What type of plant is this?

There is this plant in front of my house that has been there for years. At first it almost looks like a weed, it has a thick stalk and tons of leaves that sprout off it. At night these pink flowers open on the plant and it is actually really pretty. This thing is tough too. It has been destroyed by a few people mowing my lawn but every year around May it is back and in full bloom. If it survives the summer it dies in August. What is this plant? Thanks.