Debt | Debt The Company’s mortgage loans are collateralized by first-mortgage liens on certain of the Company’s properties. The mortgages are non-recourse except for instances of fraud or misapplication of funds. Mortgage and senior unsecured revolving credit facility debt consisted of the following (dollars in thousands): Collateral Interest Rate Maturity Date 6/30/18 Balance Outstanding on Loan as of June 30, 2018 December 31, Senior Unsecured Revolving Credit Facility (1) 3.96 % March 8, 2022 $ — $ 27,000 $ 32,000 Residence Inn by Marriott New Rochelle, NY 5.75 % September 1, 2021 18,785 13,563 13,762 Residence Inn by Marriott San Diego, CA 4.66 % February 6, 2023 46,524 28,179 28,469 Homewood Suites by Hilton San Antonio, TX 4.59 % February 6, 2023 31,647 16,086 16,253 Residence Inn by Marriott Vienna, VA 4.49 % February 6, 2023 30,172 22,017 22,251 Courtyard by Marriott Houston, TX 4.19 % May 6, 2023 31,999 18,177 18,375 Hyatt Place Pittsburgh, PA 4.65 % July 6, 2023 36,066 22,214 22,437 Residence Inn by Marriott Bellevue, WA 4.97 % December 6, 2023 66,568 45,073 45,462 Residence Inn by Marriott Garden Grove, CA 4.79 % April 6, 2024 37,852 32,891 33,160 Residence Inn by Marriott Silicon Valley I, CA 4.64 % July 1, 2024 78,125 64,800 64,800 Residence Inn by Marriott Silicon Valley II, CA 4.64 % July 1, 2024 85,477 70,700 70,700 Residence Inn by Marriott San Mateo, CA 4.64 % July 1, 2024 61,958 48,600 48,600 Residence Inn by Marriott Mountain View, CA 4.64 % July 6, 2024 56,267 37,900 37,900 SpringHill Suites by Marriott Savannah, GA 4.62 % July 6, 2024 35,942 30,000 30,000 Hilton Garden Inn Marina del Rey, CA 4.68 % July 6, 2024 41,297 21,559 21,760 Homewood Suites by Hilton Billerica, MA 4.32 % December 6, 2024 14,798 16,095 16,225 Hampton Inn & Suites Houston Medical Center, TX 4.25 % January 6, 2025 14,879 18,175 18,300 Total debt before unamortized debt issue costs $ 688,356 $ 533,029 $ 540,454 Unamortized mortgage debt issue costs (1,957 ) (2,138 ) Total debt outstanding $ 531,072 $ 538,316 (1) The interest rate for the senior unsecured revolving credit facility is variable and based on either LIBOR plus an applicable margin ranging from 1.55% to 2.3% , or prime plus an applicable margin of 0.55% to 1.3% . At June 30, 2018 and December 31, 2017 , the Company had $27.0 million and $32.0 million , respectively, of outstanding borrowings under its senior unsecured revolving credit facility. At June 30, 2018 , the maximum borrowing availability under the senior unsecured revolving credit facility was $250.0 million . The Company estimates the fair value of its fixed rate debt by discounting the future cash flows of each instrument at estimated market rates. All of the Company's mortgage loans are fixed-rate. Rates take into consideration general market conditions, quality and estimated value of collateral and maturity of debt with similar credit terms and are classified within level 3 of the fair value hierarchy. The estimated fair value of the Company’s fixed rate debt as of June 30, 2018 and December 31, 2017 was $492.0 million and $506.6 million , respectively. The Company estimates the fair value of its variable rate debt by taking into account general market conditions and the estimated credit terms it could obtain for debt with similar maturity and is classified within level 3 of the fair value hierarchy. As of June 30, 2018 , the Company’s only variable rate debt is under its senior unsecured revolving credit facility. The estimated fair value of the Company’s variable rate debt as of June 30, 2018 and December 31, 2017 was $27.0 million and $32.0 million , respectively. As of June 30, 2018 , the Company was in compliance with all of its financial covenants. At June 30, 2018 , the Company’s consolidated fixed charge coverage ratio was 3.3 and the bank covenant is 1.5 . Future scheduled principal payments of debt obligations as of June 30, 2018 , for the current year and each of the next four calendar years and thereafter are as follows (in thousands): Amount 2018 (remaining six months) $ 2,610 2019 6,992 2020 9,536 2021 21,945 2022 36,954 2023 142,509 Thereafter 312,483 Total debt before unamortized debt issue costs $ 533,029 Unamortized mortgage debt issue costs (1,957 ) Total debt outstanding $ 531,072 |