Debt | Debt The Company’s mortgage loans and its senior secured revolving credit facility 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 debt consisted of the following (dollars in thousands): Collateral Interest Rate Maturity Date 9/30/15 Balance Outstanding on Loan as of September 30, 2015 December 31, Senior Secured Revolving Credit Facility (1) 2.70 % November 5, 2016 $ 238,329 $ 60,000 $ 22,500 SpringHill Suites by Marriott Washington, PA (2) 5.84 % April 1, 2015 11,261 — 4,760 Courtyard by Marriott Altoona, PA 5.96 % April 1, 2016 10,244 6,010 6,172 Residence Inn by Marriott New Rochelle, NY 5.75 % September 1, 2021 20,762 14,582 14,832 Residence Inn by Marriott San Diego, CA 4.66 % February 6, 2023 45,999 29,685 30,062 Homewood Suites by Hilton San Antonio, TX 4.59 % February 6, 2023 32,393 16,955 17,174 Residence Inn by Marriott Vienna, VA 4.49 % February 6, 2023 32,106 23,229 23,534 Courtyard by Marriott Houston, TX 4.19 % May 6, 2023 31,561 19,213 19,475 Hyatt Place Pittsburgh, PA 4.65 % July 6, 2023 37,260 23,368 23,657 Residence Inn by Marriott Bellevue, WA 4.97 % December 6, 2023 71,415 47,080 47,580 Residence Inn by Marriott Garden Grove, CA 4.79 % April 6, 2024 41,879 34,000 34,000 Residence Inn by Marriott Silicon Valley I, CA 4.64 % July 1, 2024 87,180 64,800 64,800 Residence Inn by Marriott Silicon Valley II, CA 4.64 % July 1, 2024 95,505 70,700 70,700 Residence Inn by Marriott San Mateo, CA 4.64 % July 1, 2024 68,923 48,600 48,600 Residence Inn by Marriott Mountain View, CA 4.64 % July 6, 2024 52,565 37,900 37,900 SpringHill Suites by Marriott Savannah, GA 4.62 % July 6, 2024 37,211 30,000 30,000 Hilton Garden Inn Marina del Rey, CA 4.68 % July 6, 2024 44,496 22,570 — Homewood Suites by Hilton Billerica, MA 4.32 % December 6, 2024 11,712 16,225 16,225 Homewood Suites by Hilton Carlsbad CA 4.32 % December 6, 2024 28,236 19,950 19,950 Hampton Inn & Suites Houston Medical Center, TX 4.25 % January 6, 2025 15,305 18,300 18,300 Total $ 1,014,342 $ 603,167 $ 550,221 (1) Twelve properties in the borrowing base serve as collateral for borrowings under the senior secured revolving credit facility at September 30, 2015 . The interest rate for the senior secured revolving credit facility is variable and based on LIBOR plus 2.5% . (2) On March 31, 2015 , the Company paid off the SpringHill Suites by Marriott Washington, PA loan, due April 1, 2015 . At September 30, 2015 and December 31, 2014 , the Company had $60,000 and $22,500 , respectively, of outstanding borrowings under its senior secured revolving credit facility. At September 30, 2015 , the maximum borrowing availability under the senior secured revolving credit facility was $175,000 . The Company estimates the fair value of its fixed rate debt, which is all of the Company's mortgage loans, by discounting the future cash flows of each instrument at estimated market rates. 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 September 30, 2015 and December 31, 2014 was $555,619 and $542,538 , 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. The Company’s only variable rate debt is under its senior secured revolving credit facility. The estimated fair value of the Company’s variable rate debt as of September 30, 2015 and December 31, 2014 was $59,995 and $22,498 , respectively. As of September 30, 2015 , the Company was in compliance with all of its financial covenants. At September 30, 2015 , the Company’s consolidated fixed charge coverage ratio was 3.29 . The Company's minimum required consolidated fixed charge coverage ratio is 1.50 . Future scheduled principal payments of debt obligations as of September 30, 2015 , for the current year and each of the next four calendar years and thereafter are as follows (in thousands): Amount 2015 (remaining three months) $ 866 2016 69,870 2017 4,302 2018 5,374 2019 7,340 Thereafter 515,415 Total $ 603,167 |