to the best of
To the utmost extent of, especially of one's ability, knowledge, or power. For example, I'm sure he'll do it to the best of his ability, or To the best of my knowledge, they arrive tomorrow. [c. 1500]
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.