Sifang for home is not an idiom. Its meaning is similar to "the four seas are home", a Chinese idiom, which originally referred to the emperor's possession of the whole country, and later referred to any place can be regarded as one's own home, and also referred to the ambition to be in the four directions, not attached to one's hometown or personal small world.

From the Book of the Han Dynasty (汉书高帝记).