Note 9 — Borrowings

Borrowings consisted of FHLB advances, which represent collateralized obligations with the FHLB. The following is a summary of contractual maturities of FHLB advances:

The following is financial data pertaining to FHLB advances:

We have pledged loans receivable with market values of $2.17 billion as collateral with the FHLB for this borrowing facility. The total borrowing capacity available from the collateral that has been pledged is $1.73 billion, of which $1.44 billion remained available as of December 31, 2020. At December 31, 2020, we had $26.3 million available for use through the Federal Reserve Bank of San Francisco Discount Window, as we pledged securities with carrying values of $27.3 million, and there were no borrowings.

At December 31, 2020, advances from the FHLB were $150.0 million, an increase of $60.0 million from $90.0 million at December 31, 2019, and all of the FHLB advances were term borrowings at December 31, 2020. For the years ended December 31, 2020, 2019 and 2018, interest expense on FHLB advances were $2.2 million, $763,000 and $3.4 million, respectively, and the weighted-average interest rates were 1.42 percent, 1.89 percent and 1.94 percent, respectively.  There were no outstanding borrowings on the FRB PPP Lending Facility as of December 31, 2020 and available borrowing capacity was $300.4 million, which was extended through March 31, 2021.

Note 10 — Subordinated Debentures

The Company issued Fixed-to-Floating Subordinated Notes (“Notes”) of $100.0 million on March 21, 2017, with a final maturity on March 30, 2027. The Notes have an initial fixed interest rate of 5.45 percent per annum, payable semi-annually on March 30 and September 30 of each year. From and including March 30, 2022 and thereafter, the Notes bear interest at a floating rate equal to the then current three-month LIBOR, as calculated on each applicable date of determination, plus 3.315 percent payable quarterly. If the then current three-month LIBOR is less than zero, three-month LIBOR will be deemed to be zero. Debt issuance cost was $2.3 million, which is being amortized through the Note’s maturity date. At December 31, 2020 and 2019, the balance of Notes included in the Company’s Consolidated Balance Sheet, net of debt issuance cost, was $98.5 million and $98.3 million. The amortization of debt issuance cost was $205,000, $193,000 and $182,000 for the years ended December 31, 2020, 2019 and 2018, respectively.

The Company assumed Junior Subordinated Deferrable Interest Debentures (“Subordinated Debentures”) as a result of an acquisition in 2014 with an unpaid principal balance of $26.8 million and an estimated fair value of $18.5 million. The $8.3 million discount is being amortized to interest expense through the debentures’ maturity date of March 15, 2036. A trust was formed in 2005 which issued $26.0 million of Trust Preferred Securities (“TPS”) at a 6.26 percent fixed rate for the first five years and a variable rate at the three-month LIBOR plus 140 basis points thereafter and invested the proceeds in the Subordinated Debentures. The Company may redeem the Subordinated Debentures at an earlier date if certain conditions are met. The TPS will be subject to mandatory redemption if the Subordinated Debentures are repaid by the Company. Interest is payable quarterly, and the Company has the option to defer interest payments on the Subordinated Debentures from time to time for a period not to exceed five consecutive years. At December 31, 2020 and 2019, the balance of Subordinated Debentures included in the Company’s Consolidated Balance Sheets, net of discount of $6.4 million and $6.8 million, was $20.4 million and $20.0 million. The amortization of discount was $390,000, $376,000 and $356,000 for the years ended December 31, 2020, 2019 and 2018, respectively.