overestimation vs idea

overestimation and idea both are nouns.

Word	Noun	Adjective	Verb	Adverb
overestimation	Yes	No	No	No
idea	Yes	No	No	No

As nouns, idea is a hypernym of overestimation; that is, idea is a word with a broader meaning than overestimation:

Other hypernyms of overestimation include approximation, estimate, estimation.

overestimation (noun)	idea (noun)
a calculation that results in an estimate that is too high	the content of cognition; the main thing you are thinking about
an appraisal that is too high	your intention; what you intend to do
	an approximate calculation of quantity or degree or worth
	a personal view
	(music) melodic subject of a musical composition