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."
Best Answer
In British English, in which L is often doubled before inflectional suffixes, it is normally only doubled when there is just one of the letters A, E, I, O, U directly before the last consonant before the suffix:
L is an exception in British English. It doesn't behave for doubling purposes like other consonants, for example P, T, K, B, D, G. Importantly, it does not matter whether the syllable it occurs in is stressed or not.
American English does not have this L doubling rule. In American English, as with other consonants, the L is only doubled if the syllable before the suffix is stressed.
There are also, as always with English spelling, exceptions to the rule.