I cannot quite understand why the 'L' is not doubled when forming 'detailed' from 'detail'. Is that an exemption to the consonant doubling, or did I simply not understand the rules?
From the answers to When is "L" doubled?
When you have a verb that ends in a vowel plus "L" and you are going to add an ending that begins with a vowel then you double the "L".
Example: "They have tunnelled under the wall." vs "They have detailed the plan to tunnel under the wall."