Hello Jagannath,

Idealism as a theory was first introduced or rather conceptualized by the great philosopher Plato. He had written in great detail about idealism and idealistic state in his book the Republic. But it wasn't until Hegel and his peers that a concised view on the matter formed. According to Hegel the idealist state is one in which every individual thinks the same to such an extent that the state itself behaves as an individual with his/her own view. The individual must obey the will of the state as it's his own will as well. The state is always considered right and the supporters of this theory even argue the state as the reality and individuals are considered temporary.

This theory is heavily criticized as it limits the individual's freedom and liberty to have their own views and opinions. Hegel went as far as idolizing the state as a supreme God-like entity which must be feared and obeyed at all cost.

Hope this helps