Williams gained 120 yards and scored on runs of 56 and 4 yards and Stewart totaled 130 yards, including a 22-yard touchdown run.
Carolina (8-2) has won four straight games.
Jake Delhomme was 10-for-19 passing for 98 yards and a touchdown for the Panthers.
Daunte Culpepper made his second straight start at quarterback for the Lions (0-10) and connected on 20-of-35 passes for 207 yards and a touchdown. He was intercepted twice.