Prosper, thrive, succeed, as in He's done well in the market. [c. 1300]
do well to do something. Fare better or act prudently by doing something, as in She would do well to ask permission before she leaves. [Late 1400s]
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.