The general idea was that he had left the country.

I think the general idea behind the question is clear!

I don't play these games but get the general idea.

Yes, I got the general idea you were in some trouble.

All of you have seen that thing on the table, and can get a general idea.

"You could have got the general idea I was a girl."

They'd done a lot more than that, but she got the general idea.

I'd never been there before, but I had a general idea of where it was.

At least I had a general idea of what was on the first floor.

The last bit isn't true, of course, but you get the general idea.