I do not recall off-hand whether J. Elstrodt, E. Grunewald, J. Mennicke, {\it Eisenstein series on three-dimensional hyperbolic spaces and imaginary quadratic fields}Eisenstein series on three-dimensional hyperbolic spaces and imaginary quadratic fields, J. reine und angew. Math. {\bf 360}360 (1985), 160-213160–213 treats more general cases, but this is a standard reference, anyway.