Finding the largest delta between two integers in a list

I have a list of integers, i.e.:

values = [55, 55, 56, 57, 57, 57, 57, 62, 63, 64, 79, 80]

I am trying to find the largest difference between two consecutive numbers.

In this case it would be 15 from 64->79.

The numbers can be negative or positive, increasing or decreasing or both. The important thing is I need to find the largest delta between two consecutive numbers.

What is the fastest way to do this? These lists can contain anywhere from hundreds to thousands of integers.

This is the code I have right now:

prev_value = values[0]
largest_delta = 0

for value in values:
  delta = value - prev_value
  if delta > largest_delta:
    largest_delta = delta
  prev_value = value

  return largest_delta

Is there a faster way to do this? It takes a while.