Correct. History, especially today, does not simply take a historical text at face value. In fact a great deal of it is now historiography first - that is rather then simply quoting everything said trying to ascertain the validity of the words. When was it written, why, what were the authors motivations, potential biases, limitation, what were his sources - contemporary or not. And so on. Historians are usually careful about documents here.
And there are different kinds of documented sources. Literary sources, state sources and so on. Adding to this is the fact there is sometimes the chance to correlate it with other archaeological evidence.