It is possible for a student to double major at Villanova University. On this school's website, there is a question on the Frequently Asked Questions page which is relevant to your goal: "What happens if I am graduating with a double major?"
Here is the school's response:
"Normally, a student may receive only ONE degree, regardless of how many majors s/he earns. Students who have completed all the requirements for two or more degrees – e.g., BBA and BSA, or BBA and BA, or BA and BS – must choose which degree to take – unless they have completed 43 or more additional credits beyond the greater of the two program credit requirements, in which case they may receive two degrees and two diplomas. Multiple majors, regardless of college, will appear on a student’s transcript. For additional questions about diplomas, please contact the Office of the Registrar - (610) 519-4030."
I did not pursue a double major when I was at college, but I had friends who did. All of the the people that I knew who pursued two majors added at least a semester to their studies; many of them added a year or more. The amount of extra time you may expect to spend at a school pursuing two degrees depends on the extent to which the two curricula overlap. A person who wishes to double major in music education and music performance, for instance, will find that the two degrees share many requirements, and therefore she may expect to graduate with only a few additional semesters.