Compound adjectives that are comparative or superlative are often hyphenated:
   That is the highest-priced car I have ever seen.
   I would need a longer-term loan to purchase that vehicle.

But, of course, there are exceptions:
   He is the most talented youngster I have seen this year.

An adverb (-ly) compounded with other modifiers is not hyphenated:
   This is a highly rated bank.
   They sell publicly held securities.