My bronco lost oil pressure when it idles it

First, a couple of questions come to mind if that's o.k., such as,
Was oil changed recently, and maybe cheaper brand of oil, or different grade of oil used? Did it get the proper oil filter ? Anything else that may have been done, or happened, such as overheated the engine?
If it's got good clean quality oil in it, and you've confirm low oil pressure, then maybe it's oil pump related, or even perhaps some sludge has dislodged and is clogging up pickup tube screen in oil pan. Keeping in mind that if oil changes weren't done on a regular basis, sludge in pan, is a real good possibility. Of course mechanical problems such as a bearing are always a possibility as well, but I'd start looking at those 2 things first.

typically loss of oil pressure at idle but ok pressure at higher rpm can indicate worn camshaft bearings or main bearings. small possibilty that oil pump is tired or pickup tube for pump has sludge or debris clogging screen.

First...be sure that oil is full ! Sounds like it could be low on oil or in need of an oil & filter change.