"Could" here acts as a "buffer word" - a word which is not grammatically necessary, but which adds a sort of tentative quality, which softens the request and makes it feel more polite.
It could be readily replaced by "would" or "were to" - all softening the bald request by adding a tentative quality. ("It would be helpful" is already doing this, relative to "Provide us further details", which would be very peremptory).
Without the "could", it still needs a bit of attention because the tenses are wrong: with the condition "would", you need a past form (historically, a past subjunctive, but that's irrelevant today) in the main clause, so:
It would be helpful if you provided us further details.
Alternatively without the conditional:
It will be helpful if you provide us further details.