Big brown spider las vegas?

I found this huge,about 2 inches long, spider with a fat body and what looked like antenna(I know they weren't) had what looked like a black spot on its butt. It wasn't hairy, didn't seem aggressive, What is it? My friend said it looked like it had striped legs moved fast when it wanted but stood still in the middle of the patio for a long time while we tried to get pictures of it. We were really far out in the northwest part of Las Vegas desert across the street.