When I type this sentence in Ms Word. "It's all your fault". It is underlined in green. The reason being given is that "all" is used with plural nouns. Instead entire is recommended as a correction. But when I searched the Internet I have found the sentences like "It's all my fault or It's all your fault."
I would like to know if this sentence [It's all your fault] is idiomatic? If yes then why Ms word is showing it as incorrect?