Detailed and thorough (2-5)
I believe the answer is:
in-depth
'detailed and thorough' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for in-depth that I've seen before include "Thoroughly and comprehensively" , "Thorough and intensive" , "Detailed and thorough" , "With thorough and extensive investigation" , "Getting to the bottom of it" .)