Don't split INSERT INTO SELECT into two statements

I'm all for the simpler pattern -- it just needs a comment that covers A) what we want to do -- match up to a close paren [preferably but OPTIONALLY one that is not part of a quoted identifier] and B) how the pattern achieves that.
I could would throw my support behind a very simple pattern (like greedily match everything to the next paren) that fails miserably when an identifier contains a close paren. Release note that and done.
I don't think that a tighter pattern that generally allows embedded parens -- in the presence of quotes, yet, to be perfect, not counting quoted quotes as true quotes -- is trivial or worth the effort at this point. 
I don't see the benefit of bringing in idPattern as a sub-pattern unless you're going to go all the way with a repeating group with whitespace and commas approach -- it's just more overkill for edge cases that will probably just fail somewhere else down the line.