IOWA CITY — Forbes this week unveiled its 2015 list of America’s best employers, and the University of Iowa Hospitals and Clinics ranked No. 12 out of 500 large employers — making it the top ranked hospital of the bunch. The UIHC — which last year employed 1,617 physicians, residents, and fellows, and 6,730 non-physician employees, like nurses — was bested on the Forbes list by fewer than a dozen companies, including Google, Costco, and L.L.