to $25,000 in revolving credit loans and letters of credit.

As of June 30, 2019 and December 31, 2018, $292,500 and $294,000 in principal amount, respectively, was outstanding under the term loan facility (the “Term Loans”) and the Company did not have any outstanding borrowings under the revolving credit facility. In addition, the Company may, subject to certain conditions, including the consent of the administrative agent and the institutions providing such increases, increase the facilities by an unlimited amount so long as the Company is in compliance with specified leverage ratios, or otherwise by up to $70,000.

Borrowings under the facilities bear interest at a floating rate, which can be either a Eurodollar rate plus an applicable margin or, at the Company’s option, a base rate (defined as the highest of (x) the JPMorgan Chase, N.A. prime rate, (y) the federal funds effective rate, plus one-half percent (0.50%) per annum and (z) a one-month Eurodollar rate plus 1.00% per annum) plus an applicable margin. The applicable margin for borrowings under the term loan facility is 4.00% per annum for Eurodollar rate loans (subject to a 1.00% per annum interest rate floor) and 3.00% per annum for base rate loans. As a result of the completion of the Company’s IPO in December 2017, the applicable margin for borrowings under the revolving credit facility is 1.75% per annum for Eurodollar rate loans and 0.75% per annum for base rate loans, subject to reduction based on the Company’s maintaining of specified net leverage ratios. The interest rates payable under the facilities are subject to an increase of 2.00% per annum during the continuance of any payment default.

For Eurodollar rate loans, the Company may select interest periods of one, three or six months or, with the consent of all relevant affected lenders, twelve months. Interest will be payable at the end of the selected interest period, but no less frequently than every three months within the selected interest period. Interest on any base rate loan is not set for any specified period and is payable quarterly. The Company has the right to convert Eurodollar rate loans into base rate loans and the right to convert base rate loans into Eurodollar rate loans at its option, subject, in the case of Eurodollar rate loans, to prepayment penalties if the conversion is effected prior to the end of the applicable interest period. As of June 30, 2019, the interest rate on the Term Loans was 6.33% per annum, which was based on a three-month Eurodollar rate of 2.33% per annum plus the applicable margin of 4.00% per annum for Eurodollar rate loans. As of December 31, 2018, the interest rate on the Term Loans was 6.52% per annum, which was based on a one-month Eurodollar rate of 2.52% per annum plus the applicable margin of 4.00% per annum for Eurodollar rate loans.

Upon entering into the term loan facility, the Company incurred debt issuance costs of $7,811, which were initially recorded as a reduction of the debt liability and are amortized to interest expense using the effective interest method from the issuance date of the Term Loan until the maturity date. Principal payments of $750 were made under the term loan facility during each of the three months ended June 30, 2019 and 2018, and principal payments of $1,500 were made under the term loan facility during each of the six months ended June 30, 2019 and 2018. Interest expense, including the amortization of debt issuance costs, totaled $5,070 and $4,716 for the three months ended June 30, 2019 and 2018, respectively, and totaled $10,079 and $9,233 for the six months ended June 30, 2019 and 2018, respectively.

The revolving credit facility also requires payment of quarterly commitment fees at a rate of 0.25% per annum on the difference between committed amounts and amounts actually borrowed under the facility and customary letter of credit fees. For the three months ended June 30, 2019 and 2018, interest expense related to the fee for the unused amount of the revolving credit facility totaled $16 and $15, respectively, and for the six months ended June 30, 2019 and 2018, interest expense related to the fee for the unused amount of the revolving credit facility totaled $32 and $30, respectively.

The Term Loans mature on December 20, 2023, and the revolving credit facility matures on December 20, 2021. The Term Loans are subject to amortization in equal quarterly installments, which commenced on March 31, 2017, of principal in an annual aggregate amount equal to 1.0% of the original principal amount of the Term Loans of $300,000, with the remaining outstanding balance payable at the date of maturity.

Voluntary prepayments of principal amounts outstanding under the term loan facility are permitted at any time; however, if a prepayment of principal is made with respect to a Eurodollar loan on a date other than the last day of the applicable interest period, the Company is required to compensate the lenders for any funding losses and expenses incurred as a result of the prepayment. Prior to the revolving credit facility maturity date, funds borrowed under the revolving credit facility may be borrowed, repaid and reborrowed, without premium or penalty.

In addition, the Company is required to make mandatory prepayments under the facilities with respect to (i) 100% of the net cash proceeds from certain asset dispositions (including casualty and condemnation events) by the Company or certain of its subsidiaries, subject to certain exceptions and reinvestment provisions, (ii) 100% of the net cash proceeds from the issuance or incurrence of any additional debt by the Company or certain of its subsidiaries, subject to certain exceptions, and (iii) 50% of the Company’s excess cash flow, as defined in the credit agreement, subject to reduction upon its achievement of specified performance targets.

The facilities are secured by, among other things, a first priority security interest, subject to permitted liens, in substantially all of the Company’s assets and all of the assets of certain of its subsidiaries and a pledge of certain of the stock of certain of its subsidiaries, in each case subject to specified exceptions. The facilities contain customary affirmative and negative covenants, including certain restrictions on the Company’s ability to pay dividends, and, with respect to the revolving credit facility, a financial covenant requiring the Company to maintain a specified total net leverage ratio in the event that on the last day of any fiscal quarter the Company has utilized more than 30% of its borrowing capacity under the facility. As of June 30, 2019 and December 31, 2018, the Company had not utilized more than 30% of its borrowing capacity under the revolving credit facility and compliance with the financial covenant was not applicable.

On July 1, 2015, the Company entered into a commercial mortgage loan agreement in the amount of $7,950 (the “Mortgage Loan”). Borrowings under the Mortgage Loan bear interest at a rate of 3.5% per annum and are repayable in 60 monthly installments of $46, consisting of principal and interest based on a 20-year amortization schedule. The remaining amount of unpaid principal under the Mortgage Loan is due on the maturity date of July 1, 2020. Upon entering into the Mortgage Loan, the Company incurred debt issuance cost of $45, which was initially recorded as a direct deduction from the debt liability and is amortized to interest expense using the effective interest method from issuance date of the loan until the maturity date.

The Company made principal payments under the Mortgage Loan of $78 and $75 during the three months ended June 30, 2019 and 2018, respectively, and $156 and $151 during the six months ended June 30, 2019 and 2018, respectively. Interest expense, including the amortization of debt issuance costs, totaled $63 and $65 during the three months ended June 30, 2019 and 2018, respectively, and $126 and $130 during the six months ended June 30, 2019 and 2018, respectively.

The Mortgage Loan is secured by the land and building purchased in March 2015 and subjects the Company to various affirmative, negative and financial covenants, including maintenance of a minimum debt service ratio. The Company was in compliance with all covenants of the Mortgage Loan as of June 30, 2019 and December 31, 2018.

As of June 30, 2019, aggregate minimum future principal payments of the Company’s debt are summarized as follows:

Year Ending December 31,
2019	$	1,658
2020		9,644
2021		3,000
2022		3,000
2023		3,000
Thereafter		279,000
	$	299,302