CASH 2017 Annual Report

22 Mortgage-backed securities generally increase the quality of the Company’s assets by virtue of the insurance or guarantees that back them, are more liquid than individual mortgage loans, and may be used to collateralize borrowings or other obligations of the Company. At September 30, 2017, $514.4 million, or 74%, of the Company’s mortgage-backed securities were pledged to secure various obligations of the Company. While mortgage-backed securities carry a reduced credit risk as compared to whole loans, such securities remain subject to the risk that a fluctuating interest rate environment, along with other factors such as the geographic distribution and other underwriting risks inherent in the underlying mortgage loans, may alter the prepayment rate of such mortgage loans and so affect both the prepayment speed, and value, of such securities. The prepayment risk associated with mortgage-backed securities is continually monitored, and prepayment rate assumptions are adjusted as appropriate to update the Company’s mortgage-backed securities accounting and asset/liability reports. The following table sets forth the carrying value of the Company’s mortgage-backed securities at the dates indicated. At September 30, 2017 2016 2015 Available for Sale (Dollars in Thousands) Freddie Mac $ 100,287 $ 164,577 $ 174,322 Fannie Mae 486,167 394,363 391,846 Fannie Mae DUS — — 10,415 Total AFS $ 586,454 $ 558,940 $ 576,583 At September 30, 2017 2016 2015 Held to Maturity (Dollars in Thousands) Farmer Mac $ 61,295 $ 71,011 $ — Fannie Mae 43,458 51,894 61,026 Ginnie Mae 8,936 10,853 5,551 Total HTM $ 113,689 $ 133,758 $ 66,577