A few years back, prior to the summary of short-term covered, long-term noncovered, etc. being an option I had a day trader who did a few hundred thousand transactions (via software). At that time you could attach the detail as a .pdf but it was limited to 1mb. No matter how I tried to shrink, compress, etc. ProSeries would not accept it. So I mailed it in to the IRS with Form 8453 Transmittal for an IRS e-file Return.  The postage on that mailing was like $75 at that time. It was a huge box.

I agree with everyone posting here. Attach detail if you can. Otherwise, ignore it and if the IRS questions, you can always provide.