legal brief vs legal document

legal brief and legal document both are nouns.

Word	Noun	Adjective	Verb	Adverb
legal brief	Yes	No	No	No
legal document	Yes	No	No	No

As nouns, legal document is a hypernym of legal brief; that is, legal document is a word with a broader meaning than legal brief:

legal brief: a document stating the facts and points of law of a client's case
legal document: (law) a document that states some contractual relationship or grants some right

Other hypernyms of legal brief include instrument, legal instrument, official document.

legal brief (noun)	legal document (noun)
a document stating the facts and points of law of a client's case	(law) a document that states some contractual relationship or grants some right