The word DETAIL has 3 vowels (E,A,I) and 3 consonants (D,T,L). There are 3 odd positions (1st, 3rd, 5th). The 3 vowels can be arranged in these 3 positions in $^3P_3 = 6$ ways. The 3 consonants can be arranged in the remaining 3 even positions in $^3P_3 = 6$ ways. Total arrangements = 6 × 6 = 36.