The phrase "a firm idea of the" is correct and usable in written English.
It can be used when expressing a clear and strong understanding or concept of something.
Example: "After the meeting, I left with a firm idea of the project's objectives and timeline."
Alternatives: "a clear understanding of the" or "a solid grasp of the".
■ Have a firm idea of the overall budget before talking to architects or builders.
He has held players accountable and has a firm idea of the direction he wants the club to take on and off the pitch.
DETROIT — President Obama's auto task force pressed General Motors and Chrysler to close scores of dealerships without adequately considering the jobs that would be lost or having a firm idea of the cost savings that would be achieved, an audit of the process has concluded.
Senior Western diplomats, who have been trying without success to get a firm idea of the Soviet attitude toward the developing situation in South east Asia, said the Tass com mentary seemed to reflect the ambiguity and flexibility of the Soviet position.
The study predicted the efficacy of using simple models when the modeller has a firm idea of the influential variables of the system.
Only go to the hairdresser when you have a firm idea of the exact reason for going.
If you're absolutely committed to having some time off between jobs to get your head together, then make sure you have a firm idea of this before you talk to your boss.
We may have a firmer idea of the nature of the life course association between exposures and outcome, and perhaps some causal information.
Without a firm idea of succession, the man who is the symbol of stability becomes the symbol of instability.
What's more, few associated with the movie had a firm idea of what the Wachowskis' script was about, beyond the idea that earth's inhabitants were under the control of a huge computer program managed by anthropods.
Inherent in all these comments is a firm idea of what the Rockettes are not the music hall dancer who is a purveyor of pulchitrude.
