to the nth degree
To the utmost, as in They'd decked out the house to the nth degree. This expression comes from mathematics, where to the nth means “to any required power” (n standing for any number). It was first recorded in 1852.
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.