A nonbinary iterative detector-decoder (IDD) system. The IDD system comprises a detector, a decoder; and a nonbinary interface electrically connected between the detector and decoder. The interface is operative to convert a soft symbol and variance that is output by the detector into a corresponding nonbinary log likelihood ratio (LLR) vector that comprises one or more nonbinary LLRs, and to provide the LLR vector to the decoder. The interface is further configured to convert a nonbinary LLR vector comprised of one or more nonbinary LLRs that is output by the decoder into a corresponding soft symbol and variance, and to provide the soft symbol and variance to the detector.