The plan was thoroughly thought through and included all necessary details.

thought through 是由动词 think 和副词 through 组成的短语动词。think 的意思是"思考"，through 在这里表示"彻底、完全"的意思。 thought through 是 think through 的过去分词形式，表示"经过彻底思考的、深思熟虑的"。