What do you understand by the so called "Détente" during 1970s and 1980s? Why it is said that Détente's was a one-way street that the Soviet Union used to pursue its aims?

Post WW-II, the world was divided into two blocs viz. communist bloc led by USSR and capitalist bloc led by USA. Largely, the cold war was manifestation of this difference in ideology.  The Cuban missile crisis of 1962 had carried both the blocs near to a war and it was feared that a nuclear war might break out. After the end of Cuban missile crisis, both the blocs initiated steps consciously to improve the relation which is referred to as Detente. Detente is easing of strained relationship. Both the bloc realised the futility of cold war. This period also witnessed an improvement in relation between USA and china which also contributed to detente.
The decade of 1970s witnessed significant improvement in relations of these two blocs. In 1971 Chinese communist regime was recognised by capitalist nation and in 1975 Helsinki agreement was signed by which both the blocks recognised the existing frontier and promised not to enter them.
However, during 1980s, Soviet Union occupied Afghanistan and this renewed the memories of soviet expansionism; creating hostilities between two blocs. With the election Ronal Regan as US president, the hostility further intensified. In 1983, he pursued a policy of Star Wars. The intent of this program was to develop a sophisticated anti-ballistic missile system in order to prevent missile attacks from other countries, specifically the Soviet Union. Hence this period marked moving away from détente.
Detente a one way street
“Détente’s was a one-way street that the Soviet Union used to pursue its aims”. This statement was made by Ronald Regan which point to the fact that USA has been making concession but there is no sign of reciprocity from USSR. For Regan detente has to be ‘a two way street’ in which cooperation with the soviet should be contingent on their domestic and international behaviour given USSR invasion in Afghanistan. This mistrust between leadership created a hurdle in maintaining a collaborative relationship.