Definitely in the arum family (Aracae), I'll guess genus Zantedeschia. Looks like Z. Aethiopica. (Sometimes called "calla lily", but not related to lilies either.) It's a South African plant grown in gardens worldwide.
Yes, I'm pretty confident it's Z. Aethiopica, whose most-recognized common name is "calla lily" ("arum lily" would come in second). It's an unfortunate name since, as I said, it has nothing to do with lilies, and it's not, strictly speaking, an arum or a calla (though related). Personally I'd call it Z. Aethiopica, but then I rather enjoy seeing people try to pronounce greco-roman names.