Under what circumstances are long-term investments in debt securities reported at cost and adjusted for amortization of

Question:

Under what circumstances are long-term investments in debt securities reported at cost and adjusted for amortization of any difference between cost and value?

Maturity
Maturity is the date on which the life of a transaction or financial instrument ends, after which it must either be renewed, or it will cease to exist. The term is commonly used for deposits, foreign exchange spot, and forward transactions, interest...