Check out PRO-NOR-SRP-01-70 which says:
At the end of the Rollout:
Disconnect the autopilot.
If the flight crew does not disconnect the AP at the end of the rollout, and uses the nosewheel steering handwheel to taxi the aircraft off the runway, the following will occur:
The AP will try to steer the aircraft back to the runway centerline, if the nosewheel steering handwheel is released and the aircraft heading is less than 20 ° off the runway centerline.
The AP will automatically disconnect, if the aircraft heading is 20 ° or more off the runway centerline.