"answer in detail" is a correct and usable phrase in written English. You can use it when asking someone to provide a comprehensive explanation or response to a question or request. For example, "Can you explain why you made that decision? Please answer in detail."
In this fine, elegantly written book, Mr Buchan lays out the answer in detail.
Asked if Israel possessed similar knowledge today, General Kaplinsky said he could not answer in detail, then added, "We know what we have to know".
Mr. Carney was pressed repeatedly by reporters to explain what the president and the vice president knew and when they knew it, but he declined to answer in detail.
(In it, I said that, since I'd never seen Alice read a fashion magazine, the fact that she was able to answer in detail when I asked her about someone's bizarre outfit always stunned me, "as if I had idly wondered out loud about the meaning of some inscription on some ruin in Oaxaca and she had responded by translating fluently from the Toltec").
Independent referees provide confidential character statements in which they are expected to answer in detail about the applicant's mental state, home life and attitude towards guns.
Discuss your answer in detail.
(Not all questions can be answered in detail, and some questions have been edited).
They require that students write many of their answers in detail.
(Not all questions can be answered in detail, and some questions have been edited or, when on similar topics, combined).
Vunipola answers in detail when I ask him for his personal view on Armitage's eligibility for selection.
After 10 days, he relented, granted not one but a series of interviews and answered in detail and with good humor every question, including those about Presidential politics.
Being a terminologist, I care about word choice. Ludwig simply helps me pick the best words for any translation. Five stars!
Maria Pia Montoro
Terminologist and Q/A Analyst @ Translation Centre for the Bodies of the European Union