Determinant of an integer matrix is float

[Mason]

Possible bug in determinant calculation

You can do this without overflowing by using Rational{BigInt}, although this can get expensive quickly. I don’t think it should use BigInt unless you explicitly request this. There are specialized algorithms for integer determinants (e.g. Dodgeson condensation), but in general doing computational number theory efficiently is probably outside the scope of the standard LinearAlgebra library and is more something for packages like Nemo.jl.