September 30, 2019:
Cost
Gross Unrealized Gains
Gross Unrealized Losses
Fair Market Value
Available-for-sale securities:
U.S. Treasury, short-term
$4,240
$2
$—
$4,242
Corporate debt securities, short-term
12,258
2
—
12,260
U.S. Treasury, long-term
1,102
—
(1)
1,101
Corporate debt securities, long-term
451
—
—
451
Total
$18,051
$4
$(1)
$18,054
5 .
investments .
the company determines the appropriate designation of investments at the time of purchase and reevaluates such designation as of each balance sheet date .
all of the company ’ s investments are designated as available-for-sale debt securities .
as of september 30 2019 and 2018 the company ’ s short-term investments have maturity dates of less than one year from the balance sheet date .
the company ’ s long-term investments have maturity dates of greater than one year from the balance sheet date .
available-for-sale marketable securities are carried at fair value as determined by quoted market prices for identical or similar assets with unrealized gains and losses net of taxes and reported as a separate component of stockholders ’ equity .
management reviews the fair value of the portfolio at least monthly and evaluates individual securities with fair value below amortized cost at the balance sheet date .
for debt securities in order to determine whether impairment is other than-temporary management must conclude whether the company intends to sell the impaired security and whether it is more likely than not that the company will be required to sell the security before recovering its amortized cost basis .
if management intends to sell an impaired debt security or it is more likely than not the company will be required to sell the security prior to recovering its amortized cost basis an other-than-temporary impairment is deemed to have occurred .
the amount of an other-than-temporary impairment related to a credit loss or securities that management intends to sell before recovery is recognized in earnings .
the amount of an other-than-temporary impairment on debt securities related to other factors is recorded consistent with changes in the fair value of all other available for-sale securities as a component of stockholders ’ equity in other comprehensive income .
no other-than-temporary impairment charges were recognized in the fiscal years ended september 30 2019 2018 and 2017 .
there were no realized gains or losses from the sale of available-for-sale securities during the years ended september 30 2019 and 2017 .
the company recorded a net realized loss from the sale of available-for-sale securities of $ 49000 during the year ended september 30 2018 .
the cost of securities sold is based on the specific identification method .
amortization of premiums accretion of discounts interest dividend income and realized gains and losses are included in investment income .
the following tables summarize investments by type of security as of september 30 2019 and 2018 respectively-amounts shown in thousands : .

Question: How does the management review the fair value of the portfolio? 
Answer: at least monthly and evaluates individual securities with fair value below amortized cost at the balance sheet date