pre_text: The carrying amounts and fair values of Teradyne’s financial instruments at December 31, 2019 and 2018 were as follows: (1) The carrying value represents the bifurcated debt component only, while the fair value is based on quoted market prices for the convertible note which includes the equity conversion features. The fair values of accounts receivable, net and accounts payable approximate the carrying amount due to the short term nature of these instruments.
table: December 31, 2019 December 31, 2018
table: Carrying Value Fair Value Carrying Value Fair Value
table: (in thousands)
table: Assets
table: Cash and cash equivalents $773,924 $773,924 $926,752 $926,752
table: Marketable securities 241,793 241,793 277,827 277,827
table: Derivative assets 528 528 79 79
table: Liabilities
table: Contingent consideration 39,705 39,705 70,543 70,543
table: Derivative liabilities 203 203 514 514
table: Convertible debt (1) 394,687 1,010,275 379,981 547,113
question: Analyse this data from a financial earnings document. What was the change in the fair value of Marketable securities from 2018 to 2019?