The scientific detector systems for the ESO ELT first-light instruments, HARMONI, MICADO, and METIS, together will require 27 science detectors: seventeen 2.5 \(\mu\)m cutoff H4RG-15 detectors, four 4K x 4K 231-84 CCDs, five 5.3 \(\mu\)m cutoff H2RG detectors, and one 13.5 \(\mu\)m cutoff GEOSNAP detector. This challenging program of scientific detector system development covers everything from designing and producing state-of-the-art detector control and readout electronics, to developing new detector characterization techniques in the lab, to performance modeling and final system verification. We report briefly on the current design of these detector systems and developments underway to meet the challenging scientific performance goals of the ELT instruments.